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In Situ Toxicity Identification Evaluation (iTIE)

2026-03-17T15:46:04Z

Debra Tabron:

The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate in weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Contaminated Sediments - Introduction]]
*[[Contaminated Sediment Risk Assessment]]
*[[Passive Sampling of Sediments]]
*[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]

'''Contributor(s):''' [[Dr. G. Allen Burton]] and [[Austin Crane]]

'''Key Resource(s):'''
*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>
*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document<ref>United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]  [[Media: EPA2007.pdf | Report pdf]]</ref>
*[https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification - ESTCP Project ER18-1181]<ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- ESTCP Project ER18-1181 [[Media: ER18-1181Ph.II.pdf | Final Report]]</ref>

==Introduction==
In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]  [[Media: usepa1992.pdf | Report pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.

==System Components and Validation==
[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

===Porewater and Surface Water Collection Sub-system===
[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

===Oxygen Coil, Overflow Bag and Drip Chamber===
[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

===iTIE Units: Fractionation and Organism Exposure Chambers===
[[File: CraneFig4.png | thumb | 300px | Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.]]
At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an ''in situ'' exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

===Pumping Sub-system===
[[File: CraneFig5.png | thumb | 300px | Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.]]
Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps ([https://ecotechmarine.com/ EcoTech Marine]). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries ([https://www.bioennopower.com/ Bioenno Power]).

First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.

Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.

==Study Design Considerations==
===Diagnostic Resin Treatments===
Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.
*[https://www.dupont.com/products/ambersorb560.html DuPont Ambersorb 560] for removal of 1,4-dioxane and other organic chemicals<ref>Woodard, S., Mohr, T., Nickelsen, M.G., 2014. Synthetic media: A promising new treatment technology for 1,4-dioxane. Remediation Journal, 24(4), pp. 27-40. [https://doi.org/10.1002/rem.21402 doi: 10.1002/rem.21402]</ref>
*C18 for nonpolar organic chemicals
*[https://www.bio-rad.com/en-us Bio-Rad] [https://www.bio-rad.com/en-us/product/chelex-100-resin?ID=6448ab3e-b96a-4162-9124-7b7d2330288e Chelex] for metals
*Granular activated carbon for metals, general organic chemicals, sulfide<ref>Lemos, B.R.S., Teixeira, I.F., de Mesquita, J.P., Ribeiro, R.R., Donnici, C.L., Lago, R.M., 2012. Use of modified activated carbon for the oxidation of aqueous sulfide. Carbon, 50(3), pp. 1386-1393. [https://doi.org/10.1016/j.carbon.2011.11.011 doi: 10.1016/j.carbon.2011.11.011]</ref>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=Shop&isocode=en_US&keyword=oasis%20hlb&multiselect=true&page=1&rows=12&sort=best-sellers&xcid=ppc-ppc_23916&gad_source=1&gad_campaignid=14746094146&gbraid=0AAAAAD_uR00nhlNwrhhegNh06pBODTgiN&gclid=CjwKCAiAtLvMBhB_EiwA1u6_PsppE0raci2IhvGnAAe5ijciNcetLaGZo5qA3g3r4Z_La7YAPJtzShoC6LoQAvD_BwE Oasis HLB] for general organic chemicals<ref name="SteigmeyerEtAl2017"/>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=All&enableHL=true&isocode=en_US&keyword=Oasis%20WAX%20&multiselect=true&page=1&rows=12&sort=most-relevant Oasis WAX] for PFAS, organic chemicals of mixed polarity<ref>Iannone, A., Carriera, F., Di Fiore, C., Avino, P., 2024. Poly- and Perfluoroalkyl Substance (PFAS) Analysis in Environmental Matrices: An Overview of the Extraction and Chromatographic Detection Methods. Analytica, 5(2), pp. 187-202. [https://doi.org/10.3390/analytica5020012 doi: 10.3390/analytica5020012]  [[Media: IannoneEtAl2024.pdf | Article pdf]]</ref>
*Zeolite for ammonia, other organic chemicals

Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.

===Test Organism Species and Life Stages===
Practitioners can also select different organism species and life stages for use in the iTIE system, depending on site characteristics and study goals. The iTIE system can accommodate various small test organisms, including embryo-stage fish and most macroinvertebrates. The following common toxicity tests can be adapted for application within iTIE systems<ref>U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1994. Catalogue of Standard Toxicity Tests for Ecological Risk Assessment. ECO Update, 2(2), 4 pages. Publication No. 9345.0.05I [https://www.epa.gov/sites/default/files/2015-09/documents/v2no2.pdf Free Download]  [[Media: usepa1994.pdf | Report pdf]]</ref>.
<ul>Freshwater acute toxicity:</ul>
*[[Wikipedia: Daphnia magna | ''Daphnia magna'']] or [[Wikipedia: Daphnia pulex | ''Daphnia pulex'']] 24-, 48-, and 96-hour survival
<ul>Freshwater chronic toxicity:</ul>
*[[Wikipedia: Ceriodaphnia dubia | ''Ceriodaphnia dubia'']] 7-day survival and reproduction
*''D. magna'' 7-day survival and reproduction
*[[Wikipedia: Fathead minnow | ''Pimephales promelas'']] 7-day embryo-larval survival and teratogenicity
*[[Wikipedia: Hyalella azteca | ''Hyalella Azteca'']] 10- or 30-day survival and reproduction
<ul>Marine acute toxicity:</ul>
*[[Wikipedia: Americamysis bahia | ''Americamysis bahia'']] 24- and 48-hour survival
<ul>Marine chronic toxicity:</ul>
*''Americamysis'' survival, growth and fecundity
*[[Wikipedia: Topsmelt silverside | ''Atherinops affinis'']] embryo-larval survival and growth

Acute toxicity is quantifiable via organism survival rates immediately following the termination of an iTIE system field deployment. Chronic toxicity can be quantified by continuing to culture and observe test organisms in-lab. Common chronic endpoints include stunted growth, altered development such as teratogenicity in larval fish, decreased reproduction rates, and changes in gene expression.

Several gene expression endpoints have been detectable in bioassays following an iTIE system deployment and in-lab culturing period. Steigmeyer ''et al.''<ref name="SteigmeyerEtAl2017"/> were able to detect changes in the expression of two genes in ''D. magna'' after a 24-hour exposure to bisphenol A. In a separate study, Nichols<ref>Nichols, E., 2023. Methods for Identification and Prioritization of Stressors at Impaired Sites. Masters thesis, University of Michigan. University of Michigan Library Deep Blue Documents. [https://deepblue.lib.umich.edu/bitstream/handle/2027.42/176142/Nichols_Elizabeth_thesis.pdf?sequence=1 Free Download]  [[Media: Nichols2023.pdf | Report pdf]]</ref> found a significant decline in acetylcholinesterase activity in ''H. azteca'' after a 24-hour exposure to chlorpyrifos. These results indicate a potential to adapt other gene expression bioassays for use in conjunction with iTIE system field exposures to prove stressor-causality linkages.

===Cost Effectiveness Study===
Burton ''et al.''<ref name="BurtonEtAl2020"/> conducted a cost effectiveness study comparing the iTIE technology with the traditional US EPA Phase 1 TIE method. Comparisons were based on the estimated time required to complete various sub-tasks within each method. Sub-tasks included organism care, equipment preparation, mobilization and deployment, test maintenance, test termination, demobilization, and test termination analyses. It was ultimately estimated that the iTIE protocol requires 47% less time (67 fewer hours) to complete than the Phase 1 TIE method, with the largest time differences in equipment preparation, deployment, test maintenance, and demobilization. It is important to note that the iTIE method may require additional initial costs for equipment and training.

==Field Application==
[[File: CraneFig6.png | thumb | left | 400px | Figure 6. iTIES deployment at the Rouge River, Detroit, MI. In the foreground is the iTIE Cooler Sub-System, which contains iTIE resin treatments and test organism groups, as well as the oxygenation coil and sample collection bottles. Next to the iTIE Cooler are the two pump cases. The Trident can be seen above the pump cases, installed in the river channel near shore.]]
The iTIE system has been successfully deployed at a variety of marine and freshwater sites during the proof-of-concept phase of prototype development. One example is the 2024 iTIE system deployment completed near the mouth of the Rouge River in Detroit, MI (Figure 6). The Rouge River watershed has a long history of industrialization, with a legacy of chemical dumping, channelization, damming, and urban runoff<ref>Ridgway, J., Cave, K., DeMaria, A., O’Meara, J., Hartig, J. H., 2018. The Rouge River Area of Concern—A multi-year, multi-level successful approach to restoration of Impaired Beneficial Uses. Aquatic Ecosystem Health and Management, 21(4), pp. 398-408. [https://doi.org/10.1080/14634988.2018.1528816 doi: 10.1080/14634988.2018.1528816]</ref>. This has led to degraded environmental conditions, with previous detections of a wide range of chemicals including heavy metals and various organics.

[[File: CraneFig7.png | thumb | 300px | Figure 7. Survival and healthy development of ''P. promelas'' embryos and larvae following a 48-hour iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater as embryos for 48 hours and cultured post-exposure for an additional 5 days.]]
[[File: CraneFig8.png | thumb | 300px | Figure 8. Survival of ''C. dilutus'' larvae after an iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater for 48 hours and cultured post-exposure for an additional 5 days. Error bars show standard deviation.]]
An iTIE system deployment was designed and completed to determine which chemical classes are most responsible for causing toxicity at the site. Resin treatments included glass wool (inert, non-fractionating substance), Chelex (metals sorption), Oasis HLB (general organics sorption), and Oasis WAX (organics sorption, with a high affinity for PFAS). The study utilized fathead minnow (''P. promelas'') embryos, due to their relative sensitivity to metals and PAHs, as well as second-instar midge ([[Wikipedia: Chironomus |''Chironomus dilutus'']]) larvae due to their relative sensitivity to PFAS.

The test organisms were exposed to fractionated porewater ''in situ'' for 48 hours. Following exposure, organisms were cultured for an additional five days, and survival was recorded (Figures 7 and 8). Moderate declines in survival were seen in both species in the glass wool treatment, indicating toxicity at the site. For ''P. promelas'', the highest proportion of healthy development occurred in the Chelex treatment, supporting the hypothesis that metals are a dominant cause of toxicity. ''C. dilutus'' had the greatest survival in the Oasis WAX treatment, suggesting that an organic stressor class like PFAS is also present at harmful concentrations in the river.

Water chemical analyses of fractionated and unfractionated water samples were completed to support biological results. Analyses were conducted for a range of stressor classes including metals, PAHs, PCBs, an organophosphate pesticide (chlorpyrifos), a PFAS compound (PFOS) and a pyrethroid insecticide (permethrin). Of these analytes, only heavy metals and PFOS were detected. Some chemical classes including PAHs and PCBs were not detected at the site.
To reach similar conclusions using traditional Phase 1 TIE methods, one would need to complete the following tests: baseline toxicity, filtration, aeration, EDTA, C18 SPE, and methanol elution of C18 SPE. The iTIE method allows the same conclusions to be drawn with significantly less time and effort required.

==Summary==
The ''in situ'' Toxicity Identification Evaluation technology and protocol is a powerful tool that investigators can use to strengthen causal linkages between chemical stressors and ecological toxicity. By fractionating sampled water and exposing test organisms ''in situ'', investigators can gather toxicity response data while minimizing sample manipulation and accurately representing environmental conditions.
 

==References==
<references />

==See Also==

Austin Crane

2026-03-17T15:44:25Z

Debra Tabron:

==Work and Contact Information==

EMPLOYER:
:University of Michigan 
:440 Church Street 
:Ann Arbor, MI 48109

EMAIL: [mailto:amcrane@umich.edu amcrane@umich.edu]

WEBPAGE: [https://www.linkedin.com/in/austin-crane/ https://www.linkedin.com/in/austin-crane/]

==About the Contributor==
Mr. Austin Crane is an Environmental Quality Analyst for the Michigan Department of Environment, Great Lakes, and Energy. He was formerly a Research Laboratory Specialist with the Burton Ecotoxicology Lab at the University of Michigan School for Environment and Sustainability. His research with the Burton Ecotoxicology Lab focused on the development of novel in-situ devices for detecting and quantifying toxicity at aquatic sites. He received a master’s degree in Environment and Sustainability from the University of Michigan with a specialization in ecosystem science and management.

==Article Contributions==
*[[In Situ Toxicity Identification Evaluation (iTIE)]]

__NOTOC__

[[Category: Contributors|Crane]]

Austin Crane

2026-03-17T15:43:34Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :University of Michigan :440 Church Street :Ann Arbor, MI 48109 EMAIL: [mailto:amcrane@umich.edu amcrane@umich.edu]..."

Articles

2026-03-17T15:37:39Z

Debra Tabron:

{| class="wikitable sortable"
|-
!Title!!First Author!!Linking Phrases
|-
|[[Groundwater Sampling - No-Purge/Passive]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||passive sampling, no purge sampling, grab samplers, diffusion samplers, sorptive samplers
|-
|[[ Long-Term Monitoring (LTM)]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||long-term monitoring, LTM, LTM objectives, LTM programs, LTM challenges
|-
|[[PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)]]
|[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]
|PFAS, MNA, natural attenuation
|-
|[[Sorption of Organic Contaminants]]||[[Richelle Allen-King|Allen-King, Richelle]]||
|-
|[[PFAS Transport and Fate]]
|[[Dr. Richard Anderson|Anderson, Richard, Ph.D.]]
|PFAS, fate and transport
|-
|[[Mass Flux and Mass Discharge]]||[[Dr. Michael Annable, P.E. |Annable, Michael, Ph.D., P.E.]]||source reduction
|-
|[[PFAS Toxicology and Risk Assessment]]
|[[Jennifer Arblaster|Arblaster, Jennifer]]
|PFAS, toxicology, risk assessment
|-
|[[Metal(loid)s - Small Arms Ranges]]|| Dr. Amanda Barker |[[Dr. Amanda Barker|Barker, Amanda, Ph.D.]]
|
|-
|[[Munitions Constituents – Photolysis|Munitions Constituents - Photolysis]]
|[[Dr. Warren Kadoya|Kadoya, Warren, Ph.D.]]
|
|-
|[[Munitions Constituents - Soil Sampling]]
|[[Dr. Samuel Beal|Beal, Samuel, Ph.D.]]
|
|-
|[[Vapor Intrusion – Sewers and Utility Tunnels as Preferential Pathways|Vapor Intrusion - Sewers and Utility Tunnels as Preferential Pathways]]
|[[Lila Beckley|Beckley, Lila]]
|vapor intrusion
|-
|[[Natural Attenuation in Source Zone and Groundwater Plume - Bemidji Crude Oil Spill]]
|[[Dr. Barbara Bekins|Bekins, Barbara, Ph.D.]]||
|-
|[[Bioremediation - Anaerobic Secondary Water Quality Impacts]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||secondary impacts, water quality (in regards to anaerobic conditions)
|-
|[[Design Tool - Base Addition for ERD]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||aquifer acidity, base addition
|-
|[[Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation]]
|[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||
|-
|[[Low pH Inhibition of Reductive Dechlorination]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||low pH inhibition
|-
|[[In Situ Toxicity Identification Evaluation (iTIE)]]||[[Dr. G. Allen Burton |Burton, Allen, P.E.]]||toxicity evaluation
|-
|[[OPTically-based In-situ Characterization System (OPTICS)]]
|[[Dr. Grace Chang|Chang, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents - Electrochemical Treatment]]
|[[Dr. Brian P. Chaplin|Chaplin, Brian, Ph.D.]]
|munitions constituents remediation
|-
|[[PFAS Sources]]
|[[Dr. Dora Chiang|Chiang, Dora, Ph.D.]]
|
|-
|[[Biodegradation - Cometabolic]]||[[Dr. Kung-Hui (Bella) Chu |Chu, Kung-Hui (Bella), Ph.D]]||cometabolic biodegradation
|-
|[[Munitions Constituents - Composting]]
|[[Harry Craig|Craig, Harry]]
|
|-
|[[Chemical Oxidation (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||ISCO, chemical oxidation
|-
|[[Chemical Oxidation Oxidant Selection (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||chemical oxidant, oxidant (in regards to ISCO)
|-
|[[Chemical Oxidation Design Considerations(In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||screening, design, implementation, oxidant delivery (in regards to ISCO)
|-
|[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]||[[Dr. Rula Deeb |Deeb, Rula, Ph.D.]]||PFAS, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS)
|-
|[[Metal and Metalloid Contaminants]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal contaminant(s), metalloid contaminant(s), metal(s), metalloid(s),
|-
|[[Metals and Metalloids - Mobility in Groundwater]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal mobility, aqueous speciation, adsorption, precipitation, colloidal transport (in regards to metals)
|-
|[[Monitored Natural Attenuation (MNA) of Metal and Metalloids]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||MNA, attenuation of metal(s), natural attenuation processes, attenuation (in regards to metals)
|-
|[[Metal and Metalloids - Remediation]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||remediation, in situ technologies, contaminant removal (in regards to metals)
|-
|[[pH Buffering in Aquifers]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||ph buffer, natural pH buffer, engineered pH buffer
|-
|[[Munitions Constituents - Sorption]]||[[Dr. Katerina Dontsova |Dontsova, Katerina, Ph.D.]]||energetics, sorption
|-
|[[Biodegradation - Hydrocarbons]]||[[Dr. Elizabeth Edwards |Edwards, Elizabeth, Ph.D.]]||hydrocarbon, biodegradation
|-
|[[Source Zone Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||source zone modeling
|-
|[[Plume Response Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||plume response modeling
|-
|[[REMChlor - MD]]
|[[Dr. Ron Falta|Falta, Ron, Ph.D.]]
|
|-
|[[In Situ Groundwater Treatment with Activated Carbon]]
|[[Dr. Dimin Fan|Fan, Dimin, Ph.D.]]
|
|-
|[[LNAPL Remediation Technologies]]||[[Dr. Shahla Farhat |Farhat, Shahla, Ph.D.]]||
|-
|[[Sustainable Remediation]]||[[Paul Favara |Favara, Paul]]||sustainable remediation, social, economic and environmental impacts
|-
|[[Munitions Constituents]]||[[Dr. Kevin Finneran |Finneran, Kevin, Ph.D.]]||Explosives, energetics, insensitive munitions
|-
|[[Biodegradation - Reductive Processes]]||[[Dr. David Freedman |Freedman, David, Ph.D.]]||biotic reduction, biotic reductive processes, hydrogenolysis, dihaloelimination, coupling, organohalide respiration
|-
|[[Remediation of Stormwater Runoff Contaminated by Munition Constituents|Munitions Constituents - Remediation of Stormwater Runoff]]||Fuller, Mark, Ph.D.||energetics, insensitive munitions, stormwater runoff
|-
|[[Subgrade Biogeochemical Reactor (SBGR)]]||[[Jeff Gamlin |Gamlin, Jeff]]||SBGR, subgrade biogeochemical reactor, bioreactor
|-
|[[Thermal Remediation - Smoldering]]||[[Dr. Jason Gerhard |Gerhard, Jason, Ph.D.]]||smouldering remediation, self-sustaining treatment for active remediation, STAR
|-
|[[Contaminated Sediments - Introduction]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[Contaminated Sediment Risk Assessment]]
|[[Richard Wenning|Wenning, Richard]]
|
|-
|[[In Situ Treatment of Contaminated Sediments with Activated Carbon]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[PFAS Ex Situ Water Treatment]]
|[[Dr. Scott Grieco |Grieco, Scott, Ph.D.]]
|
|-
|[[Stream Restoration]]
|[[Dr. Natalie Griffiths|Griffiths, Natalie, Ph.D.]]
|
|-
|[[Passive Sampling of Sediments]]
|[[Dr. Philip M. Gschwend|Gschwend, Philip]]
|
|-
|[[Phytoplankton (Algae) Blooms]]
|[[Dr. Nathan Hall|Hall, Nathan]]
|
|-
|[[PFAS Soil Remediation Technologies]]||[[James_Hatton |Hatton, Jim]]||PFAS, Soil source zones
|-
|[[Proteomics and Proteogenomics]]
|[[Dr. Kate Kucharzyk|Kucharzyk, Kate, Ph.D.]]
|
|-
|[[N-nitrosodimethylamine (NDMA)]]
|[[Paul Hatzinger|Hatzinger, Paul, Ph.D.]]
|
|-
|[[Alternative Endpoints]]||[[Elisabeth Hawley |Hawley, Elisabeth]]||management of complex sites||
|-
|[[Thermal Remediation]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, in situ thermal
|-
|[[Thermal Remediation - Steam]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Steam Enhanced Extraction
|-
|[[Thermal Remediation - Electrical Resistance Heating]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Electrical Resistance Heating
|-
|[[Thermal Conduction Heating (TCH)]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal desorption
|-
|[[Thermal Remediation - Combined Remedies]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation
|-
|[[Thermal Conduction Heating for Treatment of PFAS-Impacted Soil]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, PFAS
|-
|[[Predicting Species Responses to Climate Change with Population Models]]
|[[Dr. Brian Hudgens|Hudgens, Brian, Ph.D.]]
|climate change
|-
|[[Infrastructure Resilience]]
|[[Dr. John Hummel|Hummel, John, Ph.D.]]
|
|-
|[[Munitions Constituents- TREECS™ Fate and Risk Modeling|Munitions Constituents - TREECS™ Fate and Risk Modeling]]||[[Dr. Billy E. Johnson |Johnson, Billy, Ph.D.]]||munitions constituents fate and transport modeling, TREECS
|-
|[[Munitions Constituents - Alkaline Degradation]]
|[[Jared Johnson|Johnson, Jared]]
|
|-
|[[Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)|Vapor Intrusion - Assessing VI Impacts in Neighborhoods with Groundwater Contaminated CVOCs]]
|[[Dr. Paul C. Johnson|Johnson, Paul, Ph.D.]]
|vapor intrusion
|-
|[[Munitions Constituents - IM Toxicology]]||-----||insensitive explosives, insensitive munitions, IMX-101, IMX
|-
|[[Landfarming]]
|[[Dr. Roopa Kamath|Kamath, Roopa, Ph.D.]]
|
|-
|[[NAPL Mobility]]
|[[Andrew Kirkman|Kirkman, Andrew]]
|
|-
|[[Climate Change Primer]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Perchlorate]]||[[Thomas Krug |Krug, Thomas]]||perchlorate
|-
|[[Injection Techniques for Liquid Amendments]]||[[Thomas Krug |Krug, Thomas]]||amendment injection
|-
|[[Transition of Aqueous Film Forming Foam (AFFF) Fire Suppression Infrastructure Impacted by Per and Polyfluoroalkyl Substances (PFAS)]]
|[[Dr. Johnsie Ray Lang|Lang, Johnsie Ray, Ph.D.]]||PFAS
|
|-
|[[Characterization Methods – Hydraulic Conductivity]]
|[[Dr. Gaisheng Liu|Liu, Gaisheng, Ph.D.]]
|
|-
|[[Compound Specific Isotope Analysis (CSIA)]]||[[Dr. Barbara Sherwood Lollar, F.R.S.C. |Lollar, Barbara S., FRSC]]||Compound Specific Isotope Analysis (CSIA)
|-
|[[Passive Sampling of Munitions Constituents|Munitions Constituents - Passive Sampling]]
|[[Dr. Guilherme Lotufo|Lotufo, Guilerme, Ph.D.]]
|
|-
|[[Vapor Intrusion (VI)]]||[[Chris Lutes |Lutes, Chris]]||vapor intrusion
|-
|[[Bioremediation - Anaerobic]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||anaerobic bioremediation
|-
|[[Bioremediation - Anaerobic Design Considerations]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||
|-
|[[Biodegradation - 1,4-Dioxane]]
|[[Dr. Shaily Mahendra|Mahendra, Shaily, Ph.D.]]
|
|-
|[[Direct Push (DP) Technology]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push, DP, DP machines, DP technology
|-
|[[Direct Push Sampling]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push sampling, soil sampling, groundwater sampling, well installation, soil vapor sampling (in regards to DP)
|-
|[[Direct Push Logging]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push logging, Cone Penetration Testing, CPT, Electrical Conductivity, EC, Hydraulic Profiling Tool, HPT, Membrane Interface Probe, MIP, Optical Imaging Profiler, OIP
|-
|[[Downscaled High Resolution Datasets for Climate Change Projections]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Remediation Performance Assessment at Chlorinated Solvent Sites]]||[[Travis McGuire|McGuire, Travis]]||multi-site studies
|-
|[[LNAPL Conceptual Site Models]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Long-Term Monitoring (LTM) - Data Analysis]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data analysis, analysis methods (in regards to LTM)
|-
|[[Long-Term Monitoring (LTM) - Data Variability]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data variability (in regards to LTM), LTM evaluation
|-
|-
|[[Munitions Constituents - Abiotic Reduction]]||[[Dr. Jimmy Murillo-Gelvez |Murillo-Gelvez, Jimmy, Ph.D.]]
|-
|[[Supercritical Water Oxidation (SCWO)]]
|Nagar, Kobe
|
|-
|[[Matrix Diffusion]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Groundwater Flow and Solute Transport]]||[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]||groundwater flow, advection, dispersion, diffusion, molecular diffusion, mechanical dispersion
|-
|[[Molecular Biological Tools - MBTs]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||MBT, Molecular Biological Tool(s)
|-
|[[Quantitative Polymerase Chain Reaction (qPCR)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||qPCR, Polymerase Chain Reaction
|-
|[[Sediment Capping]]
|[[Dr. Danny Reible|Reible, Danny]]
|
|-
|[[Stable Isotope Probing (SIP)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||SIP, Stable Isotope Probing
|-
|[[Metagenomics]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||metagenomics
|-
|[[Natural Source Zone Depletion (NSZD)]]||[[Tom Palaia |Palaia, Tom]]||natural source zone depletion, NSZD
|-
|[[Climate Change Effects on Wildlife]]
|[[Dr. Breanna F. Powers|Powers, Breanna, PhD.]]
|
|-
|[[Amendment Distribution in Low Conductivity Materials]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||
|-
|[[Polycyclic Aromatic Hydrocarbons (PAHs)]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||polycyclic aromatic hydrocarbons, PAH(s)
|-
|[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]
|[[Florent Risacher|Risacher, Florent, M.Sc.]]
|
|-
|[[1,2,3-Trichloropropane]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||TCP, trichloropropane
|-
|[[Zerovalent Iron (ZVI) (Chemical Reduction - ISCR)]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||ZVI
|-
|[[Mercury in Sediments]]
|[[Dr. Grace Schwartz|Schwartz, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents – Sample Extraction and Analytical Techniques|Munitions Constituents - Sample Extraction and Analytical Techniques]]
|[[Dr. Austin Scircle|Scircle, Austin]]
|
|-
|[[Geophysical Methods]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[Geophysical Methods - Case Studies]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[PFAS Treatment by Anion Exchange]]
|[[Dr. Timothy J. Strathmann|Strathmann, Timothy, Ph.D.]]
|PFAS
|-
|[[Munitions Constituents - Dissolution]]||[[Dr. Susan Taylor |Taylor, Susan, Ph.D.]]||explosive(s), dissolution,
|-
|[[PFAS Treatment by Electrical Discharge Plasma]]
|[[Dr. Selma Mededovic Thagard|Thagard, Selma Mededovic, Ph.D.]]
|PFAS
|-
|[[Restoration of Ecological Function in Terrestrial Systems Impacted by Invasive Species]]
|Thierry, Hugo, Ph.D.
|climate change, invasive species, restoration ecology
|-
|[[Chemical Reduction (In Situ - ISCR)]]||[[Dr. Paul Tratnyek |Tratnyek, Paul, Ph.D.]]||In Situ Chemical Reduction, ISCR
|-
|[[Injection Techniques - Viscosity Modification]]||[[Michael Truex |Truex, Michael]]||viscosity, viscosity modifiers, viscosity modification
|-
|[[Soil Vapor Extraction (SVE)]]||[[Michael Truex |Truex, Michael]]||soil vapor extraction, SVE
|-
|[[Munitions Constituents - Deposition]]||[[Michael R. Walsh, P.E., M.E.|Walsh, Michael, P.E.]]||explosive deposition, energetics deposition
|-
|[[Vapor Intrusion - Separation Distances from Petroleum Sources]]
|[[Dr. James Weaver|Weaver, James, Ph.D.]]
|vapor intrusion
|-
|[[Zerovalent Iron Permeable Reactive Barriers]]
|[[Dr. Richard Wilkin|Wilkin, Rick, Ph.D.]]
|
|-
|[[Monitored Natural Attenuation (MNA)]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, In Situ MNA, natural attenuation, natural attenuation processes
|-
|[[Monitored Natural Attenuation (MNA) of Fuels]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to petroleum hydrocarbons and fuel components)
|-
|[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to chlorinated solvents)
|-
|[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
|[[Dr. John Wilson|Wilson, John, Ph.D.]]
|MNA, natural attenuation
|-
|[[Chlorinated Solvents]]||[[Dr. Bilgen Yuncu, P.E. |Yuncu, Bilgen, Ph.D., P.E.]]||chlorinated solvents
|-
|[[Petroleum Hydrocarbons (PHCs)]]
|[[Dr. Bilgen Yuncu, P.E.|Yuncu, Bilgen, Ph.D., P.E.]]
|Petroleum Hydrocarbons (PHCs)
|-
|[[Photoactivated Reductive Defluorination - PFAS Destruction]]
|[[Dr. Suzanne Witt|Witt, Suzanne, Ph.D.]]
|PFAS destruction
|
|-
|[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]
|[[Dr. Lee Slater|Slater, Lee, Ph.D.]]
|geophysics, hydrogeophysical methods,
|
|-
|[[Hydrothermal Alkaline Treatment (HALT)]]
|[[Dr. Brian Pinkard|Pinkard, Brian]]
|
|-
|[[1,4-Dioxane]]
|[[Matthew Zenker|Zenker, Matthew]]
|
|-
|[[Lysimeters for Measuring PFAS Concentrations in the Vadose Zone]]
|[[Dr. John F. Stults|Stults, Dr. John]]
|PFAS, vadose zone, lysimeter, field investigation
|
|-
|[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]||[[Dr. Yida Fang |Fang, Yida, Ph.D.]]||PFAS destruction
|
|-
|}

In Situ Toxicity Identification Evaluation (iTIE)

2026-03-16T15:39:21Z

Debra Tabron:

The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate in weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Contaminated Sediments - Introduction]]
*[[Contaminated Sediment Risk Assessment]]
*[[Passive Sampling of Sediments]]
*[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]

'''Contributor(s):''' [[Dr. G. Allen Burton]] and Austin Crane

'''Key Resource(s):'''
*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>
*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document<ref>United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]  [[Media: EPA2007.pdf | Report pdf]]</ref>
*[https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification - ESTCP Project ER18-1181]<ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- ESTCP Project ER18-1181 [[Media: ER18-1181Ph.II.pdf | Final Report]]</ref>

==Introduction==
In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]  [[Media: usepa1992.pdf | Report pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.

==System Components and Validation==
[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

===Porewater and Surface Water Collection Sub-system===
[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

===Oxygen Coil, Overflow Bag and Drip Chamber===
[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

===iTIE Units: Fractionation and Organism Exposure Chambers===
[[File: CraneFig4.png | thumb | 300px | Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.]]
At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an ''in situ'' exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

===Pumping Sub-system===
[[File: CraneFig5.png | thumb | 300px | Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.]]
Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps ([https://ecotechmarine.com/ EcoTech Marine]). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries ([https://www.bioennopower.com/ Bioenno Power]).

First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.

Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.

==Study Design Considerations==
===Diagnostic Resin Treatments===
Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.
*[https://www.dupont.com/products/ambersorb560.html DuPont Ambersorb 560] for removal of 1,4-dioxane and other organic chemicals<ref>Woodard, S., Mohr, T., Nickelsen, M.G., 2014. Synthetic media: A promising new treatment technology for 1,4-dioxane. Remediation Journal, 24(4), pp. 27-40. [https://doi.org/10.1002/rem.21402 doi: 10.1002/rem.21402]</ref>
*C18 for nonpolar organic chemicals
*[https://www.bio-rad.com/en-us Bio-Rad] [https://www.bio-rad.com/en-us/product/chelex-100-resin?ID=6448ab3e-b96a-4162-9124-7b7d2330288e Chelex] for metals
*Granular activated carbon for metals, general organic chemicals, sulfide<ref>Lemos, B.R.S., Teixeira, I.F., de Mesquita, J.P., Ribeiro, R.R., Donnici, C.L., Lago, R.M., 2012. Use of modified activated carbon for the oxidation of aqueous sulfide. Carbon, 50(3), pp. 1386-1393. [https://doi.org/10.1016/j.carbon.2011.11.011 doi: 10.1016/j.carbon.2011.11.011]</ref>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=Shop&isocode=en_US&keyword=oasis%20hlb&multiselect=true&page=1&rows=12&sort=best-sellers&xcid=ppc-ppc_23916&gad_source=1&gad_campaignid=14746094146&gbraid=0AAAAAD_uR00nhlNwrhhegNh06pBODTgiN&gclid=CjwKCAiAtLvMBhB_EiwA1u6_PsppE0raci2IhvGnAAe5ijciNcetLaGZo5qA3g3r4Z_La7YAPJtzShoC6LoQAvD_BwE Oasis HLB] for general organic chemicals<ref name="SteigmeyerEtAl2017"/>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=All&enableHL=true&isocode=en_US&keyword=Oasis%20WAX%20&multiselect=true&page=1&rows=12&sort=most-relevant Oasis WAX] for PFAS, organic chemicals of mixed polarity<ref>Iannone, A., Carriera, F., Di Fiore, C., Avino, P., 2024. Poly- and Perfluoroalkyl Substance (PFAS) Analysis in Environmental Matrices: An Overview of the Extraction and Chromatographic Detection Methods. Analytica, 5(2), pp. 187-202. [https://doi.org/10.3390/analytica5020012 doi: 10.3390/analytica5020012]  [[Media: IannoneEtAl2024.pdf | Article pdf]]</ref>
*Zeolite for ammonia, other organic chemicals

Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.

===Test Organism Species and Life Stages===
Practitioners can also select different organism species and life stages for use in the iTIE system, depending on site characteristics and study goals. The iTIE system can accommodate various small test organisms, including embryo-stage fish and most macroinvertebrates. The following common toxicity tests can be adapted for application within iTIE systems<ref>U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1994. Catalogue of Standard Toxicity Tests for Ecological Risk Assessment. ECO Update, 2(2), 4 pages. Publication No. 9345.0.05I [https://www.epa.gov/sites/default/files/2015-09/documents/v2no2.pdf Free Download]  [[Media: usepa1994.pdf | Report pdf]]</ref>.
<ul>Freshwater acute toxicity:</ul>
*[[Wikipedia: Daphnia magna | ''Daphnia magna'']] or [[Wikipedia: Daphnia pulex | ''Daphnia pulex'']] 24-, 48-, and 96-hour survival
<ul>Freshwater chronic toxicity:</ul>
*[[Wikipedia: Ceriodaphnia dubia | ''Ceriodaphnia dubia'']] 7-day survival and reproduction
*''D. magna'' 7-day survival and reproduction
*[[Wikipedia: Fathead minnow | ''Pimephales promelas'']] 7-day embryo-larval survival and teratogenicity
*[[Wikipedia: Hyalella azteca | ''Hyalella Azteca'']] 10- or 30-day survival and reproduction
<ul>Marine acute toxicity:</ul>
*[[Wikipedia: Americamysis bahia | ''Americamysis bahia'']] 24- and 48-hour survival
<ul>Marine chronic toxicity:</ul>
*''Americamysis'' survival, growth and fecundity
*[[Wikipedia: Topsmelt silverside | ''Atherinops affinis'']] embryo-larval survival and growth

Acute toxicity is quantifiable via organism survival rates immediately following the termination of an iTIE system field deployment. Chronic toxicity can be quantified by continuing to culture and observe test organisms in-lab. Common chronic endpoints include stunted growth, altered development such as teratogenicity in larval fish, decreased reproduction rates, and changes in gene expression.

Several gene expression endpoints have been detectable in bioassays following an iTIE system deployment and in-lab culturing period. Steigmeyer ''et al.''<ref name="SteigmeyerEtAl2017"/> were able to detect changes in the expression of two genes in ''D. magna'' after a 24-hour exposure to bisphenol A. In a separate study, Nichols<ref>Nichols, E., 2023. Methods for Identification and Prioritization of Stressors at Impaired Sites. Masters thesis, University of Michigan. University of Michigan Library Deep Blue Documents. [https://deepblue.lib.umich.edu/bitstream/handle/2027.42/176142/Nichols_Elizabeth_thesis.pdf?sequence=1 Free Download]  [[Media: Nichols2023.pdf | Report pdf]]</ref> found a significant decline in acetylcholinesterase activity in ''H. azteca'' after a 24-hour exposure to chlorpyrifos. These results indicate a potential to adapt other gene expression bioassays for use in conjunction with iTIE system field exposures to prove stressor-causality linkages.

===Cost Effectiveness Study===
Burton ''et al.''<ref name="BurtonEtAl2020"/> conducted a cost effectiveness study comparing the iTIE technology with the traditional US EPA Phase 1 TIE method. Comparisons were based on the estimated time required to complete various sub-tasks within each method. Sub-tasks included organism care, equipment preparation, mobilization and deployment, test maintenance, test termination, demobilization, and test termination analyses. It was ultimately estimated that the iTIE protocol requires 47% less time (67 fewer hours) to complete than the Phase 1 TIE method, with the largest time differences in equipment preparation, deployment, test maintenance, and demobilization. It is important to note that the iTIE method may require additional initial costs for equipment and training.

==Field Application==
[[File: CraneFig6.png | thumb | left | 400px | Figure 6. iTIES deployment at the Rouge River, Detroit, MI. In the foreground is the iTIE Cooler Sub-System, which contains iTIE resin treatments and test organism groups, as well as the oxygenation coil and sample collection bottles. Next to the iTIE Cooler are the two pump cases. The Trident can be seen above the pump cases, installed in the river channel near shore.]]
The iTIE system has been successfully deployed at a variety of marine and freshwater sites during the proof-of-concept phase of prototype development. One example is the 2024 iTIE system deployment completed near the mouth of the Rouge River in Detroit, MI (Figure 6). The Rouge River watershed has a long history of industrialization, with a legacy of chemical dumping, channelization, damming, and urban runoff<ref>Ridgway, J., Cave, K., DeMaria, A., O’Meara, J., Hartig, J. H., 2018. The Rouge River Area of Concern—A multi-year, multi-level successful approach to restoration of Impaired Beneficial Uses. Aquatic Ecosystem Health and Management, 21(4), pp. 398-408. [https://doi.org/10.1080/14634988.2018.1528816 doi: 10.1080/14634988.2018.1528816]</ref>. This has led to degraded environmental conditions, with previous detections of a wide range of chemicals including heavy metals and various organics.

[[File: CraneFig7.png | thumb | 300px | Figure 7. Survival and healthy development of ''P. promelas'' embryos and larvae following a 48-hour iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater as embryos for 48 hours and cultured post-exposure for an additional 5 days.]]
[[File: CraneFig8.png | thumb | 300px | Figure 8. Survival of ''C. dilutus'' larvae after an iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater for 48 hours and cultured post-exposure for an additional 5 days. Error bars show standard deviation.]]
An iTIE system deployment was designed and completed to determine which chemical classes are most responsible for causing toxicity at the site. Resin treatments included glass wool (inert, non-fractionating substance), Chelex (metals sorption), Oasis HLB (general organics sorption), and Oasis WAX (organics sorption, with a high affinity for PFAS). The study utilized fathead minnow (''P. promelas'') embryos, due to their relative sensitivity to metals and PAHs, as well as second-instar midge ([[Wikipedia: Chironomus |''Chironomus dilutus'']]) larvae due to their relative sensitivity to PFAS.

The test organisms were exposed to fractionated porewater ''in situ'' for 48 hours. Following exposure, organisms were cultured for an additional five days, and survival was recorded (Figures 7 and 8). Moderate declines in survival were seen in both species in the glass wool treatment, indicating toxicity at the site. For ''P. promelas'', the highest proportion of healthy development occurred in the Chelex treatment, supporting the hypothesis that metals are a dominant cause of toxicity. ''C. dilutus'' had the greatest survival in the Oasis WAX treatment, suggesting that an organic stressor class like PFAS is also present at harmful concentrations in the river.

Water chemical analyses of fractionated and unfractionated water samples were completed to support biological results. Analyses were conducted for a range of stressor classes including metals, PAHs, PCBs, an organophosphate pesticide (chlorpyrifos), a PFAS compound (PFOS) and a pyrethroid insecticide (permethrin). Of these analytes, only heavy metals and PFOS were detected. Some chemical classes including PAHs and PCBs were not detected at the site.
To reach similar conclusions using traditional Phase 1 TIE methods, one would need to complete the following tests: baseline toxicity, filtration, aeration, EDTA, C18 SPE, and methanol elution of C18 SPE. The iTIE method allows the same conclusions to be drawn with significantly less time and effort required.

==Summary==
The ''in situ'' Toxicity Identification Evaluation technology and protocol is a powerful tool that investigators can use to strengthen causal linkages between chemical stressors and ecological toxicity. By fractionating sampled water and exposing test organisms ''in situ'', investigators can gather toxicity response data while minimizing sample manipulation and accurately representing environmental conditions.
 

==References==
<references />

==See Also==

In Situ Toxicity Identification Evaluation (iTIE)

2026-03-16T15:38:44Z

Debra Tabron:

The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate in weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Contaminated Sediments - Introduction]]
*[[Contaminated Sediment Risk Assessment]]
*[[Passive Sampling of Sediments]]
*[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]

'''Contributor(s):''' [[Dr. G. Allen Burton Jr.]] and Austin Crane

'''Key Resource(s):'''
*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>
*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document<ref>United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]  [[Media: EPA2007.pdf | Report pdf]]</ref>
*[https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification - ESTCP Project ER18-1181]<ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- ESTCP Project ER18-1181 [[Media: ER18-1181Ph.II.pdf | Final Report]]</ref>

==Introduction==
In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]  [[Media: usepa1992.pdf | Report pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.

==System Components and Validation==
[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

===Porewater and Surface Water Collection Sub-system===
[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

===Oxygen Coil, Overflow Bag and Drip Chamber===
[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

===iTIE Units: Fractionation and Organism Exposure Chambers===
[[File: CraneFig4.png | thumb | 300px | Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.]]
At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an ''in situ'' exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

===Pumping Sub-system===
[[File: CraneFig5.png | thumb | 300px | Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.]]
Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps ([https://ecotechmarine.com/ EcoTech Marine]). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries ([https://www.bioennopower.com/ Bioenno Power]).

First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.

Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.

==Study Design Considerations==
===Diagnostic Resin Treatments===
Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.
*[https://www.dupont.com/products/ambersorb560.html DuPont Ambersorb 560] for removal of 1,4-dioxane and other organic chemicals<ref>Woodard, S., Mohr, T., Nickelsen, M.G., 2014. Synthetic media: A promising new treatment technology for 1,4-dioxane. Remediation Journal, 24(4), pp. 27-40. [https://doi.org/10.1002/rem.21402 doi: 10.1002/rem.21402]</ref>
*C18 for nonpolar organic chemicals
*[https://www.bio-rad.com/en-us Bio-Rad] [https://www.bio-rad.com/en-us/product/chelex-100-resin?ID=6448ab3e-b96a-4162-9124-7b7d2330288e Chelex] for metals
*Granular activated carbon for metals, general organic chemicals, sulfide<ref>Lemos, B.R.S., Teixeira, I.F., de Mesquita, J.P., Ribeiro, R.R., Donnici, C.L., Lago, R.M., 2012. Use of modified activated carbon for the oxidation of aqueous sulfide. Carbon, 50(3), pp. 1386-1393. [https://doi.org/10.1016/j.carbon.2011.11.011 doi: 10.1016/j.carbon.2011.11.011]</ref>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=Shop&isocode=en_US&keyword=oasis%20hlb&multiselect=true&page=1&rows=12&sort=best-sellers&xcid=ppc-ppc_23916&gad_source=1&gad_campaignid=14746094146&gbraid=0AAAAAD_uR00nhlNwrhhegNh06pBODTgiN&gclid=CjwKCAiAtLvMBhB_EiwA1u6_PsppE0raci2IhvGnAAe5ijciNcetLaGZo5qA3g3r4Z_La7YAPJtzShoC6LoQAvD_BwE Oasis HLB] for general organic chemicals<ref name="SteigmeyerEtAl2017"/>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=All&enableHL=true&isocode=en_US&keyword=Oasis%20WAX%20&multiselect=true&page=1&rows=12&sort=most-relevant Oasis WAX] for PFAS, organic chemicals of mixed polarity<ref>Iannone, A., Carriera, F., Di Fiore, C., Avino, P., 2024. Poly- and Perfluoroalkyl Substance (PFAS) Analysis in Environmental Matrices: An Overview of the Extraction and Chromatographic Detection Methods. Analytica, 5(2), pp. 187-202. [https://doi.org/10.3390/analytica5020012 doi: 10.3390/analytica5020012]  [[Media: IannoneEtAl2024.pdf | Article pdf]]</ref>
*Zeolite for ammonia, other organic chemicals

Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.

===Test Organism Species and Life Stages===
Practitioners can also select different organism species and life stages for use in the iTIE system, depending on site characteristics and study goals. The iTIE system can accommodate various small test organisms, including embryo-stage fish and most macroinvertebrates. The following common toxicity tests can be adapted for application within iTIE systems<ref>U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1994. Catalogue of Standard Toxicity Tests for Ecological Risk Assessment. ECO Update, 2(2), 4 pages. Publication No. 9345.0.05I [https://www.epa.gov/sites/default/files/2015-09/documents/v2no2.pdf Free Download]  [[Media: usepa1994.pdf | Report pdf]]</ref>.
<ul>Freshwater acute toxicity:</ul>
*[[Wikipedia: Daphnia magna | ''Daphnia magna'']] or [[Wikipedia: Daphnia pulex | ''Daphnia pulex'']] 24-, 48-, and 96-hour survival
<ul>Freshwater chronic toxicity:</ul>
*[[Wikipedia: Ceriodaphnia dubia | ''Ceriodaphnia dubia'']] 7-day survival and reproduction
*''D. magna'' 7-day survival and reproduction
*[[Wikipedia: Fathead minnow | ''Pimephales promelas'']] 7-day embryo-larval survival and teratogenicity
*[[Wikipedia: Hyalella azteca | ''Hyalella Azteca'']] 10- or 30-day survival and reproduction
<ul>Marine acute toxicity:</ul>
*[[Wikipedia: Americamysis bahia | ''Americamysis bahia'']] 24- and 48-hour survival
<ul>Marine chronic toxicity:</ul>
*''Americamysis'' survival, growth and fecundity
*[[Wikipedia: Topsmelt silverside | ''Atherinops affinis'']] embryo-larval survival and growth

Acute toxicity is quantifiable via organism survival rates immediately following the termination of an iTIE system field deployment. Chronic toxicity can be quantified by continuing to culture and observe test organisms in-lab. Common chronic endpoints include stunted growth, altered development such as teratogenicity in larval fish, decreased reproduction rates, and changes in gene expression.

Several gene expression endpoints have been detectable in bioassays following an iTIE system deployment and in-lab culturing period. Steigmeyer ''et al.''<ref name="SteigmeyerEtAl2017"/> were able to detect changes in the expression of two genes in ''D. magna'' after a 24-hour exposure to bisphenol A. In a separate study, Nichols<ref>Nichols, E., 2023. Methods for Identification and Prioritization of Stressors at Impaired Sites. Masters thesis, University of Michigan. University of Michigan Library Deep Blue Documents. [https://deepblue.lib.umich.edu/bitstream/handle/2027.42/176142/Nichols_Elizabeth_thesis.pdf?sequence=1 Free Download]  [[Media: Nichols2023.pdf | Report pdf]]</ref> found a significant decline in acetylcholinesterase activity in ''H. azteca'' after a 24-hour exposure to chlorpyrifos. These results indicate a potential to adapt other gene expression bioassays for use in conjunction with iTIE system field exposures to prove stressor-causality linkages.

===Cost Effectiveness Study===
Burton ''et al.''<ref name="BurtonEtAl2020"/> conducted a cost effectiveness study comparing the iTIE technology with the traditional US EPA Phase 1 TIE method. Comparisons were based on the estimated time required to complete various sub-tasks within each method. Sub-tasks included organism care, equipment preparation, mobilization and deployment, test maintenance, test termination, demobilization, and test termination analyses. It was ultimately estimated that the iTIE protocol requires 47% less time (67 fewer hours) to complete than the Phase 1 TIE method, with the largest time differences in equipment preparation, deployment, test maintenance, and demobilization. It is important to note that the iTIE method may require additional initial costs for equipment and training.

==Field Application==
[[File: CraneFig6.png | thumb | left | 400px | Figure 6. iTIES deployment at the Rouge River, Detroit, MI. In the foreground is the iTIE Cooler Sub-System, which contains iTIE resin treatments and test organism groups, as well as the oxygenation coil and sample collection bottles. Next to the iTIE Cooler are the two pump cases. The Trident can be seen above the pump cases, installed in the river channel near shore.]]
The iTIE system has been successfully deployed at a variety of marine and freshwater sites during the proof-of-concept phase of prototype development. One example is the 2024 iTIE system deployment completed near the mouth of the Rouge River in Detroit, MI (Figure 6). The Rouge River watershed has a long history of industrialization, with a legacy of chemical dumping, channelization, damming, and urban runoff<ref>Ridgway, J., Cave, K., DeMaria, A., O’Meara, J., Hartig, J. H., 2018. The Rouge River Area of Concern—A multi-year, multi-level successful approach to restoration of Impaired Beneficial Uses. Aquatic Ecosystem Health and Management, 21(4), pp. 398-408. [https://doi.org/10.1080/14634988.2018.1528816 doi: 10.1080/14634988.2018.1528816]</ref>. This has led to degraded environmental conditions, with previous detections of a wide range of chemicals including heavy metals and various organics.

[[File: CraneFig7.png | thumb | 300px | Figure 7. Survival and healthy development of ''P. promelas'' embryos and larvae following a 48-hour iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater as embryos for 48 hours and cultured post-exposure for an additional 5 days.]]
[[File: CraneFig8.png | thumb | 300px | Figure 8. Survival of ''C. dilutus'' larvae after an iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater for 48 hours and cultured post-exposure for an additional 5 days. Error bars show standard deviation.]]
An iTIE system deployment was designed and completed to determine which chemical classes are most responsible for causing toxicity at the site. Resin treatments included glass wool (inert, non-fractionating substance), Chelex (metals sorption), Oasis HLB (general organics sorption), and Oasis WAX (organics sorption, with a high affinity for PFAS). The study utilized fathead minnow (''P. promelas'') embryos, due to their relative sensitivity to metals and PAHs, as well as second-instar midge ([[Wikipedia: Chironomus |''Chironomus dilutus'']]) larvae due to their relative sensitivity to PFAS.

The test organisms were exposed to fractionated porewater ''in situ'' for 48 hours. Following exposure, organisms were cultured for an additional five days, and survival was recorded (Figures 7 and 8). Moderate declines in survival were seen in both species in the glass wool treatment, indicating toxicity at the site. For ''P. promelas'', the highest proportion of healthy development occurred in the Chelex treatment, supporting the hypothesis that metals are a dominant cause of toxicity. ''C. dilutus'' had the greatest survival in the Oasis WAX treatment, suggesting that an organic stressor class like PFAS is also present at harmful concentrations in the river.

Water chemical analyses of fractionated and unfractionated water samples were completed to support biological results. Analyses were conducted for a range of stressor classes including metals, PAHs, PCBs, an organophosphate pesticide (chlorpyrifos), a PFAS compound (PFOS) and a pyrethroid insecticide (permethrin). Of these analytes, only heavy metals and PFOS were detected. Some chemical classes including PAHs and PCBs were not detected at the site.
To reach similar conclusions using traditional Phase 1 TIE methods, one would need to complete the following tests: baseline toxicity, filtration, aeration, EDTA, C18 SPE, and methanol elution of C18 SPE. The iTIE method allows the same conclusions to be drawn with significantly less time and effort required.

==Summary==
The ''in situ'' Toxicity Identification Evaluation technology and protocol is a powerful tool that investigators can use to strengthen causal linkages between chemical stressors and ecological toxicity. By fractionating sampled water and exposing test organisms ''in situ'', investigators can gather toxicity response data while minimizing sample manipulation and accurately representing environmental conditions.
 

==References==
<references />

==See Also==

In Situ Toxicity Identification Evaluation (iTIE)

2026-03-16T15:37:59Z

Debra Tabron:

The ''in situ'' Toxicity Identification Evaluation system is a tool to incorporate in weight-of-evidence studies at sites with numerous chemical toxicant classes present. The technology works by continuously sampling site water, immediately fractionating the water using diagnostic sorptive resins, and then exposing test organisms to the water to observe toxicity responses with minimal sample manipulation. It is compatible with various resins, test organisms, and common acute and chronic toxicity tests, and can be deployed at sites with a wide variety of physical and logistical considerations.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Contaminated Sediments - Introduction]]
*[[Contaminated Sediment Risk Assessment]]
*[[Passive Sampling of Sediments]]
*[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]

'''Contributor(s):''' [Dr. G. Allen Burton Jr.] and Austin Crane

'''Key Resource(s):'''
*A Novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites<ref name="BurtonEtAl2020">Burton, G.A., Cervi, E.C., Meyer, K., Steigmeyer, A., Verhamme, E., Daley, J., Hudson, M., Colvin, M., Rosen, G., 2020. A novel In Situ Toxicity Identification Evaluation (iTIE) System for Determining which Chemicals Drive Impairments at Contaminated Sites. Environmental Toxicology and Chemistry, 39(9), pp. 1746-1754. [https://doi.org/10.1002/etc.4799 doi: 10.1002/etc.4799]</ref>
*An in situ toxicity identification and evaluation water analysis system: Laboratory validation<ref name="SteigmeyerEtAl2017">Steigmeyer, A.J., Zhang, J., Daley, J.M., Zhang, X., Burton, G.A. Jr., 2017. An in situ toxicity identification and evaluation water analysis system: Laboratory validation. Environmental Toxicology and Chemistry, 36(6), pp. 1636-1643. [https://doi.org/10.1002/etc.3696 doi: 10.1002/etc.3696]</ref>
*Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document<ref>United States Environmental Protection Agency, 2007. Sediment Toxicity Identification Evaluation (TIE) Phases I, II, and III Guidance Document, EPA/600/R-07/080. 145 pages. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1003GR1.txt Free Download]  [[Media: EPA2007.pdf | Report pdf]]</ref>
*[https://serdp-estcp.mil/projects/details/88a8f9ba-542b-4b98-bfa4-f693435535cd/er18-1181-project-overview In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification - ESTCP Project ER18-1181]<ref>In Situ Toxicity Identification Evaluation (iTIE) Technology for Assessing Contaminated Sediments, Remediation Success, Recontamination and Source Identification- ESTCP Project ER18-1181 [[Media: ER18-1181Ph.II.pdf | Final Report]]</ref>

==Introduction==
In waterways impacted by numerous naturally occurring and anthropogenic chemical stressors, it is crucial for environmental practitioners to be able to identify which chemical classes are causing the highest degrees of toxicity to aquatic life. Previously developed methods, including the Toxicity Identification Evaluation (TIE) protocol developed by the US Environmental Protection Agency (EPA)<ref>Norberg-King, T., Mount, D.I., Amato, J.R., Jensen, D.A., Thompson, J.A., 1992. Toxicity identification evaluation: Characterization of chronically toxic effluents: Phase I. Publication No. EPA/600/6-91/005F. U.S. Environmental Protection Agency, Office of Research and Development. [https://www.epa.gov/sites/default/files/2015-09/documents/owm0255.pdf Free Download from US EPA]  [[Media: usepa1992.pdf | Report pdf]]</ref>, can be confounded by sample manipulation artifacts and temporal limitations of ''ex situ'' organism exposures<ref name="BurtonEtAl2020"/>. These factors may disrupt causal linkages and mislead investigators during site characterization and management decision-making. The ''in situ'' Toxicity Identification Evaluation (iTIE) technology was developed to allow users to strengthen stressor-causality linkages and rank chemical classes of concern at impaired sites, with high degrees of ecological realism.

The technology has undergone a series of improvements in recent years, with the most recent prototype being robust, operable in a wide variety of site conditions, and cost-effective compared to alternative site characterization methods<ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part I: Laboratory validation. Environmental Toxicology and Chemistry, 23(12), pp. 2844-2850. [https://doi.org/10.1897/03-409.1 doi: 10.1897/03-409.1]</ref><ref>Burton, G.A. Jr., Nordstrom, J.F., 2004. An in situ toxicity identification evaluation method part II: Field validation. Environmental Toxicology and Chemistry, 23(12), pp. 2851-2855. [https://doi.org/10.1897/03-468.1 doi: 10.1897/03-468.1]</ref><ref name="BurtonEtAl2020"/><ref name="SteigmeyerEtAl2017"/>. The latest prototype can be used in any of the following settings: in marine, estuarine, or freshwater sites; to study surface water or sediment pore water; in shallow waters easily accessible by foot or in deep waters only accessible by pier or boat. It can be used to study sites impacted by a wide variety of stressors including ammonia, [[Metal and Metalloid Contaminants | metals]], pesticides, polychlorinated biphenyls (PCB), [[Polycyclic Aromatic Hydrocarbons (PAHs) | polycyclic aromatic hydrocarbons (PAH)]], and [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], among others. The technology is applicable to studies of acute toxicity via organism survival or of chronic toxicity via responses in growth, reproduction, or gene expression<ref name="BurtonEtAl2020"/>.

==System Components and Validation==
[[File: CraneFig1.png | thumb | 600 px | Figure 1: A schematic diagram of the iTIE system prototype. The system is divided into three sub-systems: 1) the Pore Water/Surface Water Collection Sub-System (blue); 2) the Pumping Sub-System (red); and 3) the iTIE Resin, Exposure, and Sampling Sub-System (green). Water first enters the system through the Pore Water/Surface Water Collection Sub-System. Porewater can be collected using Trident-style probes, or surface water can be collected using a simple weighted probe. The water is composited in a manifold before being pumped to the rest of the iTIE system by the booster pump. Once in the iTIE Resin, Exposure, and Sampling Sub-System, the water is gently oxygenated by the Oxygen Coil, separated from gas bubbles by the Drip Chamber, and diverted to separate iTIE Resin and Exposure Chambers (or iTIE units) by the Splitting Manifold. Water movement through each iTIE unit is controlled by a dedicated Regulation Pump. Finally, the water is gathered in Sample Collection bottles for analysis.]]
The latest iTIE prototype consists of an array of sorptive resins that differentially fractionate sampled water, and a series of corresponding flow-through organism chambers that receive the treated water ''in situ''. Resin treatments can be selected depending on the chemicals suspected to be present at each site to selectively sequester certain chemical of concern (CoC) classes from the whole water, leaving a smaller subset of chemicals in the resulting water fraction for chemical and toxicological characterization. Test organism species and life stages can also be chosen depending on factors including site characteristics and study goals. In the full iTIE protocol, site water is continuously sampled either from the sediment pore spaces or the water column at a site, gently oxygenated, diverted to different iTIE units for fractionation and organism exposure, and collected in sample bottles for off-site chemical analysis (Figure 1). All iTIE system components are housed within waterproof Pelican cases, which allow for ease of transport and temperature control.

===Porewater and Surface Water Collection Sub-system===
[[File: CraneFig2.png | thumb | 600 px | Figure 2: a) Trident probe with auxiliary sensors attached, b) a Trident probe with end caps removed (the red arrow identifies the intermediate space where glass beads are packed to filter suspended solids), c) a Trident probe being installed using a series of push poles and a fence post driver]]
Given the importance of sediment porewater to ecosystem structure and function, investigators may employ the iTIE system to evaluate the toxic effects associated with the impacted sediment porewater. To accomplish this, the iTIE system utilizes the Trident probe, originally developed for Department of Defense site characterization studies<ref>Chadwick, D.B., Harre, B., Smith, C.F., Groves, J.G., Paulsen, R.J., 2003. Coastal Contaminant Migration Monitoring: The Trident Probe and UltraSeep System. Hardware Description, Protocols, and Procedures. Technical Report 1902. Space and Naval Warfare Systems Center.</ref>. The main body of the Trident is comprised of a stainless-steel frame with six hollow probes (Figure 2). Each probe contains a layer of inert glass beads, which filters suspended solids from the sampled water. The water is drawn through each probe into a composite manifold and transported to the rest of the iTIE system using a high-precision peristaltic pump.

The Trident also includes an adjustable stopper plate, which forms a seal against the sediment and prevents the inadvertent dilution of porewater samples with surface water. (Figure 2). Preliminary laboratory results indicate that the Trident is extremely effective in collecting porewater samples with minimal surface water infiltration in sediments ranging from coarse sand to fine clay. Underwater cameras, sensors, passive samplers, and other auxiliary equipment can be attached to the Trident probe frame to provide supplemental data.

Alternatively, practitioners may employ the iTIE system to evaluate site surface water. To sample surface water, weighted intake tubes can collect surface water from the water column using a peristaltic pump.

===Oxygen Coil, Overflow Bag and Drip Chamber===
[[File: CraneFig3.png | thumb | left | 400 px | Figure 3. Contents of the iTIE system cooler. The pictured HDPE rack (47.6 cm length x 29.7 cm width x 33.7 cm height) is removable from the iTIE cooler. Water enters the system at the red circle, flows through the oxygen coil, and then travels to each of the individual iTIE units where diagnostic resins and organisms are located. The water then briefly leaves the cooler to travel through peristaltic regulation pumps before being gathered in sample collection bottles.]]
Porewater is naturally anoxic due to limited mixing with aerated surface water and high oxygen demand of sediments, which may cause organism mortality and interfere with iTIE results. To preclude this, sampled porewater is exposed to an oxygen coil. This consists of an interior silicone tube connected to a pressurized oxygen canister, threaded through an exterior reinforced PVC tube through which water is slowly pumped (Figure 3). Pump rates are optimized to ensure adequate aeration of the water. In addition to elevating DO levels, the oxygen coil facilitates the oxidation of dissolved sulfides, which naturally occur in some marine sediments and may otherwise cause toxicity to organisms if left in its reduced form.

Gas bubbles may form in the oxygen coil over the course of a deployment. These can be disruptive, decreasing water sample volumes and posing a danger to sensitive organisms like daphnids. To account for this, the water travels to a drip chamber after exiting the oxygen coil, which allows gas bubbles to be separated and diverted to an overflow system. The sample water then flows to a manifold which divides the flow into different paths to each of the treatment units for fractionation and organism exposure.

===iTIE Units: Fractionation and Organism Exposure Chambers===
[[File: CraneFig4.png | thumb | 300px | Figure 4. A diagram of the iTIE prototype. Water flows upward into each resin chamber through the unit bottom. After being chemically fractionated in the resin chamber, water travels into the organism chamber, where test organisms have been placed. Water is drawn through the units by high-precision peristaltic pumps.]]
At the core of the iTIE system are separate dual-chamber iTIE units, each with a resin fractionation chamber and an organism exposure chamber (Figure 4). Developed by Burton ''et al.''<ref name="BurtonEtAl2020"/>, the iTIE prototype is constructed from acrylic, with rubber O-rings to connect each piece. Each iTIE unit can contain a different diagnostic resin matrix, customizable to remove specific chemical classes from the water. Sampled water flows into each unit through the bottom and is differentially fractionated by the resin matrix as it travels upward. Then it reaches the organism chamber, where test organisms are placed for exposure. The organism chamber inlet and outlet are covered by mesh to prevent the escape of the test organisms. This continuous flow-through design allows practitioners to capture the temporal heterogeneity of ambient water conditions over the duration of an ''in situ'' exposure. Currently, the iTIE system can support four independent iTIE treatment units.

After being exposed to test organisms, water is collected in sample bottles. The bottles can be pre-loaded with preservation reagents to allow for later chemical analysis. Sample bottles can be composed of polyethylene, glass or other materials depending on the CoC.

===Pumping Sub-system===
[[File: CraneFig5.png | thumb | 300px | Figure 5. The iTIE system pumping sub-system. The sub-system consists of: A) a single booster pump, which is directly connected to the water sampling device and feeds water to the rest of the iTIE system, and B) a set of four regulation pumps, which each connect to the outflow of an individual iTIE unit. Each pump set is housed in a waterproof case with self-contained rechargeable battery power. A tablet is mounted inside the lid of the four pump case, which can be used to program and operate all of the pumps when connected to the internet.]]
Water movement through the system is driven by a series of high-precision, programmable peristaltic pumps ([https://ecotechmarine.com/ EcoTech Marine]). Each pump set is housed in a Pelican storm travel case. Power is supplied to each pump by internal rechargeable lithium-iron phosphate batteries ([https://www.bioennopower.com/ Bioenno Power]).

First, water is supplied to the system by a booster pump (Figure 5A). This pump is situated between the water sampling sub-system and the oxygen coil. The booster pump: 1) facilitates pore water collection, especially from sediments with high fine particle fractions; 2) helps water overcome vertical lifts to travel to the iTIE system; and 3) prevents vacuums from forming in the iTIE system interior, which can accelerate the formation of disruptive gas bubbles in the oxygen coil. The booster pump should be programmed to supply an excess of water to prevent vacuum formation.

Second, a set of four regulation pumps ensure precise flow rates through each independent iTIE unit (Figure 5B). Each regulation pump pulls water from the top of an iTIE unit and then dispenses that water into a sample bottle for further analysis.

==Study Design Considerations==
===Diagnostic Resin Treatments===
Several commercially available resins have been verified for use in the iTIE system. Investigators can select resins based on stressor classes of interest at each site. Each resin selectively removes a CoC class from site water prior to organism exposure.
*[https://www.dupont.com/products/ambersorb560.html DuPont Ambersorb 560] for removal of 1,4-dioxane and other organic chemicals<ref>Woodard, S., Mohr, T., Nickelsen, M.G., 2014. Synthetic media: A promising new treatment technology for 1,4-dioxane. Remediation Journal, 24(4), pp. 27-40. [https://doi.org/10.1002/rem.21402 doi: 10.1002/rem.21402]</ref>
*C18 for nonpolar organic chemicals
*[https://www.bio-rad.com/en-us Bio-Rad] [https://www.bio-rad.com/en-us/product/chelex-100-resin?ID=6448ab3e-b96a-4162-9124-7b7d2330288e Chelex] for metals
*Granular activated carbon for metals, general organic chemicals, sulfide<ref>Lemos, B.R.S., Teixeira, I.F., de Mesquita, J.P., Ribeiro, R.R., Donnici, C.L., Lago, R.M., 2012. Use of modified activated carbon for the oxidation of aqueous sulfide. Carbon, 50(3), pp. 1386-1393. [https://doi.org/10.1016/j.carbon.2011.11.011 doi: 10.1016/j.carbon.2011.11.011]</ref>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=Shop&isocode=en_US&keyword=oasis%20hlb&multiselect=true&page=1&rows=12&sort=best-sellers&xcid=ppc-ppc_23916&gad_source=1&gad_campaignid=14746094146&gbraid=0AAAAAD_uR00nhlNwrhhegNh06pBODTgiN&gclid=CjwKCAiAtLvMBhB_EiwA1u6_PsppE0raci2IhvGnAAe5ijciNcetLaGZo5qA3g3r4Z_La7YAPJtzShoC6LoQAvD_BwE Oasis HLB] for general organic chemicals<ref name="SteigmeyerEtAl2017"/>
*[https://www.waters.com/nextgen/us/en.html Waters] [https://www.waters.com/nextgen/us/en/search.html?category=All&enableHL=true&isocode=en_US&keyword=Oasis%20WAX%20&multiselect=true&page=1&rows=12&sort=most-relevant Oasis WAX] for PFAS, organic chemicals of mixed polarity<ref>Iannone, A., Carriera, F., Di Fiore, C., Avino, P., 2024. Poly- and Perfluoroalkyl Substance (PFAS) Analysis in Environmental Matrices: An Overview of the Extraction and Chromatographic Detection Methods. Analytica, 5(2), pp. 187-202. [https://doi.org/10.3390/analytica5020012 doi: 10.3390/analytica5020012]  [[Media: IannoneEtAl2024.pdf | Article pdf]]</ref>
*Zeolite for ammonia, other organic chemicals

Resins must be adequately conditioned prior to use. Otherwise, they may inadequately adsorb toxicants or cause stress to organisms. New resins should be tested for efficacy and toxicity before being used in an iTIE system.

===Test Organism Species and Life Stages===
Practitioners can also select different organism species and life stages for use in the iTIE system, depending on site characteristics and study goals. The iTIE system can accommodate various small test organisms, including embryo-stage fish and most macroinvertebrates. The following common toxicity tests can be adapted for application within iTIE systems<ref>U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, 1994. Catalogue of Standard Toxicity Tests for Ecological Risk Assessment. ECO Update, 2(2), 4 pages. Publication No. 9345.0.05I [https://www.epa.gov/sites/default/files/2015-09/documents/v2no2.pdf Free Download]  [[Media: usepa1994.pdf | Report pdf]]</ref>.
<ul>Freshwater acute toxicity:</ul>
*[[Wikipedia: Daphnia magna | ''Daphnia magna'']] or [[Wikipedia: Daphnia pulex | ''Daphnia pulex'']] 24-, 48-, and 96-hour survival
<ul>Freshwater chronic toxicity:</ul>
*[[Wikipedia: Ceriodaphnia dubia | ''Ceriodaphnia dubia'']] 7-day survival and reproduction
*''D. magna'' 7-day survival and reproduction
*[[Wikipedia: Fathead minnow | ''Pimephales promelas'']] 7-day embryo-larval survival and teratogenicity
*[[Wikipedia: Hyalella azteca | ''Hyalella Azteca'']] 10- or 30-day survival and reproduction
<ul>Marine acute toxicity:</ul>
*[[Wikipedia: Americamysis bahia | ''Americamysis bahia'']] 24- and 48-hour survival
<ul>Marine chronic toxicity:</ul>
*''Americamysis'' survival, growth and fecundity
*[[Wikipedia: Topsmelt silverside | ''Atherinops affinis'']] embryo-larval survival and growth

Acute toxicity is quantifiable via organism survival rates immediately following the termination of an iTIE system field deployment. Chronic toxicity can be quantified by continuing to culture and observe test organisms in-lab. Common chronic endpoints include stunted growth, altered development such as teratogenicity in larval fish, decreased reproduction rates, and changes in gene expression.

Several gene expression endpoints have been detectable in bioassays following an iTIE system deployment and in-lab culturing period. Steigmeyer ''et al.''<ref name="SteigmeyerEtAl2017"/> were able to detect changes in the expression of two genes in ''D. magna'' after a 24-hour exposure to bisphenol A. In a separate study, Nichols<ref>Nichols, E., 2023. Methods for Identification and Prioritization of Stressors at Impaired Sites. Masters thesis, University of Michigan. University of Michigan Library Deep Blue Documents. [https://deepblue.lib.umich.edu/bitstream/handle/2027.42/176142/Nichols_Elizabeth_thesis.pdf?sequence=1 Free Download]  [[Media: Nichols2023.pdf | Report pdf]]</ref> found a significant decline in acetylcholinesterase activity in ''H. azteca'' after a 24-hour exposure to chlorpyrifos. These results indicate a potential to adapt other gene expression bioassays for use in conjunction with iTIE system field exposures to prove stressor-causality linkages.

===Cost Effectiveness Study===
Burton ''et al.''<ref name="BurtonEtAl2020"/> conducted a cost effectiveness study comparing the iTIE technology with the traditional US EPA Phase 1 TIE method. Comparisons were based on the estimated time required to complete various sub-tasks within each method. Sub-tasks included organism care, equipment preparation, mobilization and deployment, test maintenance, test termination, demobilization, and test termination analyses. It was ultimately estimated that the iTIE protocol requires 47% less time (67 fewer hours) to complete than the Phase 1 TIE method, with the largest time differences in equipment preparation, deployment, test maintenance, and demobilization. It is important to note that the iTIE method may require additional initial costs for equipment and training.

==Field Application==
[[File: CraneFig6.png | thumb | left | 400px | Figure 6. iTIES deployment at the Rouge River, Detroit, MI. In the foreground is the iTIE Cooler Sub-System, which contains iTIE resin treatments and test organism groups, as well as the oxygenation coil and sample collection bottles. Next to the iTIE Cooler are the two pump cases. The Trident can be seen above the pump cases, installed in the river channel near shore.]]
The iTIE system has been successfully deployed at a variety of marine and freshwater sites during the proof-of-concept phase of prototype development. One example is the 2024 iTIE system deployment completed near the mouth of the Rouge River in Detroit, MI (Figure 6). The Rouge River watershed has a long history of industrialization, with a legacy of chemical dumping, channelization, damming, and urban runoff<ref>Ridgway, J., Cave, K., DeMaria, A., O’Meara, J., Hartig, J. H., 2018. The Rouge River Area of Concern—A multi-year, multi-level successful approach to restoration of Impaired Beneficial Uses. Aquatic Ecosystem Health and Management, 21(4), pp. 398-408. [https://doi.org/10.1080/14634988.2018.1528816 doi: 10.1080/14634988.2018.1528816]</ref>. This has led to degraded environmental conditions, with previous detections of a wide range of chemicals including heavy metals and various organics.

[[File: CraneFig7.png | thumb | 300px | Figure 7. Survival and healthy development of ''P. promelas'' embryos and larvae following a 48-hour iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater as embryos for 48 hours and cultured post-exposure for an additional 5 days.]]
[[File: CraneFig8.png | thumb | 300px | Figure 8. Survival of ''C. dilutus'' larvae after an iTIE exposure near the mouth of the Rouge River. Organisms were exposed to site porewater for 48 hours and cultured post-exposure for an additional 5 days. Error bars show standard deviation.]]
An iTIE system deployment was designed and completed to determine which chemical classes are most responsible for causing toxicity at the site. Resin treatments included glass wool (inert, non-fractionating substance), Chelex (metals sorption), Oasis HLB (general organics sorption), and Oasis WAX (organics sorption, with a high affinity for PFAS). The study utilized fathead minnow (''P. promelas'') embryos, due to their relative sensitivity to metals and PAHs, as well as second-instar midge ([[Wikipedia: Chironomus |''Chironomus dilutus'']]) larvae due to their relative sensitivity to PFAS.

The test organisms were exposed to fractionated porewater ''in situ'' for 48 hours. Following exposure, organisms were cultured for an additional five days, and survival was recorded (Figures 7 and 8). Moderate declines in survival were seen in both species in the glass wool treatment, indicating toxicity at the site. For ''P. promelas'', the highest proportion of healthy development occurred in the Chelex treatment, supporting the hypothesis that metals are a dominant cause of toxicity. ''C. dilutus'' had the greatest survival in the Oasis WAX treatment, suggesting that an organic stressor class like PFAS is also present at harmful concentrations in the river.

Water chemical analyses of fractionated and unfractionated water samples were completed to support biological results. Analyses were conducted for a range of stressor classes including metals, PAHs, PCBs, an organophosphate pesticide (chlorpyrifos), a PFAS compound (PFOS) and a pyrethroid insecticide (permethrin). Of these analytes, only heavy metals and PFOS were detected. Some chemical classes including PAHs and PCBs were not detected at the site.
To reach similar conclusions using traditional Phase 1 TIE methods, one would need to complete the following tests: baseline toxicity, filtration, aeration, EDTA, C18 SPE, and methanol elution of C18 SPE. The iTIE method allows the same conclusions to be drawn with significantly less time and effort required.

==Summary==
The ''in situ'' Toxicity Identification Evaluation technology and protocol is a powerful tool that investigators can use to strengthen causal linkages between chemical stressors and ecological toxicity. By fractionating sampled water and exposing test organisms ''in situ'', investigators can gather toxicity response data while minimizing sample manipulation and accurately representing environmental conditions.
 

==References==
<references />

==See Also==

Dr. G. Allen Burton

2026-03-16T15:35:13Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :University of Michigan :440 Church Street :Ann Arbor, MI 48109 EMAIL: [mailto:burtonal@umich.edu burtonal@umich.edu]..."

==Work and Contact Information==

EMPLOYER:
:University of Michigan 
:440 Church Street 
:Ann Arbor, MI 48109

EMAIL: [mailto:burtonal@umich.edu burtonal@umich.edu]

WEBPAGE: [https://websites.umich.edu/~burtonal/ https://websites.umich.edu/~burtonal/]

==About the Contributor==
Dr. G. Allen Burton is a Professor at the University of Michigan at the School for Environment and Sustainability and in the Department of Earth and Environmental Sciences. He has an Honorary Doctorate from the Roskilde University in Denmark, is a Concurrent Professor at Nanjing University in China, and is an Honorary Professor at the State Key Laboratory of Environmental Criteria and Risk Assessment in Beijing, China. His research has focused on sediment and stormwater contaminants, bioavailability processes, effects and ecological risk at multiple trophic levels, and ranking stressor importance in human dominated watersheds. He assisted the U.S. EPA in developing their sediment toxicity test methods and has received over ten million dollars in extramural research funding. His research on ecological risk assessment, sediment quality criteria, and aquatic ecosystem stressors has taken him to all seven continents, with Visiting Scientist positions in New Zealand, Italy and Portugal. While at the University of Michigan he has served as Director of the Water Center and the Cooperative Institute of Limnology and Ecosystems Research (CILER). He was a Distinguished Faculty Fellow of the Graham Sustainability Institute and the Brage Golding Distinguished Professor of Research. He was formerly the Editor-in-Chief of the international journal Environmental Toxicology & Chemistry, a Fellow and past President of the Society of Environmental Toxicology and Chemistry, and has served on numerous national and international panels with over 200 peer-reviewed publications on aquatic ecosystem risk issues.

==Article Contributions==
*[[In Situ Toxicity Identification Evaluation (iTIE)]]

__NOTOC__

[[Category: Contributors|Burton]]

Articles

2026-02-11T19:09:55Z

Debra Tabron:

{| class="wikitable sortable"
|-
!Title!!First Author!!Linking Phrases
|-
|[[Groundwater Sampling - No-Purge/Passive]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||passive sampling, no purge sampling, grab samplers, diffusion samplers, sorptive samplers
|-
|[[ Long-Term Monitoring (LTM)]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||long-term monitoring, LTM, LTM objectives, LTM programs, LTM challenges
|-
|[[PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)]]
|[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]
|PFAS, MNA, natural attenuation
|-
|[[Sorption of Organic Contaminants]]||[[Richelle Allen-King|Allen-King, Richelle]]||
|-
|[[PFAS Transport and Fate]]
|[[Dr. Richard Anderson|Anderson, Richard, Ph.D.]]
|PFAS, fate and transport
|-
|[[Mass Flux and Mass Discharge]]||[[Dr. Michael Annable, P.E. |Annable, Michael, Ph.D., P.E.]]||source reduction
|-
|[[PFAS Toxicology and Risk Assessment]]
|[[Jennifer Arblaster|Arblaster, Jennifer]]
|PFAS, toxicology, risk assessment
|-
|[[Metal(loid)s - Small Arms Ranges]]|| Dr. Amanda Barker |[[Dr. Amanda Barker|Barker, Amanda, Ph.D.]]
|
|-
|[[Munitions Constituents – Photolysis|Munitions Constituents - Photolysis]]
|[[Dr. Warren Kadoya|Kadoya, Warren, Ph.D.]]
|
|-
|[[Munitions Constituents - Soil Sampling]]
|[[Dr. Samuel Beal|Beal, Samuel, Ph.D.]]
|
|-
|[[Vapor Intrusion – Sewers and Utility Tunnels as Preferential Pathways|Vapor Intrusion - Sewers and Utility Tunnels as Preferential Pathways]]
|[[Lila Beckley|Beckley, Lila]]
|vapor intrusion
|-
|[[Natural Attenuation in Source Zone and Groundwater Plume - Bemidji Crude Oil Spill]]
|[[Dr. Barbara Bekins|Bekins, Barbara, Ph.D.]]||
|-
|[[Bioremediation - Anaerobic Secondary Water Quality Impacts]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||secondary impacts, water quality (in regards to anaerobic conditions)
|-
|[[Design Tool - Base Addition for ERD]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||aquifer acidity, base addition
|-
|[[Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation]]
|[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||
|-
|[[Low pH Inhibition of Reductive Dechlorination]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||low pH inhibition
|-
|[[OPTically-based In-situ Characterization System (OPTICS)]]
|[[Dr. Grace Chang|Chang, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents - Electrochemical Treatment]]
|[[Dr. Brian P. Chaplin|Chaplin, Brian, Ph.D.]]
|munitions constituents remediation
|-
|[[PFAS Sources]]
|[[Dr. Dora Chiang|Chiang, Dora, Ph.D.]]
|
|-
|[[Biodegradation - Cometabolic]]||[[Dr. Kung-Hui (Bella) Chu |Chu, Kung-Hui (Bella), Ph.D]]||cometabolic biodegradation
|-
|[[Munitions Constituents - Composting]]
|[[Harry Craig|Craig, Harry]]
|
|-
|[[Chemical Oxidation (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||ISCO, chemical oxidation
|-
|[[Chemical Oxidation Oxidant Selection (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||chemical oxidant, oxidant (in regards to ISCO)
|-
|[[Chemical Oxidation Design Considerations(In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||screening, design, implementation, oxidant delivery (in regards to ISCO)
|-
|[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]||[[Dr. Rula Deeb |Deeb, Rula, Ph.D.]]||PFAS, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS)
|-
|[[Metal and Metalloid Contaminants]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal contaminant(s), metalloid contaminant(s), metal(s), metalloid(s),
|-
|[[Metals and Metalloids - Mobility in Groundwater]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal mobility, aqueous speciation, adsorption, precipitation, colloidal transport (in regards to metals)
|-
|[[Monitored Natural Attenuation (MNA) of Metal and Metalloids]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||MNA, attenuation of metal(s), natural attenuation processes, attenuation (in regards to metals)
|-
|[[Metal and Metalloids - Remediation]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||remediation, in situ technologies, contaminant removal (in regards to metals)
|-
|[[pH Buffering in Aquifers]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||ph buffer, natural pH buffer, engineered pH buffer
|-
|[[Munitions Constituents - Sorption]]||[[Dr. Katerina Dontsova |Dontsova, Katerina, Ph.D.]]||energetics, sorption
|-
|[[Biodegradation - Hydrocarbons]]||[[Dr. Elizabeth Edwards |Edwards, Elizabeth, Ph.D.]]||hydrocarbon, biodegradation
|-
|[[Source Zone Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||source zone modeling
|-
|[[Plume Response Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||plume response modeling
|-
|[[REMChlor - MD]]
|[[Dr. Ron Falta|Falta, Ron, Ph.D.]]
|
|-
|[[In Situ Groundwater Treatment with Activated Carbon]]
|[[Dr. Dimin Fan|Fan, Dimin, Ph.D.]]
|
|-
|[[LNAPL Remediation Technologies]]||[[Dr. Shahla Farhat |Farhat, Shahla, Ph.D.]]||
|-
|[[Sustainable Remediation]]||[[Paul Favara |Favara, Paul]]||sustainable remediation, social, economic and environmental impacts
|-
|[[Munitions Constituents]]||[[Dr. Kevin Finneran |Finneran, Kevin, Ph.D.]]||Explosives, energetics, insensitive munitions
|-
|[[Biodegradation - Reductive Processes]]||[[Dr. David Freedman |Freedman, David, Ph.D.]]||biotic reduction, biotic reductive processes, hydrogenolysis, dihaloelimination, coupling, organohalide respiration
|-
|[[Remediation of Stormwater Runoff Contaminated by Munition Constituents|Munitions Constituents - Remediation of Stormwater Runoff]]||Fuller, Mark, Ph.D.||energetics, insensitive munitions, stormwater runoff
|-
|[[Subgrade Biogeochemical Reactor (SBGR)]]||[[Jeff Gamlin |Gamlin, Jeff]]||SBGR, subgrade biogeochemical reactor, bioreactor
|-
|[[Thermal Remediation - Smoldering]]||[[Dr. Jason Gerhard |Gerhard, Jason, Ph.D.]]||smouldering remediation, self-sustaining treatment for active remediation, STAR
|-
|[[Contaminated Sediments - Introduction]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[Contaminated Sediment Risk Assessment]]
|[[Richard Wenning|Wenning, Richard]]
|
|-
|[[In Situ Treatment of Contaminated Sediments with Activated Carbon]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[PFAS Ex Situ Water Treatment]]
|[[Dr. Scott Grieco |Grieco, Scott, Ph.D.]]
|
|-
|[[Stream Restoration]]
|[[Dr. Natalie Griffiths|Griffiths, Natalie, Ph.D.]]
|
|-
|[[Passive Sampling of Sediments]]
|[[Dr. Philip M. Gschwend|Gschwend, Philip]]
|
|-
|[[Phytoplankton (Algae) Blooms]]
|[[Dr. Nathan Hall|Hall, Nathan]]
|
|-
|[[PFAS Soil Remediation Technologies]]||[[James_Hatton |Hatton, Jim]]||PFAS, Soil source zones
|-
|[[Proteomics and Proteogenomics]]
|[[Dr. Kate Kucharzyk|Kucharzyk, Kate, Ph.D.]]
|
|-
|[[N-nitrosodimethylamine (NDMA)]]
|[[Paul Hatzinger|Hatzinger, Paul, Ph.D.]]
|
|-
|[[Alternative Endpoints]]||[[Elisabeth Hawley |Hawley, Elisabeth]]||management of complex sites||
|-
|[[Thermal Remediation]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, in situ thermal
|-
|[[Thermal Remediation - Steam]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Steam Enhanced Extraction
|-
|[[Thermal Remediation - Electrical Resistance Heating]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Electrical Resistance Heating
|-
|[[Thermal Conduction Heating (TCH)]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal desorption
|-
|[[Thermal Remediation - Combined Remedies]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation
|-
|[[Thermal Conduction Heating for Treatment of PFAS-Impacted Soil]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, PFAS
|-
|[[Predicting Species Responses to Climate Change with Population Models]]
|[[Dr. Brian Hudgens|Hudgens, Brian, Ph.D.]]
|climate change
|-
|[[Infrastructure Resilience]]
|[[Dr. John Hummel|Hummel, John, Ph.D.]]
|
|-
|[[Munitions Constituents- TREECS™ Fate and Risk Modeling|Munitions Constituents - TREECS™ Fate and Risk Modeling]]||[[Dr. Billy E. Johnson |Johnson, Billy, Ph.D.]]||munitions constituents fate and transport modeling, TREECS
|-
|[[Munitions Constituents - Alkaline Degradation]]
|[[Jared Johnson|Johnson, Jared]]
|
|-
|[[Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)|Vapor Intrusion - Assessing VI Impacts in Neighborhoods with Groundwater Contaminated CVOCs]]
|[[Dr. Paul C. Johnson|Johnson, Paul, Ph.D.]]
|vapor intrusion
|-
|[[Munitions Constituents - IM Toxicology]]||-----||insensitive explosives, insensitive munitions, IMX-101, IMX
|-
|[[Landfarming]]
|[[Dr. Roopa Kamath|Kamath, Roopa, Ph.D.]]
|
|-
|[[NAPL Mobility]]
|[[Andrew Kirkman|Kirkman, Andrew]]
|
|-
|[[Climate Change Primer]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Perchlorate]]||[[Thomas Krug |Krug, Thomas]]||perchlorate
|-
|[[Injection Techniques for Liquid Amendments]]||[[Thomas Krug |Krug, Thomas]]||amendment injection
|-
|[[Transition of Aqueous Film Forming Foam (AFFF) Fire Suppression Infrastructure Impacted by Per and Polyfluoroalkyl Substances (PFAS)]]
|[[Dr. Johnsie Ray Lang|Lang, Johnsie Ray, Ph.D.]]||PFAS
|
|-
|[[Characterization Methods – Hydraulic Conductivity]]
|[[Dr. Gaisheng Liu|Liu, Gaisheng, Ph.D.]]
|
|-
|[[Compound Specific Isotope Analysis (CSIA)]]||[[Dr. Barbara Sherwood Lollar, F.R.S.C. |Lollar, Barbara S., FRSC]]||Compound Specific Isotope Analysis (CSIA)
|-
|[[Passive Sampling of Munitions Constituents|Munitions Constituents - Passive Sampling]]
|[[Dr. Guilherme Lotufo|Lotufo, Guilerme, Ph.D.]]
|
|-
|[[Vapor Intrusion (VI)]]||[[Chris Lutes |Lutes, Chris]]||vapor intrusion
|-
|[[Bioremediation - Anaerobic]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||anaerobic bioremediation
|-
|[[Bioremediation - Anaerobic Design Considerations]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||
|-
|[[Biodegradation - 1,4-Dioxane]]
|[[Dr. Shaily Mahendra|Mahendra, Shaily, Ph.D.]]
|
|-
|[[Direct Push (DP) Technology]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push, DP, DP machines, DP technology
|-
|[[Direct Push Sampling]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push sampling, soil sampling, groundwater sampling, well installation, soil vapor sampling (in regards to DP)
|-
|[[Direct Push Logging]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push logging, Cone Penetration Testing, CPT, Electrical Conductivity, EC, Hydraulic Profiling Tool, HPT, Membrane Interface Probe, MIP, Optical Imaging Profiler, OIP
|-
|[[Downscaled High Resolution Datasets for Climate Change Projections]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Remediation Performance Assessment at Chlorinated Solvent Sites]]||[[Travis McGuire|McGuire, Travis]]||multi-site studies
|-
|[[LNAPL Conceptual Site Models]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Long-Term Monitoring (LTM) - Data Analysis]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data analysis, analysis methods (in regards to LTM)
|-
|[[Long-Term Monitoring (LTM) - Data Variability]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data variability (in regards to LTM), LTM evaluation
|-
|-
|[[Munitions Constituents - Abiotic Reduction]]||[[Dr. Jimmy Murillo-Gelvez |Murillo-Gelvez, Jimmy, Ph.D.]]
|-
|[[Supercritical Water Oxidation (SCWO)]]
|Nagar, Kobe
|
|-
|[[Matrix Diffusion]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Groundwater Flow and Solute Transport]]||[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]||groundwater flow, advection, dispersion, diffusion, molecular diffusion, mechanical dispersion
|-
|[[Molecular Biological Tools - MBTs]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||MBT, Molecular Biological Tool(s)
|-
|[[Quantitative Polymerase Chain Reaction (qPCR)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||qPCR, Polymerase Chain Reaction
|-
|[[Sediment Capping]]
|[[Dr. Danny Reible|Reible, Danny]]
|
|-
|[[Stable Isotope Probing (SIP)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||SIP, Stable Isotope Probing
|-
|[[Metagenomics]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||Metagenomics
|-
|[[Natural Source Zone Depletion (NSZD)]]||[[Tom Palaia |Palaia, Tom]]||natural source zone depletion, NSZD
|-
|[[Climate Change Effects on Wildlife]]
|[[Dr. Breanna F. Powers|Powers, Breanna, PhD.]]
|
|-
|[[Amendment Distribution in Low Conductivity Materials]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||
|-
|[[Polycyclic Aromatic Hydrocarbons (PAHs)]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||Polycyclic Aromatic Hydrocarbons, PAH(s)
|-
|[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]
|[[Florent Risacher|Risacher, Florent, M.Sc.]]
|
|-
|[[1,2,3-Trichloropropane]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||TCP, trichloropropane
|-
|[[Zerovalent Iron (ZVI) (Chemical Reduction - ISCR)]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||ZVI
|-
|[[Mercury in Sediments]]
|[[Dr. Grace Schwartz|Schwartz, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents – Sample Extraction and Analytical Techniques|Munitions Constituents - Sample Extraction and Analytical Techniques]]
|[[Dr. Austin Scircle|Scircle, Austin]]
|
|-
|[[Geophysical Methods]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[Geophysical Methods - Case Studies]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[PFAS Treatment by Anion Exchange]]
|[[Dr. Timothy J. Strathmann|Strathmann, Timothy, Ph.D.]]
|PFAS
|-
|[[Munitions Constituents - Dissolution]]||[[Dr. Susan Taylor |Taylor, Susan, Ph.D.]]||explosive(s), dissolution,
|-
|[[PFAS Treatment by Electrical Discharge Plasma]]
|[[Dr. Selma Mededovic Thagard|Thagard, Selma Mededovic, Ph.D.]]
|PFAS
|-
|[[Restoration of Ecological Function in Terrestrial Systems Impacted by Invasive Species]]
|Thierry, Hugo, Ph.D.
|climate change, invasive species, restoration ecology
|-
|[[Chemical Reduction (In Situ - ISCR)]]||[[Dr. Paul Tratnyek |Tratnyek, Paul, Ph.D.]]||In Situ Chemical Reduction, ISCR
|-
|[[Injection Techniques - Viscosity Modification]]||[[Michael Truex |Truex, Michael]]||viscosity, viscosity modifiers, viscosity modification
|-
|[[Soil Vapor Extraction (SVE)]]||[[Michael Truex |Truex, Michael]]||soil vapor extraction, SVE
|-
|[[Munitions Constituents - Deposition]]||[[Michael R. Walsh, P.E., M.E.|Walsh, Michael, P.E.]]||explosive deposition, energetics deposition
|-
|[[Vapor Intrusion - Separation Distances from Petroleum Sources]]
|[[Dr. James Weaver|Weaver, James, Ph.D.]]
|vapor intrusion
|-
|[[Zerovalent Iron Permeable Reactive Barriers]]
|[[Dr. Richard Wilkin|Wilkin, Rick, Ph.D.]]
|
|-
|[[Monitored Natural Attenuation (MNA)]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, In Situ MNA, natural attenuation, natural attenuation processes
|-
|[[Monitored Natural Attenuation (MNA) of Fuels]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to petroleum hydrocarbons and fuel components)
|-
|[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to chlorinated solvents)
|-
|[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
|[[Dr. John Wilson|Wilson, John, Ph.D.]]
|MNA, natural attenuation
|-
|[[Chlorinated Solvents]]||[[Dr. Bilgen Yuncu, P.E. |Yuncu, Bilgen, Ph.D., P.E.]]||chlorinated solvents
|-
|[[Petroleum Hydrocarbons (PHCs)]]
|[[Dr. Bilgen Yuncu, P.E.|Yuncu, Bilgen, Ph.D., P.E.]]
|Petroleum Hydrocarbons (PHCs)
|-
|[[Photoactivated Reductive Defluorination - PFAS Destruction]]
|[[Dr. Suzanne Witt|Witt, Suzanne, Ph.D.]]
|PFAS
|
|-
|[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]
|[[Dr. Lee Slater|Slater, Lee, Ph.D.]]
|geophysics, hydrogeophysical methods,
|
|-
|[[Hydrothermal Alkaline Treatment (HALT)]]
|[[Dr. Brian Pinkard|Pinkard, Brian]]
|
|-
|[[1,4-Dioxane]]
|[[Matthew Zenker|Zenker, Matthew]]
|
|-
|[[Lysimeters for Measuring PFAS Concentrations in the Vadose Zone]]
|[[Dr. John F. Stults|Stults, Dr. John]]
|PFAS, vadose zone, lysimeter, field investigation
|
|-
|[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]||[[Dr. Yida Fang |Fang, Yida, Ph.D.]]||
|
|-
|}

PFAS Destruction by Ultraviolet/Sulfite Treatment

2026-02-11T18:57:47Z

Debra Tabron:

The ultraviolet (UV)/sulfite based reductive defluorination process has emerged as an effective and practical option for generating hydrated electrons (''eaq<big>'''-'''</big>'' ) which can destroy [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]] in water. It offers significant advantages for PFAS destruction, including high percentages of defluorination, high treatment efficiency for long-, short-, and ultra-short chain PFAS without mass transfer limitations, selective reactivity by hydrated electrons, low energy consumption, low capital and operation costs, and no production of harmful byproducts. A UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluorTM<ref name="EradiFluor">Haley and Aldrich, Inc. (commercial business), 2024. EradiFluor. [https://www.haleyaldrich.com/about-us/applied-research-program/eradifluor/ Comercial Website]</ref>) has been demonstrated in two field demonstrations in which it achieved near-complete defluorination and greater than 99% destruction of 40 PFAS analytes measured by EPA method 1633.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Ex Situ Water Treatment]]
*[[PFAS Sources]]
*[[PFAS Treatment by Electrical Discharge Plasma]]
*[[Supercritical Water Oxidation (SCWO)]]
*[[Photoactivated Reductive Defluorination - PFAS Destruction]]

'''Contributors:''' [[Dr. John Xiong]], [[Dr. Yida Fang]], [[Dr. Raul Tenorio]], Isobel Li, and [[Dr. Jinyong Liu]]

'''Key Resources:'''
*Defluorination of Per- and Polyfluoroalkyl Substances (PFAS) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management<ref name="BentelEtAl2019">Bentel, M.J., Yu, Y., Xu, L., Li, Z., Wong, B.M., Men, Y., Liu, J., 2019. Defluorination of Per- and Polyfluoroalkyl Substances (PFASs) with Hydrated Electrons: Structural Dependence and Implications to PFAS Remediation and Management. Environmental Science and Technology, 53(7), pp. 3718-28. [https://doi.org/10.1021/acs.est.8b06648 doi: 10.1021/acs.est.8b06648]  [[Media: BentelEtAl2019.pdf | Open Access Article]]</ref>
*Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies<ref>Liu, Z., Chen, Z., Gao, J., Yu, Y., Men, Y., Gu, C., Liu, J., 2022. Accelerated Degradation of Perfluorosulfonates and Perfluorocarboxylates by UV/Sulfite + Iodide: Reaction Mechanisms and System Efficiencies. Environmental Science and Technology, 56(6), pp. 3699-3709. [https://doi.org/10.1021/acs.est.1c07608 doi: 10.1021/acs.est.1c07608]  [[Media: LiuZEtAl2022.pdf | Open Access Article]]</ref>
*Destruction of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment<ref>Tenorio, R., Liu, J., Xiao, X., Maizel, A., Higgins, C.P., Schaefer, C.E., Strathmann, T.J., 2020. Destruction of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) with UV-Sulfite Photoreductive Treatment. Environmental Science and Technology, 54(11), pp. 6957-67. [https://doi.org/10.1021/acs.est.0c00961 doi: 10.1021/acs.est.0c00961]</ref>
*EradiFluorTM<ref name="EradiFluor"/>

==Introduction==
The hydrated electron (''eaq<big>'''-'''</big>'' ) can be described as an electron in solution surrounded by a small number of water molecules<ref name="BuxtonEtAl1988">Buxton, G.V., Greenstock, C.L., Phillips Helman, W., Ross, A.B., 1988. Critical Review of Rate Constants for Reactions of Hydrated Electrons, Hydrogen Atoms and Hydroxyl Radicals (⋅OH/⋅O-) in Aqueous Solution. Journal of Physical and Chemical Reference Data, 17(2), pp. 513-886. [https://doi.org/10.1063/1.555805 doi: 10.1063/1.555805]</ref>. Hydrated electrons can be produced by photoirradiation of solutes, including sulfite, iodide, dithionite, and ferrocyanide, and have been reported in literature to effectively decompose per- and polyfluoroalkyl substances (PFAS) in water. The hydrated electron is one of the most reactive reducing species, with a standard reduction potential of about −2.9 volts. Though short-lived, hydrated electrons react rapidly with many species having more positive reduction potentials<ref name="BuxtonEtAl1988"/>.

Among the electron source chemicals, sulfite (SO32−) has emerged as one of the most effective and practical options for generating hydrated electrons to destroy PFAS in water. The mechanism of hydrated electron production in a sulfite solution under ultraviolet is shown in Equation 1 (UV is denoted as ''hv, SO3<big>'''•-'''</big>'' is the sulfur trioxide radical anion):

::<big>'''Equation 1:'''</big>   [[File: XiongEq1.png | 200 px]]

The hydrated electron has demonstrated excellent performance in destroying PFAS such as [[Wikipedia:Perfluorooctanesulfonic acid | perfluorooctanesulfonic acid (PFOS)]], [[Wikipedia:Perfluorooctanoic acid|perfluorooctanoic acid (PFOA)]]<ref>Gu, Y., Liu, T., Wang, H., Han, H., Dong, W., 2017. Hydrated Electron Based Decomposition of Perfluorooctane Sulfonate (PFOS) in the VUV/Sulfite System. Science of The Total Environment, 607-608, pp. 541-48. [https://doi.org/10.1016/j.scitotenv.2017.06.197 doi: 10.1016/j.scitotenv.2017.06.197]</ref> and [[Wikipedia: GenX|GenX]]<ref>Bao, Y., Deng, S., Jiang, X., Qu, Y., He, Y., Liu, L., Chai, Q., Mumtaz, M., Huang, J., Cagnetta, G., Yu, G., 2018. Degradation of PFOA Substitute: GenX (HFPO–DA Ammonium Salt): Oxidation with UV/Persulfate or Reduction with UV/Sulfite? Environmental Science and Technology, 52(20), pp. 11728-34. [https://doi.org/10.1021/acs.est.8b02172 doi: 10.1021/acs.est.8b02172]</ref>. Mechanisms include cleaving carbon-to-fluorine (C-F) bonds (i.e., hydrogen/fluorine atom exchange) and chain shortening (i.e., [[Wikipedia: Decarboxylation | decarboxylation]], [[Wikipedia: Hydroxylation | hydroxylation]], [[Wikipedia: Elimination reaction | elimination]], and [[Wikipedia: Hydrolysis | hydrolysis]])<ref name="BentelEtAl2019"/>.

==Process Description==
A commercial UV/sulfite treatment system designed and developed by Haley and Aldrich (EradiFluorTM<ref name="EradiFluor"/>) includes an optional pre-oxidation step to transform PFAS precursors (when present) and a main treatment step to destroy PFAS by UV/sulfite. The effluent from the treatment process can be sent back to the influent of a pre-treatment separation system (such as a [[Wikipedia: Foam fractionation | foam fractionation]], [[PFAS Treatment by Anion Exchange | regenerable ion exchange]], or a [[Reverse Osmosis and Nanofiltration Membrane Filtration Systems for PFAS Removal | membrane filtration system]]) for further concentration or sent for off-site disposal in accordance with relevant disposal regulations. A conceptual treatment process diagram is shown in Figure 1. [[File: XiongFig1.png | thumb | left | 600 px | Figure 1: Conceptual Treatment Process for a Concentrated PFAS Stream]] 

==Advantages==
A UV/sulfite treatment system offers significant advantages for PFAS destruction compared to other technologies, including high defluorination percentage, high treatment efficiency for short-chain PFAS without mass transfer limitation, selective reactivity by ''eaq<big>'''-'''</big>'', low energy consumption, and the production of no harmful byproducts. A summary of these advantages is provided below:
*'''High efficiency for short- and ultrashort-chain PFAS:''' While the degradation efficiency for short-chain PFAS is challenging for other technologies that degrade PFAS at the heterogeneous solid-water or gas-water interface, the UV/sulfite process demonstrates excellent defluorination efficiency for both short- and ultrashort-chain PFAS, including [[Wikipedia: Trifluoroacetic acid | trifluoroacetic acid (TFA)]] and [[Wikipedia: Perfluoropropionic acid | perfluoropropionic acid (PFPrA)]].
*'''High defluorination ratio:''' As shown in Figures 2 and 3, the UV/sulfite treatment system has demonstrated near 100% defluorination for various PFAS under both laboratory and field conditions.
*'''No harmful byproducts:''' While some oxidative technologies, such as electrochemical oxidation, generate toxic byproducts, including perchlorate, bromate, and chlorate, the UV/sulfite system employs a reductive mechanism and does not generate these byproducts.
*'''Ambient pressure and low temperature:''' The system operates under ambient pressure and low temperature (<60°C), as it utilizes UV light and common chemicals to degrade PFAS.
*'''Low energy consumption:''' The electrical energy per order values for the degradation of [[Wikipedia: Perfluoroalkyl carboxylic acids | perfluorocarboxylic acids (PFCAs)]] by UV/sulfite have been reduced to less than 1.5 kilowatt-hours (kWh) per cubic meter under laboratory conditions. The energy consumption is orders of magnitude lower than that for many other destructive PFAS treatment technologies (e.g., [[Supercritical Water Oxidation (SCWO) | supercritical water oxidation]])<ref>Nzeribe, B.N., Crimi, M., Mededovic Thagard, S., Holsen, T.M., 2019. Physico-Chemical Processes for the Treatment of Per- And Polyfluoroalkyl Substances (PFAS): A Review. Critical Reviews in Environmental Science and Technology, 49(10), pp. 866-915. [https://doi.org/10.1080/10643389.2018.1542916 doi: 10.1080/10643389.2018.1542916]</ref>.
*'''Co-contaminant destruction:''' The UV/sulfite system has also been reported effective in destroying certain co-contaminants in wastewater. For example, UV/sulfite is reported to be effective in reductive dechlorination of chlorinated volatile organic compounds, such as trichloroethene, 1,2-dichloroethane, and vinyl chloride<ref>Jung, B., Farzaneh, H., Khodary, A., Abdel-Wahab, A., 2015. Photochemical degradation of trichloroethylene by sulfite-mediated UV irradiation. Journal of Environmental Chemical Engineering, 3(3), pp. 2194-2202. [https://doi.org/10.1016/j.jece.2015.07.026 doi: 10.1016/j.jece.2015.07.026]</ref><ref>Liu, X., Yoon, S., Batchelor, B., Abdel-Wahab, A., 2013. Photochemical degradation of vinyl chloride with an Advanced Reduction Process (ARP) – Effects of reagents and pH. Chemical Engineering Journal, 215-216, pp. 868-875. [https://doi.org/10.1016/j.cej.2012.11.086 doi: 10.1016/j.cej.2012.11.086]</ref><ref>Li, X., Ma, J., Liu, G., Fang, J., Yue, S., Guan, Y., Chen, L., Liu, X., 2012. Efficient Reductive Dechlorination of Monochloroacetic Acid by Sulfite/UV Process. Environmental Science and Technology, 46(13), pp. 7342-49. [https://doi.org/10.1021/es3008535 doi: 10.1021/es3008535]</ref><ref>Li, X., Fang, J., Liu, G., Zhang, S., Pan, B., Ma, J., 2014. Kinetics and efficiency of the hydrated electron-induced dehalogenation by the sulfite/UV process. Water Research, 62, pp. 220-228. [https://doi.org/10.1016/j.watres.2014.05.051 doi: 10.1016/j.watres.2014.05.051]</ref>.

==Limitations==
Several environmental factors and potential issues have been identified that may impact the performance of the UV/sulfite treatment system, as listed below. Solutions to address these issues are also proposed.
*Environmental factors, such as the presence of elevated concentrations of natural organic matter (NOM), dissolved oxygen, or nitrate, can inhibit the efficacy of UV/sulfite treatment systems by scavenging available hydrated electrons. Those interferences are commonly managed through chemical additions, reaction optimization, and/or dilution, and are therefore not considered likely to hinder treatment success.
*Coloration in waste streams may also impact the effectiveness of the UV/sulfite treatment system by blocking the transmission of UV light, thus reducing the UV lamp's effective path length. To address this, pre-treatment may be necessary to enable UV/sulfite destruction of PFAS in the waste stream. Pre-treatment may include the use of strong oxidants or coagulants to consume or remove UV-absorbing constituents.
*The degradation efficiency is strongly influenced by PFAS molecular structure, with fluorotelomer sulfonates (FTS) and [[Wikipedia: Perfluorobutanesulfonic acid | perfluorobutanesulfonate (PFBS)]] exhibiting greater resistance to degradation by UV/sulfite treatment compared to other PFAS compounds.

==State of the Practice==
[[File: XiongFig2.png | thumb | 500 px | Figure 2. Field demonstration of EradiFluorTM<ref name="EradiFluor"/> for PFAS destruction in a concentrated waste stream in a Mid-Atlantic Naval Air Station: a) Target PFAS at each step of the treatment shows that about 99% of PFAS were destroyed; meanwhile, the final degradation product, i.e., fluoride, increased to 15 mg/L in concentration, demonstrating effective PFAS destruction; b) AOF concentrations at each step of the treatment provided additional evidence to show near-complete mineralization of PFAS. Average results from multiple batches of treatment are shown here.]]
[[File: XiongFig3.png | thumb | 500 px | Figure 3. Field demonstration of a treatment train (SAFF + EradiFluorTM<ref name="EradiFluor"/>) for groundwater PFAS separation and destruction at an Air Force base in California: a) Two main components of the treatment train, i.e. SAFF and EradiFluorTM<ref name="EradiFluor"/>; b) Results showed the effective destruction of various PFAS in the foam fractionate. The target PFAS at each step of the treatment shows that about 99.9% of PFAS were destroyed. Meanwhile, the final degradation product, i.e., fluoride, increased to 30 mg/L in concentration, demonstrating effective destruction of PFAS in a foam fractionate concentrate. After a polishing treatment step (GAC) via the onsite groundwater extraction and treatment system, all PFAS were removed to concentrations below their MCLs.]]
The effectiveness of UV/sulfite technology for treating PFAS has been evaluated in two field demonstrations using the EradiFluorTM<ref name="EradiFluor"/> system. Aqueous samples collected from the system were analyzed using EPA Method 1633, the [[Wikipedia: TOP Assay | total oxidizable precursor (TOP) assay]], adsorbable organic fluorine (AOF) method, and non-target analysis. A summary of each demonstration and their corresponding PFAS treatment efficiency is provided below.
*Under the [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)] [https://serdp-estcp.mil/projects/details/4c073623-e73e-4f07-a36d-e35c7acc75b6/er21-5152-project-overview Project ER21-5152], a field demonstration of EradiFluorTM<ref name="EradiFluor"/> was conducted at a Navy site on the east coast, and results showed that the technology was highly effective in destroying various PFAS in a liquid concentrate produced from an ''in situ'' foam fractionation groundwater treatment system. As shown in Figure 2a, total PFAS concentrations were reduced from 17,366 micrograms per liter (µg/L) to 195 µg/L at the end of the UV/sulfite reaction, representing 99% destruction. After the ion exchange resin polishing step, all residual PFAS had been removed to the non-detect level, except one compound (PFOS) reported as 1.5 nanograms per liter (ng/L), which is below the current Maximum Contaminant Level (MCL) of 4 ng/L. Meanwhile, the fluoride concentration increased up to 15 milligrams per liter (mg/L), confirming near complete defluorination. Figure 2b shows the adsorbable organic fluorine results from the same treatment test, which similarly demonstrates destruction of 99% of PFAS.
*Another field demonstration was completed at an Air Force base in California, where a treatment train combining [https://serdp-estcp.mil/projects/details/263f9b50-8665-4ecc-81bd-d96b74445ca2 Surface Active Foam Fractionation (SAFF)] and EradiFluorTM<ref name="EradiFluor"/> was used to treat PFAS in groundwater. As shown in Figure 3, PFAS analytical data and fluoride results demonstrated near-complete destruction of various PFAS. In addition, this demonstration showed: a) high PFAS destruction ratio was achieved in the foam fractionate, even in very high concentration (up to 1,700 mg/L of booster), and b) the effluent from EradiFluorTM<ref name="EradiFluor"/> was sent back to the influent of the SAFF system for further concentration and treatment, resulting in a closed-loop treatment system and no waste discharge from EradiFluorTM<ref name="EradiFluor"/>. This field demonstration was conducted with the approval of three regulatory agencies (United States Environmental Protection Agency, California Regional Water Quality Control Board, and California Department of Toxic Substances Control).

==References==
<references />

==See Also==

Dr. Jinyong Liu

2026-02-11T18:55:55Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :University of California, Riverside :Department of Chemical and Environmental Engineering :900 University Ave :Riverside, CA 92521..."

==Work and Contact Information==
EMPLOYER:
:University of California, Riverside
:Department of Chemical and Environmental Engineering
:900 University Ave
:Riverside, CA 92521

EMAIL: [mailto:jinyongl@ucr.edu jinyongl@ucr.edu]

WEBPAGE: https://profiles.ucr.edu/app/home/profile/jinyongl

==About the Contributor==
Dr. Jinyong Liu is currently an Associate Professor and Won and Insook Yoo Endowed Chair in Environmental Engineering at the University of California, Riverside. He has over 20 years of research experience in environmental engineering and chemistry, particularly related to the destruction and detection of recalcitrant water pollutants such as PFAS and perchlorate. Dr. Liu's lab has made significant advances in both fundamental understanding and treatment performance for photochemical degradation of a wide spectrum of PFAS pollutants. In particular, he elucidated the degradation mechanisms and pathways of 150+ PFAS structures, substantially reduced the energy consumption for PFOA degradation under UV from several hundred to <2 kWh/m3, overcame various challenges posed by water matrices, and achieved near 100% defluorination of most PFAS in real waste streams. Dr. Liu is leading multiple research projects funded by federal agencies to advance basic science and develop new technologies for PFAS treatment. He holds a PhD degree in Environmental Engineering from the University of Illinois at Urbana-Champaign and a bachelor’s degree in chemistry from Tsinghua University.

==Article Contributions==
*[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]

__NOTOC__

[[Category: Contributors|Liu]]

Dr. Raul Tenorio

2026-02-11T18:49:42Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Haley and Aldrich, Inc. EMAIL: [mailto:rtenorio@haleyaldrich.com rtenorio@haleyaldrich.com] ==About the Contributor== Dr. Raul i..."

==Work and Contact Information==
EMPLOYER:
:Haley and Aldrich, Inc.

EMAIL: [mailto:rtenorio@haleyaldrich.com rtenorio@haleyaldrich.com]

==About the Contributor==
Dr. Raul is a senior technical specialist and environmental engineer with expertise in per- and polyfluoroalkyl substances (PFAS). Raul has 4 years of experience in consulting and 9 years of experience in both experimental and applied PFAS research. He has extensive research experience in developing an advanced photochemical destruction technology (UV-sulfite) for PFAS remediation. As a PFAS expert, Raul is established in emerging treatment technologies, chemical transformation pathways, and target/suspect screening analysis. He has also presented at 9 technical conferences on PFAS treatment technologies. At Haley & Aldrich, he is a key contributor to 5 applied research projects funded by the Department of Defense focused on PFAS remediation. He also contributes his expertise in environmental chemistry and emerging contaminants to contaminated site management projects on inorganic and organic contaminant monitoring and treatment. Raul holds a doctoral and master’s degree in civil and environmental engineering from the University of Illinois Urbana-Champaign and a bachelor’s degree in civil engineering from the University of Texas at Austin.

==Article Contributions==
*[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]

__NOTOC__

[[Category: Contributors|Tenorio]]

Dr. John Xiong

2026-02-11T18:43:21Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Haley and Aldrich, Inc. :3187 Red Hill Avenue, Suite 155 :Costa Mesa, CA 92626 EMAIL: [mailto:jxiong@haleyaldrich.com jxiong@hale..."

==Work and Contact Information==
EMPLOYER:
:Haley and Aldrich, Inc.
:3187 Red Hill Avenue, Suite 155
:Costa Mesa, CA 92626

EMAIL: [mailto:jxiong@haleyaldrich.com jxiong@haleyaldrich.com]

WEBPAGE: https://www.haleyaldrich.com/about-us/our-people/john-xiong/

==About the Contributor==
Dr. John Xiong is a Principal Consultant and Applied Research Leader at Haley & Aldrich. He has over 20 years of experience in environmental engineering, consulting, applied research, and litigation support. He has developed cost-effective and streamlined strategies for final remedies accepted by federal and state regulatory agencies on projects that entail complex technical and policy issues. As a PFAS subject-matter expert, he has led PFAS investigations at multiple commercial and industrial sites. He is currently leading multiple applied research projects funded by federal agencies to develop and demonstrate innovative technologies for PFAS treatment and assessment. John is a licensed Professional Engineer in California and holds a doctoral degree in civil engineering from Auburn University, a master’s degree and a bachelor’s degree from Chongqing University in China.

==Article Contributions==
*[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]

__NOTOC__

[[Category: Contributors|Xiong]]

Dr. Yida Fang

2026-02-11T14:41:00Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Haley & Aldrich, Inc. :3131 Elliot Avenue :Suite 600 :Seattle, WA 98121 EMAIL: [mailto:yfang@haleyaldric.com yfang@ha..."

==Work and Contact Information==

EMPLOYER:
:Haley & Aldrich, Inc. 
:3131 Elliot Avenue
:Suite 600 
:Seattle, WA 98121

EMAIL: [mailto:yfang@haleyaldric.com yfang@haleyaldric.com]

==About the Contributor==
Yida Fang is a senior environmental engineer at Haley & Aldrich in Seattle, Washington. Yida has over nine years of combined experience in consulting and applied research. As a consulting engineer, Yida has led and supported environmental site investigation and remediation efforts. In the realm of applied research, Yida has served as the principal investigator in SERDP and ESTCP projects. Specializing in the fate, transformation, and remediation of per- and polyfluoroalkyl substances (PFAS), Yida is involved in airport projects aimed at assisting clients in managing and disposing of their aqueous film-forming foam (AFFF) stockpiles, as well as delineating PFAS plumes resulting from AFFF discharges. Yida has authored and co-authored over ten peer-reviewed publications on the transport and treatment of PFAS and has been invited to present findings at multiple national conferences. Yida is a Licensed Professional Engineer in Washington and Montana and holds a doctoral degree in environmental engineering from the Colorado School.

==Article Contributions==
*[[PFAS Destruction by Ultraviolet/Sulfite Treatment]]

__NOTOC__

[[Category: Contributors|Fang]]

Thermal Conduction Heating for Treatment of PFAS-Impacted Soil

2026-01-22T20:37:04Z

Debra Tabron:

<onlyinclude>Removal of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] from impacted soils is challenging due to the modest volatility and varying properties of PFAS compounds. Thermal treatment technologies have been developed for treatment of semi-volatile compounds such as dioxins, furans, poly-aromatic hydrocarbons and poly-chlorinated biphenyls in soils at temperatures near 325°C. In controlled bench-scale testing, removal of targeted PFAS compounds to concentrations below reporting limits </onlyinclude>of 0.5 µg/kg <onlyinclude>was demonstrated at temperatures of 400°C</onlyinclude><ref name="CrownoverEtAl2019"> Crownover, E., Oberle, D., Heron, G., Kluger, M., 2019. Perfluoroalkyl and polyfluoroalkyl substances thermal desorption evaluation. Remediation Journal, 29(4), pp. 77-81. [https://doi.org/10.1002/rem.21623 doi: 10.1002/rem.21623]</ref><onlyinclude>. T</onlyinclude>hree field-scale thermal PFAS treatment projects that have been completed in the US include an in-pile treatment demonstration, an ''in situ'' vadose zone treatment demonstration and a larger scale treatment demonstration with excavated PFAS-impacted soil in a constructed pile. Based on the results, t<onlyinclude>hermal treatment temperatures of at least 400°C and a holding time of 7-10 days are recommended</onlyinclude> for reaching local and federal PFAS soil standards<onlyinclude>. The energy requirement to treat typical wet soil ranges from 300 to 400 kWh per cubic yard</onlyinclude>, exclusive of heat losses which are scale dependent<onlyinclude>. Extracted vapors have typically been treated using condensation and granular activated charcoal filtration, with thermal and catalytic oxidation as another option which is currently being evaluated for field scale applications.</onlyinclude> Compared to other options such as soil washing, the ability to treat on site and to treat all soil fractions is an advantage.
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'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[Thermal Conduction Heating (TCH)]]

'''Contributor(s):''' [[Dr. Gorm Heron]], [[Dr. Emily Crownover]], Patrick Joyce, [[Dr. Ramona Iery]]

'''Key Resource:'''
*Perfluoroalkyl and polyfluoroalkyl substances thermal desorption evaluation<ref name="CrownoverEtAl2019"/>

==Introduction==
[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] have become prominent emerging contaminants in soil and groundwater. Soil source zones have been identified at locations where the chemicals were produced, handled or used. Few effective options exist for treatments that can meet local and federal soil standards. Over the past 30 plus years, thermal remediation technologies have grown from experimental and innovative prospects to mature and accepted solutions deployed effectively at many sites. More than 600 thermal case studies have been summarized by Horst and colleagues<ref name="HorstEtAl2021">Horst, J., Munholland, J., Hegele, P., Klemmer, M., Gattenby, J., 2021. In Situ Thermal Remediation for Source Areas: Technology Advances and a Review of the Market From 1988–2020. Groundwater Monitoring & Remediation, 41(1), p. 17. [https://doi.org/10.1111/gwmr.12424 doi: 10.1111/gwmr.12424]  [[Media: gwmr.12424.pdf | Open Access Manuscript]]</ref>. [[Thermal Conduction Heating (TCH)]] has been used for higher temperature applications such as removal of [[Wikipedia: Dioxins and dioxin-like compounds | dioxins]]. This article reports recent experience with TCH treatment of PFAS-impacted soil.

==Target Temperature and Duration==
PFAS behave differently from most other organics subjected to TCH treatment. While the boiling points of individual PFAS fall in the range of 150-400°C, their chemical and physical behavior creates additional challenges. Some PFAS form ionic species in certain pH ranges and salts under other chemical conditions. This intricate behavior and our limited understanding of what this means for our ability to remove the PFAS from soils means that direct testing of thermal treatment options is warranted. Crownover and colleagues<ref name="CrownoverEtAl2019"/> subjected PFAS-laden soil to bench-scale heating to temperatures between 200 and 400°C which showed strong reductions of PFAS concentrations at 350°C and complete removal of many PFAS compounds at 400°C. The soil concentrations of targeted PFAS were reduced to nearly undetectable levels in this study.

==Heating Method==
For semi-volatile compounds such as dioxins, furans, poly-chlorinated biphenyls (PCBs) and Poly-Aromatic Hydrocarbons (PAH), thermal conduction heating has evolved as the dominant thermal technology because it is capable of achieving soil temperatures higher than the boiling point of water, which are necessary for complete removal of these organic compounds. Temperatures between 200 and 500°C have been required to achieve the desired reduction in contaminant concentrations<ref name="StegemeierVinegar2001">Stegemeier, G.L., Vinegar, H.J., 2001. Thermal Conduction Heating for In-Situ Thermal Desorption of Soils. Ch. 4.6, pp. 1-37. In: Chang H. Oh (ed.), Hazardous and Radioactive Waste Treatment Technologies Handbook, CRC Press, Boca Raton, FL. ISBN 9780849395864 [[Media: StegemeierVinegar2001.pdf | Open Access Article]]</ref>. TCH has become a popular technology for PFAS treatment because temperatures in the 400°C range are needed.

The energy source for TCH can be electricity (most commonly used), or fossil fuels (typically gas, diesel or fuel oil). Electrically powered TCH offers the largest flexibility for power input which also can be supplied by renewable and sustainable energy sources.

==Energy Usage==
Treating PFAS-impacted soil with heat requires energy to first bring the soil and porewater to the boiling point of water, then to evaporate the porewater until the soil is dry, and finally to heat the dry soil up to the target treatment temperature. The energy demand for wet soils falls in the 300-400 kWh/cy range, dependent on porosity and water saturation. Additional energy is consumed as heat is lost to the surroundings and by vapor treatment equipment, yielding a typical usage of 400-600 kWh/cy total for larger soil treatment volumes. Wetter soils and small treatment volumes drive the energy usage towards the higher number, whereas larger soil volumes and dry soil can be treated with less energy.

==Vapor Treatment==
During the TCH process a significant fraction of the PFAS compounds are volatilized by the heat and then removed from the soil by vacuum extraction. The vapors must be treated and eventually discharged while meeting local and/or federal standards. Two types of vapor treatment have been used in past TCH applications for organics: (1) thermal and catalytic oxidation and (2) condensation followed by granular activated charcoal (GAC) filtration. Due to uncertainties related to thermal destruction of fluorinated compounds and future requirements for treatment temperature and residence time, condensation and GAC filtration have been used in the first three PFAS treatment field demonstrations. It should be noted that PFAS compounds will stick to surfaces and that decontamination of the equipment is important. This could generate additional waste as GAC vessels, pipes and other wetted equipment need careful cleaning with solvents or rinsing agents such as PerfluorAdTM.

==PFAS Reactivity and Fate==
While evaluating initial soil treatment results, Crownover ''et al''<ref name="CrownoverEtAl2019"/> noted the lack of complete data sets when the soils were analyzed for non-targeted compounds or extractable precursors. Attempts to establish the fluorine balance suggest that the final fate of the fluorine in the PFAS is not yet fully understood. Transformations are likely occurring in the heated soil as demonstrated in laboratory experiments with and without calcium hydroxide (Ca(OH)2) amendment<ref>Koster van Groos, P.G., 2021. Small-Scale Thermal Treatment of Investigation-Derived Wastes Containing PFAS. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/2f1577ac-c8ea-4ae8-804e-c9f97a12edb3/small-scale-thermal-treatment-of-investigation-derived-wastes-idw-containing-pfas Project ER18-1556 Website], [[Media: ER18-1556_Final_Report.pdf | Final Report.pdf]]</ref>. Amendments such as Ca(OH)2 may be useful in reducing the required treatment temperature by catalyzing PFAS degradation. With thousands of PFAS potentially present, the interactions are complex and may never be fully understood. Therefore, successful thermal treatment may require a higher target temperature than for other organics with similar boiling points – simply to provide a buffer against the uncertainty.

==Case Studies==
===Stockpile Treatment, Eielson AFB, Alaska ([https://serdp-estcp.mil/projects/details/62098505-de86-43b2-bead-ae8018854141 ESTCP project ER20-5198]<ref name="CrownoverEtAl2023">Crownover, E., Heron, G., Pennell, K., Ramsey, B., Rickabaugh, T., Stallings, P., Stauch, L., Woodcock, M., 2023. Ex Situ Thermal Treatment of PFAS-Impacted Soils, [[Media: ER20-5198 Final Report.pdf | Final Report.]] Eielson Air Force Base, Alaska. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/62098505-de86-43b2-bead-ae8018854141 Project ER20-5198 Website]</ref>)===
[[File: HeronFig1.png | thumb | 400 px | Figure 1. TCH treatment of a PFAS-laden stockpile at Eielson AFB, Alaska<ref name="CrownoverEtAl2023"/>]]
Since there has been no approved or widely accepted method for treating soils impacted by PFAS, a common practice has been to excavate PFAS-impacted soil and place it in lined stockpiles. Eielson AFB in Alaska is an example where approximately 50 stockpiles were constructed to temporarily store 150,000 cubic yards of soil. One of the stockpiles containing 134 cubic yards of PFAS-impacted soil was heated to 350-450°C over 90 days (Figure 1). Volatilized PFAS was extracted from the soil using vacuum extraction and treated via condensation and filtration by granular activated charcoal. Under field conditions, PFAS concentration reductions from 230 µg/kg to below 0.5 µg/kg were demonstrated for soils that reached 400°C or higher for 7 days. These soils achieved the Alaska soil standards of 3 µg/kg for PFOS and 1.7 µg/kg for PFOA. Cooler soils near the top of the stockpile had remaining PFOS in the range of 0.5-20 µg/kg with an overall average of 4.1 µg/kg. Sampling of all soils heated to 400°C or higher demonstrated that the soils achieved undetectable levels of targeted PFAS (typical reporting limit was 0.5 µg/kg).

===''In situ'' Vadose Zone Treatment, Beale AFB, California ([https://serdp-estcp.mil/projects/details/94949542-f9f7-419d-8028-8ba318495641/er20-5250-project-overview ESTCP project ER20-5250]<ref name="Iery2024">Iery, R. 2024. In Situ Thermal Treatment of PFAS in the Vadose Zone. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/94949542-f9f7-419d-8028-8ba318495641 Project ER20-5250 Website]. [[Media: ER20-5250 Fact Sheet.pdf | Fact Sheet.pdf]]</ref>)===
[[File: HeronFig2.png | thumb | 600 px | Figure 2. ''In situ'' TCH treatment of a PFAS-rich vadose zone hotspot at Beale AFB, California]]
A former fire-training area at Beale AFB had PFAS concentrations as high as 1,970 µg/kg in shallow soils. In situ treatment of a PFAS-rich soil was demonstrated using 16 TCH borings installed in the source area to a depth of 18 ft (Figure 2). Soils which reached the target temperatures were reduced to PFAS concentrations below 1 µg/kg. Perched water which entered in one side of the area delayed heating in that area, and soils which were affected had more modest PFAS concentration reductions. As a lesson learned, future in situ TCH treatments will include provisions for minimizing water entering the treated volume<ref name="Iery2024"/>. It was demonstrated that with proper water management, even highly impacted soils can be treated to near non-detect concentrations (greater than 99% reduction).

===Constructed Pile Treatment, JBER, Alaska ([https://serdp-estcp.mil/projects/details/eb7311db-6233-4c7f-b23a-e003ac1926c5/pfas-treatment-in-soil-using-thermal-conduction-heating ESTCP Project ER23-8369]<ref name="CrownoverHeron2024">Crownover, E., Heron, G., 2024. PFAS Treatment in Soil Using Thermal Conduction Heating. Defense Innovation Unit (DIU) and [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/eb7311db-6233-4c7f-b23a-e003ac1926c5/pfas-treatment-in-soil-using-thermal-conduction-heating Project ER23-8369 Website]</ref>)===
[[File: HeronFig3.png | thumb | 600 px | Figure 3. Treatment of a 2,000 cubic yard soil pile at JBER, Alaska]]
In 2024, a stockpile of 2,000 cubic yards of PFAS-impacted soil was thermally treated at Joint Base Elmendorf-Richardson (JBER) in Anchorage, Alaska<ref name="CrownoverHeron2024"/>. This ESTCP project was implemented in partnership with DOD’s Defense Innovation Unit (DIU). Three technology demonstrations were conducted at the site where approximately 6,000 cy of PFAS-impacted soil was treated (TCH, smoldering and kiln-style thermal desorption). Figure 3 shows the fully constructed pile used for the TCH demonstration. In August 2024 the soil temperature for the TCH treatment exceeded 400°C in all monitoring locations. At an energy density of 355 kWh/cy, Alaska Department of Environmental Conservation (ADEC) standards and EPA Residential Regional Screening Levels (RSLs) for PFAS in soil were achieved. At JBER, all 30 post-treatment soil samples were near or below detection limits for all targeted PFAS compounds using EPA Method 1633. The composite of all 30 soil samples was below all detection limits for EPA Method 1633. Detection limits ranged from 0.0052 µg/kg to 0.19 µg/kg for individaul PFAS.

==Advantages and Disadvantages==
<onlyinclude>Thermal treatment of PFAS in soils is energy intensive, and the cost of that energy may be prohibitive for some clients. Also, while it often is the least costly option for complete PFAS removal when compared to excavation followed by offsite disposal or destruction, heating soil to treatment temperatures on site or ''in situ'' typically takes longer than excavation.</onlyinclude> Major advantages include:
*On site or ''in situ'' treatment eliminates the need to transport and dispose of the contaminated soil.
*Site liabilities are removed once and for all.
*Treatment costs are competitive with excavation, transportation and off-site treatment or disposal.

==Recommendations==
Recent research suggests:
*Successful thermal treatment of PFAS may require a higher target temperature than for other organics with similar boiling points.
*Prevention of influx of water into treatment zone may be necessary.
Future studies should examine the potential for enhanced degradation during the thermal process by using soil amendments and/or manipulation of the local geochemistry to reduce the required treatment temperatures and therefore also reduce energy demand.

==References==
<references />

==See Also==

Dr. Emily Crownover

2026-01-22T20:36:17Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :TRS Group, a Parsons Company :St. Charles, MO 63304 EMAIL: [mailto:ecrownover@thermalrs.com ecrownover@thermalrs.com] WEB..."

==Work and Contact Information==

EMPLOYER:
:TRS Group, a Parsons Company 
:St. Charles, MO 63304

EMAIL: [mailto:ecrownover@thermalrs.com ecrownover@thermalrs.com]

WEBPAGE: https://www.parsons.com/thermal-remediation/

==About the Contributor==
Dr. Crownover is a Managing Principal Engineer at TRS. With more than 20 years of engineering experience, she has designed and implemented thermal remediation systems at sites across the United States and in Canada, ranging from active facilities to large Superfund sites. Her areas of expertise include electrical resistance heating (ERH) and thermal conduction heating (TCH) for VOC, SVOC, and PFAS remediation.

==Article Contributions==
*[[Thermal Conduction Heating for Treatment of PFAS-Impacted Soil]]

__NOTOC__

[[Category: Contributors|Crownover]]

Articles

2026-01-20T18:14:29Z

Debra Tabron:

{| class="wikitable sortable"
|-
!Title!!First Author!!Linking Phrases
|-
|[[Groundwater Sampling - No-Purge/Passive]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||passive sampling, no purge sampling, grab samplers, diffusion samplers, sorptive samplers
|-
|[[ Long-Term Monitoring (LTM)]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||long-term monitoring, LTM, LTM objectives, LTM programs, LTM challenges
|-
|[[PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)]]
|[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]
|PFAS, MNA, natural attenuation
|-
|[[Sorption of Organic Contaminants]]||[[Richelle Allen-King|Allen-King, Richelle]]||
|-
|[[PFAS Transport and Fate]]
|[[Dr. Richard Anderson|Anderson, Richard, Ph.D.]]
|PFAS, fate and transport
|-
|[[Mass Flux and Mass Discharge]]||[[Dr. Michael Annable, P.E. |Annable, Michael, Ph.D., P.E.]]||source reduction
|-
|[[PFAS Toxicology and Risk Assessment]]
|[[Jennifer Arblaster|Arblaster, Jennifer]]
|PFAS, toxicology, risk assessment
|-
|[[Metal(loid)s - Small Arms Ranges]]|| Dr. Amanda Barker |[[Dr. Amanda Barker|Barker, Amanda, Ph.D.]]
|
|-
|[[Munitions Constituents – Photolysis|Munitions Constituents - Photolysis]]
|[[Dr. Warren Kadoya|Kadoya, Warren, Ph.D.]]
|
|-
|[[Munitions Constituents - Soil Sampling]]
|[[Dr. Samuel Beal|Beal, Samuel, Ph.D.]]
|
|-
|[[Vapor Intrusion – Sewers and Utility Tunnels as Preferential Pathways|Vapor Intrusion - Sewers and Utility Tunnels as Preferential Pathways]]
|[[Lila Beckley|Beckley, Lila]]
|vapor intrusion
|-
|[[Natural Attenuation in Source Zone and Groundwater Plume - Bemidji Crude Oil Spill]]
|[[Dr. Barbara Bekins|Bekins, Barbara, Ph.D.]]||
|-
|[[Bioremediation - Anaerobic Secondary Water Quality Impacts]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||secondary impacts, water quality (in regards to anaerobic conditions)
|-
|[[Design Tool - Base Addition for ERD]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||aquifer acidity, base addition
|-
|[[Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation]]
|[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||
|-
|[[Low pH Inhibition of Reductive Dechlorination]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||low pH inhibition
|-
|[[OPTically-based In-situ Characterization System (OPTICS)]]
|[[Dr. Grace Chang|Chang, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents - Electrochemical Treatment]]
|[[Dr. Brian P. Chaplin|Chaplin, Brian, Ph.D.]]
|munitions constituents remediation
|-
|[[PFAS Sources]]
|[[Dr. Dora Chiang|Chiang, Dora, Ph.D.]]
|
|-
|[[Biodegradation - Cometabolic]]||[[Dr. Kung-Hui (Bella) Chu |Chu, Kung-Hui (Bella), Ph.D]]||cometabolic biodegradation
|-
|[[Munitions Constituents - Composting]]
|[[Harry Craig|Craig, Harry]]
|
|-
|[[Chemical Oxidation (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||ISCO, chemical oxidation
|-
|[[Chemical Oxidation Oxidant Selection (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||chemical oxidant, oxidant (in regards to ISCO)
|-
|[[Chemical Oxidation Design Considerations(In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||screening, design, implementation, oxidant delivery (in regards to ISCO)
|-
|[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]||[[Dr. Rula Deeb |Deeb, Rula, Ph.D.]]||PFAS, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS)
|-
|[[Metal and Metalloid Contaminants]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal contaminant(s), metalloid contaminant(s), metal(s), metalloid(s),
|-
|[[Metals and Metalloids - Mobility in Groundwater]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal mobility, aqueous speciation, adsorption, precipitation, colloidal transport (in regards to metals)
|-
|[[Monitored Natural Attenuation (MNA) of Metal and Metalloids]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||MNA, attenuation of metal(s), natural attenuation processes, attenuation (in regards to metals)
|-
|[[Metal and Metalloids - Remediation]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||remediation, in situ technologies, contaminant removal (in regards to metals)
|-
|[[pH Buffering in Aquifers]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||ph buffer, natural pH buffer, engineered pH buffer
|-
|[[Munitions Constituents - Sorption]]||[[Dr. Katerina Dontsova |Dontsova, Katerina, Ph.D.]]||energetics, sorption
|-
|[[Biodegradation - Hydrocarbons]]||[[Dr. Elizabeth Edwards |Edwards, Elizabeth, Ph.D.]]||hydrocarbon, biodegradation
|-
|[[Source Zone Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||source zone modeling
|-
|[[Plume Response Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||plume response modeling
|-
|[[REMChlor - MD]]
|[[Dr. Ron Falta|Falta, Ron, Ph.D.]]
|
|-
|[[In Situ Groundwater Treatment with Activated Carbon]]
|[[Dr. Dimin Fan|Fan, Dimin, Ph.D.]]
|
|-
|[[LNAPL Remediation Technologies]]||[[Dr. Shahla Farhat |Farhat, Shahla, Ph.D.]]||
|-
|[[Sustainable Remediation]]||[[Paul Favara |Favara, Paul]]||sustainable remediation, social, economic and environmental impacts
|-
|[[Munitions Constituents]]||[[Dr. Kevin Finneran |Finneran, Kevin, Ph.D.]]||Explosives, energetics, insensitive munitions
|-
|[[Biodegradation - Reductive Processes]]||[[Dr. David Freedman |Freedman, David, Ph.D.]]||biotic reduction, biotic reductive processes, hydrogenolysis, dihaloelimination, coupling, organohalide respiration
|-
|[[Remediation of Stormwater Runoff Contaminated by Munition Constituents|Munitions Constituents - Remediation of Stormwater Runoff]]||Fuller, Mark, Ph.D.||energetics, insensitive munitions, stormwater runoff
|-
|[[Subgrade Biogeochemical Reactor (SBGR)]]||[[Jeff Gamlin |Gamlin, Jeff]]||SBGR, subgrade biogeochemical reactor, bioreactor
|-
|[[Thermal Remediation - Smoldering]]||[[Dr. Jason Gerhard |Gerhard, Jason, Ph.D.]]||smouldering remediation, self-sustaining treatment for active remediation, STAR
|-
|[[Contaminated Sediments - Introduction]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[Contaminated Sediment Risk Assessment]]
|[[Richard Wenning|Wenning, Richard]]
|
|-
|[[In Situ Treatment of Contaminated Sediments with Activated Carbon]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[PFAS Ex Situ Water Treatment]]
|[[Dr. Scott Grieco |Grieco, Scott, Ph.D.]]
|
|-
|[[Stream Restoration]]
|[[Dr. Natalie Griffiths|Griffiths, Natalie, Ph.D.]]
|
|-
|[[Passive Sampling of Sediments]]
|[[Dr. Philip M. Gschwend|Gschwend, Philip]]
|
|-
|[[Phytoplankton (Algae) Blooms]]
|[[Dr. Nathan Hall|Hall, Nathan]]
|
|-
|[[PFAS Soil Remediation Technologies]]||[[James_Hatton |Hatton, Jim]]||PFAS, Soil source zones
|-
|[[Proteomics and Proteogenomics]]
|[[Dr. Kate Kucharzyk|Kucharzyk, Kate, Ph.D.]]
|
|-
|[[N-nitrosodimethylamine (NDMA)]]
|[[Paul Hatzinger|Hatzinger, Paul, Ph.D.]]
|
|-
|[[Alternative Endpoints]]||[[Elisabeth Hawley |Hawley, Elisabeth]]||management of complex sites||
|-
|[[Thermal Remediation]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, in situ thermal
|-
|[[Thermal Remediation - Steam]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Steam Enhanced Extraction
|-
|[[Thermal Remediation - Electrical Resistance Heating]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Electrical Resistance Heating
|-
|[[Thermal Conduction Heating (TCH)]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal desorption
|-
|[[Thermal Remediation - Combined Remedies]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation
|-
|[[Thermal Conduction Heating for Treatment of PFAS-Impacted Soil]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, PFAS
|-
|[[Predicting Species Responses to Climate Change with Population Models]]
|[[Dr. Brian Hudgens|Hudgens, Brian, Ph.D.]]
|climate change
|-
|[[Infrastructure Resilience]]
|[[Dr. John Hummel|Hummel, John, Ph.D.]]
|
|-
|[[Munitions Constituents- TREECS™ Fate and Risk Modeling|Munitions Constituents - TREECS™ Fate and Risk Modeling]]||[[Dr. Billy E. Johnson |Johnson, Billy, Ph.D.]]||munitions constituents fate and transport modeling, TREECS
|-
|[[Munitions Constituents - Alkaline Degradation]]
|[[Jared Johnson|Johnson, Jared]]
|
|-
|[[Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)|Vapor Intrusion - Assessing VI Impacts in Neighborhoods with Groundwater Contaminated CVOCs]]
|[[Dr. Paul C. Johnson|Johnson, Paul, Ph.D.]]
|vapor intrusion
|-
|[[Munitions Constituents - IM Toxicology]]||-----||insensitive explosives, insensitive munitions, IMX-101, IMX
|-
|[[Landfarming]]
|[[Dr. Roopa Kamath|Kamath, Roopa, Ph.D.]]
|
|-
|[[NAPL Mobility]]
|[[Andrew Kirkman|Kirkman, Andrew]]
|
|-
|[[Climate Change Primer]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Perchlorate]]||[[Thomas Krug |Krug, Thomas]]||perchlorate
|-
|[[Injection Techniques for Liquid Amendments]]||[[Thomas Krug |Krug, Thomas]]||amendment injection
|-
|[[Transition of Aqueous Film Forming Foam (AFFF) Fire Suppression Infrastructure Impacted by Per and Polyfluoroalkyl Substances (PFAS)]]
|[[Dr. Johnsie Ray Lang|Lang, Johnsie Ray, Ph.D.]]||PFAS
|
|-
|[[Characterization Methods – Hydraulic Conductivity]]
|[[Dr. Gaisheng Liu|Liu, Gaisheng, Ph.D.]]
|
|-
|[[Compound Specific Isotope Analysis (CSIA)]]||[[Dr. Barbara Sherwood Lollar, F.R.S.C. |Lollar, Barbara S., FRSC]]||Compound Specific Isotope Analysis (CSIA)
|-
|[[Passive Sampling of Munitions Constituents|Munitions Constituents - Passive Sampling]]
|[[Dr. Guilherme Lotufo|Lotufo, Guilerme, Ph.D.]]
|
|-
|[[Vapor Intrusion (VI)]]||[[Chris Lutes |Lutes, Chris]]||vapor intrusion
|-
|[[Bioremediation - Anaerobic]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||anaerobic bioremediation
|-
|[[Bioremediation - Anaerobic Design Considerations]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||
|-
|[[Biodegradation - 1,4-Dioxane]]
|[[Dr. Shaily Mahendra|Mahendra, Shaily, Ph.D.]]
|
|-
|[[Direct Push (DP) Technology]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push, DP, DP machines, DP technology
|-
|[[Direct Push Sampling]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push sampling, soil sampling, groundwater sampling, well installation, soil vapor sampling (in regards to DP)
|-
|[[Direct Push Logging]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push logging, Cone Penetration Testing, CPT, Electrical Conductivity, EC, Hydraulic Profiling Tool, HPT, Membrane Interface Probe, MIP, Optical Imaging Profiler, OIP
|-
|[[Downscaled High Resolution Datasets for Climate Change Projections]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Remediation Performance Assessment at Chlorinated Solvent Sites]]||[[Travis McGuire|McGuire, Travis]]||multi-site studies
|-
|[[LNAPL Conceptual Site Models]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Long-Term Monitoring (LTM) - Data Analysis]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data analysis, analysis methods (in regards to LTM)
|-
|[[Long-Term Monitoring (LTM) - Data Variability]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data variability (in regards to LTM), LTM evaluation
|-
|-
|[[Munitions Constituents - Abiotic Reduction]]||[[Dr. Jimmy Murillo-Gelvez |Murillo-Gelvez, Jimmy, Ph.D.]]
|-
|[[Supercritical Water Oxidation (SCWO)]]
|Nagar, Kobe
|
|-
|[[Matrix Diffusion]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Groundwater Flow and Solute Transport]]||[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]||groundwater flow, advection, dispersion, diffusion, molecular diffusion, mechanical dispersion
|-
|[[Molecular Biological Tools - MBTs]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||MBT, Molecular Biological Tool(s)
|-
|[[Quantitative Polymerase Chain Reaction (qPCR)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||qPCR, Polymerase Chain Reaction
|-
|[[Sediment Capping]]
|[[Dr. Danny Reible|Reible, Danny]]
|
|-
|[[Stable Isotope Probing (SIP)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||SIP, Stable Isotope Probing
|-
|[[Metagenomics]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||Metagenomics
|-
|[[Natural Source Zone Depletion (NSZD)]]||[[Tom Palaia |Palaia, Tom]]||natural source zone depletion, NSZD
|-
|[[Climate Change Effects on Wildlife]]
|[[Dr. Breanna F. Powers|Powers, Breanna, PhD.]]
|
|-
|[[Amendment Distribution in Low Conductivity Materials]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||
|-
|[[Polycyclic Aromatic Hydrocarbons (PAHs)]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||Polycyclic Aromatic Hydrocarbons, PAH(s)
|-
|[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]
|[[Florent Risacher|Risacher, Florent, M.Sc.]]
|
|-
|[[1,2,3-Trichloropropane]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||TCP, trichloropropane
|-
|[[Zerovalent Iron (ZVI) (Chemical Reduction - ISCR)]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||ZVI
|-
|[[Mercury in Sediments]]
|[[Dr. Grace Schwartz|Schwartz, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents – Sample Extraction and Analytical Techniques|Munitions Constituents - Sample Extraction and Analytical Techniques]]
|[[Dr. Austin Scircle|Scircle, Austin]]
|
|-
|[[Geophysical Methods]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[Geophysical Methods - Case Studies]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[PFAS Treatment by Anion Exchange]]
|[[Dr. Timothy J. Strathmann|Strathmann, Timothy, Ph.D.]]
|PFAS
|-
|[[Munitions Constituents - Dissolution]]||[[Dr. Susan Taylor |Taylor, Susan, Ph.D.]]||explosive(s), dissolution,
|-
|[[PFAS Treatment by Electrical Discharge Plasma]]
|[[Dr. Selma Mededovic Thagard|Thagard, Selma Mededovic, Ph.D.]]
|PFAS
|-
|[[Restoration of Ecological Function in Terrestrial Systems Impacted by Invasive Species]]
|Thierry, Hugo, Ph.D.
|climate change, invasive species, restoration ecology
|-
|[[Chemical Reduction (In Situ - ISCR)]]||[[Dr. Paul Tratnyek |Tratnyek, Paul, Ph.D.]]||In Situ Chemical Reduction, ISCR
|-
|[[Injection Techniques - Viscosity Modification]]||[[Michael Truex |Truex, Michael]]||viscosity, viscosity modifiers, viscosity modification
|-
|[[Soil Vapor Extraction (SVE)]]||[[Michael Truex |Truex, Michael]]||soil vapor extraction, SVE
|-
|[[Munitions Constituents - Deposition]]||[[Michael R. Walsh, P.E., M.E.|Walsh, Michael, P.E.]]||explosive deposition, energetics deposition
|-
|[[Vapor Intrusion - Separation Distances from Petroleum Sources]]
|[[Dr. James Weaver|Weaver, James, Ph.D.]]
|vapor intrusion
|-
|[[Zerovalent Iron Permeable Reactive Barriers]]
|[[Dr. Richard Wilkin|Wilkin, Rick, Ph.D.]]
|
|-
|[[Monitored Natural Attenuation (MNA)]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, In Situ MNA, natural attenuation, natural attenuation processes
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|[[Monitored Natural Attenuation (MNA) of Fuels]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to petroleum hydrocarbons and fuel components)
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|[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to chlorinated solvents)
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|[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
|[[Dr. John Wilson|Wilson, John, Ph.D.]]
|MNA, natural attenuation
|-
|[[Chlorinated Solvents]]||[[Dr. Bilgen Yuncu, P.E. |Yuncu, Bilgen, Ph.D., P.E.]]||chlorinated solvents
|-
|[[Petroleum Hydrocarbons (PHCs)]]
|[[Dr. Bilgen Yuncu, P.E.|Yuncu, Bilgen, Ph.D., P.E.]]
|Petroleum Hydrocarbons (PHCs)
|-
|[[Photoactivated Reductive Defluorination - PFAS Destruction]]
|[[Dr. Suzanne Witt|Witt, Suzanne, Ph.D.]]
|PFAS
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|-
|[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]
|[[Dr. Lee Slater|Slater, Lee, Ph.D.]]
|geophysics, hydrogeophysical methods,
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|-
|[[Hydrothermal Alkaline Treatment (HALT)]]
|[[Dr. Brian Pinkard|Pinkard, Brian]]
|
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|[[1,4-Dioxane]]
|[[Matthew Zenker|Zenker, Matthew]]
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|[[Lysimeters for Measuring PFAS Concentrations in the Vadose Zone]]
|[[Dr. John F. Stults|Stults, Dr. John]]
|
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|}

Dr. Charles Schaefer

2026-01-20T18:07:27Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :CDM Smith :110 Fieldcrest Avenue :6th Floor :Edison, NJ 08837 EMAIL: [mailto:schaeferce@cdmsmith.com schaeferce@cdmsm..."

==Work and Contact Information==

EMPLOYER:
:CDM Smith 
:110 Fieldcrest Avenue
:6th Floor 
:Edison, NJ 08837

EMAIL: [mailto:schaeferce@cdmsmith.com schaeferce@cdmsmith.com]

WEBPAGE: https://www.cdmsmith.com/en/experts/charles-schaefer

==About the Contributor==
Charles Schaefer is a chemical engineer with over 25 years of years of experience in laboratory and field evaluations of contaminant transport in subsurface systems and engineered water systems. Dr. Schaefer is the director of CDM Smith’s Research and Testing laboratory located in Bellevue, WA

==Article Contributions==
*[[Lysimeters for Measuring PFAS Concentrations in the Vadose Zone]]

__NOTOC__

[[Category: Contributors|Schaefer]]

Lysimeters for Measuring PFAS Concentrations in the Vadose Zone

2026-01-20T18:02:45Z

Debra Tabron:

[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] are frequently introduced to the environment through soil surface applications which then transport through the vadose zone to reach underlying groundwater receptors. Due to their unique properties and resulting transport and retention behaviors, PFAS in the vadose zone can be a persistent contaminant source to underlying groundwater systems. Determining the fraction of PFAS present in the mobile porewater relative to the total concentrations in soils is critical to understanding the risk posed by PFAS in vadose zone source areas. Lysimeters are instruments that have been used by agronomists and vadose zone researchers for decades to determine water flux and solute concentrations in unsaturated porewater. Lysimeters have recently been developed as a critical tool for field investigations and characterizations of PFAS impacted source zones.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Transport and Fate]]
*[[PFAS Toxicology and Risk Assessment]]
*[[Mass Flux and Mass Discharge]]

'''Contributors:''' [[Dr. John F. Stults]] and [[Dr. Charles Schaefer]]

'''Key Resources:'''
*Assessment of PFAS in Collocated Soil and Porewater Samples at an AFFF-Impacted Source Zone: Field-Scale Validation of Suction Lysimeters<ref name="AndersonEtAl2022"/>
*PFAS Concentrations in Soil versus Soil Porewater: Mass Distributions and the Impact of Adsorption at Air-Water Interfaces<ref name="BrusseauGuo2022"/>
*Using Suction Lysimeters for Determining the Potential of Per- and Polyfluoroalkyl Substances to Leach from Soil to Groundwater: A Review<ref name="CostanzaEtAl2025"/>
*Use of Lysimeters for Monitoring Soil Water Balance Parameters and Nutrient Leaching<ref name="MeissnerEtAl2020"/>
*PFAS Porewater Concentrations in Unsaturated Soil: Field and Laboratory Comparisons Inform on PFAS Accumulation at Air-Water Interfaces<ref name="SchaeferEtAl2024"/>

==Introduction==
Lysimeters are devices that are placed in the subsurface above the groundwater table to monitor the movement of water through the soil<ref name="GossEhlers2009">Goss, M.J., Ehlers, W., 2009. The Role of Lysimeters in the Development of Our Understanding of Soil Water and Nutrient Dynamics in Ecosystems. Soil Use and Management, 25(3), pp. 213–223. [https://doi.org/10.1111/j.1475-2743.2009.00230.x doi: 10.1111/j.1475-2743.2009.00230.x]</ref><ref>Pütz, T., Fank, J., Flury, M., 2018. Lysimeters in Vadose Zone Research. Vadose Zone Journal, 17 (1), pp. 1-4. [https://doi.org/10.2136/vzj2018.02.0035 doi: 10.2136/vzj2018.02.0035]  [[Media: PutzEtAl2018.pdf | Open Access Article]]</ref><ref name="CostanzaEtAl2025">Costanza, J., Clabaugh, C.D., Leibli, C., Ferreira, J., Wilkin, R.T., 2025. Using Suction Lysimeters for Determining the Potential of Per- and Polyfluoroalkyl Substances to Leach from Soil to Groundwater: A Review. Environmental Science and Technology, 59(9), pp. 4215-4229. [https://doi.org/10.1021/acs.est.4c10246 doi: 10.1021/acs.est.4c10246]</ref>. Lysimeters have historically been used in agricultural sciences for monitoring nutrient or contaminant movement, soil moisture release curves, natural drainage patterns, and dynamics of plant-water interactions<ref name="GossEhlers2009"/><ref>Bergström, L., 1990. Use of Lysimeters to Estimate Leaching of Pesticides in Agricultural Soils. Environmental Pollution, 67 (4), 325–347. [https://doi.org/10.1016/0269-7491(90)90070-S doi: 10.1016/0269-7491(90)90070-S]</ref><ref>Dabrowska, D., Rykala, W., 2021. A Review of Lysimeter Experiments Carried Out on Municipal Landfill Waste. Toxics, 9(2), Article 26. [https://doi.org/10.3390/toxics9020026 doi: 10.3390/toxics9020026]  [[Media: Dabrowska Rykala2021.pdf | Open Access Article]]</ref><ref>Fernando, S.U., Galagedara, L., Krishnapillai, M., Cuss, C.W., 2023. Lysimeter Sampling System for Optimal Determination of Trace Elements in Soil Solutions. Water, 15(18), Article 3277. [https://doi.org/10.3390/w15183277 doi: 10.3390/w15183277]  [[Media: FernandoEtAl2023.pdf | Open Access Article]]</ref><ref name="MeissnerEtAl2020">Meissner, R., Rupp, H., Haselow, L., 2020. Use of Lysimeters for Monitoring Soil Water Balance Parameters and Nutrient Leaching. In: Climate Change and Soil Interactions. Elsevier, pp. 171-205. [https://doi.org/10.1016/B978-0-12-818032-7.00007-2 doi: 10.1016/B978-0-12-818032-7.00007-2]</ref><ref name="RogersMcConnell1993">Rogers, R.D., McConnell, J.W. Jr., 1993. Lysimeter Literature Review, Nuclear Regulatory Commission Report Numbers: NUREG/CR--6073, EGG--2706. [https://www.osti.gov/] ID: 10183270. [https://doi.org/10.2172/10183270 doi: 10.2172/10183270]  [[Media: RogersMcConnell1993.pdf | Open Access Article]]</ref><ref>Sołtysiak, M., Rakoczy, M., 2019. An Overview of the Experimental Research Use of Lysimeters. Environmental and Socio-Economic Studies, 7(2), pp. 49-56. [https://doi.org/10.2478/environ-2019-0012 doi: 10.2478/environ-2019-0012]  [[Media: SołtysiakRakoczy2019.pdf | Open Access Article]]</ref><ref name="Stannard1992">Stannard, D.I., 1992. Tensiometers—Theory, Construction, and Use. Geotechnical Testing Journal, 15(1), pp. 48-58. [https://doi.org/10.1520/GTJ10224J doi: 10.1520/GTJ10224J]</ref><ref name="WintonWeber1996">Winton, K., Weber, J.B., 1996. A Review of Field Lysimeter Studies to Describe the Environmental Fate of Pesticides. Weed Technology, 10(1), pp. 202-209. [https://doi.org/10.1017/S0890037X00045929 doi: 10.1017/S0890037X00045929]</ref>. Recently, there has been strong interest in the use of lysimeters to measure and monitor movement of per- and polyfluoroalkyl substances (PFAS) through the vadose zone<ref name="Anderson2021">Anderson, R.H., 2021. The Case for Direct Measures of Soil-to-Groundwater Contaminant Mass Discharge at AFFF-Impacted Sites. Environmental Science and Technology, 55(10), pp. 6580-6583. [https://doi.org/10.1021/acs.est.1c01543 doi: 10.1021/acs.est.1c01543]</ref><ref name="AndersonEtAl2022">Anderson, R.H., Feild, J.B., Dieffenbach-Carle, H., Elsharnouby, O., Krebs, R.K., 2022. Assessment of PFAS in Collocated Soil and Porewater Samples at an AFFF-Impacted Source Zone: Field-Scale Validation of Suction Lysimeters. Chemosphere, 308(1), Article 136247. [https://doi.org/10.1016/j.chemosphere.2022.136247 doi: 10.1016/j.chemosphere.2022.136247]</ref><ref name="SchaeferEtAl2024">Schaefer, C.E., Nguyen, D., Fang, Y., Gonda, N., Zhang, C., Shea, S., Higgins, C.P., 2024. PFAS Porewater Concentrations in Unsaturated Soil: Field and Laboratory Comparisons Inform on PFAS Accumulation at Air-Water Interfaces. Journal of Contaminant Hydrology, 264, Article 104359. [https://doi.org/10.1016/j.jconhyd.2024.104359 doi: 10.1016/j.jconhyd.2024.104359]  [[Media: SchaeferEtAl2024.pdf | Open Access Manuscript]]</ref><ref name="SchaeferEtAl2023">Schaefer, C.E., Lavorgna, G.M., Lippincott, D.R., Nguyen, D., Schaum, A., Higgins, C.P., Field, J., 2023. Leaching of Perfluoroalkyl Acids During Unsaturated Zone Flushing at a Field Site Impacted with Aqueous Film Forming Foam. Environmental Science and Technology, 57(5), pp. 1940-1948. [https://doi.org/10.1021/acs.est.2c06903 doi: 10.1021/acs.est.2c06903]</ref><ref name="SchaeferEtAl2022">Schaefer, C.E., Lavorgna, G.M., Lippincott, D.R., Nguyen, D., Christie, E., Shea, S., O’Hare, S., Lemes, M.C.S., Higgins, C.P., Field, J., 2022. A Field Study to Assess the Role of Air-Water Interfacial Sorption on PFAS Leaching in an AFFF Source Area. Journal of Contaminant Hydrology, 248, Article 104001. [https://doi.org/10.1016/j.jconhyd.2022.104001 doi: 10.1016/j.jconhyd.2022.104001]  [[Media: SchaeferEtAl2022.pdf | Open Access Manuscript]]</ref><ref name="QuinnanEtAl2021">Quinnan, J., Rossi, M., Curry, P., Lupo, M., Miller, M., Korb, H., Orth, C., Hasbrouck, K., 2021. Application of PFAS-Mobile Lab to Support Adaptive Characterization and Flux-Based Conceptual Site Models at AFFF Releases. Remediation, 31(3), pp. 7-26. [https://doi.org/10.1002/rem.21680 doi: 10.1002/rem.21680]</ref>. PFAS are frequently introduced to the environment through land surface application and have been found to be strongly retained within the upper 5 feet of soil<ref name="BrusseauEtAl2020">Brusseau, M.L., Anderson, R.H., Guo, B., 2020. PFAS Concentrations in Soils: Background Levels versus Contaminated Sites. Science of The Total Environment, 740, Article 140017. [https://doi.org/10.1016/j.scitotenv.2020.140017 doi: 10.1016/j.scitotenv.2020.140017]</ref><ref name="BiglerEtAl2024">Bigler, M.C., Brusseau, M.L., Guo, B., Jones, S.L., Pritchard, J.C., Higgins, C.P., Hatton, J., 2024. High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site. Environmental Science and Technology, 58(22), pp. 9863-9874. [https://doi.org/10.1021/acs.est.4c01615 doi: 10.1021/acs.est.4c01615]</ref>. PFAS recalcitrance in the vadose zone means that environmental program managers and consultants need a cost-effective way of monitoring concentration conditions within the vadose zone. Repeated soil sampling and extraction processes are time consuming and only give a representative concentration of total PFAS in the matrix<ref name="NickersonEtAl2020">Nickerson, A., Maizel, A.C., Kulkarni, P.R., Adamson, D.T., Kornuc, J. J., Higgins, C.P., 2020. Enhanced Extraction of AFFF-Associated PFASs from Source Zone Soils. Environmental Science and Technology, 54(8), pp. 4952-4962. [https://doi.org/10.1021/acs.est.0c00792 doi: 10.1021/acs.est.0c00792]</ref>, not what is readily transportable in mobile porewater<ref name="SchaeferEtAl2023"/><ref name="StultsEtAl2024">Stults, J.F., Schaefer, C.E., Fang, Y., Devon, J., Nguyen, D., Real, I., Hao, S., Guelfo, J.L., 2024. Air-Water Interfacial Collapse and Rate-Limited Solid Desorption Control Perfluoroalkyl Acid Leaching from the Vadose Zone. Journal of Contaminant Hydrology, 265, Article 104382. [https://doi.org/10.1016/j.jconhyd.2024.104382 doi: 10.1016/j.jconhyd.2024.104382]  [[Media: StultsEtAl2024.pdf | Open Access Manuscript]]</ref><ref name="StultsEtAl2023">Stults, J.F., Choi, Y.J., Rockwell, C., Schaefer, C.E., Nguyen, D.D., Knappe, D.R.U., Illangasekare, T.H., Higgins, C.P., 2023. Predicting Concentration- and Ionic-Strength-Dependent Air–Water Interfacial Partitioning Parameters of PFASs Using Quantitative Structure–Property Relationships (QSPRs). Environmental Science and Technology, 57(13), pp. 5203-5215. [https://doi.org/10.1021/acs.est.2c07316 doi: 10.1021/acs.est.2c07316]</ref><ref name="BrusseauGuo2022">Brusseau, M.L., Guo, B., 2022. PFAS Concentrations in Soil versus Soil Porewater: Mass Distributions and the Impact of Adsorption at Air-Water Interfaces. Chemosphere, 302, Article 134938. [https://doi.org/10.1016/j.chemosphere.2022.134938 doi: 10.1016/j.chemosphere.2022.134938]  [[Media: BrusseauGuo2022.pdf | Open Access Manuscript]]</ref>. Fortunately, lysimeters have been found to be a viable option for monitoring the concentration of PFAS in the mobile porewater phase in the vadose zone<ref name="Anderson2021"/><ref name="AndersonEtAl2022"/>. Note that while some lysimeters, known as weighing lysimeters, can directly measure water flux, the most commonly utilized lysimeters in PFAS investigations only provide measurements of porewater concentrations.

==PFAS Background==
PFAS are a broad class of chemicals with highly variable chemical structures<ref>Moody, C.A., Field, J.A., 1999. Determination of Perfluorocarboxylates in Groundwater Impacted by Fire-Fighting Activity. Environmental Science and Technology, 33(16), pp. 2800-2806. [https://doi.org/10.1021/es981355+ doi: 10.1021/es981355+]</ref><ref name="MoodyField2000">Moody, C.A., Field, J.A., 2000. Perfluorinated Surfactants and the Environmental Implications of Their Use in Fire-Fighting Foams. Environmental Science and Technology, 34(18), pp. 3864-3870. [https://doi.org/10.1021/es991359u doi: 10.1021/es991359u]</ref><ref name="GlügeEtAl2020">Glüge, J., Scheringer, M., Cousins, I.T., DeWitt, J.C., Goldenman, G., Herzke, D., Lohmann, R., Ng, C.A., Trier, X., Wang, Z., 2020. An Overview of the Uses of Per- and Polyfluoroalkyl Substances (PFAS). Environmental Science: Processes and Impacts, 22(12), pp. 2345-2373. [https://doi.org/10.1039/D0EM00291G doi: 10.1039/D0EM00291G]  [[Media: GlügeEtAl2020.pdf | Open Access Article]]</ref>. One characteristic feature of PFAS is that they are fluorosurfactants, distinct from more traditional hydrocarbon surfactants<ref name="MoodyField2000"/><ref name="Brusseau2018">Brusseau, M.L., 2018. Assessing the Potential Contributions of Additional Retention Processes to PFAS Retardation in the Subsurface. Science of The Total Environment, 613-614, pp. 176-185. [https://doi.org/10.1016/j.scitotenv.2017.09.065 doi: 10.1016/j.scitotenv.2017.09.065]  [[Media: Brusseau2018.pdf | Open Access Manuscript]]</ref><ref>Dave, N., Joshi, T., 2017. A Concise Review on Surfactants and Its Significance. International Journal of Applied Chemistry, 13(3), pp. 663-672. [https://doi.org/10.37622/IJAC/13.3.2017.663-672 doi: 10.37622/IJAC/13.3.2017.663-672]  [[Media: DaveJoshi2017.pdf | Open Access Article]]</ref><ref>García, R.A., Chiaia-Hernández, A.C., Lara-Martin, P.A., Loos, M., Hollender, J., Oetjen, K., Higgins, C.P., Field, J.A., 2019. Suspect Screening of Hydrocarbon Surfactants in Afffs and Afff-Contaminated Groundwater by High-Resolution Mass Spectrometry. Environmental Science and Technology, 53(14), pp. 8068-8077. [https://doi.org/10.1021/acs.est.9b01895 doi: 10.1021/acs.est.9b01895]</ref>. Fluorosurfactants typically have a fully or partially fluorinated, hydrophobic tail with ionic (cationic, zwitterionic, or anionic) head group that is hydrophilic<ref name="MoodyField2000"/><ref name="GlügeEtAl2020"/>. The hydrophobic tail and ionic head group mean PFAS are very stable at hydrophobic adsorption interfaces when present in the aqueous phase<ref>Krafft, M.P., Riess, J.G., 2015. Per- and Polyfluorinated Substances (PFASs): Environmental Challenges. Current Opinion in Colloid and Interface Science, 20(3), pp. 192-212. [https://doi.org/10.1016/j.cocis.2015.07.004 doi: 10.1016/j.cocis.2015.07.004]</ref>. Examples of these interfaces include naturally occurring organic matter in soils and the air-water interface in the vadose zone<ref>Schaefer, C.E., Culina, V., Nguyen, D., Field, J., 2019. Uptake of Poly- and Perfluoroalkyl Substances at the Air–Water Interface. Environmental Science and Technology, 53(21), pp. 12442-12448. [https://doi.org/10.1021/acs.est.9b04008 doi: 10.1021/acs.est.9b04008]</ref><ref>Lyu, Y., Brusseau, M.L., Chen, W., Yan, N., Fu, X., Lin, X., 2018. Adsorption of PFOA at the Air–Water Interface during Transport in Unsaturated Porous Media. Environmental Science and Technology, 52(14), pp. 7745-7753. [https://doi.org/10.1021/acs.est.8b02348 doi: 10.1021/acs.est.8b02348]</ref><ref>Costanza, J., Arshadi, M., Abriola, L.M., Pennell, K.D., 2019. Accumulation of PFOA and PFOS at the Air-Water Interface. Environmental Science and Technology Letters, 6(8), pp. 487-491. [https://doi.org/10.1021/acs.estlett.9b00355 doi: 10.1021/acs.estlett.9b00355]</ref><ref>Li, F., Fang, X., Zhou, Z., Liao, X., Zou, J., Yuan, B., Sun, W., 2019. Adsorption of Perfluorinated Acids onto Soils: Kinetics, Isotherms, and Influences of Soil Properties. Science of The Total Environment, 649, pp. 504-514. [https://doi.org/10.1016/j.scitotenv.2018.08.209 doi: 10.1016/j.scitotenv.2018.08.209]</ref><ref>Nguyen, T.M.H., Bräunig, J., Thompson, K., Thompson, J., Kabiri, S., Navarro, D.A., Kookana, R.S., Grimison, C., Barnes, C.M., Higgins, C.P., McLaughlin, M.J., Mueller, J.F., 2020. Influences of Chemical Properties, Soil Properties, and Solution pH on Soil–Water Partitioning Coefficients of Per- and Polyfluoroalkyl Substances (PFASs). Environmental Science and Technology, 54(24), pp. 15883-15892. [https://doi.org/10.1021/acs.est.0c05705 doi: 10.1021/acs.est.0c05705]  [[Media: NguyenEtAl2020.pdf | Open Access Article]]</ref>. Their strong adsorption to both soil organic matter and the air-water interface is a major contributor to elevated concentrations of PFAS observed in the upper 5 feet of the soil column<ref name="BrusseauEtAl2020"/><ref name="BiglerEtAl2024"/>. While several other PFAS partitioning processes exist<ref name="Brusseau2018"/>, adsorption to solid phase soils and air-water interfaces are the two primary processes present at nearly all PFAS sites<ref>Brusseau, M.L., Yan, N., Van Glubt, S., Wang, Y., Chen, W., Lyu, Y., Dungan, B., Carroll, K.C., Holguin, F.O., 2019. Comprehensive Retention Model for PFAS Transport in Subsurface Systems. Water Research, 148, pp. 41-50. [https://doi.org/10.1016/j.watres.2018.10.035 doi: 10.1016/j.watres.2018.10.035]</ref>. The total PFAS mass obtained from a vadose zone soil sample contains the solid phase, air-water interfacial, and aqueous phase PFAS mass, which can be converted to porewater concentrations using Equation 1<ref name="BrusseauGuo2022"/>.
:: <big>'''Equation 1:'''</big>   [[File: StultsEq1.png | 400 px]]
Where ''Cp'' is the porewater concentration, ''Ct'' is the total PFAS concentration, ''ρb'' is the bulk density of the soil, ''θw'' is the volumetric water content, ''Rd'' is the PFAS retardation factor, ''Kd'' is the solid phase adsorption coefficient, ''Kia'' is the air-water interfacial adsorption coefficient, and ''Aaw'' is the air-water interfacial area. The air-water interfacial area of the soil is primarily a function of both the soil properties and the degree of volumetric water saturation in the soil. There are several methods of estimating air-water interfacial areas including thermodynamic functions based on the soil moisture retention curve. However, the thermodynamic function has been shown to underestimate air-water interfacial area<ref name="Brusseau2023">Brusseau, M.L., 2023. Determining Air-Water Interfacial Areas for the Retention and Transport of PFAS and Other Interfacially Active Solutes in Unsaturated Porous Media. Science of The Total Environment, 884, Article 163730. [https://doi.org/10.1016/j.scitotenv.2023.163730 doi: 10.1016/j.scitotenv.2023.163730]  [[Media: Brusseau2023.pdf | Open Access Article]]</ref>, and must typically be scaled using empirical scaling factors. An empirical method recently developed to estimate air-water interfacial area is presented in Equation 2<ref name="Brusseau2023"/>.
:: <big>'''Equation 2:'''</big>   [[File: StultsEq2.png | 400 px]]
Where ''Sw'' is the water phase saturation as a ratio of the water content over the volumetric soil porosity, and ''d50'' is the median grain diameter.

==Lysimeters Background==
[[File: StultsFig1.png |thumb|600 px|Figure 1. (a) A field suction lysimeter with labeled parts typically used in field settings – Credit: Bibek Acharya and Dr. Vivek Sharma, UF/IFAS, https://edis.ifas.ufl.edu/publication/AE581. (b) Laboratory suction lysimeters used in Schaefer ''et al.'' 2024<ref name="SchaeferEtAl2024"/>, which employed the use of micro-sampling suction lysimeters. (c) A field lysimeter used in Schaefer ''et al.'' 2023<ref name="SchaeferEtAl2023"/>. (d) Diagram of a drainage wicking lysimeter – Credit: Edaphic Scientific, https://edaphic.com.au/products/water/lysimeter-wick-for-drainage/]]
Lysimeters, generally speaking, refer to instruments which collect water from unsaturated soils<ref name="MeissnerEtAl2020"/><ref name="RogersMcConnell1993"/>. However, there are multiple types of lysimeters which can be employed in field or laboratory settings. There are three primary types of lysimeters relevant to PFAS listed here and shown in Figure 1a-d.
# Suction Lysimeters (Figure 1a,b): These lysimeters are the most relevant for PFAS sampling and are the majority of discussion in this article. These lysimeters operate by extracting liquid from the unsaturated vadose zone by applying negative suction pressure at the sampling head<ref name="CostanzaEtAl2025"/><ref name="SchaeferEtAl2024"/><ref name="QuinnanEtAl2021"/>. The sampling head is typically constructed of porous ceramic or stainless steel. A PVC case or stainless-steel case is attached to the sampling head and extends upward above the ground surface. Suction lysimeters are typically installed between 1 and 9 feet below ground surface, but can extend as deep as 40-60 feet in some cases<ref name="CostanzaEtAl2025"/>. Shallow lysimeters (< 10 feet) are typically installed using a hand auger. For ceramic lysimeters, a silica flour slurry should be placed at the base of the bore hole and allowed to cover the ceramic head before backfilling the hole partially with natural soil. Once the hole is partially backfilled with soil to cover the sampling head, the remainder of the casing should be sealed with hydrated bentonite chips. When sampling events occur, suction is applied at the ground surface using a rubber gasket seal and a hand pump or electric pump. After sufficient porewater is collected (the time for which can vary greatly based on the soil permeability and moisture content), the seal can be removed and a peristaltic pump used to extract liquid from the lysimeter.
# Field Lysimeters (Figure 1c): These large lysimeters can be constructed from plastic or metal sidings. They can range from approximately 2 feet in diameter to as large as several meters in diameter<ref name="MeissnerEtAl2020"/>. Instrumentation such as soil moisture probes and tensiometers, or even multiple suction lysimeters, are typically placed throughout the lysimeter to measure the movement of water and determine characteristic soil moisture release curves<ref name="Stannard1992"/><ref name="WintonWeber1996"/><ref name="SchaeferEtAl2023"/><ref name="SchaeferEtAl2022"/><ref>van Genuchten, M.Th. , 1980. A Closed‐form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Science Society of America Journal, 44(5), pp. 892-898. [https://doi.org/10.2136/sssaj1980.03615995004400050002x doi: 10.2136/sssaj1980.03615995004400050002x]</ref>. Water is typically collected at the base of the field lysimeter to determine net recharge through the system. These field lysimeters are intended to represent more realistic, intermediate scale conditions of field systems.
# Drainage Lysimeters (Figure 1d): Also known as a “wick” lysimeter, these lysimeters typically consist of a hollow cup attached to a spout which protrudes above ground to relieve air pressure from the system and act as a sampling port. The hollow cup typically has filters and wicking devices at the base to collect water from the soil. The cup is filled with natural soil and collects water as it percolates through the vadose zone. These lysimeters are used to directly monitor net recharge from the vadose zone to the groundwater table and could be useful in determining PFAS mass flux.

==Analysis of PFAS Concentrations in Soil and Porewater==
{| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;"
|+Table 1. Measured and Predicted PFAS Concentrations in Porewater for Select PFAS in Three Different Soils
|-
!Site
!PFAS
!FieldPorewaterConcentration(μg/L)
!Lab CorePorewaterConcentration(μg/L)
!PredictedPorewaterConcentration(μg/L)
|-
|Site A||PFOS||6.2 ± 3.4||3.0 ± 0.37||6.6 ± 3.3
|-
|Site B||PFOS||2.2 ± 2.0||0.78 ± 0.38||2.8
|-
|rowspan="3"|Site C||PFOS||13 ± 4.1||680 ± 460||164 ± 75
|-
|8:2 FTS||1.2 ± 0.46||52 ± 13||16 ± 6.0
|-
|PFHpS||0.36 ± 0.051||2.9 ± 2.0||5.9 ± 3.4
|}
[[File: StultsFig2.png | thumb | 600 px | Figure 2. Field Measured PFAS concentration Data (Orange) and Lab Core Measured Concentration Data (Blue) for four PFAS impacted sites<ref name="AndersonEtAl2022"/>]]
[[File: StultsFig3.png | thumb | 400 px | Figure 3. Measured and predicted data for PFAS concentrations from a single site field lysimeter study. Model predictions both with and without PFAS sorption to the air-water interface were considered<ref name="SchaeferEtAl2023"/>.]]
Schaefer ''et al.''<ref name="SchaeferEtAl2024"/> measured PFAS porewater concentrations with field and laboratory suction lysimeters across several sites. Intact cores from the site were collected for soil water extraction using laboratory lysimeters. The lysimeters were used to directly compare field derived measurements of PFAS concentration in the mobile porewater phase. Results from measurements are for four sites presented in Figure 2.

Data from sites A and B showed reasonably good agreement (within ½ order of magnitude) for most PFAS measured in the systems. At site C, more hydrophobic constituents (> C6 PFAS) tended to have higher concentrations in the lab core than the field site while less hydrophobic constituents (< C6) had higher concentrations in the field than lab cores. Site D showed substantially greater (1 order of magnitude or more) PFAS concentrations measured in the laboratory-collected porewater sample compared to what was measured in the field lysimeters. This discrepancy for the Site D soil can likely be attributed to soil heterogeneity (as indicated by ground penetrating radar) and the fact that the soil consisted of back-filled materials rather than undisturbed native soils.

Site C showed elevated PFAS concentrations in the laboratory collected porewater for the more surface-active compounds. This increase was attributed to the soil wetting that occurred at the bench scale, which was reasonably described by the model shown in Equations 1 and 2 (see Table 1<ref name="AndersonEtAl2022"/>). Equations 1 and 2 were also used to predict PFAS porewater concentrations (using porous cup lysimeters) in a highly instrumented test cell<ref name="SchaeferEtAl2023"/>(Figure 3). The ability to predict soil concentrations from recurring porewater samples is critical to the practical application of lysimeters in field settings<ref name="AndersonEtAl2022"/>.

Results from suction lysimeters studies and field lysimeter studies show that PFAS concentrations in porewater predicted from soil concentrations using Equations 1 and 2 generally have reasonable agreement with measured ''in situ'' porewater data when air-water interfacial partitioning is considered. Results show that for less hydrophobic components like PFOA, the impact of air-water interfacial adsorption is less significant than for highly hydrophobic components like PFOS. The soil for the field lysimeter in Figure 3 was a sandy soil with a relatively low air-water interfacial area. The effect of air-water interfacial partitioning is expected to be much more significant for a greater range of PFAS in soils with high capillary pressure (i.e. silts/clays) with higher associated air-water interfacial areas<ref name="Brusseau2023"/><ref>Peng, S., Brusseau, M.L., 2012. Air-Water Interfacial Area and Capillary Pressure: Porous-Medium Texture Effects and an Empirical Function. Journal of Hydrologic Engineering, 17(7), pp. 829-832. [https://doi.org/10.1061/(asce)he.1943-5584.0000515 doi: 10.1061/(asce)he.1943-5584.0000515]</ref><ref>Brusseau, M.L., Peng, S., Schnaar, G., Costanza-Robinson, M.S., 2006. Relationships among Air-Water Interfacial Area, Capillary Pressure, and Water Saturation for a Sandy Porous Medium. Water Resources Research, 42(3), Article W03501, 5 pages. [https://doi.org/10.1029/2005WR004058 doi: 10.1029/2005WR004058]  [[Media: BrusseauEtAl2006.pdf | Free Access Article]]</ref>.

==Summary and Recommendations==
The majority of research with lysimeters for PFAS site investigations has been done using porous cup suction lysimeters<ref name="CostanzaEtAl2025"/><ref name="AndersonEtAl2022"/><ref name="SchaeferEtAl2024"/><ref name="QuinnanEtAl2021"/>. Porous cup suction lysimeters are advantageous because they can be routinely sampled or sampled after specific wetting or drying events much like groundwater wells. This sampling is easier and more efficient than routinely collecting soil samples from the same locations. Co-locating lysimeters with soil samples is important for establishing the baseline soil concentration levels at the lysimeter location and developing correlations between the soil concentrations and the mobile porewater concentration<ref name="CostanzaEtAl2025"/>. Appropriate standard operation procedures for lysimeter installation and operation have been established and have been reviewed in recent literature<ref name="CostanzaEtAl2025"/><ref name="SchaeferEtAl2024"/>. Lysimeters should typically be installed near the source area and just above the maximum groundwater level elevation to obtain accurate results of porewater concentrations year round. Depending upon the geology and vertical PFAS distribution in the soil, multilevel lysimeter installations should also be considered.

Results from several lysimeters studies across multiple field sites and modelling analysis has shown that lysimeters can produce reasonable results between field and laboratory studies<ref name="SchaeferEtAl2024"/><ref name="SchaeferEtAl2023"/><ref name="SchaeferEtAl2022"/>. Transient effects of wetting and drying as well as media heterogeneity affects appear to be responsible for some variability and uncertainty in lysimeter based PFAS measurements in the vadose zone. These mobile porewater concentrations can be coupled with effective recharge estimates and simplified modelling approaches to determine mass flux from the vadose zone to the underlying groundwater<ref name="Anderson2021"/><ref name="StultsEtAl2024"/><ref name="BrusseauGuo2022"/><ref>Stults, J.F., Schaefer, C.E., MacBeth, T., Fang, Y., Devon, J., Real, I., Liu, F., Kosson, D., Guelfo, J.L., 2025. Laboratory Validation of a Simplified Model for Estimating Equilibrium PFAS Mass Leaching from Unsaturated Soils. Science of The Total Environment, 970, Article 179036. [https://doi.org/10.1016/j.scitotenv.2025.179036 doi: 10.1016/j.scitotenv.2025.179036]</ref><ref>Smith, J. Brusseau, M.L., Guo, B., 2024. An Integrated Analytical Modeling Framework for Determining Site-Specific Soil Screening Levels for PFAS. Water Research, 252, Article121236. [https://doi.org/10.1016/j.watres.2024.121236 doi: 10.1016/j.watres.2024.121236]</ref>.

Future research opportunities should address the current key uncertainties related to the use of lysimeters for PFAS investigations, including:
#Collect larger datasets of PFAS concentrations to determine how transient wetting or drying periods and media type affect PFAS concentrations in the mobile porewater. Some research has shown that non-equilibrium processes can occur in the vadose zone, which can affect grab sample concentration in the porewater at specific time periods.
#More work should be done with flux averaging lysimeters like the drainage cup or wicking lysimeter. These lysimeters can directly measure net recharge and provide time averaged concentrations of PFAS in water over the sampling period. However, there is little work detailing their potential applications in PFAS research, or operational considerations for their use in remedial investigations for PFAS.
#Lysimeters should be coupled with monitoring of wetting and drying in the vadose zone using ''in situ'' soil moisture sensors or tensiometers and groundwater levels. Direct measurements of soil saturation at field sites are vital to directly correlate porewater concentrations with soil concentrations. Similarly, groundwater level fluctuations can inform net recharge estimates. By collecting these data we can continue to improve partitioning and leaching models which can relate porewater concentrations to total PFAS mass in soils and PFAS leaching at field sites.
#Comparisons of various bench-scale leaching or desorption tests to field-based lysimeter data are recommended. The ability to correlate field measurements of PFAS concentrations with estimates of leaching from laboratory studies would provide a powerful method to empirically estimate PFAS leaching from field sites.

==References==
<references />

==See Also==

Lysimeters for Measuring PFAS Concentrations in the Vadose Zone

2026-01-20T18:02:05Z

Debra Tabron:

[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | PFAS]] are frequently introduced to the environment through soil surface applications which then transport through the vadose zone to reach underlying groundwater receptors. Due to their unique properties and resulting transport and retention behaviors, PFAS in the vadose zone can be a persistent contaminant source to underlying groundwater systems. Determining the fraction of PFAS present in the mobile porewater relative to the total concentrations in soils is critical to understanding the risk posed by PFAS in vadose zone source areas. Lysimeters are instruments that have been used by agronomists and vadose zone researchers for decades to determine water flux and solute concentrations in unsaturated porewater. Lysimeters have recently been developed as a critical tool for field investigations and characterizations of PFAS impacted source zones.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Transport and Fate]]
*[[PFAS Toxicology and Risk Assessment]]
*[[Mass Flux and Mass Discharge]]

'''Contributors:''' [Dr. John F. Stults] and [Dr. Charles Schaefer]

'''Key Resources:'''
*Assessment of PFAS in Collocated Soil and Porewater Samples at an AFFF-Impacted Source Zone: Field-Scale Validation of Suction Lysimeters<ref name="AndersonEtAl2022"/>
*PFAS Concentrations in Soil versus Soil Porewater: Mass Distributions and the Impact of Adsorption at Air-Water Interfaces<ref name="BrusseauGuo2022"/>
*Using Suction Lysimeters for Determining the Potential of Per- and Polyfluoroalkyl Substances to Leach from Soil to Groundwater: A Review<ref name="CostanzaEtAl2025"/>
*Use of Lysimeters for Monitoring Soil Water Balance Parameters and Nutrient Leaching<ref name="MeissnerEtAl2020"/>
*PFAS Porewater Concentrations in Unsaturated Soil: Field and Laboratory Comparisons Inform on PFAS Accumulation at Air-Water Interfaces<ref name="SchaeferEtAl2024"/>

==Introduction==
Lysimeters are devices that are placed in the subsurface above the groundwater table to monitor the movement of water through the soil<ref name="GossEhlers2009">Goss, M.J., Ehlers, W., 2009. The Role of Lysimeters in the Development of Our Understanding of Soil Water and Nutrient Dynamics in Ecosystems. Soil Use and Management, 25(3), pp. 213–223. [https://doi.org/10.1111/j.1475-2743.2009.00230.x doi: 10.1111/j.1475-2743.2009.00230.x]</ref><ref>Pütz, T., Fank, J., Flury, M., 2018. Lysimeters in Vadose Zone Research. Vadose Zone Journal, 17 (1), pp. 1-4. [https://doi.org/10.2136/vzj2018.02.0035 doi: 10.2136/vzj2018.02.0035]  [[Media: PutzEtAl2018.pdf | Open Access Article]]</ref><ref name="CostanzaEtAl2025">Costanza, J., Clabaugh, C.D., Leibli, C., Ferreira, J., Wilkin, R.T., 2025. Using Suction Lysimeters for Determining the Potential of Per- and Polyfluoroalkyl Substances to Leach from Soil to Groundwater: A Review. Environmental Science and Technology, 59(9), pp. 4215-4229. [https://doi.org/10.1021/acs.est.4c10246 doi: 10.1021/acs.est.4c10246]</ref>. Lysimeters have historically been used in agricultural sciences for monitoring nutrient or contaminant movement, soil moisture release curves, natural drainage patterns, and dynamics of plant-water interactions<ref name="GossEhlers2009"/><ref>Bergström, L., 1990. Use of Lysimeters to Estimate Leaching of Pesticides in Agricultural Soils. Environmental Pollution, 67 (4), 325–347. [https://doi.org/10.1016/0269-7491(90)90070-S doi: 10.1016/0269-7491(90)90070-S]</ref><ref>Dabrowska, D., Rykala, W., 2021. A Review of Lysimeter Experiments Carried Out on Municipal Landfill Waste. Toxics, 9(2), Article 26. [https://doi.org/10.3390/toxics9020026 doi: 10.3390/toxics9020026]  [[Media: Dabrowska Rykala2021.pdf | Open Access Article]]</ref><ref>Fernando, S.U., Galagedara, L., Krishnapillai, M., Cuss, C.W., 2023. Lysimeter Sampling System for Optimal Determination of Trace Elements in Soil Solutions. Water, 15(18), Article 3277. [https://doi.org/10.3390/w15183277 doi: 10.3390/w15183277]  [[Media: FernandoEtAl2023.pdf | Open Access Article]]</ref><ref name="MeissnerEtAl2020">Meissner, R., Rupp, H., Haselow, L., 2020. Use of Lysimeters for Monitoring Soil Water Balance Parameters and Nutrient Leaching. In: Climate Change and Soil Interactions. Elsevier, pp. 171-205. [https://doi.org/10.1016/B978-0-12-818032-7.00007-2 doi: 10.1016/B978-0-12-818032-7.00007-2]</ref><ref name="RogersMcConnell1993">Rogers, R.D., McConnell, J.W. Jr., 1993. Lysimeter Literature Review, Nuclear Regulatory Commission Report Numbers: NUREG/CR--6073, EGG--2706. [https://www.osti.gov/] ID: 10183270. [https://doi.org/10.2172/10183270 doi: 10.2172/10183270]  [[Media: RogersMcConnell1993.pdf | Open Access Article]]</ref><ref>Sołtysiak, M., Rakoczy, M., 2019. An Overview of the Experimental Research Use of Lysimeters. Environmental and Socio-Economic Studies, 7(2), pp. 49-56. [https://doi.org/10.2478/environ-2019-0012 doi: 10.2478/environ-2019-0012]  [[Media: SołtysiakRakoczy2019.pdf | Open Access Article]]</ref><ref name="Stannard1992">Stannard, D.I., 1992. Tensiometers—Theory, Construction, and Use. Geotechnical Testing Journal, 15(1), pp. 48-58. [https://doi.org/10.1520/GTJ10224J doi: 10.1520/GTJ10224J]</ref><ref name="WintonWeber1996">Winton, K., Weber, J.B., 1996. A Review of Field Lysimeter Studies to Describe the Environmental Fate of Pesticides. Weed Technology, 10(1), pp. 202-209. [https://doi.org/10.1017/S0890037X00045929 doi: 10.1017/S0890037X00045929]</ref>. Recently, there has been strong interest in the use of lysimeters to measure and monitor movement of per- and polyfluoroalkyl substances (PFAS) through the vadose zone<ref name="Anderson2021">Anderson, R.H., 2021. The Case for Direct Measures of Soil-to-Groundwater Contaminant Mass Discharge at AFFF-Impacted Sites. Environmental Science and Technology, 55(10), pp. 6580-6583. [https://doi.org/10.1021/acs.est.1c01543 doi: 10.1021/acs.est.1c01543]</ref><ref name="AndersonEtAl2022">Anderson, R.H., Feild, J.B., Dieffenbach-Carle, H., Elsharnouby, O., Krebs, R.K., 2022. Assessment of PFAS in Collocated Soil and Porewater Samples at an AFFF-Impacted Source Zone: Field-Scale Validation of Suction Lysimeters. Chemosphere, 308(1), Article 136247. [https://doi.org/10.1016/j.chemosphere.2022.136247 doi: 10.1016/j.chemosphere.2022.136247]</ref><ref name="SchaeferEtAl2024">Schaefer, C.E., Nguyen, D., Fang, Y., Gonda, N., Zhang, C., Shea, S., Higgins, C.P., 2024. PFAS Porewater Concentrations in Unsaturated Soil: Field and Laboratory Comparisons Inform on PFAS Accumulation at Air-Water Interfaces. Journal of Contaminant Hydrology, 264, Article 104359. [https://doi.org/10.1016/j.jconhyd.2024.104359 doi: 10.1016/j.jconhyd.2024.104359]  [[Media: SchaeferEtAl2024.pdf | Open Access Manuscript]]</ref><ref name="SchaeferEtAl2023">Schaefer, C.E., Lavorgna, G.M., Lippincott, D.R., Nguyen, D., Schaum, A., Higgins, C.P., Field, J., 2023. Leaching of Perfluoroalkyl Acids During Unsaturated Zone Flushing at a Field Site Impacted with Aqueous Film Forming Foam. Environmental Science and Technology, 57(5), pp. 1940-1948. [https://doi.org/10.1021/acs.est.2c06903 doi: 10.1021/acs.est.2c06903]</ref><ref name="SchaeferEtAl2022">Schaefer, C.E., Lavorgna, G.M., Lippincott, D.R., Nguyen, D., Christie, E., Shea, S., O’Hare, S., Lemes, M.C.S., Higgins, C.P., Field, J., 2022. A Field Study to Assess the Role of Air-Water Interfacial Sorption on PFAS Leaching in an AFFF Source Area. Journal of Contaminant Hydrology, 248, Article 104001. [https://doi.org/10.1016/j.jconhyd.2022.104001 doi: 10.1016/j.jconhyd.2022.104001]  [[Media: SchaeferEtAl2022.pdf | Open Access Manuscript]]</ref><ref name="QuinnanEtAl2021">Quinnan, J., Rossi, M., Curry, P., Lupo, M., Miller, M., Korb, H., Orth, C., Hasbrouck, K., 2021. Application of PFAS-Mobile Lab to Support Adaptive Characterization and Flux-Based Conceptual Site Models at AFFF Releases. Remediation, 31(3), pp. 7-26. [https://doi.org/10.1002/rem.21680 doi: 10.1002/rem.21680]</ref>. PFAS are frequently introduced to the environment through land surface application and have been found to be strongly retained within the upper 5 feet of soil<ref name="BrusseauEtAl2020">Brusseau, M.L., Anderson, R.H., Guo, B., 2020. PFAS Concentrations in Soils: Background Levels versus Contaminated Sites. Science of The Total Environment, 740, Article 140017. [https://doi.org/10.1016/j.scitotenv.2020.140017 doi: 10.1016/j.scitotenv.2020.140017]</ref><ref name="BiglerEtAl2024">Bigler, M.C., Brusseau, M.L., Guo, B., Jones, S.L., Pritchard, J.C., Higgins, C.P., Hatton, J., 2024. High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site. Environmental Science and Technology, 58(22), pp. 9863-9874. [https://doi.org/10.1021/acs.est.4c01615 doi: 10.1021/acs.est.4c01615]</ref>. PFAS recalcitrance in the vadose zone means that environmental program managers and consultants need a cost-effective way of monitoring concentration conditions within the vadose zone. Repeated soil sampling and extraction processes are time consuming and only give a representative concentration of total PFAS in the matrix<ref name="NickersonEtAl2020">Nickerson, A., Maizel, A.C., Kulkarni, P.R., Adamson, D.T., Kornuc, J. J., Higgins, C.P., 2020. Enhanced Extraction of AFFF-Associated PFASs from Source Zone Soils. Environmental Science and Technology, 54(8), pp. 4952-4962. [https://doi.org/10.1021/acs.est.0c00792 doi: 10.1021/acs.est.0c00792]</ref>, not what is readily transportable in mobile porewater<ref name="SchaeferEtAl2023"/><ref name="StultsEtAl2024">Stults, J.F., Schaefer, C.E., Fang, Y., Devon, J., Nguyen, D., Real, I., Hao, S., Guelfo, J.L., 2024. Air-Water Interfacial Collapse and Rate-Limited Solid Desorption Control Perfluoroalkyl Acid Leaching from the Vadose Zone. Journal of Contaminant Hydrology, 265, Article 104382. [https://doi.org/10.1016/j.jconhyd.2024.104382 doi: 10.1016/j.jconhyd.2024.104382]  [[Media: StultsEtAl2024.pdf | Open Access Manuscript]]</ref><ref name="StultsEtAl2023">Stults, J.F., Choi, Y.J., Rockwell, C., Schaefer, C.E., Nguyen, D.D., Knappe, D.R.U., Illangasekare, T.H., Higgins, C.P., 2023. Predicting Concentration- and Ionic-Strength-Dependent Air–Water Interfacial Partitioning Parameters of PFASs Using Quantitative Structure–Property Relationships (QSPRs). Environmental Science and Technology, 57(13), pp. 5203-5215. [https://doi.org/10.1021/acs.est.2c07316 doi: 10.1021/acs.est.2c07316]</ref><ref name="BrusseauGuo2022">Brusseau, M.L., Guo, B., 2022. PFAS Concentrations in Soil versus Soil Porewater: Mass Distributions and the Impact of Adsorption at Air-Water Interfaces. Chemosphere, 302, Article 134938. [https://doi.org/10.1016/j.chemosphere.2022.134938 doi: 10.1016/j.chemosphere.2022.134938]  [[Media: BrusseauGuo2022.pdf | Open Access Manuscript]]</ref>. Fortunately, lysimeters have been found to be a viable option for monitoring the concentration of PFAS in the mobile porewater phase in the vadose zone<ref name="Anderson2021"/><ref name="AndersonEtAl2022"/>. Note that while some lysimeters, known as weighing lysimeters, can directly measure water flux, the most commonly utilized lysimeters in PFAS investigations only provide measurements of porewater concentrations.

==PFAS Background==
PFAS are a broad class of chemicals with highly variable chemical structures<ref>Moody, C.A., Field, J.A., 1999. Determination of Perfluorocarboxylates in Groundwater Impacted by Fire-Fighting Activity. Environmental Science and Technology, 33(16), pp. 2800-2806. [https://doi.org/10.1021/es981355+ doi: 10.1021/es981355+]</ref><ref name="MoodyField2000">Moody, C.A., Field, J.A., 2000. Perfluorinated Surfactants and the Environmental Implications of Their Use in Fire-Fighting Foams. Environmental Science and Technology, 34(18), pp. 3864-3870. [https://doi.org/10.1021/es991359u doi: 10.1021/es991359u]</ref><ref name="GlügeEtAl2020">Glüge, J., Scheringer, M., Cousins, I.T., DeWitt, J.C., Goldenman, G., Herzke, D., Lohmann, R., Ng, C.A., Trier, X., Wang, Z., 2020. An Overview of the Uses of Per- and Polyfluoroalkyl Substances (PFAS). Environmental Science: Processes and Impacts, 22(12), pp. 2345-2373. [https://doi.org/10.1039/D0EM00291G doi: 10.1039/D0EM00291G]  [[Media: GlügeEtAl2020.pdf | Open Access Article]]</ref>. One characteristic feature of PFAS is that they are fluorosurfactants, distinct from more traditional hydrocarbon surfactants<ref name="MoodyField2000"/><ref name="Brusseau2018">Brusseau, M.L., 2018. Assessing the Potential Contributions of Additional Retention Processes to PFAS Retardation in the Subsurface. Science of The Total Environment, 613-614, pp. 176-185. [https://doi.org/10.1016/j.scitotenv.2017.09.065 doi: 10.1016/j.scitotenv.2017.09.065]  [[Media: Brusseau2018.pdf | Open Access Manuscript]]</ref><ref>Dave, N., Joshi, T., 2017. A Concise Review on Surfactants and Its Significance. International Journal of Applied Chemistry, 13(3), pp. 663-672. [https://doi.org/10.37622/IJAC/13.3.2017.663-672 doi: 10.37622/IJAC/13.3.2017.663-672]  [[Media: DaveJoshi2017.pdf | Open Access Article]]</ref><ref>García, R.A., Chiaia-Hernández, A.C., Lara-Martin, P.A., Loos, M., Hollender, J., Oetjen, K., Higgins, C.P., Field, J.A., 2019. Suspect Screening of Hydrocarbon Surfactants in Afffs and Afff-Contaminated Groundwater by High-Resolution Mass Spectrometry. Environmental Science and Technology, 53(14), pp. 8068-8077. [https://doi.org/10.1021/acs.est.9b01895 doi: 10.1021/acs.est.9b01895]</ref>. Fluorosurfactants typically have a fully or partially fluorinated, hydrophobic tail with ionic (cationic, zwitterionic, or anionic) head group that is hydrophilic<ref name="MoodyField2000"/><ref name="GlügeEtAl2020"/>. The hydrophobic tail and ionic head group mean PFAS are very stable at hydrophobic adsorption interfaces when present in the aqueous phase<ref>Krafft, M.P., Riess, J.G., 2015. Per- and Polyfluorinated Substances (PFASs): Environmental Challenges. Current Opinion in Colloid and Interface Science, 20(3), pp. 192-212. [https://doi.org/10.1016/j.cocis.2015.07.004 doi: 10.1016/j.cocis.2015.07.004]</ref>. Examples of these interfaces include naturally occurring organic matter in soils and the air-water interface in the vadose zone<ref>Schaefer, C.E., Culina, V., Nguyen, D., Field, J., 2019. Uptake of Poly- and Perfluoroalkyl Substances at the Air–Water Interface. Environmental Science and Technology, 53(21), pp. 12442-12448. [https://doi.org/10.1021/acs.est.9b04008 doi: 10.1021/acs.est.9b04008]</ref><ref>Lyu, Y., Brusseau, M.L., Chen, W., Yan, N., Fu, X., Lin, X., 2018. Adsorption of PFOA at the Air–Water Interface during Transport in Unsaturated Porous Media. Environmental Science and Technology, 52(14), pp. 7745-7753. [https://doi.org/10.1021/acs.est.8b02348 doi: 10.1021/acs.est.8b02348]</ref><ref>Costanza, J., Arshadi, M., Abriola, L.M., Pennell, K.D., 2019. Accumulation of PFOA and PFOS at the Air-Water Interface. Environmental Science and Technology Letters, 6(8), pp. 487-491. [https://doi.org/10.1021/acs.estlett.9b00355 doi: 10.1021/acs.estlett.9b00355]</ref><ref>Li, F., Fang, X., Zhou, Z., Liao, X., Zou, J., Yuan, B., Sun, W., 2019. Adsorption of Perfluorinated Acids onto Soils: Kinetics, Isotherms, and Influences of Soil Properties. Science of The Total Environment, 649, pp. 504-514. [https://doi.org/10.1016/j.scitotenv.2018.08.209 doi: 10.1016/j.scitotenv.2018.08.209]</ref><ref>Nguyen, T.M.H., Bräunig, J., Thompson, K., Thompson, J., Kabiri, S., Navarro, D.A., Kookana, R.S., Grimison, C., Barnes, C.M., Higgins, C.P., McLaughlin, M.J., Mueller, J.F., 2020. Influences of Chemical Properties, Soil Properties, and Solution pH on Soil–Water Partitioning Coefficients of Per- and Polyfluoroalkyl Substances (PFASs). Environmental Science and Technology, 54(24), pp. 15883-15892. [https://doi.org/10.1021/acs.est.0c05705 doi: 10.1021/acs.est.0c05705]  [[Media: NguyenEtAl2020.pdf | Open Access Article]]</ref>. Their strong adsorption to both soil organic matter and the air-water interface is a major contributor to elevated concentrations of PFAS observed in the upper 5 feet of the soil column<ref name="BrusseauEtAl2020"/><ref name="BiglerEtAl2024"/>. While several other PFAS partitioning processes exist<ref name="Brusseau2018"/>, adsorption to solid phase soils and air-water interfaces are the two primary processes present at nearly all PFAS sites<ref>Brusseau, M.L., Yan, N., Van Glubt, S., Wang, Y., Chen, W., Lyu, Y., Dungan, B., Carroll, K.C., Holguin, F.O., 2019. Comprehensive Retention Model for PFAS Transport in Subsurface Systems. Water Research, 148, pp. 41-50. [https://doi.org/10.1016/j.watres.2018.10.035 doi: 10.1016/j.watres.2018.10.035]</ref>. The total PFAS mass obtained from a vadose zone soil sample contains the solid phase, air-water interfacial, and aqueous phase PFAS mass, which can be converted to porewater concentrations using Equation 1<ref name="BrusseauGuo2022"/>.
:: <big>'''Equation 1:'''</big>   [[File: StultsEq1.png | 400 px]]
Where ''Cp'' is the porewater concentration, ''Ct'' is the total PFAS concentration, ''ρb'' is the bulk density of the soil, ''θw'' is the volumetric water content, ''Rd'' is the PFAS retardation factor, ''Kd'' is the solid phase adsorption coefficient, ''Kia'' is the air-water interfacial adsorption coefficient, and ''Aaw'' is the air-water interfacial area. The air-water interfacial area of the soil is primarily a function of both the soil properties and the degree of volumetric water saturation in the soil. There are several methods of estimating air-water interfacial areas including thermodynamic functions based on the soil moisture retention curve. However, the thermodynamic function has been shown to underestimate air-water interfacial area<ref name="Brusseau2023">Brusseau, M.L., 2023. Determining Air-Water Interfacial Areas for the Retention and Transport of PFAS and Other Interfacially Active Solutes in Unsaturated Porous Media. Science of The Total Environment, 884, Article 163730. [https://doi.org/10.1016/j.scitotenv.2023.163730 doi: 10.1016/j.scitotenv.2023.163730]  [[Media: Brusseau2023.pdf | Open Access Article]]</ref>, and must typically be scaled using empirical scaling factors. An empirical method recently developed to estimate air-water interfacial area is presented in Equation 2<ref name="Brusseau2023"/>.
:: <big>'''Equation 2:'''</big>   [[File: StultsEq2.png | 400 px]]
Where ''Sw'' is the water phase saturation as a ratio of the water content over the volumetric soil porosity, and ''d50'' is the median grain diameter.

==Lysimeters Background==
[[File: StultsFig1.png |thumb|600 px|Figure 1. (a) A field suction lysimeter with labeled parts typically used in field settings – Credit: Bibek Acharya and Dr. Vivek Sharma, UF/IFAS, https://edis.ifas.ufl.edu/publication/AE581. (b) Laboratory suction lysimeters used in Schaefer ''et al.'' 2024<ref name="SchaeferEtAl2024"/>, which employed the use of micro-sampling suction lysimeters. (c) A field lysimeter used in Schaefer ''et al.'' 2023<ref name="SchaeferEtAl2023"/>. (d) Diagram of a drainage wicking lysimeter – Credit: Edaphic Scientific, https://edaphic.com.au/products/water/lysimeter-wick-for-drainage/]]
Lysimeters, generally speaking, refer to instruments which collect water from unsaturated soils<ref name="MeissnerEtAl2020"/><ref name="RogersMcConnell1993"/>. However, there are multiple types of lysimeters which can be employed in field or laboratory settings. There are three primary types of lysimeters relevant to PFAS listed here and shown in Figure 1a-d.
# Suction Lysimeters (Figure 1a,b): These lysimeters are the most relevant for PFAS sampling and are the majority of discussion in this article. These lysimeters operate by extracting liquid from the unsaturated vadose zone by applying negative suction pressure at the sampling head<ref name="CostanzaEtAl2025"/><ref name="SchaeferEtAl2024"/><ref name="QuinnanEtAl2021"/>. The sampling head is typically constructed of porous ceramic or stainless steel. A PVC case or stainless-steel case is attached to the sampling head and extends upward above the ground surface. Suction lysimeters are typically installed between 1 and 9 feet below ground surface, but can extend as deep as 40-60 feet in some cases<ref name="CostanzaEtAl2025"/>. Shallow lysimeters (< 10 feet) are typically installed using a hand auger. For ceramic lysimeters, a silica flour slurry should be placed at the base of the bore hole and allowed to cover the ceramic head before backfilling the hole partially with natural soil. Once the hole is partially backfilled with soil to cover the sampling head, the remainder of the casing should be sealed with hydrated bentonite chips. When sampling events occur, suction is applied at the ground surface using a rubber gasket seal and a hand pump or electric pump. After sufficient porewater is collected (the time for which can vary greatly based on the soil permeability and moisture content), the seal can be removed and a peristaltic pump used to extract liquid from the lysimeter.
# Field Lysimeters (Figure 1c): These large lysimeters can be constructed from plastic or metal sidings. They can range from approximately 2 feet in diameter to as large as several meters in diameter<ref name="MeissnerEtAl2020"/>. Instrumentation such as soil moisture probes and tensiometers, or even multiple suction lysimeters, are typically placed throughout the lysimeter to measure the movement of water and determine characteristic soil moisture release curves<ref name="Stannard1992"/><ref name="WintonWeber1996"/><ref name="SchaeferEtAl2023"/><ref name="SchaeferEtAl2022"/><ref>van Genuchten, M.Th. , 1980. A Closed‐form Equation for Predicting the Hydraulic Conductivity of Unsaturated Soils. Soil Science Society of America Journal, 44(5), pp. 892-898. [https://doi.org/10.2136/sssaj1980.03615995004400050002x doi: 10.2136/sssaj1980.03615995004400050002x]</ref>. Water is typically collected at the base of the field lysimeter to determine net recharge through the system. These field lysimeters are intended to represent more realistic, intermediate scale conditions of field systems.
# Drainage Lysimeters (Figure 1d): Also known as a “wick” lysimeter, these lysimeters typically consist of a hollow cup attached to a spout which protrudes above ground to relieve air pressure from the system and act as a sampling port. The hollow cup typically has filters and wicking devices at the base to collect water from the soil. The cup is filled with natural soil and collects water as it percolates through the vadose zone. These lysimeters are used to directly monitor net recharge from the vadose zone to the groundwater table and could be useful in determining PFAS mass flux.

==Analysis of PFAS Concentrations in Soil and Porewater==
{| class="wikitable mw-collapsible" style="float:left; margin-right:20px; text-align:center;"
|+Table 1. Measured and Predicted PFAS Concentrations in Porewater for Select PFAS in Three Different Soils
|-
!Site
!PFAS
!FieldPorewaterConcentration(μg/L)
!Lab CorePorewaterConcentration(μg/L)
!PredictedPorewaterConcentration(μg/L)
|-
|Site A||PFOS||6.2 ± 3.4||3.0 ± 0.37||6.6 ± 3.3
|-
|Site B||PFOS||2.2 ± 2.0||0.78 ± 0.38||2.8
|-
|rowspan="3"|Site C||PFOS||13 ± 4.1||680 ± 460||164 ± 75
|-
|8:2 FTS||1.2 ± 0.46||52 ± 13||16 ± 6.0
|-
|PFHpS||0.36 ± 0.051||2.9 ± 2.0||5.9 ± 3.4
|}
[[File: StultsFig2.png | thumb | 600 px | Figure 2. Field Measured PFAS concentration Data (Orange) and Lab Core Measured Concentration Data (Blue) for four PFAS impacted sites<ref name="AndersonEtAl2022"/>]]
[[File: StultsFig3.png | thumb | 400 px | Figure 3. Measured and predicted data for PFAS concentrations from a single site field lysimeter study. Model predictions both with and without PFAS sorption to the air-water interface were considered<ref name="SchaeferEtAl2023"/>.]]
Schaefer ''et al.''<ref name="SchaeferEtAl2024"/> measured PFAS porewater concentrations with field and laboratory suction lysimeters across several sites. Intact cores from the site were collected for soil water extraction using laboratory lysimeters. The lysimeters were used to directly compare field derived measurements of PFAS concentration in the mobile porewater phase. Results from measurements are for four sites presented in Figure 2.

Data from sites A and B showed reasonably good agreement (within ½ order of magnitude) for most PFAS measured in the systems. At site C, more hydrophobic constituents (> C6 PFAS) tended to have higher concentrations in the lab core than the field site while less hydrophobic constituents (< C6) had higher concentrations in the field than lab cores. Site D showed substantially greater (1 order of magnitude or more) PFAS concentrations measured in the laboratory-collected porewater sample compared to what was measured in the field lysimeters. This discrepancy for the Site D soil can likely be attributed to soil heterogeneity (as indicated by ground penetrating radar) and the fact that the soil consisted of back-filled materials rather than undisturbed native soils.

Site C showed elevated PFAS concentrations in the laboratory collected porewater for the more surface-active compounds. This increase was attributed to the soil wetting that occurred at the bench scale, which was reasonably described by the model shown in Equations 1 and 2 (see Table 1<ref name="AndersonEtAl2022"/>). Equations 1 and 2 were also used to predict PFAS porewater concentrations (using porous cup lysimeters) in a highly instrumented test cell<ref name="SchaeferEtAl2023"/>(Figure 3). The ability to predict soil concentrations from recurring porewater samples is critical to the practical application of lysimeters in field settings<ref name="AndersonEtAl2022"/>.

Results from suction lysimeters studies and field lysimeter studies show that PFAS concentrations in porewater predicted from soil concentrations using Equations 1 and 2 generally have reasonable agreement with measured ''in situ'' porewater data when air-water interfacial partitioning is considered. Results show that for less hydrophobic components like PFOA, the impact of air-water interfacial adsorption is less significant than for highly hydrophobic components like PFOS. The soil for the field lysimeter in Figure 3 was a sandy soil with a relatively low air-water interfacial area. The effect of air-water interfacial partitioning is expected to be much more significant for a greater range of PFAS in soils with high capillary pressure (i.e. silts/clays) with higher associated air-water interfacial areas<ref name="Brusseau2023"/><ref>Peng, S., Brusseau, M.L., 2012. Air-Water Interfacial Area and Capillary Pressure: Porous-Medium Texture Effects and an Empirical Function. Journal of Hydrologic Engineering, 17(7), pp. 829-832. [https://doi.org/10.1061/(asce)he.1943-5584.0000515 doi: 10.1061/(asce)he.1943-5584.0000515]</ref><ref>Brusseau, M.L., Peng, S., Schnaar, G., Costanza-Robinson, M.S., 2006. Relationships among Air-Water Interfacial Area, Capillary Pressure, and Water Saturation for a Sandy Porous Medium. Water Resources Research, 42(3), Article W03501, 5 pages. [https://doi.org/10.1029/2005WR004058 doi: 10.1029/2005WR004058]  [[Media: BrusseauEtAl2006.pdf | Free Access Article]]</ref>.

==Summary and Recommendations==
The majority of research with lysimeters for PFAS site investigations has been done using porous cup suction lysimeters<ref name="CostanzaEtAl2025"/><ref name="AndersonEtAl2022"/><ref name="SchaeferEtAl2024"/><ref name="QuinnanEtAl2021"/>. Porous cup suction lysimeters are advantageous because they can be routinely sampled or sampled after specific wetting or drying events much like groundwater wells. This sampling is easier and more efficient than routinely collecting soil samples from the same locations. Co-locating lysimeters with soil samples is important for establishing the baseline soil concentration levels at the lysimeter location and developing correlations between the soil concentrations and the mobile porewater concentration<ref name="CostanzaEtAl2025"/>. Appropriate standard operation procedures for lysimeter installation and operation have been established and have been reviewed in recent literature<ref name="CostanzaEtAl2025"/><ref name="SchaeferEtAl2024"/>. Lysimeters should typically be installed near the source area and just above the maximum groundwater level elevation to obtain accurate results of porewater concentrations year round. Depending upon the geology and vertical PFAS distribution in the soil, multilevel lysimeter installations should also be considered.

Results from several lysimeters studies across multiple field sites and modelling analysis has shown that lysimeters can produce reasonable results between field and laboratory studies<ref name="SchaeferEtAl2024"/><ref name="SchaeferEtAl2023"/><ref name="SchaeferEtAl2022"/>. Transient effects of wetting and drying as well as media heterogeneity affects appear to be responsible for some variability and uncertainty in lysimeter based PFAS measurements in the vadose zone. These mobile porewater concentrations can be coupled with effective recharge estimates and simplified modelling approaches to determine mass flux from the vadose zone to the underlying groundwater<ref name="Anderson2021"/><ref name="StultsEtAl2024"/><ref name="BrusseauGuo2022"/><ref>Stults, J.F., Schaefer, C.E., MacBeth, T., Fang, Y., Devon, J., Real, I., Liu, F., Kosson, D., Guelfo, J.L., 2025. Laboratory Validation of a Simplified Model for Estimating Equilibrium PFAS Mass Leaching from Unsaturated Soils. Science of The Total Environment, 970, Article 179036. [https://doi.org/10.1016/j.scitotenv.2025.179036 doi: 10.1016/j.scitotenv.2025.179036]</ref><ref>Smith, J. Brusseau, M.L., Guo, B., 2024. An Integrated Analytical Modeling Framework for Determining Site-Specific Soil Screening Levels for PFAS. Water Research, 252, Article121236. [https://doi.org/10.1016/j.watres.2024.121236 doi: 10.1016/j.watres.2024.121236]</ref>.

Future research opportunities should address the current key uncertainties related to the use of lysimeters for PFAS investigations, including:
#Collect larger datasets of PFAS concentrations to determine how transient wetting or drying periods and media type affect PFAS concentrations in the mobile porewater. Some research has shown that non-equilibrium processes can occur in the vadose zone, which can affect grab sample concentration in the porewater at specific time periods.
#More work should be done with flux averaging lysimeters like the drainage cup or wicking lysimeter. These lysimeters can directly measure net recharge and provide time averaged concentrations of PFAS in water over the sampling period. However, there is little work detailing their potential applications in PFAS research, or operational considerations for their use in remedial investigations for PFAS.
#Lysimeters should be coupled with monitoring of wetting and drying in the vadose zone using ''in situ'' soil moisture sensors or tensiometers and groundwater levels. Direct measurements of soil saturation at field sites are vital to directly correlate porewater concentrations with soil concentrations. Similarly, groundwater level fluctuations can inform net recharge estimates. By collecting these data we can continue to improve partitioning and leaching models which can relate porewater concentrations to total PFAS mass in soils and PFAS leaching at field sites.
#Comparisons of various bench-scale leaching or desorption tests to field-based lysimeter data are recommended. The ability to correlate field measurements of PFAS concentrations with estimates of leaching from laboratory studies would provide a powerful method to empirically estimate PFAS leaching from field sites.

==References==
<references />

==See Also==

Dr. John F. Stults

2026-01-20T18:01:19Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :CDM Smith :14432 SE Eastgate Way :Suite 100 :Bellevue, WA 98007 EMAIL: [mailto:stultsjf@cdmsmith.com stultsjf@cdmsmit..."

==Work and Contact Information==

EMPLOYER:
:CDM Smith 
:14432 SE Eastgate Way
:Suite 100 
:Bellevue, WA 98007

EMAIL: [mailto:stultsjf@cdmsmith.com stultsjf@cdmsmith.com]

WEBPAGE: https://www.cdmsmith.com/en/experts/john-stults

==About the Contributor==
John F. Stults is a research engineer with the CDM Smith Bellevue Research and Testing Laboratory. Dr. Stults doctoral research focused on developing and improving models of PFAS fate and transport in unsaturated systems at the Colorado School of Mines. Since joining CDM Smith, Dr. Stults has continued this work.

==Article Contributions==
*[[Lysimeters for Measuring PFAS Concentrations in the Vadose Zone]]

__NOTOC__

[[Category: Contributors|Stults]]

Thermal Conduction Heating for Treatment of PFAS-Impacted Soil

2026-01-02T15:38:52Z

Debra Tabron:

Removal of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] from impacted soils is challenging due to the modest volatility and varying properties of PFAS compounds. Thermal treatment technologies have been developed for treatment of semi-volatile compounds such as dioxins, furans, poly-aromatic hydrocarbons and poly-chlorinated biphenyls in soils at temperatures near 325°C. In controlled bench-scale testing, complete removal of targeted PFAS compounds to concentrations below reporting limits of 0.5 µg/kg was demonstrated at temperatures of 400°C<ref name="CrownoverEtAl2019"> Crownover, E., Oberle, D., Heron, G., Kluger, M., 2019. Perfluoroalkyl and polyfluoroalkyl substances thermal desorption evaluation. Remediation Journal, 29(4), pp. 77-81. [https://doi.org/10.1002/rem.21623 doi: 10.1002/rem.21623]</ref>. Three field-scale thermal PFAS treatment projects that have been completed in the US include an in-pile treatment demonstration, an ''in situ'' vadose zone treatment demonstration and a larger scale treatment demonstration with excavated PFAS-impacted soil in a constructed pile. Based on the results, thermal treatment temperatures of at least 400°C and a holding time of 7-10 days are recommended for reaching local and federal PFAS soil standards. The energy requirement to treat typical wet soil ranges from 300 to 400 kWh per cubic yard, exclusive of heat losses which are scale dependent. Extracted vapors have typically been treated using condensation and granular activated charcoal filtration, with thermal and catalytic oxidation as another option which is currently being evaluated for field scale applications. Compared to other options such as soil washing, the ability to treat on site and to treat all soil fractions is an advantage.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[Thermal Conduction Heating (TCH)]]

'''Contributor(s):''' [[Dr. Gorm Heron]], Dr. Emily Crownover, Patrick Joyce, [[Dr. Ramona Iery]]

'''Key Resource:'''
*Perfluoroalkyl and polyfluoroalkyl substances thermal desorption evaluation<ref name="CrownoverEtAl2019"/>

==Introduction==
[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] have become prominent emerging contaminants in soil and groundwater. Soil source zones have been identified at locations where the chemicals were produced, handled or used. Few effective options exist for treatments that can meet local and federal soil standards. Over the past 30 plus years, thermal remediation technologies have grown from experimental and innovative prospects to mature and accepted solutions deployed effectively at many sites. More than 600 thermal case studies have been summarized by Horst and colleagues<ref name="HorstEtAl2021">Horst, J., Munholland, J., Hegele, P., Klemmer, M., Gattenby, J., 2021. In Situ Thermal Remediation for Source Areas: Technology Advances and a Review of the Market From 1988–2020. Groundwater Monitoring & Remediation, 41(1), p. 17. [https://doi.org/10.1111/gwmr.12424 doi: 10.1111/gwmr.12424]  [[Media: gwmr.12424.pdf | Open Access Manuscript]]</ref>. [[Thermal Conduction Heating (TCH)]] has been used for higher temperature applications such as removal of [[1,4-Dioxane]]. This article reports recent experience with TCH treatment of PFAS-impacted soil.

==Target Temperature and Duration==
PFAS behave differently from most other organics subjected to TCH treatment. While the boiling points of individual PFAS fall in the range of 150-400°C, their chemical and physical behavior creates additional challenges. Some PFAS form ionic species in certain pH ranges and salts under other chemical conditions. This intricate behavior and our limited understanding of what this means for our ability to remove the PFAS from soils means that direct testing of thermal treatment options is warranted. Crownover and colleagues<ref name="CrownoverEtAl2019"/> subjected PFAS-laden soil to bench-scale heating to temperatures between 200 and 400°C which showed strong reductions of PFAS concentrations at 350°C and complete removal of many PFAS compounds at 400°C. The soil concentrations of targeted PFAS were reduced to nearly undetectable levels in this study.

==Heating Method==
For semi-volatile compounds such as dioxins, furans, poly-chlorinated biphenyls (PCBs) and Poly-Aromatic Hydrocarbons (PAH), thermal conduction heating has evolved as the dominant thermal technology because it is capable of achieving soil temperatures higher than the boiling point of water, which are necessary for complete removal of these organic compounds. Temperatures between 200 and 500°C have been required to achieve the desired reduction in contaminant concentrations<ref name="StegemeierVinegar2001">Stegemeier, G.L., Vinegar, H.J., 2001. Thermal Conduction Heating for In-Situ Thermal Desorption of Soils. Ch. 4.6, pp. 1-37. In: Chang H. Oh (ed.), Hazardous and Radioactive Waste Treatment Technologies Handbook, CRC Press, Boca Raton, FL. ISBN 9780849395864 [[Media: StegemeierVinegar2001.pdf | Open Access Article]]</ref>. TCH has become a popular technology for PFAS treatment because temperatures in the 400°C range are needed.

The energy source for TCH can be electricity (most commonly used), or fossil fuels (typically gas, diesel or fuel oil). Electrically powered TCH offers the largest flexibility for power input which also can be supplied by renewable and sustainable energy sources.

==Energy Usage==
Treating PFAS-impacted soil with heat requires energy to first bring the soil and porewater to the boiling point of water, then to evaporate the porewater until the soil is dry, and finally to heat the dry soil up to the target treatment temperature. The energy demand for wet soils falls in the 300-400 kWh/cy range, dependent on porosity and water saturation. Additional energy is consumed as heat is lost to the surroundings and by vapor treatment equipment, yielding a typical usage of 400-600 kWh/cy total for larger soil treatment volumes. Wetter soils and small treatment volumes drive the energy usage towards the higher number, whereas larger soil volumes and dry soil can be treated with less energy.

==Vapor Treatment==
During the TCH process a significant fraction of the PFAS compounds are volatilized by the heat and then removed from the soil by vacuum extraction. The vapors must be treated and eventually discharged while meeting local and/or federal standards. Two types of vapor treatment have been used in past TCH applications for organics: (1) thermal and catalytic oxidation and (2) condensation followed by granular activated charcoal (GAC) filtration. Due to uncertainties related to thermal destruction of fluorinated compounds and future requirements for treatment temperature and residence time, condensation and GAC filtration have been used in the first three PFAS treatment field demonstrations. It should be noted that PFAS compounds will stick to surfaces and that decontamination of the equipment is important. This could generate additional waste as GAC vessels, pipes and other wetted equipment need careful cleaning with solvents or rinsing agents such as PerfluorAdTM.

==PFAS Reactivity and Fate==
While evaluating initial soil treatment results, Crownover ''et al''<ref name="CrownoverEtAl2019"/> noted the lack of complete data sets when the soils were analyzed for non-targeted compounds or extractable precursors. Attempts to establish the fluorine balance suggest that the final fate of the fluorine in the PFAS is not yet fully understood. Transformations are likely occurring in the heated soil as demonstrated in laboratory experiments with and without calcium hydroxide (Ca(OH)2) amendment<ref>Koster van Groos, P.G., 2021. Small-Scale Thermal Treatment of Investigation-Derived Wastes Containing PFAS. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/2f1577ac-c8ea-4ae8-804e-c9f97a12edb3/small-scale-thermal-treatment-of-investigation-derived-wastes-idw-containing-pfas Project ER18-1556 Website], [[Media: ER18-1556_Final_Report.pdf | Final Report.pdf]]</ref>. Amendments such as Ca(OH)2 may be useful in reducing the required treatment temperature by catalyzing PFAS degradation. With thousands of PFAS potentially present, the interactions are complex and may never be fully understood. Therefore, successful thermal treatment may require a higher target temperature than for other organics with similar boiling points – simply to provide a buffer against the uncertainty.

==Case Studies==
===Stockpile Treatment, Eielson AFB, Alaska ([https://serdp-estcp.mil/projects/details/62098505-de86-43b2-bead-ae8018854141 ESTCP project ER20-5198]<ref name="CrownoverEtAl2023">Crownover, E., Heron, G., Pennell, K., Ramsey, B., Rickabaugh, T., Stallings, P., Stauch, L., Woodcock, M., 2023. Ex Situ Thermal Treatment of PFAS-Impacted Soils, [[Media: ER20-5198 Final Report.pdf | Final Report.]] Eielson Air Force Base, Alaska. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/62098505-de86-43b2-bead-ae8018854141 Project ER20-5198 Website]</ref>)===
[[File: HeronFig1.png | thumb | 400 px | Figure 1. TCH treatment of a PFAS-laden stockpile at Eielson AFB, Alaska<ref name="CrownoverEtAl2023"/>]]
Since there has been no approved or widely accepted method for treating soils impacted by PFAS, a common practice has been to excavate PFAS-impacted soil and place it in lined stockpiles. Eielson AFB in Alaska is an example where approximately 50 stockpiles were constructed to temporarily store 150,000 cubic yards of soil. One of the stockpiles containing 134 cubic yards of PFAS-impacted soil was heated to 350-450°C over 90 days (Figure 1). Volatilized PFAS was extracted from the soil using vacuum extraction and treated via condensation and filtration by granular activated charcoal. Under field conditions, PFAS concentration reductions from 230 µg/kg to below 0.5 µg/kg were demonstrated for soils that reached 400°C or higher for 7 days. These soils achieved the Alaska soil standards of 3 µg/kg for PFOS and 1.7 µg/kg for PFOA. Cooler soils near the top of the stockpile had remaining PFOS in the range of 0.5-20 µg/kg with an overall average of 4.1 µg/kg. Sampling of all soils heated to 400°C or higher demonstrated that the soils achieved undetectable levels of targeted PFAS (typical reporting limit was 0.5 µg/kg).

===''In situ'' Vadose Zone Treatment, Beale AFB, California ([https://serdp-estcp.mil/projects/details/94949542-f9f7-419d-8028-8ba318495641/er20-5250-project-overview ESTCP project ER20-5250]<ref name="Iery2024">Iery, R. 2024. In Situ Thermal Treatment of PFAS in the Vadose Zone. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/94949542-f9f7-419d-8028-8ba318495641 Project ER20-5250 Website]. [[Media: ER20-5250 Fact Sheet.pdf | Fact Sheet.pdf]]</ref>)===
[[File: HeronFig2.png | thumb | 600 px | Figure 2. ''In situ'' TCH treatment of a PFAS-rich vadose zone hotspot at Beale AFB, California]]
A former fire-training area at Beale AFB had PFAS concentrations as high as 1,970 µg/kg in shallow soils. In situ treatment of a PFAS-rich soil was demonstrated using 16 TCH borings installed in the source area to a depth of 18 ft (Figure 2). Soils which reached the target temperatures were reduced to PFAS concentrations below 1 µg/kg. Perched water which entered in one side of the area delayed heating in that area, and soils which were affected had more modest PFAS concentration reductions. As a lesson learned, future in situ TCH treatments will include provisions for minimizing water entering the treated volume<ref name="Iery2024"/>. It was demonstrated that with proper water management, even highly impacted soils can be treated to near non-detect concentrations (greater than 99% reduction).

===Constructed Pile Treatment, JBER, Alaska ([https://serdp-estcp.mil/projects/details/eb7311db-6233-4c7f-b23a-e003ac1926c5/pfas-treatment-in-soil-using-thermal-conduction-heating ESTCP Project ER23-8369]<ref name="CrownoverHeron2024">Crownover, E., Heron, G., 2024. PFAS Treatment in Soil Using Thermal Conduction Heating. Defense Innovation Unit (DIU) and [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/eb7311db-6233-4c7f-b23a-e003ac1926c5/pfas-treatment-in-soil-using-thermal-conduction-heating Project ER23-8369 Website]</ref>)===
[[File: HeronFig3.png | thumb | 600 px | Figure 3. Treatment of a 2,000 cubic yard soil pile at JBER, Alaska]]
In 2024, a stockpile of 2,000 cubic yards of PFAS-impacted soil was thermally treated at Joint Base Elmendorf-Richardson (JBER) in Anchorage, Alaska<ref name="CrownoverHeron2024"/>. This ESTCP project was implemented in partnership with DOD’s Defense Innovation Unit (DIU). Three technology demonstrations were conducted at the site where approximately 6,000 cy of PFAS-impacted soil was treated (TCH, smoldering and kiln-style thermal desorption). Figure 3 shows the fully constructed pile used for the TCH demonstration. In August 2024 the soil temperature for the TCH treatment exceeded 400°C in all monitoring locations. At an energy density of 355 kWh/cy, Alaska Department of Environmental Conservation (ADEC) standards and EPA Residential Regional Screening Levels (RSLs) for PFAS in soil were achieved. At JBER, all 30 post-treatment soil samples were near or below detection limits for all targeted PFAS compounds using EPA Method 1633. The composite of all 30 soil samples was below all detection limits for EPA Method 1633. Detection limits ranged from 0.0052 µg/kg to 0.19 µg/kg.

==Advantages and Disadvantages==
Thermal treatment of PFAS in soils is energy intensive, and the cost of that energy may be prohibitive for some clients. Also, while it often is the least costly option for complete PFAS removal when compared to excavation followed by offsite disposal or destruction, heating soil to treatment temperatures on site or ''in situ'' typically takes longer than excavation. Major advantages include:
*On site or ''in situ'' treatment eliminates the need to transport and dispose of the contaminated soil
*Site liabilities are removed once and for all
*Treatment costs are competitive with excavation, transportation and off-site treatment or disposal.

==Recommendations==
Recent research suggests:
*Successful thermal treatment of PFAS may require a higher target temperature than for other organics with similar boiling points
*Prevention of influx of water into treatment zone may be necessary.
Future studies should examine the potential for enhanced degradation during the thermal process by using soil amendments and/or manipulation of the local geochemistry to reduce the required treatment temperatures and therefore also reduce energy demand.

==References==
<references />

==See Also==

Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges

2026-01-02T15:36:01Z

Debra Tabron:

Hydrogeophysical methods can be used to cost-effectively locate and characterize regions of enhanced groundwater/surface water exchange (GWSWE) and to guide effective follow up investigations based on more traditional invasive methods. The most established methods exploit the contrasts in temperature and/or specific conductance that commonly exist between groundwater and surface water.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Geophysical Methods]]
*[[Geophysical Methods - Case Studies]]

'''Contributor(s):''' [[Dr. Lee Slater]], [[Dr. Ramona Iery]], [[Dr. Dimitrios Ntarlagiannis]], [[Henry Moore]] and Dr. Martin Briggs

'''Key Resource(s):'''

*USGS Method Selection Tool: https://code.usgs.gov/water/espd/hgb/gw-sw-mst
*USGS Water Resources: https://www.usgs.gov/mission-areas/water-resources/science/groundwatersurface-water-interaction

==Introduction==
Discharges of contaminated groundwater (GW) to surface water (SW) threaten ecosystems and degrade the quality of SW resources. Subsurface heterogeneity associated with geological structure and stratigraphy often results in such discharges occurring as localized zones (or seeps) of contaminated GW. Traditional methods for investigating groundwater-surface water exchanges (GWSWE) include [https://books.gw-project.org/groundwater-surface-water-exchange/chapter/seepage-meters/#:~:text=Seepage%20meters%20measure%20the%20flux,that%20it%20isolates%20water%20exchange. seepage meters]<ref>Rosenberry, D.O., Duque, C., and Lee, D.R., 2020. History and Evolution of Seepage Meters for Quantifying Flow between Groundwater and Surface Water: Part 1 – Freshwater Settings. Earth-Science Reviews, 204(103167). [https://doi.org/10.1016/j.earscirev.2020.103167 doi: 10.1016/j.earscirev.2020.103167].</ref><ref>Duque, C., Russoniello, C.J., Rosenberry, D.O., 2020. History and Evolution of Seepage Meters for Quantifying Flow between Groundwater and Surface Water: Part 2 – Marine Settings and Submarine Groundwater Discharge. Earth-Science Reviews, 204, Article 103168. [https://doi.org/10.1016/j.earscirev.2020.103168 doi: 10.1016/j.earscirev.2020.103168].</ref>, which directly quantify the volumetric flux crossing the bed of a surface-water body (i.e, a lake, river or wetland) and point probes that locally measure key water quality parameters (e.g., temperature, pore water velocity, specific conductance, dissolved oxygen, pH). Seepage meters provide direct estimates of seepage fluxes between groundwater and surface water but are time consuming and can be difficult to deploy in high energy surface-water environments and along armored bed sediments. Manual seepage meters rely on quantifying volume changes in a bag of water that is hydraulically connected to the bed. Although automated seepage meters such as the [https://clu-in.org/programs/21m2/navytools/gsw/#ultraseep Ultraseep system] have been developed, they are generally not suitable for long-term deployment (weeks to months). The United States (US) Navy has developed the [https://clu-in.org/programs/21m2/navytools/gsw/#trident Trident probe] for more rapid (relative to seepage meters) sampling, whereby the probe is inserted into the bed and point-in-time pore-water quality and sediment parameters are directly recorded (note that the Trident probe does not measure seepage flux). Such direct probe-based measurements are still relatively time consuming to acquire, particularly when reconnaissance information is required over large areas to determine the location of discrete seeps for further, more quantitative analysis.

Over the last few decades, a broader [https://www.usgs.gov/mission-areas/water-resources/science/geophysics-usgs-groundwatersurface-water-exchange-studies toolbox of hydrogeophysical technologies] has been developed to rapidly and non-invasively evaluate zones of GWSWE in a variety of SW settings, spanning from freshwater bodies to saline coastal environments. Many of these technologies are currently being deployed under a Department of Defense Environmental Security Technology Certification Program ([https://serdp-estcp.mil/ ESTCP]) project ([https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ER21-5237]) to demonstrate the value of the toolbox to remedial program managers (RPMs) dealing with the challenge of characterizing surface-water contamination via groundwater from facilities proximal to surface-water bodies. This article summarizes these technologies and provides references to key resources, mostly provided by the [https://www.usgs.gov/mission-areas/water-resources Water Resources Mission Area] of the US Geological Survey (USGS) that describes the technologies in further detail.

==Hydrogeophysical Technologies for Understanding Groundwater-Surface Water Exchanges==
[[Wikipedia: Hydrogeophysics |Hydrogeophysical technologies]] exploit contrasts in the physical properties between groundwater and surface water to detect and monitor zones of pronounced GWSWE. The two most valuable properties to measure are temperature and electrical conductivity (EC). Temperature has been used for decades as an indicator of GWSWE<ref>Constantz, J., 2008. Heat as a Tracer to Determine Streambed Water Exchanges. Water Resources Research, 44 (4). [https://doi.org/https://doi.org/10.1029/2008WR006996 doi: 10.1029/2008WR006996]. [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2008WR006996 Open Access Article]</ref> with early uses including pushing a thermistor into the bed of a surface-water body to assess zones of SW downwelling and GW upwelling. Today, a variety of novel technologies that measure temperature over a wide range of spatial and temporal scales are being used to investigate GWSWE. The evaluation of EC measurements using point probes and geophysical imaging is also well established. However, new technologies are now available to exploit EC contrasts from GWSWE occurring over a range of spatial and temporal scales.

===Temperature-Based Technologies===
Several temperature-based GWSWE methodologies exploit the gradient in temperature between surface water and groundwater that exists during certain times of day or seasons of the year. The thermal insulation provided by the Earth’s land surface means that GW is warmer than SW in winter months, but colder than SW in summer months away from the equator. Therefore, in temperate climates, localized (or ‘preferential’) groundwater discharge into surface-water bodies is often observed as cold temperature anomalies in the summer and warm temperature anomalies in the winter. However, there are times of the year such as fall and spring when contrasts in the temperature between GW and SW will be minimal, or even undetectable. These seasonal-driven points in time correspond to the switch in the polarity of the temperature contrast between GW and SW. Consequently, SW to GW temperature gradient based methods are most effective when deployed at times of the year when the temperature contrasts between GW and SW are greatest. Other time-series temperature monitoring methods depend more on natural daily signals measured at the bed interface and in bed sediments, and those signals may exist year-round except where strongly muted by ice cover or surface water stratification. A variety of sensing technologies now exist within the GWSWE toolbox, including techniques that rapidly characterize temperature contrasts over large areas as well as powerful monitoring methods that can continuously quantify GWSWE fluxes at discrete locations identified as hotspots.

====Characterization Methods====
The primary use of the characterization methods is to rapidly determine precise locations of GW upwelling over large areas in order to pinpoint locations for subsequent ground-based observations. A common limitation of these methods is that they can only detect GW fluxes into SW. Methods applied at the water surface and in the surface-water column generally cannot identify localized regions of surface-water transfer to groundwater, for which temperature measurements collected within the bed sediments are needed. This is a more challenging characterization task that may in some cases be addressed using electrical conductivity-based methods described later in this article.

=====''Unoccupied Aerial Vehicle Infrared (UAV-IR)''=====
[[File:IeryFig1.png | thumb |600px|Figure 1. UAV-IR orthomosaics with estimated scale of (a) a wetland in winter (modified from Briggs ''et al.''<ref>Briggs, M.A., Jackson, K.E., Liu, F., Moore, E.M., Bisson, A., Helton, A.M., 2022. Exploring Local Riverbank Sediment Controls on the Occurrence of Preferential Groundwater Discharge Points. Water, 14(1). [https://doi.org/10.3390/w14010011 doi: 10.3390/w14010011]  [https://www.mdpi.com/2073-4441/14/1/11 Open Access Article].</ref>) and (b) a mountain stream in summer (modified from Briggs ''et al.''<ref>Briggs, M.A., Wang, C., Day-Lewis, F.D., Williams, K.H., Dong, W., Lane, J.W., 2019. Return Flows from Beaver Ponds Enhance Floodplain-to-River Metals Exchange in Alluvial Mountain Catchments. Science of the Total Environment, 685, pp. 357–369. [https://doi.org/10.1016/j.scitotenv.2019.05.371 doi: 10.1016/j.scitotenv.2019.05.371].  [//www.enviro.wiki/images/6/63/BriggsEtAl2019.pdf Open Access Manuscript]</ref>) that both capture multiscale groundwater discharge processes. Figure reproduced from Mangel ''et al.''<ref>Mangel, A.R., Dawson, C.B., Rey, D.M., Briggs, M.A., 2022. Drone Applications in Hydrogeophysics: Recent Examples and a Vision for the Future. The Leading Edge, 41 (8), pp. 540–547. [https://doi.org/10.1190/tle41080540.1 doi: 10.1190/tle41080540].</ref>]]
[[Wikipedia: Unmanned aerial vehicle | Unoccupied aerial vehicles (UAVs)]] equipped with infrared (IR) cameras can provide a very powerful tool for rapidly determining zones of pronounced upwelling of GW into SW. Large areas can be covered with high spatial resolution. The information obtained can be used to rapidly define locations of focused GW upwelling and prioritize these for more intensive surface-based observations (Figure 1). As with all thermal methods, flights must be performed when adequate contrasts in temperature between SW and GW are expected to exist. Not just time of year but, because of the effect of the diurnal temperature signal on surface water bodies, time of day might need to be considered in order to maximize the chance of success. Calibration of UAV-IR camera measurements against simultaneously acquired direct measurements of temperature is recommended to optimize the value of these datasets. UAV-IR methods will not work in all situations. One major limitation of the technology is that the temperature expression of groundwater upwelling must be manifested at the surface of the surface-water body. Consequently, the technology will not detect relatively small discharges occurring beneath a relatively deep surface-water layer, and thermal imaging over the water surface can be complicated by thermal IR reflection. The chances of success with UAV-IR will be strongest in regions of exposed banks or shallow water where there are no strong currents causing mixing (and thus dilution) of the upwelling GW temperature signals. UAV-IR methods will therefore likely be most successful close to shorelines of lakes and ponds, over shallow, low-flow streams and rivers, and in wetland environments. UAV-IR methods require a licensed pilot, and restrictions on the use of airspace may limit the application of this technology.

=====''Handheld Thermal Infrared (TIR) Cameras''=====
[[File:IeryFig2.png | thumb|left |600px|Figure 2. (a) A TIR camera set up to image groundwater discharges to surface water (b) TIR data inset on a visible light photograph. Cooler (blue) bank seepage groundwater is discharging into warmer (red) stream water (temperature scale in degrees). Both photographs courtesy of Martin Briggs, USGS.]]
Hand-held thermal infrared (TIR) cameras are powerful tools for visual identification of localized seeps of upwelling groundwater. TIR cameras may be used to follow up on UAV-IR surveys to better characterize local seeps identified from the air using UAV-IR. Alternatively, a TIR camera is a valuable tool when performing initial walks of prospective study sites as they may quickly confirm the presence of suspected seeps. TIR cameras provide high resolution images that can define the structure of localized seeps and may provide valuable insights into the role of discrete features (e.g., fractures in rocks or pipes in soil) in determining seep morphology (Figure 2). Like UAV-IR, TIR provides primarily qualitative information (location, extent) of seeps, and it only succeeds when there are adequate contrasts between GW and SW that are expressed at the surface of the investigated water body or along bank sediments. The USGS has made extensive use of TIR cameras for studying GWSWE.

=====''Continuous Near-bed Temperature Sensing''=====
When performing surveys from a boat, a simple yet often powerful technology is continuous
near-bed temperature sensing, whereby a temperature probe is strategically suspended to float in the water column just above the bed or dragged along it. Compared to UAV-IR, this approach does not rely on upwelling groundwater being expressed as a temperature anomaly at the surface. The utility of the method can be enhanced when a specific conductance (SC) probe is co-located with the temperature probe so that anomalies in both temperature and SC can be investigated.

====Monitoring Methods====
Monitoring methods allow temperature signals to be recorded with high temporal resolution along the bed interface or within bank or bed sediments. These methods can capture temporal trends in GWSWE driven by variations in the hydraulic gradients around surface water bodies, as well as changes in [[Wikipedia: Hydraulic conductivity | hydraulic conductivity]] due to sedimentation, clogging, scour or microbial mass. If vertical profiles of bed temperature are collected, a range of analytical and numerical models can be applied to infer the vertical water flux rate and direction, similar to a seepage meter. These fluxes may vary as a function of season, rainfall events (enhanced during storm activity), tidal variability in coastal settings and due to engineered controls such as dam discharges. The methods can capture evidence of GWSWE that may not be detected during a single ‘characterization’ survey if the local hydraulic conditions at that point in time result in relatively weak hydraulic gradients.

=====''Fiber-optic Distributed Temperature Sensing (FO-DTS)''=====
[[File:IeryFig3.png | thumb|600px|Figure 3. (a) Basic concept of FO-DTS based on backscattering of light transmitted down a fiber optic cable (b) Example of riverbed temperature data acquired over time and space in relation to variation in river stage (black line) modified from Mwakanyamale ''et al.''<ref>Mwakanyamale, K., Slater, L., Day-Lewis, F., Elwaseif, M., Johnson, C., 2012. Spatially Variable Stage-Driven Groundwater-Surface Water Interaction Inferred from Time-Frequency Analysis of Distributed Temperature Sensing Data. Geophysical Research Letters, 39(6). [https://doi.org/10.1029/2011GL050824 doi: 10.1029/2011GL050824].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011GL050824 Open Access Article]</ref> (c) spatial distribution of riverbed temperature and correlation coefficient (CC) between riverbed temperature and river stage for a 1.5 km stretch along the Hanford 300 Area adjacent to the Columbia River (modified from Slater ''et al.''<ref name="Slater2010" />). Data are shown for winter and summer. Orange contours show uranium concentrations (μg/L) in groundwater measured in boreholes.]]
Fiber-optic distributed temperature sensing (FO-DTS) is a powerful monitoring technology used in fire detection, industrial process monitoring, and petroleum reservoir monitoring. The method is also used to obtain [https://www.usgs.gov/mission-areas/water-resources/science/fiber-optic-distributed-temperature-sensing-technology spatially rich datasets for monitoring GWSWE]<ref name="Selker2006">Selker, J.S., Thévenaz, L., Huwald, H., Mallet, A., Luxemburg, W., van de Giesen, N., Stejskal, M., Zeman, J., Westhoff, M., Parlange, M.B., 2006. Distributed Fiber-Optic Temperature Sensing for Hydrologic Systems. Water Resources Research, 42 (12). [https://doi.org/10.1029/2006WR005326 doi: 10.1029/2006WR005326].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2006WR005326 Open Access Article]</ref><ref name="Tyler2009">Tyler, S.W., Selker, J.S., Hausner, M.B., Hatch, C.E., Torgersen, T., Thodal, C.E., Schladow, S.G., 2009. Environmental Temperature Sensing Using Raman Spectra DTS Fiber-Optic Methods. Water Resources Research, 45(4). [https://doi.org/https://doi.org/10.1029/2008WR007052 doi: 10.1029/2008WR007052].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2008WR007052 Open Access Article]</ref>. The FO-DTS sensor consists of standard telecommunications optical fiber typically housed in an armored cable. The physics underlying FO-DTS measurements is based on temperature-dependent backscatter mechanisms including [[Wikipedia: Brillouin scattering | Brillouin]] and [[Wikipedia: Raman scattering | Raman backscatter]]<ref name="Selker2006" />. Most commercially available systems are based on analysis of Raman scatter. As laser light is transmitted down the fiber-optic cable, light scatters continuously back toward the instrument from all along the fiber, with some of the scattered light at frequencies above and below the frequency of incident light, i.e., [[Wikipedia: Raman scattering#Raman scattering | anti-Stokes and Stokes-Raman backscatter]], respectively. The ratio of anti-Stokes to Stokes energy provides the basis for FO-DTS measurements. Measurements are localized to a section of cable according to a time-of-flight calculation (i.e., [[Wikipedia: Optical time-domain reflectometer | optical time-domain reflectometry]]). Assuming the speed of light within the fiber is constant, scatter collected over a specific time window corresponds to a specific spatial interval of the fiber. Although there are tradeoffs between spatial resolution, thermal precision, and sampling time, in practice it is possible to achieve sub meter-scale spatial resolution and approximately 0.1°C thermal precision for measurement cycle times on the order of minutes and cables extending several kilometers<ref name="Tyler2009" />; thus, thousands of temperature measurements can be made simultaneously along a single cable. The method allows the visualization of a large amount of temperature data and rapid identification of major trends in GWSWE. Figure 3 illustrates the use of FO-DTS to detect and monitor zones of focused GW discharge along a 1.5 km reach of the Columbia River that is threatened by contaminated groundwater<ref name="Slater2010">Slater, L.D., Ntarlagiannis, D., Day-Lewis, F.D., Mwakanyamale, K., Versteeg, R.J., Ward, A., Strickland, C., Johnson, C.D., Lane Jr., J.W., 2010. Use of Electrical Imaging and Distributed Temperature Sensing Methods to Characterize Surface Water-Groundwater Exchange Regulating Uranium Transport at the Hanford 300 Area, Washington. Water Resources Research, 46(10). [https://doi.org/10.1029/2010WR009110 doi: 10.1029/2010WR009110].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2010WR009110 Open Access Article]</ref>. As temperature is only sensed at the location of the cable on the bed, FO-DTS can only detect GW inputs to SW. It cannot detect losses of surface water to groundwater. The USGS public domain software tool [https://www.usgs.gov/software/dtsgui DTSGUI] allows a user to import, manage, visualize and analyze FO-DTS datasets.

=====''Vertical Temperature Profilers (VTPs)''=====
Analysis methods now allow for the accurate quantification of groundwater fluxes over time based on temperature measurements. Vertical temperature profilers (VTPs) are sensors applied for diurnal temperature data collection within saturated geologic matrices (Figure 4). Extensive experience with VTPs indicates that the methodology is equal to traditional seepage meters in terms of flux accuracy<ref>Hare, D.K., Briggs, M.A., Rosenberry, D.O., Boutt, D.F., Lane Jr., J.W., 2015. A Comparison of Thermal Infrared to Fiber-Optic Distributed Temperature Sensing for Evaluation of Groundwater Discharge to Surface Water. Journal of Hydrology, 530, pp. 153–166. [https://doi.org/10.1016/j.jhydrol.2015.09.059 doi: 10.1016/j.jhydrol.2015.09.059].</ref>. However, VTPs have the advantage of measuring continuous temporal variations in flux rates while such information is impractical to obtain with traditional seepage meters.
[[File:IeryFig4.png |thumb|600px|left|Figure 4. (a) Schematic of different VTP setups including (from left to right) thermistors in a piezometer, thermistors embedded in a solid rod and wrapped FO-DTS cable modified from Irvine et al.<ref name="Irvine2017a">Irvine, D.J., Briggs, M.A., Cartwright, I., Scruggs, C.R., Lautz, L.K., 2016. Improved Vertical Streambed Flux Estimation Using Multiple Diurnal Temperature Methods in Series. Groundwater, 55(1), pp. 73-80. [https://doi.org/10.1111/gwat.12436 doi: 10.1111/gwat.12436].</ref>; (b) construction of VTPs showing thermistors embedded in rods and subsequent insulation; (c) example dataset plotted in 1DTempPro showing 5 days of streambed temperature at 6 streambed depths<ref>Koch, F.W., Voytek, E.B., Day-Lewis, F.D., Healy, R., Briggs, M.A., Lane Jr., J.W., Werkema, D., 2016. 1DTempPro V2: New Features for Inferring Groundwater/Surface-Water Exchange. Groundwater, 54(3), pp. 434–439. [https://doi.org/10.1111/gwat.12369 doi: 10.1111/gwat.12369].</ref>.]]

The low-cost design, ease of data collection, and straightforward interpretation of the data using open-source software make VTP sensors increasingly attractive for quantifying flux rates. These sensors typically consist of at least two temperature loggers installed within a steel or plastic pipe filled with foam insulation<ref name="Irvine2017a" /> although the use of loggers installed in well screens or FO-DTS cable wrapped around a piezometer casing (for high vertical resolution data) are also possible (Figure 4a). Loggers are inserted into the insulated housing at different depths, typically starting from one centimeter within the geologic matrix of interest<ref name="Irvine2017b"> Irvine, D.J., Briggs, M.A., Lautz, L.K., Gordon, R.P., McKenzie, J.M., Cartwright, I., 2017. Using Diurnal Temperature Signals to Infer Vertical Groundwater-Surface Water Exchange. Groundwater, 55(1), pp. 10–26. [https://doi.org/10.1111/gwat.12459 doi: 10.1111/gwat.12459].  [https://ngwa.onlinelibrary.wiley.com/doi/am-pdf/10.1111/gwat.12459 Open Access Manuscript]</ref>. Temperature loggers usually remain within the first 0.2 meters of the geologic matrix based on the observed limits of diurnal signal influence<ref>Briggs, M.A., Lautz, L.K., Buckley, S.F., Lane Jr., J.W., 2014. Practical Limitations on the Use of Diurnal Temperature Signals to Quantify Groundwater Upwelling. Journal of Hydrology, 519(B), pp. 1739–1751. [https://doi.org/10.1016/j.jhydrol.2014.09.030 doi: 10.1016/j.jhydrol.2014.09.030].</ref>, though zones of strong surface-water downwelling may necessitate deeper temperature data collection. Reliability of flux values generated from the temperature signal analysis is dependent in part on the temperature logger precision, VTP placement, sediment heterogeneity, flow direction, flow magnitude<ref name="Irvine2017b" />, and absence of macropore flow. Application of single dimension temperature-based fluid flux models assumes that all flow is vertical, and therefore lateral flow within upwelling systems cannot be quantified using VTPs, emphasizing the importance of installing the VTP directly over the active area of exchange<ref name="Irvine2017b" /> at shallow depths. Thermal parameters of the geologic matrix where the VTP is installed can be measured using a thermal properties analyzer to record heat capacity and thermal conductivity for later analytical and numerical modeling.

One-dimensional (1D) analytical and numerical solutions, used to solve or estimate the advection-conduction equation within the geologic matrix (bed sediments), continue to evolve to better quantify flux values over time. Analytical solutions to the heat transport equation are used to solve for flux values between sensor pairs from VTP datasets<ref name="Gordon2012">Gordon, R.P., Lautz, L.K., Briggs, M.A., McKenzie, J.M., 2012. Automated Calculation of Vertical Pore-Water Flux from Field Temperature Time Series Using the VFLUX Method and Computer Program. Journal of Hydrology, 420–421, pp. 142–158. [https://doi.org/10.1016/j.jhydrol.2011.11.053 doi: 10.1016/j.jhydrol.2011.11.053].</ref><ref name="Irvine2015">Irvine, D.J., Lautz, L.K., Briggs, M.A., Gordon, R.P., McKenzie, J.M., 2015. Experimental Evaluation of the Applicability of Phase, Amplitude, and Combined Methods to Determine Water Flux and Thermal Diffusivity from Temperature Time Series Using VFLUX 2. Journal of Hydrology, 531(3), pp. 728–737. [https://doi.org/10.1016/j.jhydrol.2015.10.054 doi: 10.1016/j.jhydrol.2015.10.054].</ref>. [https://data.usgs.gov/modelcatalog/model/a54608c5-ea6c-4d61-afc4-1ae851f46744 VFLUX] is an open-source [https://www.mathworks.com/products/matlab.html MATLAB] package that allows the user to solve for flux values from a VTP dataset using a variety of analytical solutions<ref name="Gordon2012" /><ref name="Irvine2015" /> based on the vertical propagation of diurnal temperature signals. Other emerging ‘spectral’ methods make use of a wide range of natural temperature signals to estimate vertical flux and bed sediment thermal diffusivity<ref>Sohn, R.A., Harris, R.N., 2021. Spectral Analysis of Vertical Temperature Profile Time-Series Data in Yellowstone Lake Sediments. Water Resources Research, 57(4), e2020WR028430. [https://doi.org/10.1029/2020WR028430 doi: 10.1029/2020WR028430].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020WR028430 Open Access Article]</ref>. VFLUX analytical solutions are limited by subsurface heterogeneity and diurnal temperature signal strength<ref name="Irvine2017b" />. [https://data.usgs.gov/modelcatalog/model/82fe0c15-97f5-4f6a-b389-b90f9bad615e 1DTempPro] (Figure 4c), a free open-source program available from USGS, provides a graphical user interface (GUI) for numerical solutions to heat transport<ref>Koch, F.W., Voytek, E.B., Day-Lewis, F.D., Healy, R., Briggs, M.A., Werkema, D., Lane Jr., J.W., 2015. 1DTempPro: A Program for Analysis of Vertical One-Dimensional (1D) Temperature Profiles v2.0. U.S. Geological Survey Software Release. [http://dx.doi.org/10.5066/F76T0JQS doi: 10.5066/F76T0JQS].  [https://data.usgs.gov/modelcatalog/model/82fe0c15-97f5-4f6a-b389-b90f9bad615e Free Download from USGS]</ref> and does not depend on diurnal signals. Numerical models can produce more accurate flux estimates in the case of complex boundary conditions, significant heterogeneity, or abrupt changes in flux rates, but require significant user calibration efforts for longer time series<ref name="McAliley2022"> McAliley, W.A., Day-Lewis, F.D., Rey, D., Briggs, M.A., Shapiro, A.M., Werkema, D., 2022. Application of Recursive Estimation to Heat Tracing for Groundwater/Surface-Water Exchange. Water Resources Research, 58(6), Article e2021WR030443. [https://doi.org/10.1029/2021WR030443 doi: 10.1029/2021WR030443].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2021WR030443 Open Access Article]</ref>. A hybrid approach between the analytical and numerical solutions, known as [https://www.sciencebase.gov/catalog/item/60a55c71d34ea221ce48b9e7 Tempest1d]<ref name="McAliley2022" /> improves flux modeling with enhanced computational efficiency, resolution of abrupt changes, evaluation of complex boundary conditions, and uncertainty estimations with each step. This new state-space modeling approach uses recursive estimation techniques to automatically estimate highly dynamic vertical flux patterns ranging from sub-daily to seasonal time scales<ref name="McAliley2022" />.

===Electrical Conductivity (EC) Based Technologies===
Electrical conductivity (EC)-based technologies exploit contrasts in EC between surface water and groundwater<ref>Cox, M.H., Su, G.W., Constantz, J., 2007. Heat, Chloride, and Specific Conductance as Ground Water Tracers near Streams. Groundwater, 45(2), pp. 187–195. [https://doi.org/10.1111/j.1745-6584.2006.00276.x doi: 10.1111/j.1745-6584.2006.00276.x].</ref>. EC-based technologies are mostly applied as characterization tools, although the opportunity to monitor GWSWE dynamics with one of these technologies does exist. With the exception of specific conductance probes, the technologies measure the bulk EC of sediments, which will often (but not always) reveal evidence of GWSWE.

Electrical conduction (i.e., the transport of charges) in SW occurs via dissolved ions. Electrical conduction in soils similarly occurs via the ions dissolved in groundwater, with an additional contribution from ions in the electrical double layer that exists at mineral-pore fluid interfaces (known as surface conduction)<ref name="Binley2020">Binley, A., Slater, L., 2020. Resistivity and Induced Polarization: Theory and Applications to the Near-Surface Earth. Cambridge University Press. [https://doi.org/10.1017/9781108685955 doi: 10.1017/9781108685955].</ref>. In relatively fresh surface-water environments, GW is typically more electrically conductive than SW due to the higher ionic concentrations in GW. In these settings, GW inputs to SW may be identified as zones of higher bulk EC beneath the bed. In coastal settings where SW is saline, inputs of relatively fresh GW will give rise to zones of lower conductivity. Whereas the temperature-based methods rely on point measurements at the location of the sensor, EC-based technologies (with the exception of specific conductance measurements at localized points) incorporate inverse modeling to estimate distributions of EC away from the sensors and beneath the bed. Consequently, these technologies may also image losses of SW to GW<ref>Johnson, T.C., Slater, L.D., Ntarlagiannis, D., Day-Lewis, F.D., Elwaseif, M., 2012. Monitoring Groundwater-Surface Water Interaction Using Time-Series and Time-Frequency Analysis of Transient Three-Dimensional Electrical Resistivity Changes. Water Resources Research, 48(7). [https://doi.org/10.1029/2012WR011893 doi: 10.1029/2012WR011893].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2012WR011893 Open Access Article]</ref>. Another advantage is that they may provide information on structural controls on zones of focused GWSWE expressed at the surface. However, interpretation of EC patterns from these technologies is inherently uncertain due to the fact that (with the exception of specific conductance probes) the bulk EC of the sediments is measured. Variations in lithology (e.g., porosity, grain size distribution, which determine the strength of surface conduction) can be misinterpreted as variations in the ionic composition of water.

====Characterization Methods====

=====''Specific Conductance Probes''=====
The simplest EC-based technology is a specific conductance probe, which measures the specific conductance of water between a small pair of metal plates at the end of the sensor probe. Many commercially available water quality sensors have a specific conductance sensor and a temperature sensor integrated into a single probe (they often also measure other water quality parameters, including pH and dissolved oxygen (DO) content). These are direct sensing measurements with a small footprint (the size of the sensor), so this is usually a time-consuming, inefficient method for observing GWSWE dynamics. Furthermore, the sampling volume of the measurement is small (on the order of a cubic centimeter or less), so the degree to which the spot measurement is representative of larger-scale hydrological exchanges is often uncertain. However, specific conductance sensors remain popular, especially when integrated with a point temperature sensor, such as in the [https://clu-in.org/programs/21m2/navytools/gsw/#trident Trident Probe].

=====''Frequency Domain Electromagnetic (EM) Sensing Systems''=====
[[File:IeryFig5.png |thumb|600px|Figure 5. (a) FDEM survey path within a stream and drainage channel network bisecting a wetland complex experiencing localized upwelling of contaminated groundwater (b) operation of an FDEM sensor (Dualem 421S, Dualem, CA) in this shallow stream environment (c) resulting imaging of EC structure in the upper 6 m of streambed sediments. In this case, variations in EC may result from changes in sediment texture that determine the location of focused GWSWE. Dataset acquired under [https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ESTCP project ER21-5237].]]
Electromagnetic (EM) sensors non-invasively measure the bulk EC of sediments (a function of both fluid composition and lithology as mentioned above) by measuring eddy currents induced in conductors using time varying electric and magnetic fields based on the physics of electromagnetic induction. Modern EM systems can simultaneously image across a range of depths. Frequency domain EM (FDEM) instruments generate a current that varies sinusoidally with time at a fixed frequency that is selected on the basis of desired exploration depth and resolution. Modern FDEM sensors use a combination of different coil separations and/or frequencies to resolve conductivity structure over a range of depths. These instruments typically provide high-resolution (sub-meter) information on the bulk EC structure in the upper 5 m of the subsurface (approximately, depending on subsurface EC). Measurements are non-invasively and continuously made, meaning that large areas can be quickly surveyed on foot (e.g., along a shoreline) or from a boat in shallow water (1 m or less deep), for example when pulled along a river or stream channel. The method can also be deployed in wetlands (Figure 5). FDEM data are often presented in terms of variations in the raw measurements because apparent EC values do not represent the true EC of the subsurface. However, with the increasing popularity of sensors with combinations of coil separations, the datasets can be inverted to obtain a model of the distribution of the true EC of the subsurface on land or below a water layer. Inversion of FDEM datasets is usually performed as a series of 1D models, constrained to have a limited variance from each other, to generate a pseudo-2D model of the subsurface. Open-source software, such as [https://hkex.gitlab.io/emagpy/ EMagPy]<ref>McLachlan, P., Blanchy, G., Binley, A., 2021. EMagPy: Open-Source Standalone Software for Processing, Forward Modeling and Inversion of Electromagnetic Induction Data. Computers and Geosciences, 146, 104561. [https://doi.org/10.1016/j.cageo.2020.104561 doi: 10.1016/j.cageo.2020.104561].</ref>, is freely available to manage, visualize and interpret FDEM datasets.

=====''Time Domain EM Sensing Systems''=====
Time domain EM (TEM) systems transmit a current that is abruptly shut off (reduced to zero), resulting in a transient current flow that propagates (with decaying amplitude) into the earth. The time-decaying voltage recorded in a receiver coil contains information on the EC variation with depth below the instrument. TEM systems specifically designed for waterborne surveys provide investigation depths of up to 70 m (again depending on bulk EC structure)<ref>Lane Jr., J.W., Briggs, M.A., Maurya, P.K., White, E.A., Pedersen, J.B., Auken, E., Terry, N., Minsley, B., Kress, W., LeBlanc, D.R., Adams, R., Johnson, C.D., 2020. Characterizing the Diverse Hydrogeology Underlying Rivers and Estuaries Using New Floating Transient Electromagnetic Methodology. Science of the Total Environment, 740, 140074. [https://doi.org/10.1016/j.scitotenv.2020.140074 doi: 10.1016/j.scitotenv.2020.140074].  [//www.enviro.wiki/images/4/4d/LaneEtAl2020.pdf Open Access Manuscript]</ref>. Airborne TEM systems can also be deployed to look at large-scale surface-water/groundwater dynamics, for example submarine discharge or saline intrusion along coastlines<ref>d’Ozouville, N., Auken, E., Sorensen, K., Violette, S., de Marsily, G., Deffontaines, B., Merlen, G., 2008. Extensive Perched Aquifer and Structural Implications Revealed by 3D Resistivity Mapping in a Galapagos Volcano. Earth and Planetary Science Letters, 269(3–4), pp. 518–522. [https://doi.org/10.1016/j.epsl.2008.03.011 doi: 10.1016/j.epsl.2008.03.011].</ref>. Inverse modelling methods are employed to convert the raw measurements obtained along a transect into a distribution of conductivity.

=====''Waterborne Electrical Imaging''=====
[[File:IeryFig6.png |thumb|600px|left|Figure 6. Waterborne electrical imaging in a coastal setting with expected zones of upwelling groundwater (a) typical operation with floating electrode cable pulled behind boat (b) inverted 2D cross section of electrical resistivity along the survey path with possible zones of fresh groundwater discharges indicated from relatively high resistivity sediments. Dataset acquired under [https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ESTCP project ER21-5237].]]
Direct current (DC) electrical imaging techniques are based on galvanic (direct) contact between electrodes used to inject currents (and measure voltages) and the subsurface<ref name="Binley2020" />. Relative to EM methods, this can be a disadvantage when surveying on land. However, when making measurements from a water body, the electrodes used to acquire the data can be deployed as a floating array that is pulled behind a vessel. Waterborne electrical imaging relies on acquiring measurements of electrical potential differences between different pairs of electrodes on the array while current is passed between one pair of electrodes<ref>Day-Lewis, F.D., White, E.A., Johnson, C.D., Lane Jr, J.W., Belaval, M., 2006. Continuous Resistivity Profiling to Delineate Submarine Groundwater Discharge—Examples and Limitations. The Leading Edge, 25(6), pp. 724–728. [https://doi.org/10.1190/1.2210056 doi: 10.1190/1.2210056]</ref>. As the array is pulled behind the boat, thousands of measurements are made along a survey transect. Similar to the EM methods, inverse methods are used to process these datasets and generate a 2D image of the variation in the conductivity of the sediments below the bed. Open-source software such as [https://hkex.gitlab.io/resipy/ ResIPy] support 2D or 3D inversion of waterborne datasets. Figure 6 shows results of a waterborne electrical imaging survey conducted to locate regions where relative fresh (low EC) groundwater is discharging into the near shore environment in a coastal setting. Beneath the saline (high EC) water layer, spatial variability in bulk EC may partly be related to variations in conductivity of the pore-filling fluid, with localized low bulk EC zones possibly indicating upwelling of fresh groundwater. However, the variation in bulk EC in the sediments below the water layer may reflect variations in lithology. An extension of the electrical imaging method involves collecting induced polarization (IP) data<ref name="Binley2020" /> in addition to bulk EC data. IP measurements capture the temporary charge storage characteristics of the subsurface, which are strongly controlled by lithology, with finer-grained (e.g. clay rich) sediments being more chargeable than coarser grained sediments. The method can be particularly useful for differentiating between EC variations resulting from variations in pore fluid specific conductance and those conductivity variations associated with lithology. For example, based on electrical imaging methods alone (or the EM method alone), it may not be possible to distinguish a zone of high EC groundwater entering into freshwater from a region of relatively finer-grained sediments without additional supporting data (e.g. a core). IP measurements may be able to resolve this ambiguity as the region of finer-grained sediments will be more chargeable than the surrounding areas.

====Monitoring Methods====

=====''Land-based Electrical Monitoring''=====
There is increasing interest in the use of electrical imaging methods as monitoring systems. Semi-permanent arrays of electrodes can be installed to monitor GWSWE dynamics over periods of days to years. Low-power prototype instrumentation has been developed to specifically address the needs for long-term monitoring, although such instrumentation is not yet commercially available. Consequently, electrical monitoring of GWSWE currently remains in the realm of research-driven specialists.

===Considerations for Using Waterborne EM and Electrical Imaging Methods===
The waterborne EM and electrical imaging methods both provide a way to determine variations in bulk electrical conductivity associated with GWSWE. However, each method has some advantages and some disadvantages. One consideration is maneuverability, particularly in shallow water environments. FDEM instruments are the most maneuverable, although they offer only limited investigation depths. Although bigger than the shallow-sensing FDEM systems, TEM systems are still relatively maneuverable on water bodies. Whereas FDEM systems can be operated from a single small vessel, the TEM deployments require the use of pontoons as the transmitter and receiver coils need to be separated 9 m apart. This still equates to good maneuverability compared to waterborne electrical imaging where a floating electrode cable, typically 30-50 m long, is pulled behind a vessel.

In all three methods, variations in the water layer depth and the specific conductance of the water can significantly affect the data, especially in deeper water. Therefore, it is common to continuously record these parameters with an echo depth sounder and a specific conductance probe suspended in the water layer, with a GPS receiver to record continuous spatial data.

===Other Hydrogeophysical Technologies===
A number of other hydrogeophysical technologies exist, with proven applications to the characterization of settings where GWSWE occurs. Seismic [[Wikipedia:Reflection seismology | reflection]] and [[Wikipedia:Seismic refraction | refraction]] methods are used to image the depositional environments along coastlines. [[Wikipedia:Ground-penetrating radar | Ground penetrating radar]] has been effectively used to image depositional environments around freshwater lake shorelines, and across streams and rivers. Such information may help to identify depositional features that promote GWSWE but, unlike the temperature- and conductivity-based methods, do not sense changes in physical properties associated with the exchanging water itself.

One promising technique for detecting GWSWE is known as the [https://www.epa.gov/environmental-geophysics/self-potential-sp self-potential (SP)] method. This simple to deploy geophysical technique is based on mapping voltage differences caused by natural sources of electric current in the Earth that are generated through a number of coupled flow processes, one being the coupling of pore fluid flow and transport of electric charge. Zones of enhanced seepage within a porous medium can result in a significant ‘streaming potential’ due to charge transport induced by fluid flow. This phenomenon has been effectively used to locate zones of leakage through dams and embankments<ref>Panthulu, T.V, Krishnaiah, C., Shirke, J.M., 2001. Detection of Seepage Paths in Earth Dams Using Self-Potential and Electrical Resistivity Methods. Engineering Geology, 59(3-4), pp. 281–295. [https://doi.org/10.1016/S0013-7952(00)00082-X doi: 10.1016/S0013-7952(00)00082-X].</ref>. Recently, floating SP measurements have been used to define gaining and losing portions of streams and to identify evidence of focused exchange<ref>Ikard, S.J., Teeple, A.P., Payne, J.D., Stanton, G.P., Banta, J.R., 2018. New Insights On Scale-Dependent Surface-Groundwater Exchange from a Floating Self-Potential Dipole. Journal of Environmental and Engineering Geophysics, 23(2), pp. 261–287. [https://doi.org/10.2113/JEEG23.2.261 doi: 10.2113/JEEG23.2.261].</ref>. Although the data acquisition is simple, consisting of a pair of non-polarizing electrodes and a voltmeter, the interpretation of SP measurements requires expert knowledge to filter out confounding contributions to the recorded signals.

==Guidelines for Implementing Hydrogeophysical Methods into GWSWE Studies==
A number of factors will affect the success of individual hydrogeophysical methods at a specific
site of GWSWE. Depending on site conditions and the objective, some methods may be inappropriate to deploy. For example, temperature-based methods will most likely succeed at times of the year and times of day when contrasts between upwelling groundwater and surface water are greatest. In contrast, it is quite possible that some sites of GWSWE will have an insufficient contrast in the specific conductance of the GW versus the SW to make techniques based on EC measurements effective. A groundwater-surface water method selection tool ([https://water.usgs.gov/water-resources/software/GW-SW-MST/ GW/SW-MST]<ref>Hammett, S., Day-Lewis, F.D., Trottier, B., Barlow, P.M., Briggs, M.A., Delin, G., Harvey, J.W., Johnson, C.D., Lane Jr., J.W., Rosenberry, D.O., Werkema, D.D., 2022. GW/SW-MST: A Groundwater/Surface-Water Method Selection Tool. Groundwater, 60(6), pp. 784-791. [https://doi.org/10.1111/gwat.13194 doi: 10.1111/gwat.13194].  [https://ngwa.onlinelibrary.wiley.com/doi/am-pdf/10.1111/gwat.13194 Open Access Manuscript]</ref>) has recently been developed to assist practitioners in the informed selection of the methods that will be most effective for a particular site at a particular time. The tool guides the user through a series of questions that consider both the specific conditions at the site and the primary objectives of the investigation. The methods selection tool covers the application of a number of additional technologies besides those included in this article. The selection tool is recommended as the starting point for any practitioner needing to investigate potential GWSWE.

==Summary==
A number of temperature-based and electrical conductivity-based technologies exist for monitoring GWSWE over a range of spatial scales. Many of these technologies are most powerful when used as reconnaissance tools to rapidly identify probable locations of GWSWE to be verified with a limited campaign of direct sensing measurements (traditionally seepage meters). Vertical temperature profilers (VTPs) offer direct quantification of fluxes at sites identified by the reconnaissance tools, and some studies show that these methods are more reliable than traditional seepage meters. Given the number of sites across the globe where contaminated groundwater is impacting surface water resources, use of these technologies for both characterization and monitoring is expected to become more common.

==References==
<references />

==See Also==
USGS Water Resources:

*https://www.usgs.gov/mission-areas/water-resources/science/geophysics-usgs-groundwatersurface-water-exchange-studies

*https://www.usgs.gov/mission-areas/water-resources/science/thermal-imaging-cameras-studying-groundwatersurface-water

*https://www.usgs.gov/mission-areas/water-resources/science/fiber-optic-distributed-temperature-sensing-technology

*https://www.usgs.gov/mission-areas/water-resources/science/integration-suas-hydrogeophysical-studies

Dr. Ramona Iery

2026-01-02T15:27:15Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :NAVFAC EXWC :Shore Department :1000 23rd Ave :Port Hueneme, CA 93043 EMAIL: [mailto:Ramona.iery.civ@us.navy.mil..."

==Work and Contact Information==

EMPLOYER:
:NAVFAC EXWC 
:Shore Department
:1000 23rd Ave 
:Port Hueneme, CA 93043 

EMAIL: [mailto:Ramona.iery.civ@us.navy.mil Ramona.iery.civ@us.navy.mil]

==About the Contributor==
Ramona Iery is an environmental engineer with 15 years of experience in the field of environmental remediation. Her areas of expertise include fate and transport, site characterization, long-term monitoring and remediation of contaminants such as chlorinated solvents, petroleum hydrocarbons and emerging contaminants such as 1,4-dioxane and per-and polyfluoroalkyl substances (PFAS). She has been conducting research on PFAS for the past 9 years and currently manages multiple SERDP/ESTCP and NAVFAC PFAS research projects. She received a PhD in environmental engineering and science from Clemson University and a master of engineering in civil and environmental engineering from Tennessee State University.

==Article Contributions==
*[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]
*[[Thermal Conduction Heating for Treatment of PFAS-Impacted Soil]]

__NOTOC__

[[Category: Contributors|Iery]]

Dr. Robert Borden, P.E.

2025-11-06T21:25:30Z

Debra Tabron:

==Work and Contact Information==

:WEBPAGE: [https://www.ccee.ncsu.edu/people/rcborden/ http://www4.ncsu.edu/~rcborden/]

==About the Contributor==
Dr. Borden served as Editor-in-Chief for ENVIRO.wiki. Bob was an internationally recognized expert on monitored natural attenuation and in situ bioremediation. At EOS Remediation, he lead new product development and provided technical support to our customers. Bob also served as Professor of Civil, Construction and Environmental Engineering at North Carolina State University (NCSU) where he conducted research and advised students.

==Article Contributions==

*[[Bioremediation - Anaerobic Secondary Water Quality Impacts]]
*[[Design Tool - Base Addition for ERD]][[Munitions Constituents]]
*[[Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation]]
*[[Groundwater Flow and Solute Transport]]
*[[Low pH Inhibition of Reductive Dechlorination]]

__NOTOC__

[[Contributors]]

Remediation of Stormwater Runoff Contaminated by Munition Constituents

2025-11-06T20:58:32Z

Debra Tabron:

Past and ongoing military operations have resulted in contamination of surface soil with [[Munitions Constituents | munition constituents (MC)]], which have human and environmental health impacts. These compounds can be transported off site via stormwater runoff during precipitation events. Technologies to “trap and treat” surface runoff before it enters downstream receiving bodies (e.g., streams, rivers, ponds) (see Figure 1), and which are compatible with ongoing range activities are needed. This article describes a passive and sustainable approach for effective management of munition constituents in stormwater runoff.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Munitions Constituents]]

'''Contributor:''' [[Dr. Mark Fuller]]

'''Key Resource(s):'''
*[[Media: ER19-1106 Final Report.pdf | Development of Innovative Passive and Sustainable Treatment Technologies for Energetic Compounds in Surface Runoff on Active Ranges - Final Report. SERDP Project ER19-1106]]<ref name="FullerChiu2024">Fuller, M., Chiu, P., 2024. Development of Innovative Passive and Sustainable Treatment Technologies for Energetic Compounds in Surface Runoff on Active Ranges - [[Media: ER19-1106 Final Report.pdf | Final Report]]. [https://serdp-estcp.mil/ Strategic Environmental Research and Development Program (SERDP) - Environmental Security Technology Certification Program (ESTCP)], Project ER19-1106.</ref>

==Background==
===Surface Runoff Characteristics and Treatment Approaches===
[[File: FullerFig1.png | thumb | 400 px | left | Figure 1. Conceptual model of passive trap and treat approach for MC removal from stormwater runoff]]
During large precipitation events the rate of water deposition exceeds the rate of water infiltration, resulting in surface runoff (also called stormwater runoff). Surface characteristics including soil texture, presence of impermeable surfaces (natural and artificial), slope, and density and type of vegetation all influence the amount of surface runoff from a given land area. The use of passive systems such as retention ponds and biofiltration cells for treatment of surface runoff is well established for urban and roadway runoff. Treatment in those cases is typically achieved by directing runoff into and through a small constructed wetland, often at the outlet of a retention basin, or via filtration by directing runoff through a more highly engineered channel or vault containing the treatment materials. Filtration based technologies have proven to be effective for the removal of metals, organics, and suspended solids<ref>Sansalone, J.J., 1999. In-situ performance of a passive treatment system for metal source control. Water Science and Technology, 39(2), pp. 193-200. [https://doi.org/10.1016/S0273-1223(99)00023-2 doi: 10.1016/S0273-1223(99)00023-2]</ref><ref>Deletic, A., Fletcher, T.D., 2006. Performance of grass filters used for stormwater treatment—A field and modelling study. Journal of Hydrology, 317(3-4), pp. 261-275. [http://dx.doi.org/10.1016/j.jhydrol.2005.05.021 doi: 10.1016/j.jhydrol.2005.05.021]</ref><ref>Grebel, J.E., Charbonnet, J.A., Sedlak, D.L., 2016. Oxidation of organic contaminants by manganese oxide geomedia for passive urban stormwater treatment systems. Water Research, 88, pp. 481-491. [http://dx.doi.org/10.1016/j.watres.2015.10.019 doi: 10.1016/j.watres.2015.10.019]</ref><ref>Seelsaen, N., McLaughlan, R., Moore, S., Ball, J.E., Stuetz, R.M., 2006. Pollutant removal efficiency of alternative filtration media in stormwater treatment. Water Science and Technology, 54(6-7), pp. 299-305. [https://doi.org/10.2166/wst.2006.617 doi: 10.2166/wst.2006.617]</ref>.

===Surface Runoff on Ranges===
[[File: FullerFig2.png | thumb | 600 px | Figure 2. Conceptual illustration of munition constituent production and transport on military ranges. Mesoscale residues are qualitatively defined as being easily visible to the naked eye (e.g., from around 50 µm to multiple cm in size) and less likely to be transported by moving water. Microscale residues are defined as <50 µm down to below 1 µm, and more likely to be entrained in, and transported by, moving water as particulates. Blue arrows represent possible water flow paths and include both dissolved and solid phase energetics. The red vertical arrow represents the predominant energetics dissolution process in close proximity to the residues due to precipitation.]]
Surface runoff represents a major potential mechanism through which energetics residues and related materials are transported off site from range soils to groundwater and surface water receptors (Figure 2). This process is particularly important for energetics that are water soluble (e.g., [[Wikipedia: Nitrotriazolone | NTO]] and [[Wikipedia: Nitroguanidine | NQ]]) or generate soluble daughter products (e.g., [[Wikipedia: 2,4-Dinitroanisole | DNAN]] and [[Wikipedia: TNT | TNT]]). While traditional MC such as [[Wikipedia: RDX | RDX]] and [[Wikipedia: HMX | HMX]] have limited aqueous solubility, they also exhibit recalcitrance to degrade under most natural conditions. RDX and [[Wikipedia: Perchlorate | perchlorate]] are frequent groundwater contaminants on military training ranges. While actual field measurements of energetics in surface runoff are limited, laboratory experiments have been performed to predict mobile energetics contamination levels based on soil mass loadings<ref>Cubello, F., Polyakov, V., Meding, S.M., Kadoya, W., Beal, S., Dontsova, K., 2024. Movement of TNT and RDX from composition B detonation residues in solution and sediment during runoff. Chemosphere, 350, Article 141023. [https://doi.org/10.1016/j.chemosphere.2023.141023 doi: 10.1016/j.chemosphere.2023.141023]</ref><ref>Karls, B., Meding, S.M., Li, L., Polyakov, V., Kadoya, W., Beal, S., Dontsova, K., 2023. A laboratory rill study of IMX-104 transport in overland flow. Chemosphere, 310, Article 136866. [https://doi.org/10.1016/j.chemosphere.2022.136866 doi: 10.1016/j.chemosphere.2022.136866]  [[Media: KarlsEtAl2023.pdf | Article]]</ref><ref>Polyakov, V., Beal, S., Meding, S.M., Dontsova, K., 2025. Effect of gypsum on transport of IMX-104 constituents in overland flow under simulated rainfall. Journal of Environmental Quality, 54(1), pp. 191-203. [https://doi.org/10.1002/jeq2.20652 doi: 10.1002/jeq2.20652]  [[Media: PolyakovEtAl2025.pdf|Article]]</ref><ref>Polyakov, V., Kadoya, W., Beal, S., Morehead, H., Hunt, E., Cubello, F., Meding, S.M., Dontsova, K., 2023. Transport of insensitive munitions constituents, NTO, DNAN, RDX, and HMX in runoff and sediment under simulated rainfall. Science of the Total Environment, 866, Article 161434. [https://doi.org/10.1016/j.scitotenv.2023.161434 doi: 10.1016/j.scitotenv.2023.161434]  [[Media: PolyakovEtAl2023.pdf|Article]]</ref><ref>Price, R.A., Bourne, M., Price, C.L., Lindsay, J., Cole, J., 2011. Transport of RDX and TNT from Composition-B Explosive During Simulated Rainfall. In: Environmental Chemistry of Explosives and Propellant Compounds in Soils and Marine Systems: Distributed Source Characterization and Remedial Technologies. American Chemical Society, pp. 229-240. [https://doi.org/10.1021/bk-2011-1069.ch013 doi: 10.1021/bk-2011-1069.ch013]</ref>. For example, in a previous small study, MC were detected in surface runoff from an active live-fire range<ref>Fuller, M.E., 2015. Fate and Transport of Colloidal Energetic Residues. Department of Defense Strategic Environmental Research and Development Program (SERDP), Project ER-1689. [https://serdp-estcp.mil/projects/details/10760fd6-fb55-4515-a629-f93c555a92f0 Project Website]   [[Media: ER-1689-FR.pdf|Final Report]]</ref>, and more recent sampling has detected MC in marsh surface water adjacent to the same installation (personal communication). Another recent report from Canada also detected RDX in both surface runoff and surface water at low part per billion levels in a survey of several military demolition sites<ref>Lapointe, M.-C., Martel, R., Diaz, E., 2017. A Conceptual Model of Fate and Transport Processes for RDX Deposited to Surface Soils of North American Active Demolition Sites. Journal of Environmental Quality, 46(6), pp. 1444-1454. [https://doi.org/10.2134/jeq2017.02.0069 doi: 10.2134/jeq2017.02.0069]</ref>. However, overall, data regarding the MC contaminant profile of surface runoff from ranges is very limited, and the possible presence of non-energetic constituents (e.g., metals, binders, plasticizers) in runoff has not been examined. Additionally, while energetics-contaminated surface runoff is an important concern, mitigation technologies specifically for surface runoff have not yet been developed and widely deployed in the field. To effectively capture and degrade MC and associated compounds that are present in surface runoff, novel treatment media are needed to sorb a broad range of energetic materials and to transform the retained compounds through abiotic and/or microbial processes.

Surface runoff of organic and inorganic contaminants from live-fire ranges is a challenging issue for the Department of Defense (DoD). Potentially even more problematic is the fact that inputs to surface waters from large testing and training ranges typically originate from multiple sources, often encompassing hundreds of acres. No available technologies are currently considered effective for controlling non-point source energetics-laden surface runoff. While numerous technologies exist to treat collected explosives residues, contaminated soil and even groundwater, the decentralized nature and sheer volume of military range runoff have precluded the use of treatment technologies at full scale in the field.

==Range Runoff Treatment Technology Components==
Based on the conceptual foundation of previous research into surface water runoff treatment for other contaminants, and with a goal to “trap and treat” the target compounds, the following components were selected for inclusion in the technology developed to address range runoff contaminated with energetic compounds.

===Peat===
Previous research demonstrated that a peat-based system provided a natural and sustainable sorptive medium for organic explosives such as HMX, RDX, and TNT, allowing much longer residence times than predicted from hydraulic loading alone<ref>Fuller, M.E., Hatzinger, P.B., Rungkamol, D., Schuster, R.L., Steffan, R.J., 2004. Enhancing the attenuation of explosives in surface soils at military facilities: Combined sorption and biodegradation. Environmental Toxicology and Chemistry, 23(2), pp. 313-324. [https://doi.org/10.1897/03-187 doi: 10.1897/03-187]</ref><ref>Fuller, M.E., Lowey, J.M., Schaefer, C.E., Steffan, R.J., 2005. A Peat Moss-Based Technology for Mitigating Residues of the Explosives TNT, RDX, and HMX in Soil. Soil and Sediment Contamination: An International Journal, 14(4), pp. 373-385. [https://doi.org/10.1080/15320380590954097 doi: 10.1080/15320380590954097]</ref><ref name="FullerEtAl2009">Fuller, M.E., Schaefer, C.E., Steffan, R.J., 2009. Evaluation of a peat moss plus soybean oil (PMSO) technology for reducing explosive residue transport to groundwater at military training ranges under field conditions. Chemosphere, 77(8), pp. 1076-1083. [https://doi.org/10.1016/j.chemosphere.2009.08.044 doi: 10.1016/j.chemosphere.2009.08.044]</ref><ref>Hatzinger, P.B., Fuller, M.E., Rungkamol, D., Schuster, R.L., Steffan, R.J., 2004. Enhancing the attenuation of explosives in surface soils at military facilities: Sorption-desorption isotherms. Environmental Toxicology and Chemistry, 23(2), pp. 306-312. [https://doi.org/10.1897/03-186 doi: 10.1897/03-186]</ref><ref name="SchaeferEtAl2005">Schaefer, C.E., Fuller, M.E., Lowey, J.M., Steffan, R.J., 2005. Use of Peat Moss Amended with Soybean Oil for Mitigation of Dissolved Explosive Compounds Leaching into the Subsurface: Insight into Mass Transfer Mechanisms. Environmental Engineering Science, 22(3), pp. 337-349. [https://doi.org/10.1089/ees.2005.22.337 doi: 10.1089/ees.2005.22.337]</ref>. Peat moss represents a bioactive environment for treatment of the target contaminants. While the majority of the microbial reactions are aerobic due to the presence of measurable dissolved oxygen in the bulk solution, anaerobic reactions (including methanogenesis) can occur in microsites within the peat. The peat-based substrate acts not only as a long term electron donor as it degrades but also acts as a strong sorbent. This is important in intermittently loaded systems in which a large initial pulse of MC can be temporarily retarded on the peat matrix and then slowly degraded as they desorb<ref name="FullerEtAl2009"/><ref name="SchaeferEtAl2005"/>. This increased residence time enhances the biotransformation of energetics and promotes the immobilization and further degradation of breakdown products. Abiotic degradation reactions are also likely enhanced by association with the organic-rich peat (e.g., via electron shuttling reactions of [[Wikipedia: Humic substance | humics]])<ref>Roden, E.E., Kappler, A., Bauer, I., Jiang, J., Paul, A., Stoesser, R., Konishi, H., Xu, H., 2010. Extracellular electron transfer through microbial reduction of solid-phase humic substances. Nature Geoscience, 3, pp. 417-421. [https://doi.org/10.1038/ngeo870 doi: 10.1038/ngeo870]</ref>.

===Soybean Oil===
Modeling has indicated that peat moss amended with crude soybean oil would significantly reduce the flux of dissolved TNT, RDX, and HMX through the vadose zone to groundwater compared to a non-treated soil (see [https://serdp-estcp.mil/projects/details/20e2f05c-fd50-4fd3-8451-ba73300c7531 ESTCP ER-200434]). The technology was validated in field soil plots, showing a greater than 500-fold reduction in the flux of dissolved RDX from macroscale Composition B detonation residues compared to a non-treated control plot<ref name="FullerEtAl2009"/>. Laboratory testing and modeling indicated that the addition of soybean oil increased the biotransformation rates of RDX and HMX at least 10-fold compared to rates observed with peat moss alone<ref name="SchaeferEtAl2005"/>. Subsequent experiments also demonstrated the effectiveness of the amended peat moss material for stimulating perchlorate transformation when added to a highly contaminated soil (Fuller et al., unpublished data). These previous findings clearly demonstrate the effectiveness of peat-based materials for mitigating transport of both organic and inorganic energetic compounds through soil to groundwater.

===Biochar===
Recent reports have highlighted additional materials that, either alone, or in combination with electron donors such as peat moss and soybean oil, may further enhance the sorption and degradation of surface runoff contaminants, including both legacy energetics and [[Wikipedia: Insensitive_munition#Insensitive_high_explosives | insensitive high explosives (IHE)]]. For instance, [[Wikipedia: Biochar | biochar]], a type of black carbon, has been shown to not only sorb a wide range of organic and inorganic contaminants including MCs<ref>Ahmad, M., Rajapaksha, A.U., Lim, J.E., Zhang, M., Bolan, N., Mohan, D., Vithanage, M., Lee, S.S., Ok, Y.S., 2014. Biochar as a sorbent for contaminant management in soil and water: A review. Chemosphere, 99, pp. 19-33. [https://doi.org/10.1016/j.chemosphere.2013.10.071 doi: 10.1016/j.chemosphere.2013.10.071]</ref><ref>Mohan, D., Sarswat, A., Ok, Y.S., Pittman, C.U., 2014. Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent – A critical review. Bioresource Technology, 160, pp. 191-202. [https://doi.org/10.1016/j.biortech.2014.01.120 doi: 10.1016/j.biortech.2014.01.120]</ref><ref>Oh, S.-Y., Seo, Y.-D., Jeong, T.-Y., Kim, S.-D., 2018. Sorption of Nitro Explosives to Polymer/Biomass-Derived Biochar. Journal of Environmental Quality, 47(2), pp. 353-360. [https://doi.org/10.2134/jeq2017.09.0357 doi: 10.2134/jeq2017.09.0357]</ref><ref>Xie, T., Reddy, K.R., Wang, C., Yargicoglu, E., Spokas, K., 2015. Characteristics and Applications of Biochar for Environmental Remediation: A Review. Critical Reviews in Environmental Science and Technology, 45(9), pp. 939-969. [https://doi.org/10.1080/10643389.2014.924180 doi: 10.1080/10643389.2014.924180]</ref>, but also to facilitate their degradation<ref>Oh, S.-Y., Cha, D.K., Kim, B.-J., Chiu, P.C., 2002. Effect of adsorption to elemental iron on the transformation of 2,4,6-trinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine in solution. Environmental Toxicology and Chemistry, 21(7), pp. 1384-1389. [https://doi.org/10.1002/etc.5620210708 doi: 10.1002/etc.5620210708]</ref><ref>Ye, J., Chiu, P.C., 2006. Transport of Atomic Hydrogen through Graphite and its Reaction with Azoaromatic Compounds. Environmental Science and Technology, 40(12), pp. 3959-3964. [https://doi.org/10.1021/es060038x doi: 10.1021/es060038x]</ref><ref name="OhChiu2009">Oh, S.-Y., Chiu, P.C., 2009. Graphite- and Soot-Mediated Reduction of 2,4-Dinitrotoluene and Hexahydro-1,3,5-trinitro-1,3,5-triazine. Environmental Science and Technology, 43(18), pp. 6983-6988. [https://doi.org/10.1021/es901433m doi: 10.1021/es901433m]</ref><ref name="OhEtAl2013">Oh, S.-Y., Son, J.-G., Chiu, P.C., 2013. Biochar-mediated reductive transformation of nitro herbicides and explosives. Environmental Toxicology and Chemistry, 32(3), pp. 501-508. [https://doi.org/10.1002/etc.2087 doi: 10.1002/etc.2087]   [[Media: OhEtAl2013.pdf|Article]]</ref><ref name="XuEtAl2010">Xu, W., Dana, K.E., Mitch, W.A., 2010. Black Carbon-Mediated Destruction of Nitroglycerin and RDX by Hydrogen Sulfide. Environmental Science and Technology, 44(16), pp. 6409-6415. [https://doi.org/10.1021/es101307n doi: 10.1021/es101307n]</ref><ref>Xu, W., Pignatello, J.J., Mitch, W.A., 2013. Role of Black Carbon Electrical Conductivity in Mediating Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) Transformation on Carbon Surfaces by Sulfides. Environmental Science and Technology, 47(13), pp. 7129-7136. [https://doi.org/10.1021/es4012367 doi: 10.1021/es4012367]</ref>. Depending on the source biomass and [[Wikipedia: Pyrolysis| pyrolysis]] conditions, biochar can possess a high [[Wikipedia: Specific surface area | specific surface area]] (on the order of several hundred m2/g)<ref>Zhang, J., You, C., 2013. Water Holding Capacity and Absorption Properties of Wood Chars. Energy and Fuels, 27(5), pp. 2643-2648. [https://doi.org/10.1021/ef4000769 doi: 10.1021/ef4000769]</ref><ref>Gray, M., Johnson, M.G., Dragila, M.I., Kleber, M., 2014. Water uptake in biochars: The roles of porosity and hydrophobicity. Biomass and Bioenergy, 61, pp. 196-205. [https://doi.org/10.1016/j.biombioe.2013.12.010 doi: 10.1016/j.biombioe.2013.12.010]</ref> and hence a high sorption capacity. Biochar and other black carbon also exhibit especially high affinity for [[Wikipedia: Nitro compound | nitroaromatic compounds (NACs)]] including TNT and 2,4-dinitrotoluene (DNT)<ref>Sander, M., Pignatello, J.J., 2005. Characterization of Charcoal Adsorption Sites for Aromatic Compounds: Insights Drawn from Single-Solute and Bi-Solute Competitive Experiments. Environmental Science and Technology, 39(6), pp. 1606-1615. [https://doi.org/10.1021/es049135l doi: 10.1021/es049135l]</ref><ref name="ZhuEtAl2005">Zhu, D., Kwon, S., Pignatello, J.J., 2005. Adsorption of Single-Ring Organic Compounds to Wood Charcoals Prepared Under Different Thermochemical Conditions. Environmental Science and Technology 39(11), pp. 3990-3998. [https://doi.org/10.1021/es050129e doi: 10.1021/es050129e]</ref><ref name="ZhuPignatello2005">Zhu, D., Pignatello, J.J., 2005. Characterization of Aromatic Compound Sorptive Interactions with Black Carbon (Charcoal) Assisted by Graphite as a Model. Environmental Science and Technology, 39(7), pp. 2033-2041. [https://doi.org/10.1021/es0491376 doi: 10.1021/es0491376]</ref>. This is due to the strong [[Wikipedia: Pi-interaction | ''π-π'' electron donor-acceptor interactions]] between electron-rich graphitic domains in black carbon and the electron-deficient aromatic ring of the NAC<ref name="ZhuEtAl2005"/><ref name="ZhuPignatello2005"/>. These characteristics make biochar a potentially effective, low cost, and sustainable sorbent for removing MC and other contaminants from surface runoff and retaining them for subsequent degradation ''in situ''.

Furthermore, black carbon such as biochar can promote abiotic and microbial transformation reactions by facilitating electron transfer. That is, biochar is not merely a passive sorbent for contaminants, but also a redox mediator for their degradation. Biochar can promote contaminant degradation through two different mechanisms: electron conduction and electron storage<ref>Sun, T., Levin, B.D.A., Guzman, J.J.L., Enders, A., Muller, D.A., Angenent, L.T., Lehmann, J., 2017. Rapid electron transfer by the carbon matrix in natural pyrogenic carbon. Nature Communications, 8, Article 14873. [https://doi.org/10.1038/ncomms14873 doi: 10.1038/ncomms14873]   [[Media: SunEtAl2017.pdf|Article]]</ref>.

First, the microscopic graphitic regions in biochar can adsorb contaminants like NACs strongly, as noted above, and also conduct reducing equivalents such as electrons and atomic hydrogen to the sorbed contaminants, thus promoting their reductive degradation. This catalytic process has been demonstrated for TNT, DNT, RDX, HMX, and [[Wikipedia: Nitroglycerin | nitroglycerin]]<ref>Oh, S.-Y., Cha, D.K., Chiu, P.C., 2002. Graphite-Mediated Reduction of 2,4-Dinitrotoluene with Elemental Iron. Environmental Science and Technology, 36(10), pp. 2178-2184. [https://doi.org/10.1021/es011474g doi: 10.1021/es011474g]</ref><ref>Oh, S.-Y., Cha, D.K., Kim, B.J., Chiu, P.C., 2004. Reduction of Nitroglycerin with Elemental Iron: Pathway, Kinetics, and Mechanisms. Environmental Science and Technology, 38(13), pp. 3723-3730. [https://doi.org/10.1021/es0354667 doi: 10.1021/es0354667]</ref><ref>Oh, S.-Y., Cha, D.K., Kim, B.J., Chiu, P.C., 2005. Reductive transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, and methylenedinitramine with elemental iron. Environmental Toxicology and Chemistry, 24(11), pp. 2812-2819. [https://doi.org/10.1897/04-662R.1 doi: 10.1897/04-662R.1]</ref><ref name="OhChiu2009"/><ref name="XuEtAl2010"/> and is expected to occur also for IHE including DNAN and NTO.

Second, biochar contains in its structure abundant redox-facile functional groups such as [[Wikipedia: Quinone | quinones]] and [[Wikipedia: Hydroquinone | hydroquinones]], which are known to accept and donate electrons reversibly. Depending on the biomass and pyrolysis temperature, certain biochar can possess a rechargeable electron storage capacity (i.e., reversible electron accepting and donating capacity) on the order of several millimoles e–/g<ref>Klüpfel, L., Keiluweit, M., Kleber, M., Sander, M., 2014. Redox Properties of Plant Biomass-Derived Black Carbon (Biochar). Environmental Science and Technology, 48(10), pp. 5601-5611. [https://doi.org/10.1021/es500906d doi: 10.1021/es500906d]</ref><ref>Prévoteau, A., Ronsse, F., Cid, I., Boeckx, P., Rabaey, K., 2016. The electron donating capacity of biochar is dramatically underestimated. Scientific Reports, 6, Article 32870. [https://doi.org/10.1038/srep32870 doi: 10.1038/srep32870]   [[Media: PrevoteauEtAl2016.pdf|Article]]</ref><ref>Xin, D., Xian, M., Chiu, P.C., 2018. Chemical methods for determining the electron storage capacity of black carbon. MethodsX, 5, pp. 1515-1520. [https://doi.org/10.1016/j.mex.2018.11.007 doi: 10.1016/j.mex.2018.11.007]   [[Media: XinEtAl2018.pdf|Article]]</ref>. This means that when "charged", biochar can provide electrons for either abiotic or biotic degradation of reducible compounds such as MC. The abiotic reduction of DNT and RDX mediated by biochar has been demonstrated<ref name="OhEtAl2013"/> and similar reactions are expected to occur for DNAN and NTO as well. Recent studies have shown that the electron storage capacity of biochar is also accessible to microbes. For example, soil bacteria such as [[Wikipedia: Geobacter | ''Geobacter'']] and [[Wikipedia: Shewanella | ''Shewanella'']] species can utilize oxidized (or "discharged") biochar as an electron acceptor for the oxidation of organic substrates such as lactate and acetate<ref>Kappler, A., Wuestner, M.L., Ruecker, A., Harter, J., Halama, M., Behrens, S., 2014. Biochar as an Electron Shuttle between Bacteria and Fe(III) Minerals. Environmental Science and Technology Letters, 1(8), pp. 339-344. [https://doi.org/10.1021/ez5002209 doi: 10.1021/ez5002209]</ref><ref name="SaquingEtAl2016">Saquing, J.M., Yu, Y.-H., Chiu, P.C., 2016. Wood-Derived Black Carbon (Biochar) as a Microbial Electron Donor and Acceptor. Environmental Science and Technology Letters, 3(2), pp. 62-66. [https://doi.org/10.1021/acs.estlett.5b00354 doi: 10.1021/acs.estlett.5b00354]</ref> and reduced (or "charged") biochar as an electron donor for the reduction of nitrate<ref name="SaquingEtAl2016"/>. This is significant because, through microbial access of stored electrons in biochar, contaminants that do not sorb strongly to biochar can still be degraded.

Similar to nitrate, perchlorate and other relatively water-soluble energetic compounds (e.g., NTO and NQ) may also be similarly transformed using reduced biochar as an electron donor. Unlike other electron donors, biochar can be recharged through biodegradation of organic substrates<ref name="SaquingEtAl2016"/> and thus can serve as a long-lasting sorbent and electron repository in soil. Similar to peat moss, the high porosity and surface area of biochar not only facilitate contaminant sorption but also create anaerobic reducing microenvironments in its inner pores, where reductive degradation of energetic compounds can take place.

===Other Sorbents===
Chitin and unmodified cellulose were predicted by [[Wikipedia: Density functional theory | Density Functional Theory]] methods to be favorable for absorption of NTO and NQ, as well as the legacy explosives<ref>Todde, G., Jha, S.K., Subramanian, G., Shukla, M.K., 2018. Adsorption of TNT, DNAN, NTO, FOX7, and NQ onto Cellulose, Chitin, and Cellulose Triacetate. Insights from Density Functional Theory Calculations. Surface Science, 668, pp. 54-60. [https://doi.org/10.1016/j.susc.2017.10.004 doi: 10.1016/j.susc.2017.10.004]   [[Media: ToddeEtAl2018.pdf | Manuscript]]</ref>. Cationized cellulosic materials (e.g., cotton, wood shavings) have been shown to effectively remove negatively charged energetics like perchlorate and NTO from solution<ref name="FullerEtAl2022">Fuller, M.E., Farquharson, E.M., Hedman, P.C., Chiu, P., 2022. Removal of munition constituents in stormwater runoff: Screening of native and cationized cellulosic sorbents for removal of insensitive munition constituents NTO, DNAN, and NQ, and legacy munition constituents HMX, RDX, TNT, and perchlorate. Journal of Hazardous Materials, 424(C), Article 127335. [https://doi.org/10.1016/j.jhazmat.2021.127335 doi: 10.1016/j.jhazmat.2021.127335]   [[Media: FullerEtAl2022.pdf | Manuscript]]</ref>. A substantial body of work has shown that modified cellulosic biopolymers can also be effective sorbents for removing metals from solution<ref>Burba, P., Willmer, P.G., 1983. Cellulose: a biopolymeric sorbent for heavy-metal traces in waters. Talanta, 30(5), pp. 381-383. [https://doi.org/10.1016/0039-9140(83)80087-3 doi: 10.1016/0039-9140(83)80087-3]</ref><ref>Brown, P.A., Gill, S.A., Allen, S.J., 2000. Metal removal from wastewater using peat. Water Research, 34(16), pp. 3907-3916. [https://doi.org/10.1016/S0043-1354(00)00152-4 doi: 10.1016/S0043-1354(00)00152-4]</ref><ref>O’Connell, D.W., Birkinshaw, C., O’Dwyer, T.F., 2008. Heavy metal adsorbents prepared from the modification of cellulose: A review. Bioresource Technology, 99(15), pp. 6709-6724. [https://doi.org/10.1016/j.biortech.2008.01.036 doi: 10.1016/j.biortech.2008.01.036]</ref><ref>Wan Ngah, W.S., Hanafiah, M.A.K.M., 2008. Removal of heavy metal ions from wastewater by chemically modified plant wastes as adsorbents: A review. Bioresource Technology, 99(10), pp. 3935-3948. [https://doi.org/10.1016/j.biortech.2007.06.011 doi: 10.1016/j.biortech.2007.06.011]</ref> and therefore will also likely be applicable for some of the metals that may be found in surface runoff at firing ranges.

==Technology Evaluation==
Based on the properties of the target munition constituents, a combination of materials was expected to yield the best results to facilitate the sorption and subsequent biotic and abiotic degradation of the contaminants.

===Sorbents===
{| class="wikitable" style="margin-right: 30px; margin-left: auto; float:left; text-align:center;"
|+Table 1. [[Wikipedia: Freundlich equation | Freundlich]] and [[Wikipedia: Langmuir adsorption model | Langmuir]] adsorption parameters for insensitive and legacy explosives
|-
! rowspan="2" | Compound
! colspan="5" | Freundlich
! colspan="5" | Langmuir
|-
! Parameter !! Peat !! CAT Pine !! CAT Burlap !! CAT Cotton !! Parameter !! Peat !! CAT Pine !! CAT Burlap !! CAT Cotton
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | HMX
! ''Kf''
| 0.08 +/- 0.00 || -- || -- || --
! ''qm'' (mg/g)
| 0.29 +/- 0.04 || -- || -- || --
|-
! ''n''
| 1.70 +/- 0.18 || -- || -- || --
! ''b'' (L/mg)
| 0.39 +/- 0.09 || -- || -- || --
|-
! ''r2''
| 0.91 || -- || -- || --
! ''r2''
| 0.93 || -- || -- || --
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | RDX
! ''Kf''
| 0.11 +/- 0.02 || -- || -- || --
! ''qm'' (mg/g)
| 0.38 +/- 0.05 || -- || -- || --
|-
! ''n''
| 2.75 +/- 0.63 || -- || -- || --
! ''b'' (L/mg)
| 0.23 +/- 0.08 || -- || -- || --
|-
! ''r2''
| 0.69 || -- || -- || --
! ''r2''
| 0.69 || -- || -- || --
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | TNT
! ''Kf''
| 1.21 +/- 0.15 || 1.02 +/- 0.04 || 0.36 +/- 0.02 || --
! ''qm'' (mg/g)
| 3.63 +/- 0.18 || 1.26 +/- 0.06 || -- || --
|-
! ''n''
| 2.78 +/- 0.67 || 4.01 +/- 0.44 || 1.59 +/- 0.09 || --
! ''b'' (L/mg)
| 0.89 +/- 0.13 || 0.76 +/- 0.10 || -- || --
|-
! ''r2''
| 0.81 || 0.93 || 0.98 || --
! ''r2''
| 0.97 || 0.97 || -- || --
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | NTO
! ''Kf''
| -- || 0.94 +/- 0.05 || 0.41 +/- 0.05 || 0.26 +/- 0.06
! ''qm'' (mg/g)
| -- || 4.07 +/- 0.26 || 1.29 +/- 0.12 || 0.83 +/- 0.15
|-
! ''n''
| -- || 1.61 +/- 0.11 || 2.43 +/- 0.41 || 2.53 +/- 0.76
! ''b'' (L/mg)
| -- || 0.30 +/- 0.04 || 0.36 +/- 0.08 || 0.30 +/- 0.15
|-
! ''r2''
| -- || 0.97 || 0.82 || 0.57
! ''r2''
| -- || 0.99 || 0.89 || 0.58
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | DNAN
! ''Kf''
| 0.38 +/- 0.05 || 0.01 +/- 0.01 || -- || --
! ''qm'' (mg/g)
| 2.57 +/- 0.33 || -- || -- || --
|-
! ''n''
| 1.71 +/- 0.20 || 0.70 +/- 0.13 || -- || --
! ''b'' (L/mg)
| 0.13 +/- 0.03 || -- || -- || --
|-
! ''r2''
| 0.89 || 0.76 || -- || --
! ''r2''
| 0.92 || -- || -- || --
|-
| colspan="12" style="background-color:white;" |
|-
! rowspan="3" | ClO4
! ''Kf''
| -- || 1.54 +/- 0.06 || 0.53 +/- 0.03 || --
! ''qm'' (mg/g)
| -- || 3.63 +/- 0.18 || 1.26 +/- 0.06 || --
|-
! ''n''
| -- || 2.42 +/- 0.16 || 2.42 +/- 0.26 || --
! ''b'' (L/mg)
| -- || 0.89 +/- 0.13 || 0.76 +/- 0.10 || --
|-
! ''r2''
| -- || 0.97 || 0.92 || --
! ''r2''
| -- || 0.97 || 0.97 || --
|-
| colspan="12" style="text-align:left; background-color:white;" |Notes: <big>'''--'''</big> Indicates the algorithm failed to converge on the model fitting parameters, therefore there was no successful model fit. '''CAT''' Indicates cationized material.
|}

The materials screened included [[Wikipedia: Sphagnum | ''Sphagnum'' peat moss]], primarily for sorption of HMX, RDX, TNT, and DNAN, as well as [[Wikipedia: Cationization of cotton | cationized cellulosics]] for removal of perchlorate and NTO. The cationized cellulosics that were examined included: pine sawdust, pine shavings, aspen shavings, cotton linters (fine, silky fibers which adhere to cotton seeds after ginning), [[Wikipedia: Chitin | chitin]], [[Wikipedia: Chitosan | chitosan]], burlap (landscaping grade), [[Wikipedia: Coir | coconut coir]], raw cotton, raw organic cotton, cleaned raw cotton, cotton fabric, and commercially cationized fabrics.

As shown in Table 1<ref name="FullerEtAl2022"/>, batch sorption testing indicated that a combination of Sphagnum peat moss and cationized pine shavings provided good removal of both the neutral organic energetics (HMX, RDX, TNT, DNAN) as well as the negatively charged energetics (perchlorate, NTO).

===Slow Release Carbon Sources===
{| class="wikitable" style="margin-right: 30px; margin-left: auto; float:left; text-align:center;"
|+Table 2. Slow-release Carbon Sources
|-
! Material !! Abbreviation !! Commercial Source !! Notes
|-
| polylactic acid || PLA6 || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || high molecular weight thermoplastic polyester
|-
| polylactic acid || PLA80 || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || low molecular weight thermoplastic polyester
|-
| polyhydroxybutyrate || PHB || [https://www.goodfellow.com/usa?srsltid=AfmBOoqEiqIbrvWb1Hn1Bc090efBUUfg6V4N3Vrn6ytajHMJR-FG1Ez- Goodfellow] || bacterial polyester
|-
| polycaprolactone || PCL || [https://www.sarchemlabs.com/?hsa_acc=4540346154&hsa_cam=20281343997&hsa_grp&hsa_ad&hsa_src=x&hsa_tgt&hsa_kw&hsa_mt&hsa_net=adwords&hsa_ver=3&gad_source=1&gad_campaignid=21209931835 Sarchem Labs] || biodegradable polyester
|-
| polybutylene succinate || BioPBS || [https://us.mitsubishi-chemical.com/company/performance-polymers/ Mitsubishi Chemical Performance Polymers] || compostable bio-based product
|-
| sucrose ester of fatty acids || SEFA SP10 || [https://www.sisterna.com/ Sisterna] || food and cosmetics additive
|-
| sucrose ester of fatty acids || SEFA SP70 || [https://www.sisterna.com/ Sisterna] || food and cosmetics additive
|}

A range of biopolymers widely used in the production of biodegradable plastics were screened for their ability to support aerobic and anoxic biodegradation of the target munition constituents. These compounds and their sources are listed in Table 2.

[[File: FullerFig3.png | thumb | 400 px | Figure 3. Schematic of interactions between biochar and munitions constituents]]
Multiple pure bacterial strains and mixed cultures were screened for their ability to utilize the solid biopolymers as a carbon source to support energetic compound transformation and degradation. Pure strains included the aerobic RDX degrader [[Wikipedia: Rhodococcus | ''Rhodococcus'']] species DN22 (DN22 henceforth)<ref name="ColemanEtAl1998">Coleman, N.V., Nelson, D.R., Duxbury, T., 1998. Aerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) as a nitrogen source by a Rhodococcus sp., strain DN22. Soil Biology and Biochemistry, 30(8-9), pp. 1159-1167. [https://doi.org/10.1016/S0038-0717(97)00172-7 doi: 10.1016/S0038-0717(97)00172-7]</ref> and [[Wikipedia: Gordonia (bacterium)|''Gordonia'']] species KTR9 (KTR9 henceforth)<ref name="ColemanEtAl1998"/>, the anoxic RDX degrader [[Wikipedia: Pseudomonas fluorencens | ''Pseudomonas fluorencens'']] species I-C (I-C henceforth)<ref>Pak, J.W., Knoke, K.L., Noguera, D.R., Fox, B.G., Chambliss, G.H., 2000. Transformation of 2,4,6-Trinitrotoluene by Purified Xenobiotic Reductase B from Pseudomonas fluorescens I-C. Applied and Environmental Microbiology, 66(11), pp. 4742-4750. [https://doi.org/10.1128/AEM.66.11.4742-4750.2000 doi: 10.1128/AEM.66.11.4742-4750.2000]   [[Media: PakEtAl2000.pdf|Article]]</ref><ref>Fuller, M.E., McClay, K., Hawari, J., Paquet, L., Malone, T.E., Fox, B.G., Steffan, R.J., 2009. Transformation of RDX and other energetic compounds by xenobiotic reductases XenA and XenB. Applied Microbiology and Biotechnology, 84, pp. 535-544. [https://doi.org/10.1007/s00253-009-2024-6 doi: 10.1007/s00253-009-2024-6]   [[Media: FullerEtAl2009.pdf | Manuscript]]</ref>, and the aerobic NQ degrader [[Wikipedia: Pseudomonas | ''Pseudomonas extremaustralis'']] species NQ5 (NQ5 henceforth)<ref>Kim, J., Fuller, M.E., Hatzinger, P.B., Chu, K.-H., 2024. Isolation and characterization of nitroguanidine-degrading microorganisms. Science of the Total Environment, 912, Article 169184. [https://doi.org/10.1016/j.scitotenv.2023.169184 doi: 10.1016/j.scitotenv.2023.169184]</ref>. Anaerobic mixed cultures were obtained from a membrane bioreactor (MBR) degrading a mixture of six explosives (HMX, RDX, TNT, NTO, NQ, DNAN), as well as perchlorate and nitrate<ref name="FullerEtAl2023">Fuller, M.E., Hedman, P.C., Chu, K.-H., Webster, T.S., Hatzinger, P.B., 2023. Evaluation of a sequential anaerobic-aerobic membrane bioreactor system for treatment of traditional and insensitive munitions constituents. Chemosphere, 340, Article 139887. [https://doi.org/10.1016/j.chemosphere.2023.139887 doi: 10.1016/j.chemosphere.2023.139887]</ref>. The results indicated that the slow-release carbon sources [[Wikipedia: Polyhydroxybutyrate | polyhydroxybutyrate (PHB)]], [[Wikipedia: Polycaprolactone | polycaprolactone (PCL)]], and [[Wikipedia: Polybutylene succinate | polybutylene succinate (BioPBS)]] were effective for supporting the biodegradation of the mixture of energetics.

===Biochar===
[[File: FullerFig4.png | thumb | left | 500 px | Figure 4. Composition of the columns during the sorption-biodegradation experiments]]
[[File: FullerFig5.png | thumb | 500 px | Figure 5. Representative breakthrough curves of energetics during the second replication of the column sorption-biodegradation experiment]]
The ability of biochar to sorb and abiotically reduce legacy and insensitive munition constituents, as well as biochar’s use as an electron donor for microbial biodegradation of energetic compounds was examined. Batch experiments indicated that biochar was a reasonable sorbent for some of the energetics (RDX, DNAN), but could also serve as both an electron acceptor and an electron donor to facilitate abiotic (RDX, DNAN, NTO) and biotic (perchlorate) degradation (Figure 3)<ref>Xin, D., Giron, J., Fuller, M.E., Chiu, P.C., 2022. Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO), DNAN, and RDX by wood-derived biochars through their rechargeable electron storage capacity. Environmental Science: Processes and Impacts, 24(2), pp. 316-329. [https://doi.org/10.1039/D1EM00447F doi: 10.1039/D1EM00447F]   [[Media: XinEtAl2022.pdf | Manuscript]]</ref>.

===Sorption-Biodegradation Column Experiments===
The selected materials and cultures discussed above, along with a small amount of range soil and crushed oyster shell as a slow-release pH buffering agent, were packed into columns, and a steady flow of dissolved energetics was passed through the columns. The composition of the four columns is presented in Figure 4. The influent and effluent concentrations of the energetics was monitored over time. The column experiment was performed twice. As seen in Figure 5, there was sustained almost complete removal of RDX and ClO4-, and more removal of the other energetics in the bioactive columns compared to the sorption only columns, over the course of the experiments. For reference, 100 PV is approximately equivalent to three months of operation. The higher effectiveness of sorption with biodegradation compared to sorption only is further illustrated in Figure 6, where the energetics mass removal in the bioactive columns was shown to be 2-fold (TNT) to 20-fold (RDX) higher relative to that observed in the sorption only column. The mass removal of HMX and NQ were both over 40% higher with biochar added to the sorption with biodegradation treatment, although biochar showed little added benefit for removal of other energetics tested.

===Trap and Treat Technology===
[[File: FullerFig6.png | thumb | left | 400 px | Figure 6. Energetic mass removal relative to the sorption only removal during the column sorption-biodegradation experiments. Dashed line given for reference to C1 removal = 1.]]
These results provide a proof-of-concept for the further development of a passive and sustainable “trap-and-treat” technology for remediation of energetic compounds in stormwater runoff at military testing and training ranges. At a given site, the stormwater runoff would need to be fully characterized with respect to key parameters (e.g., pH, major anions), and site specific treatability testing would be recommended to assure there was nothing present in the runoff that would reduce performance. Effluent monitoring on a regular basis would also be needed (and would be likely be expected by state and local regulators) to assess performance over time.

The components of the technology would be predominantly peat moss and cationized pine shavings, supplemented with biochar, ground oyster shell, the biopolymer carbon sources, and the bioaugmentation cultures. The entire mix would likely be emplaced in a concrete vault at the outflow end of the stormwater runoff retention basin at the contaminated site. The deployed treatment system would have further design elements, such as a system to trap and retain suspended solids in the runoff in order to minimize clogging the matrix. The inside of the vault would be baffled to maximize the hydraulic retention time of the contaminated runoff. The biopolymer carbon sources and oyster shell may need to be refreshed periodically (perhaps yearly) to maintain performance. However, a complete removal and replacement of the base media (peat moss, CAT pine) would not be advised, as that would lead to a loss of the acclimated biomass.

==Summary==
Novel sorbents and slow-release carbon sources can be an effective way to promote the sorption and biodegradation of a range of legacy and insensitive munition constituents from surface runoff, and the added benefits of biochar for both sorption and biotic and abiotic degradation of these compounds was demonstrated. These results establish a foundation for a passive, sustainable surface runoff treatment technology for both active and inactive military ranges.

==References==
<references />

==See Also==
*[https://serdp-estcp.mil/projects/details/10760fd6-fb55-4515-a629-f93c555a92f0/er-1689-project-overview Fate and Transport of Colloidal Energetic Residues, SERDP Project ER-1689]
*[https://serdp-estcp.mil/projects/details/20e2f05c-fd50-4fd3-8451-ba73300c7531/er-200434-project-overview In Place Soil Treatments for Prevention of Explosives Contamination, ESTCP Project ER-200434]

Dr. Mark Fuller

2025-11-06T20:56:29Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Aptim Federal Services, LLC :17 Princess Road :Lawrenceville, NJ 27560 EMAIL: [mailto:mark.fuller@aptim.com mark.fuller@apt..."

==Work and Contact Information==

EMPLOYER:
:Aptim Federal Services, LLC 
:17 Princess Road
:Lawrenceville, NJ 27560

EMAIL: [mailto:mark.fuller@aptim.com mark.fuller@aptim.com]

==About the Contributor==
Dr. Fuller, Senior Research Scientist at Aptim, is a broadly trained environmental microbiologist with over 25 years of experience. He has extensive expertise in the environmental fate and removal of explosive compounds, development of innovative technologies for sustainable management of munitions constituents on ranges, and application of stable isotope probing methods to identify organisms involved with RDX biodegradation in groundwater. More recently, Dr. Fuller has performed research on various methods for the remediation of per- and polyfluoroalkyl substances (PFAS), including evaluation of single use and regenerable ion exchange resins and destruction of PFAS residuals using sonochemical processes.

==Article Contributions==
*[[Remediation of Stormwater Runoff Contaminated by Munition Constituents]]

__NOTOC__

[[Category: Contributors|Fuller]]

PFAS Toxicology and Risk Assessment

2025-10-15T14:49:55Z

Debra Tabron:

This article presents an overview of current practices for human health and ecological risk assessment related to [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and poly-fluoroalkyl substances (PFAS)]] exposures at [[Wikipedia: Firefighting foam | aqueous film-forming foam (AFFF)]] impacted sites.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Sources]]
*[[PFAS Transport and Fate]]

'''Contributors:''' [[Jennifer Arblaster]], [[Dr. Jason Conder]], [[Dr. Jean Zodrow]] and [[Elizabeth Nichols]]

'''Key Resource(s):'''
*State of the Science for Risk Assessment of PFAS at Contaminated Sites<ref name="ZodrowEtAl2021">Zodrow, J., Arblaster, J., Conder, J., 2021. State of the Science for Risk Assessment of PFAS at Contaminated Sites. In: ''Forever Chemicals: Environmental, Economic, and Social Equity Concerns with PFAS in the Environment'', Kempisty, D., Racz, L., (Ed.s). pp. 161-186. CRC Press. [https://doi.org/10.1201/9781003024521 doi: 10.1201/9781003024521]</ref>
*[https://itrcweb.org/ Interstate Technology Regulatory Council (ITRC)], [https://pfas-1.itrcweb.org/ PFAS – Per- and Polyfluoroalkyl Substances]

==PFAS Exposure and Conceptual Site Models==
[[File:ConderFig1.png|thumb|500px|Figure 1. Simplified Conceptual Site Model for Sites Impacted by AFFF or other PFAS Sources. Used with permission<ref name="ConderEtAl2021">Conder, J., Zodrow, J., Arblaster, J., Kelly, B., Gobas, F., Suski, J., Osborn, E., Frenchmeyer, M., Divine, C., Leeson, A., 2021. Strategic resources for assessing PFAS ecological risks at AFFF sites. Integrated Environmental Assessment and Management, 17(4), pp. 746-752. [https://doi.org/10.1002/ieam.4405 doi: 10.1002/ieam.4405]</ref>]]
This article provides a brief overview of the environmental toxicology and risk assessment of per- and polyfluoroalkyl substances (PFAS). The article’s main focus is on the environmental toxicology and risk assessment of PFAS derived from aqueous film-forming foam (AFFF).

The use of AFFF can release PFAS into the environment during fire training, an emergency response, or as a result of leaks or spills from AFFF systems. Following AFFF releases, perfluoroalkyl acids (PFAAs), particularly PFOS, PFOA, and PFHxS, tend to be the most commonly detected PFAS in environmental media. Due to their solubility, sorption, and bioaccumulation properties, perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) can be prevalent in a variety of environmental media, including groundwater, surface water, soil, sediment, biosolids, landfill leachate, plants, fish, invertebrates, and wildlife<ref>Lau, C., 2012. Perfluorinated Compounds. In: ''Molecular, Clinical and Environmental Toxicology, Volume 3: Environmental Toxicology'', A. Luch (Ed.), pp. 47-86. Springer Science and Business Media. [https://doi.org/10.1007/978-3-7643-8340-4_3 doi: 10.1007/978-3-7643-8340-4_3]</ref>.

PFAS exhibit a range of physical and chemical properties, with the fate of the PFAAs, particularly the PFCAs and PFSAs, being the most studied PFAS. PFAAs are relatively water-soluble and mobile in the environment, are not volatile (i.e., they do not evaporate to the atmosphere readily<ref>Field, J., Higgins, C., Deeb, R., Conder, J., 2017. FAQs Regarding PFASs Associated with AFFF Use at U.S. Military Sites. Environmental Security Technology Certification Program (ESTCP) Project ER-201574. [https://serdp-estcp.mil/resources/details/ccf87a8d-f8b2-4fce-bc4a-78c32091f896 Project Website]  [[Media: FAQ_ER-201574.pdf | Report.pdf]]</ref>) and can sorb to the organic carbon present in soil or sediment. PFAAs are more soluble and mobile compared to other persistent organic chemicals of concern documented at contaminated sites. PFAS can bioaccumulate in animals and plants, and persistent PFAS, such as PFCAs and PFSAs, do not undergo significant biodegradation or biotransformation once present in a biological system<ref>Conder, J.M., Hoke, R.A., de Wolf, W., Russell, M.H., Buck, R.C., 2008. Are PFCAs Bioaccumulative? A Critical Review and Comparison with Regulatory Criteria and Persistent Lipophilic Compounds. Environmental Science and Technology, 42(4), pp. 995-1003. [https://doi.org/10.1021/es070895g doi: 10.1021/es070895g]</ref>.

The current state of the science and understanding of PFAS fate and transport indicates that the human health issues associated with PFAS AFFF sites are primarily the exposure pathways associated with drinking water ingestion and dietary intake of PFAS<ref name="ZodrowEtAl2021"/>. Incidental soil ingestion and/or dust inhalation are typically of moderate concern and are recommended for inclusion into human health risk assessments, but compared to drinking water and dietary ingestion, generally result in lower exposures for most receptors. Exposures via dermal contact with soils and water, and inhalation of vapors (due to volatilization of PFAS), are generally of even lower concern for most sites with AFFF PFAS sources. Human health conceptual site models (CSMs) for AFFF sites typically reflect common receptors including current or future residents and industrial or commercial workers, depending on the current and reasonable anticipated future land uses at the site, along with potential exposures in offsite areas. Receptors associated with recreation and fishing activities may be incorporated if water resources used for recreational purposes are located near the site. Additional considerations may need to be incorporated into the CSM, such as the source of PFAS release into the environment. Release mechanism can differ based on site uses of PFAS. For example, while AFFF use often resulted in historic releases to ground surfaces, industrial emissions can result in aerial deposition, and biosolids application can result in widespread releases to soils which result in different exposure pathways that should be considered.

Ecological CSMs generally focus on exposures in areas adjacent to or downgradient of initial AFFF releases which have habitats present which support ecological resources (Figure 1). Most areas at the point of AFFF releases (and many industrial areas where PFAS products are or were used) do not generally feature favorable ecological habitats that make these areas relevant for ecological risk assessment. However, the relatively high solubility of PFAS in water results in a high potential for offsite transport via groundwater, surface water and stormwater, or by erosion of impacted soils and sediment<ref name="ConderEtAl2021"/>.

==Toxicological Effects of PFAS==
The characterization of toxicological effects in human health risk assessments is based on toxicological studies of mammalian exposures to per- and polyfluoroalkyl substances (PFAS), primarily studies involving [[Wikipedia:Perfluorooctanesulfonic acid | perfluorooctanesulfonic acid (PFOS)]] and [[Wikipedia:Perfluorooctanoic acid|perfluorooctanoic acid (PFOA)]]. The most sensitive noncancer adverse effects involve the liver and kidney, immune system, and various developmental and reproductive endpoints<ref name="USEPA2024b">United States Environmental Protection Agency (USEPA), 2024. Per- and Polyfluoroalkyl Substances (PFAS) Final PFAS National Primary Drinking Water Regulation. [https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas Website]</ref>. A select number of PFAS have been evaluated for carcinogenicity, primarily using epidemiological data. Only PFOS and PFOA (and their derivatives) have sufficient data for USEPA to characterize as ''Likely to Be Carcinogenic to Humans'' via the oral route of exposure. Epidemiological studies provided evidence of bladder, prostate, liver, kidney, and breast cancers in humans related to PFOS exposure, as well as kidney and testicular cancer in humans and limited evidence of breast cancer related to PFOA exposure<ref name="USEPA2024b"/><ref name="USEPA2016a">United States Environmental Protection Agency (USEPA), 2016. Drinking Water Health Advisory for Perfluorooctane Sulfonate (PFOS). Office of Water, EPA 822-R-16-004. [https://www.epa.gov/sites/production/files/2016-05/documents/pfos_health_advisory_final-plain.pdf Free Download]  [[Media: USEPA-2016-pfos_health_advisory_final-plain.pdf | Report.pdf]]</ref><ref name="USEPA2016b">United States Environmental Protection Agency (USEPA), 2016b. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA). Office of Water, EPA 822-R-16-005. [https://www.epa.gov/sites/production/files/2016-05/documents/pfoa_health_advisory_final_508.pdf Free Download]  [[Media: pfoa_EPA 822-R-16-005.pdf | Report.pdf]]</ref>.

USEPA’s Integrated Risk Management System (IRIS) Program is developing Toxicological Reviews to improve understanding of the toxicity of several additional PFAS (i.e., not solely PFOA and PFOS). Toxicological Reviews provide an overview of cancer and noncancer health effects based on current literature and, where data are sufficient, derive human health toxicity criteria (i.e., human health oral reference doses and cancer slope factors) that form the basis for risk-based decision making. For risk assessors, these documents provide USEPA reference doses and cancer slope factors that can be used with exposure information and other considerations to assess human health risk. Final Toxicological Reviews have been completed for the following PFAS:
*Perfluorooctanesulfonic acid (PFOS)
*Perfluorooctanoic acid (PFOA)
*Perfluorobutanoic acid (PFBA)
*Perfluorohexanoic acid (PFHxA)
*Perfluorobutane sulfonic acid (PFBS)
*Perfluoropropionic acid (PFPrA)
*Perfluorohexane sulfonic acid (PFHxS)
*Lithium bis[(trifluoromethyl)sulfonyl]azanide (HQ-115)
*Hexafluoropropylene oxide dimer acid (HFPO DA) and its Ammonium Salt

Toxicity assessments are ongoing for the following PFAS:
*Perfluorononanoic acid (PFNA)
*Perfluorodecanoic acid (PFDA)

It is important to note human health toxicity criteria for inhalation of PFAS are not included in the Final Toxicological Reviews and are not currently available.
In addition to IRIS, state agencies have developed peer-reviewed provisional toxicity values that have been incorporated into USEPA’s RSLs, which are updated biannually. These values have not been reviewed by or incorporated into IRIS.

With respect to ecological toxicity, effects on reproduction, growth, and development of avian and mammalian wildlife have been documented in controlled laboratory studies of exposures of standard toxicological test species (e.g., mice, quail) to PFAS. Many of these studies have been reviewed<ref name="ConderEtAl2020"> Conder, J., Arblaster, J., Larson, E., Brown, J., Higgins, C., 2020. Guidance for Assessing the Ecological Risks of PFAS to Threatened and Endangered Species at Aqueous Film Forming Foam-Impacted Sites. Strategic Environmental Research and Development Program (SERDP) Project ER 18-1614. [https://serdp-estcp.mil/projects/details/3f890c9b-7f72-4303-8d2e-52a89613b5f6 Project Website]  [[Media: ER18-1614_Guidance.pdf | Guidance Document]]</ref><ref name="GobasEtAl2020">Gobas, F.A.P.C., Kelly, B.C., Kim, J.J., 2020. Final Report: A Framework for Assessing Bioaccumulation and Exposure Risks of PFAS in Threatened and Endangered Species on AFFF-Impacted Sites. SERDP Project ER18-1502. [https://serdp-estcp.mil/projects/details/09c93894-bc73-404a-8282-51196c4be163 Project Website]  [[Media: ER18-1502_Final.pdf | Final Report]]</ref><ref name="Suski2020">Suski, J.G., 2020. Investigating Potential Risk to Threatened and Endangered Species from Per- and Polyfluoroalkyl Substances (PFAS) on Department of Defense (DoD) Sites. SERDP Project ER18-1626. [https://serdp-estcp.mil/projects/details/c328f8e3-95a4-4820-a0d4-ef5835134636 Project Website]  [[Media: ER18-1626_Final.pdf | Report.pdf]]</ref><ref name="ZodrowEtAl2021a">Zodrow, J.M., Frenchmeyer, M., Dally, K., Osborn, E., Anderson, P. and Divine, C., 2021. Development of Per and Polyfluoroalkyl Substances Ecological Risk-Based Screening Levels. Environmental Toxicology and Chemistry, 40(3), pp. 921-936. [https://doi.org/10.1002/etc.4975 doi: 10.1002/etc.4975]   [[Media: ZodrowEtAl2021a.pdf | Open Access Article]]</ref> to derive ecological Toxicity Reference Values (TRVs). TRVs can be used alongside exposure information and other considerations to assess ecological risk. Avian and mammalian wildlife receptors are generally expected to have the highest risks due to PFAS exposure. Direct toxicity to aquatic life, such as fish and invertebrates, from exposure to sediment and surface water also occurs, though concentrations in water associated with adverse effects to aquatic life are generally higher than those that could result in adverse effects to aquatic-dependent wildlife. Soil invertebrates and plants are less sensitive to PFAS when compared to terrestrial wildlife, with risk-based PFAS concentrations in soil being much higher than those associated with potential effects to terrestrial wildlife<ref name="ZodrowEtAl2021a"/>.

==PFAS Screening Levels for Human Health and Ecological Risk Assessments==
===Human Health Screening Levels===
Human health screening levels for PFAS have been modified multiple times over the last decade and, in the United States, are currently available for drinking water and soil exposures as Maximum Contaminant Levels (MCLs) and USEPA Regional Screening Levels (RSLs). USEPA finalized a National Primary Drinking Water Regulation (NPDWR) for six PFAS<ref name="USEPA2024b"/>:
*Perfluorooctanoic acid (PFOA)
*Perfluorooctane sulfonic acid (PFOS)
*Perfluorohexane sulfonic acid (PFHxS)
*Perfluorononanoic acid (PFNA)
*Hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX chemicals)
*Perfluorobutane sulfonic acid (PFBS)

MCLs are enforceable drinking water standards based on the most recently available toxicity information that consider available treatment technologies and costs. The MCLs for PFAS include a Hazard Index of 1 for combined exposures to four PFAS. RSLs are developed for use in risk assessments and include soil and tap water screening levels for multiple PFAS. Soil RSLs are based on residential/unrestricted and commercial/industrial land uses, and calculations of site-specific RSLs are available.

Internationally, Canada and the European Union have also promulgated drinking water standards for select PFAS. However, large discrepancies exist among the various regulatory organizations, largely due to the different effect endpoints and exposure doses being used to calculate risk-based levels. The PFAS guidance from the Interstate Technology and Regulatory Council (ITRC) in the US includes a regularly updated compilation of screening values for PFAS and is available on their PFAS website<ref name="ITRC2023">Interstate Technology and Regulatory Council (ITRC) 2023. PFAS Technical and Regulatory Guidance Document. [https://pfas-1.itrcweb.org/ ITRC PFAS Website]</ref>: https://pfas-1.itrcweb.org.

===Ecological Screening Levels===
Most peer-reviewed literature and regulatory-based environmental quality benchmarks have been developed using data for PFOS and PFOA; however, other select PFAAs have been evaluated for potential effects to aquatic receptors<ref name="ITRC2023"/><ref name="ZodrowEtAl2021a"/><ref name="ConderEtAl2020"/>. USEPA has developed water quality criteria for aquatic life<ref name="USEPA2022"> United States Environmental Protection Agency (USEPA), 2022. Fact Sheet: Draft 2022 Aquatic Life Ambient Water Quality Criteria for Perfluorooctanoic acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS)). Office of Water, EPA 842-D-22-005. [[Media: USEPA2022.pdf | Fact Sheet]]</ref><ref name="USEPA2024c">United States Environmental Protection Agency (USEPA), 2024. Final Freshwater Aquatic Life Ambient Water Quality Criteria and Acute Saltwater Aquatic Life Benchmark for Perfluorooctanoic Acid (PFOA). Office of Water, EPA-842-R-24-002. [[Media: USEPA2024c.pdf | Report.pdf]]</ref><ref name="USEPA2024d">United States Environmental Protection Agency (USEPA), 2024. Final Freshwater Aquatic Life Ambient Water Quality Criteria and Acute Saltwater Aquatic Life Benchmark for Perfluorooctane Sulfonate (PFOS). Office of Water, EPA-842-R-24-003. [[Media: USEPA2024d.pdf | Report.pdf]]</ref> for PFOA and PFOS. Following extensive reviews of the peer-reviewed literature, Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> used the USEPA Great Lakes Initiative methodology<ref>United States Environmental Protection Agency (USEPA), 2012. Water Quality Guidance for the Great Lakes System. Part 132. [https://www.govinfo.gov/app/details/CFR-2013-title40-vol23/CFR-2013-title40-vol23-part132 Government Website]  [[Media: CFR-2013-title40-vol23-part132.pdf | Part132.pdf]]</ref> to calculate acute and chronic screening levels for aquatic life for 23 PFAS. The Argonne National Laboratory has also developed Ecological Screening Levels for multiple PFAS<ref name="GrippoEtAl2024">Grippo, M., Hayse, J., Hlohowskyj, I., Picel, K., 2024. Derivation of PFAS Ecological Screening Values - Update. Argonne National Laboratory Environmental Science Division. [[Media: GrippoEtAl2024.pdf | Report.pdf]]</ref>. In contrast to surface water aquatic life benchmarks, sediment benchmark values are limited. For terrestrial systems, screening levels for direct exposure of soil plants and invertebrates to PFAS in soils have been developed for multiple AFFF-related PFAS<ref name="ConderEtAl2020"/><ref name="ZodrowEtAl2021a"/>, and the Canadian Council of Ministers of Environment developed several draft thresholds protective of direct toxicity of PFOS in soil<ref>Canadian Council of Ministers of the Environment (CCME), 2021. Canadian Soil and Groundwater Quality Guidelines for the Protection of Environmental and Human Health, Perfluorooctane Sulfonate (PFOS). [[Media: CCME2018.pdf | Open Access Government Document]]</ref>.

Wildlife screening levels for abiotic media are back-calculated from food web models developed for representative receptors. Both Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> and Grippo ''et al.''<ref name="GrippoEtAl2024"/> include the development of risk-based screening levels for wildlife. The Michigan Department of Community Health<ref>Dykema, L.D., 2015. Michigan Department of Community Health Final Report, USEPA Great Lakes Restoration Initiative (GLRI) Project, Measuring Perfluorinated Compounds in Michigan Surface Waters and Fish. Grant GL-00E01122. [https://www.michigan.gov/documents/mdch/MDCH_GL-00E01122-0_Final_Report_493494_7.pdf Free Download]  [[Media: MDCH_Geart_Lakes_PFAS.pdf | Report.pdf]]</ref> derived a provisional PFOS surface water value for avian and mammalian wildlife. In California, the San Francisco Bay Regional Water Quality Control Board developed terrestrial habitat soil ecological screening levels based on values developed in Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/>. For PFOS only, a dietary screening level (i.e. applicable to the concentration of PFAS measured in dietary items) has been developed for mammals at 4.6 micrograms per kilogram (μg/kg) wet weight (ww), and for avians at 8.2 μg/kg ww<ref>Environment and Climate Change Canada, 2018. Federal Environmental Quality Guidelines, Perfluorooctane Sulfonate (PFOS). [[Media: ECCC2018.pdf | Repoprt.pdf]]</ref>.

==Approaches for Evaluating Exposures and Effects in AFFF Site Environmental Risk Assessment: Human Health==
Exposure pathways and effects for select PFAS are well understood, such that standard human health risk assessment approaches can be used to quantify risks for populations relevant to a site. Human health exposures via drinking water have been the focus in risk assessments and investigations at PFAS sites<ref>Post, G.B., Cohn, P.D., Cooper, K.R., 2012. Perfluorooctanoic acid (PFOA), an emerging drinking water contaminant: A critical review of recent literature. Environmental Research, 116, pp. 93-117. [https://doi.org/10.1016/j.envres.2012.03.007 doi: 10.1016/j.envres.2012.03.007]</ref><ref>Guelfo, J.L., Marlow, T., Klein, D.M., Savitz, D.A., Frickel, S., Crimi, M., Suuberg, E.M., 2018. Evaluation and Management Strategies for Per- and Polyfluoroalkyl Substances (PFASs) in Drinking Water Aquifers: Perspectives from Impacted U.S. Northeast Communities. Environmental Health Perspectives,126(6), 13 pages. [https://doi.org/10.1289/EHP2727 doi: 10.1289/EHP2727]  [[Media: GuelfoEtAl2018.pdf | Open Access Article]]</ref>. Risk assessment approaches for PFAS in drinking water follow typical, well-established drinking water risk assessment approaches for chemicals as detailed in regulatory guidance documents for various jurisdictions.

Incidental exposures to soil and dusts for PFAS can occur during a variety of soil disturbance activities, such as gardening and digging, hand-to-mouth activities, and intrusive groundwork by industrial or construction workers. As detailed by the ITRC<ref name="ITRC2023"/>, many US states and USEPA have calculated risk-based screening levels for these soil and drinking water pathways (and many also include dermal exposures to soils) using well-established risk assessment guidance.

Field and laboratory studies have shown that some PFCAs and PFSAs bioaccumulate in fish and other aquatic life at rates that could result in relevant dietary PFAS exposures for consumers of fish and other seafood<ref>Martin, J.W., Mabury, S.A., Solomon, K.R., Muir, D.C., 2003. Dietary accumulation of perfluorinated acids in juvenile rainbow trout (Oncorhynchus mykiss). Environmental Toxicology and Chemistry, 22(1), pp.189-195. [https://doi.org/10.1002/etc.5620220125 doi: 10.1002/etc.5620220125]</ref><ref>Martin, J.W., Mabury, S.A., Solomon, K.R., Muir, D.C., 2003. Bioconcentration and tissue distribution of perfluorinated acids in rainbow trout (Oncorhynchus mykiss). Environmental Toxicology and Chemistry, 22(1), pp.196-204. [https://doi.org/10.1002/etc.5620220126 doi: 10.1002/etc.5620220126]</ref><ref>Chen, F., Gong, Z., Kelly, B.C., 2016. Bioavailability and bioconcentration potential of perfluoroalkyl-phosphinic and -phosphonic acids in zebrafish (Danio rerio): Comparison to perfluorocarboxylates and perfluorosulfonates. Science of The Total Environment, 568, pp. 33-41. [https://doi.org/10.1016/j.scitotenv.2016.05.215 doi: 10.1016/j.scitotenv.2016.05.215]</ref><ref>Fang, S., Zhang, Y., Zhao, S., Qiang, L., Chen, M., Zhu, L., 2016. Bioaccumulation of per fluoroalkyl acids including the isomers of perfluorooctane sulfonate in carp (Cyprinus carpio) in a sediment/water microcosm. Environmental Toxicology and Chemistry, 35(12), pp. 3005-3013. [https://doi.org/10.1002/etc.3483 doi: 10.1002/etc.3483]</ref><ref>Bertin, D., Ferrari, B.J.D. Labadie, P., Sapin, A., Garric, J., Budzinski, H., Houde, M., Babut, M., 2014. Bioaccumulation of perfluoroalkyl compounds in midge (Chironomus riparius) larvae exposed to sediment. Environmental Pollution, 189, pp. 27-34. [https://doi.org/10.1016/j.envpol.2014.02.018 doi: 10.1016/j.envpol.2014.02.018]</ref><ref>Bertin, D., Labadie, P., Ferrari, B.J.D., Sapin, A., Garric, J., Geffard, O., Budzinski, H., Babut. M., 2016. Potential exposure routes and accumulation kinetics for poly- and perfluorinated alkyl compounds for a freshwater amphipod: Gammarus spp. (Crustacea). Chemosphere, 155, pp. 380-387. [https://doi.org/10.1016/j.chemosphere.2016.04.006 doi: 10.1016/j.chemosphere.2016.04.006]</ref><ref>Dai, Z., Xia, X., Guo, J., Jiang, X., 2013. Bioaccumulation and uptake routes of perfluoroalkyl acids in Daphnia magna. Chemosphere, 90(5), pp.1589-1596. [https://doi.org/10.1016/j.chemosphere.2012.08.026 doi: 10.1016/j.chemosphere.2012.08.026]</ref><ref>Prosser, R.S., Mahon, K., Sibley, P.K., Poirier, D., Watson-Leung, T. 2016. Bioaccumulation of perfluorinated carboxylates and sulfonates and polychlorinated biphenyls in laboratory-cultured Hexagenia spp., Lumbriculus variegatus and Pimephales promelas from field-collected sediments. Science of The Total Environment, 543(A), pp. 715-726. [https://doi.org/10.1016/j.scitotenv.2015.11.062 doi: 10.1016/j.scitotenv.2015.11.062]</ref><ref>Rich, C.D., Blaine, A.C., Hundal, L., Higgins, C., 2015. Bioaccumulation of Perfluoroalkyl Acids by Earthworms (Eisenia fetida) Exposed to Contaminated Soils. Environmental Science and Technology, 49(2) pp. 881-888. [https://doi.org/10.1021/es504152d doi: 10.1021/es504152d]</ref><ref>Muller, C.E., De Silva, A.O., Small, J., Williamson, M., Wang, X., Morris, A., Katz, S., Gamberg, M., Muir, D.C.G., 2011. Biomagnification of Perfluorinated Compounds in a Remote Terrestrial Food Chain: Lichen–Caribou–Wolf. Environmental Science and Technology, 45(20), pp. 8665-8673. [https://doi.org/10.1021/es201353v doi: 10.1021/es201353v]</ref>. In addition to fish, terrestrial wildlife can accumulate contaminants from impacted sites, resulting in potential exposures to consumers of wild game<ref name="ConderEtAl2021"/>. Additionally, exposures can occur though consumption of homegrown produce or agricultural products that originate from areas irrigated with PFAS-impacted groundwater, or that are amended with biosolids that contain PFAS, or that contain soils that were directly affected by PFAS releases<ref>Brown, J.B, Conder, J.M., Arblaster, J.A., Higgins, C.P., 2020. Assessing Human Health Risks from Per- and Polyfluoroalkyl Substance (PFAS)-Impacted Vegetable Consumption: A Tiered Modeling Approach. Environmental Science and Technology, 54(23), pp. 15202-15214. [https://doi.org/10.1021/acs.est.0c03411 doi: 10.1021/acs.est.0c03411]  [[Media: BrownEtAl2020.pdf | Open Access Article]]</ref>. Multiple studies have found PFAS can be taken up by plants from soil porewater<ref>Blaine, A.C., Rich, C.D., Hundal, L.S., Lau, C., Mills, M.A., Harris, K.M., Higgins, C.P., 2013. Uptake of Perfluoroalkyl Acids into Edible Crops via Land Applied Biosolids: Field and Greenhouse Studies. Environmental Science and Technology, 47(24), pp. 14062-14069. [https://doi.org/10.1021/es403094q doi: 10.1021/es403094q]  [https://www.epa.gov/sites/production/files/2019-11/documents/508_pfascropuptake.pdf Free Download from epa.gov]</ref><ref>Blaine, A.C., Rich, C.D., Sedlacko, E.M., Hyland, K.C., Stushnoff, C., Dickenson, E.R.V., Higgins, C.P., 2014. Perfluoroalkyl Acid Uptake in Lettuce (Lactuca sativa) and Strawberry (Fragaria ananassa) Irrigated with Reclaimed Water. Environmental Science and Technology, 48(24), pp. 14361-14368. [https://doi.org/10.1021/es504150h doi: 10.1021/es504150h]</ref><ref>Ghisi, R., Vamerali, T., Manzetti, S., 2019. Accumulation of perfluorinated alkyl substances (PFAS) in agricultural plants: A review. Environmental Research, 169, pp. 326-341. [https://doi.org/10.1016/j.envres.2018.10.023 doi: 10.1016/j.envres.2018.10.023]</ref>, and livestock can accumulate PFAS from drinking water and/or feed<ref>van Asselt, E.D., Kowalczyk, J., van Eijkeren, J.C.H., Zeilmaker, M.J., Ehlers, S., Furst, P., Lahrssen-Wiederhold, M., van der Fels-Klerx, H.J., 2013. Transfer of perfluorooctane sulfonic acid (PFOS) from contaminated feed to dairy milk. Food Chemistry, 141(2), pp.1489-1495. [https://doi.org/10.1016/j.foodchem.2013.04.035 doi: 10.1016/j.foodchem.2013.04.035]</ref>. Thus, when PFAS are present in surface water bodies where fishing or shellfish harvesting occurs or terrestrial areas where produce is grown or game is hunted, the bioaccumulation of PFAS into dietary items can be an important pathway for human exposure.

PFAAs such as PFOA and PFOS are not expected to volatilize from PFAS-impacted environmental media<ref name="USEPA2016a"/><ref name="USEPA2016b"/> such as soil and groundwater, which are the primary focus of most site-specific risk assessments. In contrast to non-volatile PFAAs, fluorotelomer alcohols (FTOHs) are among the more widely studied of the volatile PFAS. FTOHs are transient in the atmosphere with a lifetime of 20 days<ref>Ellis, D.A., Martin, J.W., De Silva, A.O., Mabury, S.A., Hurley, M.D., Sulbaek Andersen, M.P., Wallington, T.J., 2004. Degradation of Fluorotelomer Alcohols: A Likely Atmospheric Source of Perfluorinated Carboxylic Acids. Environmental Science and Technology, 38(12), pp. 3316-3321. [https://doi.org/10.1021/es049860w doi: 10.1021/es049860w]</ref>. At most AFFF sites under evaluation, AFFF releases have occurred many years before such that FTOH may no longer be present. As such, the current assumption is that volatile PFAS, such as FTOHs historically released at the site, will have transformed to stable, low-volatility PFAS, such as PFAAs in soil or groundwater, or will they have diffused to the outdoor atmosphere. There is no evidence that FTOHs or other volatile PFAS are persistent in groundwater or soils such that they present an indoor vapor intrusion pathway risk concern as observed for chlorinated solvents. Ongoing research continues for the vapor pathway<ref name="ITRC2023"/>.

General and site-specific human health exposure pathways and risk assessment methods as outlined by USEPA<ref>United States Environmental Protection Agency (USEPA), 1989. Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part A). Office of Solid Waste and Emergency Response, EPA/540/1-89/002. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=10001FQY.txt Free Download]  [[Media: USEPA1989.pdf | Report.pdf]]</ref><ref name="USEPA1997">United States Environmental Protection Agency (USEPA), 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments, Interim Final. Office of Solid Waste and Emergency Response, EPA 540-R-97-006. [http://semspub.epa.gov/src/document/HQ/157941 Free Download]  [[Media: EPA540-R-97-006.pdf | Report.pdf]]</ref> can be applied to PFAS risk assessments for which human health toxicity values have been developed. Additionally, for risk assessments with dietary exposures of PFAS, standard risk assessment food web modeling can be used to develop initial estimates of dietary concentrations which can be confirmed with site-specific tissue sampling programs.

==Approaches for Evaluating Exposures and Effects in AFFF Site Environmental Risk Assessment: Ecological==
Information available currently on exposures and effects of PFAS in ecological receptors indicate that the PFAS ecological risk issues at most sites are primarily associated with risks to vertebrate wildlife. Avian and mammalian wildlife are relatively sensitive to PFAS, and dietary intake via bioaccumulation in terrestrial and aquatic food webs can result in exposures that are dominated by the more accumulative PFAS<ref name="LarsonEtAl2018">Larson, E.S., Conder, J.M., Arblaster, J.A., 2018. Modeling avian exposures to perfluoroalkyl substances in aquatic habitats impacted by historical aqueous film forming foam releases. Chemosphere, 201, pp. 335-341. [https://doi.org/10.1016/j.chemosphere.2018.03.004 doi: 10.1016/j.chemosphere.2018.03.004]</ref><ref name="ConderEtAl2020"/><ref name="ZodrowEtAl2021a"/>. Direct toxicity to aquatic life (e.g., fish, pelagic life, benthic invertebrates, and aquatic plants) can occur from exposure to sediment and surface water at effected sites. For larger areas, surface water concentrations associated with adverse effects to aquatic life are generally higher than those that could result in adverse effects to aquatic-dependent wildlife. Soil invertebrates and plants are generally less sensitive, with risk-based concentrations in soil being much higher than those associated with potential effects to terrestrial wildlife<ref name="ZodrowEtAl2021a"/>.

Aquatic life are exposed to PFAS through direct exposure in surface water and sediment. Ecological risk assessment approaches for PFAS for aquatic life follow standard risk assessment approaches. The evaluation of potential risks for aquatic life with direct exposure to PFAS in environmental media relies on comparing concentrations in external exposure media to protective, media-specific benchmarks, including the aquatic life risk-based screening levels discussed above<ref name="ZodrowEtAl2021a"/><ref name="USEPA2024a">United States Environmental Protection Agency (USEPA), 2024. National Recommended Water Quality Criteria - Aquatic Life Criteria Table. [https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table USEPA Website]</ref>.

When an area at the point of PFAS release is an industrial setting which does not feature favorable habitats for terrestrial and aquatic-dependent wildlife, the transport mechanisms may allow PFAS to travel offsite. If offsite or downgradient areas contain ecological habitat, then PFAS transported to these areas are expected to pose the highest risk potential to wildlife, particularly those areas that feature aquatic habitat<ref>Ahrens, L., Bundschuh, M., 2014. Fate and effects of poly- and perfluoroalkyl substances in the aquatic environment: A review. Environmental Toxicology and Chemistry, 33(9), pp. 1921-1929. [https://doi.org/10.1002/etc.2663 doi: 10.1002/etc.2663]  [[Media: AhrensBundschuh2014.pdf | Open Access Article]]</ref><ref name="LarsonEtAl2018"/>.

Wildlife receptors, specifically birds and mammals, are typically exposed to PFAS through uptake from dietary sources such as plants and invertebrates, along with direct soil ingestion during foraging activities. Dietary intake modeling typical for ecological risk assessments is the recommended approach for an evaluation of potential risks to wildlife species where PFAS exposure occurs primarily via dietary uptake from bioaccumulation pathways. Dietary intake modeling uses relevant exposure factors for each receptor group (terrestrial birds, terrestrial mammals, aquatic-dependent birds, and aquatic mammals) to determine a total daily intake (TDI) of PFAS via all potential exposure pathways. This approach requires determination of concentrations of PFAS in dietary items, which can be obtained by measuring PFAS in biota at sites or by using food web models to predict concentrations in biota using measured concentrations of PFAS in soil, sediment, or surface water. Food web models use bioaccumulation metrics such as bioaccumulation factors (BAFs) and biomagnification factors (BMFs) with measurements of PFAS in abiotic media to estimate concentrations in dietary items, including plants and benthic or pelagic invertebrates, to model wildlife exposure and calculate TDI. Once site-specific TDI values are calculated, they are compared to known TRVs identified from toxicity data with exposure doses associated with a lack of adverse effects (termed no observed adverse effect level [NOAEL]) or low adverse effects (termed lowest observed adverse effect level [LOAEL]), per standard risk assessment practice<ref name="USEPA1997"/>.

Recently, Conder ''et al.''<ref name="ConderEtAl2020"/>, Gobas ''et al.''<ref name="GobasEtAl2020"/>, and Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> compiled bioaccumulation modeling parameters and approaches for terrestrial and aquatic food web modeling of a variety of commonly detected PFAS at AFFF sites. There are also several sources of TRVs which can be relied upon for estimating TDI values<ref name="ConderEtAl2020"/><ref name="GobasEtAl2020"/><ref name="ZodrowEtAl2021a"/><ref>Newsted, J.L., Jones, P.D., Coady, K., Giesy, J.P., 2005. Avian Toxicity Reference Values for Perfluorooctane Sulfonate. Environmental Science and Technology, 39(23), pp. 9357-9362. [https://doi.org/10.1021/es050989v doi: 10.1021/es050989v]</ref><ref name="Suski2020"/>. In general, the highest risk for PFAS is expected for smaller insectivore and omnivore receptors (e.g., shrews and other small rodents, small nonmigratory birds), which tend to be lower in trophic level and spend more time foraging in small areas similar to or smaller in size than the impacted area. Compared to smaller, lower-trophic level organisms, larger mammalian and avian carnivores are expected to have lower exposures from site-specific PFAS sources because they forage over larger areas that may include areas that are not impacted, as compared to small organisms with small home ranges<ref name="LarsonEtAl2018"/><ref name="ConderEtAl2020"/><ref name="GobasEtAl2020"/><ref name="Suski2020"/><ref name="ZodrowEtAl2021a"/>.

Available information regarding PFAS exposure pathways and effects in aquatic life, terrestrial invertebrates and plants, as well as aquatic and terrestrial wildlife allow ecological risk assessment methods to be applied as outlined by USEPA<ref name="USEPA1997"/> to site-specific PFAS risk assessments. Additionally, food web modeling can be used in site-specific PFAS risk assessment to develop initial estimates of dietary concentrations for aquatic and terrestrial wildlife, which can be confirmed with tissue sampling programs at a site.

==PFAS Risk Assessment Data Gaps==
There are a number of data gaps currently associated with PFAS risk assessment including the following:
*'''Unmeasured PFAS:''' There are a number of additional PFAS that we know little about and many PFAS that we are unable to quantify in the environment. The approach to dealing with the lack of information on the overwhelming number of PFAS is being debated; in the meantime, however, PFAS beyond PFOS and PFOA are being studied more, and this information will result in improved characterization of risks for other PFAS.

*'''Mixtures:''' Another major challenge in effects assessment for PFAS, for both human health risk assessments and environmental risk assessments, is understanding the potential importance of mixtures of PFAS. Considering the limited human health and ecological toxicity data available for just a few PFAS, the understanding of the relative toxicity, additivity, or synergistic effects of PFAS in mixtures is just beginning.

*'''Toxicity Data Gaps:''' For environmental risk assessments, some organisms such as reptiles and benthic invertebrates do not have toxicity data available. Benchmark or threshold concentrations of PFAS in environmental media intended to be protective of wildlife and aquatic organisms suffer from significant uncertainty in their derivation due to the limited number of species for which data are available. As species-specific data becomes available for more types of organisms, the accuracy of environmental risk assessments is likely to improve.

==References==
<references />

==See Also==
[https://www.atsdr.cdc.gov/pfas/health-studies/index.html Agency for Toxic Substances and Disease Registry (ATSDR) PFAS Health Studies]

Elizabeth Nichols

2025-10-15T14:31:37Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Geosyntec Consultants EMAIL: [mailto:Elizabeth.Nichols@Geosyntec.com Elizabeth.Nichols@Geosyntec.com] ==About the Contrib..."

==Work and Contact Information==

EMPLOYER:
:Geosyntec Consultants 

EMAIL: [mailto:Elizabeth.Nichols@Geosyntec.com Elizabeth.Nichols@Geosyntec.com]

==About the Contributor==
Elizabeth Nichols has 3 years of experience in ecological risk assessment, environmental toxicology, and environmental chemistry. Liz received her MS degree in Ecosystem Science and Management from University of Michigan where she completed a thesis focused on aquatic toxicology and in situ sampling methods of contaminated sites.

==Article Contributions==
*[[PFAS Toxicology and Risk Assessment]]

__NOTOC__

[[Category: Contributors|Nichols]]

Dr. Jean Zodrow

2025-10-15T14:25:59Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Geosyntec Consultants EMAIL: [mailto:JZodrow@Geosyntec.com JZodrow@Geosyntec.com] WEBPAGE: [https://geosyntec.com/people/..."

==Work and Contact Information==

EMPLOYER:
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==About the Contributor==
Jean Zodrow has 20 years of experience in environmental toxicology, bioaccumulation modeling, evaluation of toxicity and development of toxicity reference values, and site-specific risk assessment of PFAS. She has published peer-reviewed articles and a book chapter on PFAS risk assessment.

==Article Contributions==
*[[PFAS Toxicology and Risk Assessment]]

__NOTOC__

[[Category: Contributors|Zodrow]]

PFAS Toxicology and Risk Assessment

2025-10-15T14:18:38Z

Debra Tabron:

This article presents an overview of current practices for human health and ecological risk assessment related to [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and poly-fluoroalkyl substances (PFAS)]] exposures at [[Wikipedia: Firefighting foam | aqueous film-forming foam (AFFF)]] impacted sites.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Sources]]
*[[PFAS Transport and Fate]]

'''Contributors:''' [[Jennifer Arblaster]], [[Dr. Jason Conder]], [[Dr. Jean Zodrow and Elizabeth Nichols]]

'''Key Resource(s):'''
*State of the Science for Risk Assessment of PFAS at Contaminated Sites<ref name="ZodrowEtAl2021">Zodrow, J., Arblaster, J., Conder, J., 2021. State of the Science for Risk Assessment of PFAS at Contaminated Sites. In: ''Forever Chemicals: Environmental, Economic, and Social Equity Concerns with PFAS in the Environment'', Kempisty, D., Racz, L., (Ed.s). pp. 161-186. CRC Press. [https://doi.org/10.1201/9781003024521 doi: 10.1201/9781003024521]</ref>
*[https://itrcweb.org/ Interstate Technology Regulatory Council (ITRC)], [https://pfas-1.itrcweb.org/ PFAS – Per- and Polyfluoroalkyl Substances]

==PFAS Exposure and Conceptual Site Models==
[[File:ConderFig1.png|thumb|500px|Figure 1. Simplified Conceptual Site Model for Sites Impacted by AFFF or other PFAS Sources. Used with permission<ref name="ConderEtAl2021">Conder, J., Zodrow, J., Arblaster, J., Kelly, B., Gobas, F., Suski, J., Osborn, E., Frenchmeyer, M., Divine, C., Leeson, A., 2021. Strategic resources for assessing PFAS ecological risks at AFFF sites. Integrated Environmental Assessment and Management, 17(4), pp. 746-752. [https://doi.org/10.1002/ieam.4405 doi: 10.1002/ieam.4405]</ref>]]
This article provides a brief overview of the environmental toxicology and risk assessment of per- and polyfluoroalkyl substances (PFAS). The article’s main focus is on the environmental toxicology and risk assessment of PFAS derived from aqueous film-forming foam (AFFF).

The use of AFFF can release PFAS into the environment during fire training, an emergency response, or as a result of leaks or spills from AFFF systems. Following AFFF releases, perfluoroalkyl acids (PFAAs), particularly PFOS, PFOA, and PFHxS, tend to be the most commonly detected PFAS in environmental media. Due to their solubility, sorption, and bioaccumulation properties, perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) can be prevalent in a variety of environmental media, including groundwater, surface water, soil, sediment, biosolids, landfill leachate, plants, fish, invertebrates, and wildlife<ref>Lau, C., 2012. Perfluorinated Compounds. In: ''Molecular, Clinical and Environmental Toxicology, Volume 3: Environmental Toxicology'', A. Luch (Ed.), pp. 47-86. Springer Science and Business Media. [https://doi.org/10.1007/978-3-7643-8340-4_3 doi: 10.1007/978-3-7643-8340-4_3]</ref>.

PFAS exhibit a range of physical and chemical properties, with the fate of the PFAAs, particularly the PFCAs and PFSAs, being the most studied PFAS. PFAAs are relatively water-soluble and mobile in the environment, are not volatile (i.e., they do not evaporate to the atmosphere readily<ref>Field, J., Higgins, C., Deeb, R., Conder, J., 2017. FAQs Regarding PFASs Associated with AFFF Use at U.S. Military Sites. Environmental Security Technology Certification Program (ESTCP) Project ER-201574. [https://serdp-estcp.mil/resources/details/ccf87a8d-f8b2-4fce-bc4a-78c32091f896 Project Website]  [[Media: FAQ_ER-201574.pdf | Report.pdf]]</ref>) and can sorb to the organic carbon present in soil or sediment. PFAAs are more soluble and mobile compared to other persistent organic chemicals of concern documented at contaminated sites. PFAS can bioaccumulate in animals and plants, and persistent PFAS, such as PFCAs and PFSAs, do not undergo significant biodegradation or biotransformation once present in a biological system<ref>Conder, J.M., Hoke, R.A., de Wolf, W., Russell, M.H., Buck, R.C., 2008. Are PFCAs Bioaccumulative? A Critical Review and Comparison with Regulatory Criteria and Persistent Lipophilic Compounds. Environmental Science and Technology, 42(4), pp. 995-1003. [https://doi.org/10.1021/es070895g doi: 10.1021/es070895g]</ref>.

The current state of the science and understanding of PFAS fate and transport indicates that the human health issues associated with PFAS AFFF sites are primarily the exposure pathways associated with drinking water ingestion and dietary intake of PFAS<ref name="ZodrowEtAl2021"/>. Incidental soil ingestion and/or dust inhalation are typically of moderate concern and are recommended for inclusion into human health risk assessments, but compared to drinking water and dietary ingestion, generally result in lower exposures for most receptors. Exposures via dermal contact with soils and water, and inhalation of vapors (due to volatilization of PFAS), are generally of even lower concern for most sites with AFFF PFAS sources. Human health conceptual site models (CSMs) for AFFF sites typically reflect common receptors including current or future residents and industrial or commercial workers, depending on the current and reasonable anticipated future land uses at the site, along with potential exposures in offsite areas. Receptors associated with recreation and fishing activities may be incorporated if water resources used for recreational purposes are located near the site. Additional considerations may need to be incorporated into the CSM, such as the source of PFAS release into the environment. Release mechanism can differ based on site uses of PFAS. For example, while AFFF use often resulted in historic releases to ground surfaces, industrial emissions can result in aerial deposition, and biosolids application can result in widespread releases to soils which result in different exposure pathways that should be considered.

Ecological CSMs generally focus on exposures in areas adjacent to or downgradient of initial AFFF releases which have habitats present which support ecological resources (Figure 1). Most areas at the point of AFFF releases (and many industrial areas where PFAS products are or were used) do not generally feature favorable ecological habitats that make these areas relevant for ecological risk assessment. However, the relatively high solubility of PFAS in water results in a high potential for offsite transport via groundwater, surface water and stormwater, or by erosion of impacted soils and sediment<ref name="ConderEtAl2021"/>.

==Toxicological Effects of PFAS==
The characterization of toxicological effects in human health risk assessments is based on toxicological studies of mammalian exposures to per- and polyfluoroalkyl substances (PFAS), primarily studies involving [[Wikipedia:Perfluorooctanesulfonic acid | perfluorooctanesulfonic acid (PFOS)]] and [[Wikipedia:Perfluorooctanoic acid|perfluorooctanoic acid (PFOA)]]. The most sensitive noncancer adverse effects involve the liver and kidney, immune system, and various developmental and reproductive endpoints<ref name="USEPA2024b">United States Environmental Protection Agency (USEPA), 2024. Per- and Polyfluoroalkyl Substances (PFAS) Final PFAS National Primary Drinking Water Regulation. [https://www.epa.gov/sdwa/and-polyfluoroalkyl-substances-pfas Website]</ref>. A select number of PFAS have been evaluated for carcinogenicity, primarily using epidemiological data. Only PFOS and PFOA (and their derivatives) have sufficient data for USEPA to characterize as ''Likely to Be Carcinogenic to Humans'' via the oral route of exposure. Epidemiological studies provided evidence of bladder, prostate, liver, kidney, and breast cancers in humans related to PFOS exposure, as well as kidney and testicular cancer in humans and limited evidence of breast cancer related to PFOA exposure<ref name="USEPA2024b"/><ref name="USEPA2016a">United States Environmental Protection Agency (USEPA), 2016. Drinking Water Health Advisory for Perfluorooctane Sulfonate (PFOS). Office of Water, EPA 822-R-16-004. [https://www.epa.gov/sites/production/files/2016-05/documents/pfos_health_advisory_final-plain.pdf Free Download]  [[Media: USEPA-2016-pfos_health_advisory_final-plain.pdf | Report.pdf]]</ref><ref name="USEPA2016b">United States Environmental Protection Agency (USEPA), 2016b. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA). Office of Water, EPA 822-R-16-005. [https://www.epa.gov/sites/production/files/2016-05/documents/pfoa_health_advisory_final_508.pdf Free Download]  [[Media: pfoa_EPA 822-R-16-005.pdf | Report.pdf]]</ref>.

USEPA’s Integrated Risk Management System (IRIS) Program is developing Toxicological Reviews to improve understanding of the toxicity of several additional PFAS (i.e., not solely PFOA and PFOS). Toxicological Reviews provide an overview of cancer and noncancer health effects based on current literature and, where data are sufficient, derive human health toxicity criteria (i.e., human health oral reference doses and cancer slope factors) that form the basis for risk-based decision making. For risk assessors, these documents provide USEPA reference doses and cancer slope factors that can be used with exposure information and other considerations to assess human health risk. Final Toxicological Reviews have been completed for the following PFAS:
*Perfluorooctanesulfonic acid (PFOS)
*Perfluorooctanoic acid (PFOA)
*Perfluorobutanoic acid (PFBA)
*Perfluorohexanoic acid (PFHxA)
*Perfluorobutane sulfonic acid (PFBS)
*Perfluoropropionic acid (PFPrA)
*Perfluorohexane sulfonic acid (PFHxS)
*Lithium bis[(trifluoromethyl)sulfonyl]azanide (HQ-115)
*Hexafluoropropylene oxide dimer acid (HFPO DA) and its Ammonium Salt

Toxicity assessments are ongoing for the following PFAS:
*Perfluorononanoic acid (PFNA)
*Perfluorodecanoic acid (PFDA)

It is important to note human health toxicity criteria for inhalation of PFAS are not included in the Final Toxicological Reviews and are not currently available.
In addition to IRIS, state agencies have developed peer-reviewed provisional toxicity values that have been incorporated into USEPA’s RSLs, which are updated biannually. These values have not been reviewed by or incorporated into IRIS.

With respect to ecological toxicity, effects on reproduction, growth, and development of avian and mammalian wildlife have been documented in controlled laboratory studies of exposures of standard toxicological test species (e.g., mice, quail) to PFAS. Many of these studies have been reviewed<ref name="ConderEtAl2020"> Conder, J., Arblaster, J., Larson, E., Brown, J., Higgins, C., 2020. Guidance for Assessing the Ecological Risks of PFAS to Threatened and Endangered Species at Aqueous Film Forming Foam-Impacted Sites. Strategic Environmental Research and Development Program (SERDP) Project ER 18-1614. [https://serdp-estcp.mil/projects/details/3f890c9b-7f72-4303-8d2e-52a89613b5f6 Project Website]  [[Media: ER18-1614_Guidance.pdf | Guidance Document]]</ref><ref name="GobasEtAl2020">Gobas, F.A.P.C., Kelly, B.C., Kim, J.J., 2020. Final Report: A Framework for Assessing Bioaccumulation and Exposure Risks of PFAS in Threatened and Endangered Species on AFFF-Impacted Sites. SERDP Project ER18-1502. [https://serdp-estcp.mil/projects/details/09c93894-bc73-404a-8282-51196c4be163 Project Website]  [[Media: ER18-1502_Final.pdf | Final Report]]</ref><ref name="Suski2020">Suski, J.G., 2020. Investigating Potential Risk to Threatened and Endangered Species from Per- and Polyfluoroalkyl Substances (PFAS) on Department of Defense (DoD) Sites. SERDP Project ER18-1626. [https://serdp-estcp.mil/projects/details/c328f8e3-95a4-4820-a0d4-ef5835134636 Project Website]  [[Media: ER18-1626_Final.pdf | Report.pdf]]</ref><ref name="ZodrowEtAl2021a">Zodrow, J.M., Frenchmeyer, M., Dally, K., Osborn, E., Anderson, P. and Divine, C., 2021. Development of Per and Polyfluoroalkyl Substances Ecological Risk-Based Screening Levels. Environmental Toxicology and Chemistry, 40(3), pp. 921-936. [https://doi.org/10.1002/etc.4975 doi: 10.1002/etc.4975]   [[Media: ZodrowEtAl2021a.pdf | Open Access Article]]</ref> to derive ecological Toxicity Reference Values (TRVs). TRVs can be used alongside exposure information and other considerations to assess ecological risk. Avian and mammalian wildlife receptors are generally expected to have the highest risks due to PFAS exposure. Direct toxicity to aquatic life, such as fish and invertebrates, from exposure to sediment and surface water also occurs, though concentrations in water associated with adverse effects to aquatic life are generally higher than those that could result in adverse effects to aquatic-dependent wildlife. Soil invertebrates and plants are less sensitive to PFAS when compared to terrestrial wildlife, with risk-based PFAS concentrations in soil being much higher than those associated with potential effects to terrestrial wildlife<ref name="ZodrowEtAl2021a"/>.

==PFAS Screening Levels for Human Health and Ecological Risk Assessments==
===Human Health Screening Levels===
Human health screening levels for PFAS have been modified multiple times over the last decade and, in the United States, are currently available for drinking water and soil exposures as Maximum Contaminant Levels (MCLs) and USEPA Regional Screening Levels (RSLs). USEPA finalized a National Primary Drinking Water Regulation (NPDWR) for six PFAS<ref name="USEPA2024b"/>:
*Perfluorooctanoic acid (PFOA)
*Perfluorooctane sulfonic acid (PFOS)
*Perfluorohexane sulfonic acid (PFHxS)
*Perfluorononanoic acid (PFNA)
*Hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX chemicals)
*Perfluorobutane sulfonic acid (PFBS)

MCLs are enforceable drinking water standards based on the most recently available toxicity information that consider available treatment technologies and costs. The MCLs for PFAS include a Hazard Index of 1 for combined exposures to four PFAS. RSLs are developed for use in risk assessments and include soil and tap water screening levels for multiple PFAS. Soil RSLs are based on residential/unrestricted and commercial/industrial land uses, and calculations of site-specific RSLs are available.

Internationally, Canada and the European Union have also promulgated drinking water standards for select PFAS. However, large discrepancies exist among the various regulatory organizations, largely due to the different effect endpoints and exposure doses being used to calculate risk-based levels. The PFAS guidance from the Interstate Technology and Regulatory Council (ITRC) in the US includes a regularly updated compilation of screening values for PFAS and is available on their PFAS website<ref name="ITRC2023">Interstate Technology and Regulatory Council (ITRC) 2023. PFAS Technical and Regulatory Guidance Document. [https://pfas-1.itrcweb.org/ ITRC PFAS Website]</ref>: https://pfas-1.itrcweb.org.

===Ecological Screening Levels===
Most peer-reviewed literature and regulatory-based environmental quality benchmarks have been developed using data for PFOS and PFOA; however, other select PFAAs have been evaluated for potential effects to aquatic receptors<ref name="ITRC2023"/><ref name="ZodrowEtAl2021a"/><ref name="ConderEtAl2020"/>. USEPA has developed water quality criteria for aquatic life<ref name="USEPA2022"> United States Environmental Protection Agency (USEPA), 2022. Fact Sheet: Draft 2022 Aquatic Life Ambient Water Quality Criteria for Perfluorooctanoic acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS)). Office of Water, EPA 842-D-22-005. [[Media: USEPA2022.pdf | Fact Sheet]]</ref><ref name="USEPA2024c">United States Environmental Protection Agency (USEPA), 2024. Final Freshwater Aquatic Life Ambient Water Quality Criteria and Acute Saltwater Aquatic Life Benchmark for Perfluorooctanoic Acid (PFOA). Office of Water, EPA-842-R-24-002. [[Media: USEPA2024c.pdf | Report.pdf]]</ref><ref name="USEPA2024d">United States Environmental Protection Agency (USEPA), 2024. Final Freshwater Aquatic Life Ambient Water Quality Criteria and Acute Saltwater Aquatic Life Benchmark for Perfluorooctane Sulfonate (PFOS). Office of Water, EPA-842-R-24-003. [[Media: USEPA2024d.pdf | Report.pdf]]</ref> for PFOA and PFOS. Following extensive reviews of the peer-reviewed literature, Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> used the USEPA Great Lakes Initiative methodology<ref>United States Environmental Protection Agency (USEPA), 2012. Water Quality Guidance for the Great Lakes System. Part 132. [https://www.govinfo.gov/app/details/CFR-2013-title40-vol23/CFR-2013-title40-vol23-part132 Government Website]  [[Media: CFR-2013-title40-vol23-part132.pdf | Part132.pdf]]</ref> to calculate acute and chronic screening levels for aquatic life for 23 PFAS. The Argonne National Laboratory has also developed Ecological Screening Levels for multiple PFAS<ref name="GrippoEtAl2024">Grippo, M., Hayse, J., Hlohowskyj, I., Picel, K., 2024. Derivation of PFAS Ecological Screening Values - Update. Argonne National Laboratory Environmental Science Division. [[Media: GrippoEtAl2024.pdf | Report.pdf]]</ref>. In contrast to surface water aquatic life benchmarks, sediment benchmark values are limited. For terrestrial systems, screening levels for direct exposure of soil plants and invertebrates to PFAS in soils have been developed for multiple AFFF-related PFAS<ref name="ConderEtAl2020"/><ref name="ZodrowEtAl2021a"/>, and the Canadian Council of Ministers of Environment developed several draft thresholds protective of direct toxicity of PFOS in soil<ref>Canadian Council of Ministers of the Environment (CCME), 2021. Canadian Soil and Groundwater Quality Guidelines for the Protection of Environmental and Human Health, Perfluorooctane Sulfonate (PFOS). [[Media: CCME2018.pdf | Open Access Government Document]]</ref>.

Wildlife screening levels for abiotic media are back-calculated from food web models developed for representative receptors. Both Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> and Grippo ''et al.''<ref name="GrippoEtAl2024"/> include the development of risk-based screening levels for wildlife. The Michigan Department of Community Health<ref>Dykema, L.D., 2015. Michigan Department of Community Health Final Report, USEPA Great Lakes Restoration Initiative (GLRI) Project, Measuring Perfluorinated Compounds in Michigan Surface Waters and Fish. Grant GL-00E01122. [https://www.michigan.gov/documents/mdch/MDCH_GL-00E01122-0_Final_Report_493494_7.pdf Free Download]  [[Media: MDCH_Geart_Lakes_PFAS.pdf | Report.pdf]]</ref> derived a provisional PFOS surface water value for avian and mammalian wildlife. In California, the San Francisco Bay Regional Water Quality Control Board developed terrestrial habitat soil ecological screening levels based on values developed in Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/>. For PFOS only, a dietary screening level (i.e. applicable to the concentration of PFAS measured in dietary items) has been developed for mammals at 4.6 micrograms per kilogram (μg/kg) wet weight (ww), and for avians at 8.2 μg/kg ww<ref>Environment and Climate Change Canada, 2018. Federal Environmental Quality Guidelines, Perfluorooctane Sulfonate (PFOS). [[Media: ECCC2018.pdf | Repoprt.pdf]]</ref>.

==Approaches for Evaluating Exposures and Effects in AFFF Site Environmental Risk Assessment: Human Health==
Exposure pathways and effects for select PFAS are well understood, such that standard human health risk assessment approaches can be used to quantify risks for populations relevant to a site. Human health exposures via drinking water have been the focus in risk assessments and investigations at PFAS sites<ref>Post, G.B., Cohn, P.D., Cooper, K.R., 2012. Perfluorooctanoic acid (PFOA), an emerging drinking water contaminant: A critical review of recent literature. Environmental Research, 116, pp. 93-117. [https://doi.org/10.1016/j.envres.2012.03.007 doi: 10.1016/j.envres.2012.03.007]</ref><ref>Guelfo, J.L., Marlow, T., Klein, D.M., Savitz, D.A., Frickel, S., Crimi, M., Suuberg, E.M., 2018. Evaluation and Management Strategies for Per- and Polyfluoroalkyl Substances (PFASs) in Drinking Water Aquifers: Perspectives from Impacted U.S. Northeast Communities. Environmental Health Perspectives,126(6), 13 pages. [https://doi.org/10.1289/EHP2727 doi: 10.1289/EHP2727]  [[Media: GuelfoEtAl2018.pdf | Open Access Article]]</ref>. Risk assessment approaches for PFAS in drinking water follow typical, well-established drinking water risk assessment approaches for chemicals as detailed in regulatory guidance documents for various jurisdictions.

Incidental exposures to soil and dusts for PFAS can occur during a variety of soil disturbance activities, such as gardening and digging, hand-to-mouth activities, and intrusive groundwork by industrial or construction workers. As detailed by the ITRC<ref name="ITRC2023"/>, many US states and USEPA have calculated risk-based screening levels for these soil and drinking water pathways (and many also include dermal exposures to soils) using well-established risk assessment guidance.

Field and laboratory studies have shown that some PFCAs and PFSAs bioaccumulate in fish and other aquatic life at rates that could result in relevant dietary PFAS exposures for consumers of fish and other seafood<ref>Martin, J.W., Mabury, S.A., Solomon, K.R., Muir, D.C., 2003. Dietary accumulation of perfluorinated acids in juvenile rainbow trout (Oncorhynchus mykiss). Environmental Toxicology and Chemistry, 22(1), pp.189-195. [https://doi.org/10.1002/etc.5620220125 doi: 10.1002/etc.5620220125]</ref><ref>Martin, J.W., Mabury, S.A., Solomon, K.R., Muir, D.C., 2003. Bioconcentration and tissue distribution of perfluorinated acids in rainbow trout (Oncorhynchus mykiss). Environmental Toxicology and Chemistry, 22(1), pp.196-204. [https://doi.org/10.1002/etc.5620220126 doi: 10.1002/etc.5620220126]</ref><ref>Chen, F., Gong, Z., Kelly, B.C., 2016. Bioavailability and bioconcentration potential of perfluoroalkyl-phosphinic and -phosphonic acids in zebrafish (Danio rerio): Comparison to perfluorocarboxylates and perfluorosulfonates. Science of The Total Environment, 568, pp. 33-41. [https://doi.org/10.1016/j.scitotenv.2016.05.215 doi: 10.1016/j.scitotenv.2016.05.215]</ref><ref>Fang, S., Zhang, Y., Zhao, S., Qiang, L., Chen, M., Zhu, L., 2016. Bioaccumulation of per fluoroalkyl acids including the isomers of perfluorooctane sulfonate in carp (Cyprinus carpio) in a sediment/water microcosm. Environmental Toxicology and Chemistry, 35(12), pp. 3005-3013. [https://doi.org/10.1002/etc.3483 doi: 10.1002/etc.3483]</ref><ref>Bertin, D., Ferrari, B.J.D. Labadie, P., Sapin, A., Garric, J., Budzinski, H., Houde, M., Babut, M., 2014. Bioaccumulation of perfluoroalkyl compounds in midge (Chironomus riparius) larvae exposed to sediment. Environmental Pollution, 189, pp. 27-34. [https://doi.org/10.1016/j.envpol.2014.02.018 doi: 10.1016/j.envpol.2014.02.018]</ref><ref>Bertin, D., Labadie, P., Ferrari, B.J.D., Sapin, A., Garric, J., Geffard, O., Budzinski, H., Babut. M., 2016. Potential exposure routes and accumulation kinetics for poly- and perfluorinated alkyl compounds for a freshwater amphipod: Gammarus spp. (Crustacea). Chemosphere, 155, pp. 380-387. [https://doi.org/10.1016/j.chemosphere.2016.04.006 doi: 10.1016/j.chemosphere.2016.04.006]</ref><ref>Dai, Z., Xia, X., Guo, J., Jiang, X., 2013. Bioaccumulation and uptake routes of perfluoroalkyl acids in Daphnia magna. Chemosphere, 90(5), pp.1589-1596. [https://doi.org/10.1016/j.chemosphere.2012.08.026 doi: 10.1016/j.chemosphere.2012.08.026]</ref><ref>Prosser, R.S., Mahon, K., Sibley, P.K., Poirier, D., Watson-Leung, T. 2016. Bioaccumulation of perfluorinated carboxylates and sulfonates and polychlorinated biphenyls in laboratory-cultured Hexagenia spp., Lumbriculus variegatus and Pimephales promelas from field-collected sediments. Science of The Total Environment, 543(A), pp. 715-726. [https://doi.org/10.1016/j.scitotenv.2015.11.062 doi: 10.1016/j.scitotenv.2015.11.062]</ref><ref>Rich, C.D., Blaine, A.C., Hundal, L., Higgins, C., 2015. Bioaccumulation of Perfluoroalkyl Acids by Earthworms (Eisenia fetida) Exposed to Contaminated Soils. Environmental Science and Technology, 49(2) pp. 881-888. [https://doi.org/10.1021/es504152d doi: 10.1021/es504152d]</ref><ref>Muller, C.E., De Silva, A.O., Small, J., Williamson, M., Wang, X., Morris, A., Katz, S., Gamberg, M., Muir, D.C.G., 2011. Biomagnification of Perfluorinated Compounds in a Remote Terrestrial Food Chain: Lichen–Caribou–Wolf. Environmental Science and Technology, 45(20), pp. 8665-8673. [https://doi.org/10.1021/es201353v doi: 10.1021/es201353v]</ref>. In addition to fish, terrestrial wildlife can accumulate contaminants from impacted sites, resulting in potential exposures to consumers of wild game<ref name="ConderEtAl2021"/>. Additionally, exposures can occur though consumption of homegrown produce or agricultural products that originate from areas irrigated with PFAS-impacted groundwater, or that are amended with biosolids that contain PFAS, or that contain soils that were directly affected by PFAS releases<ref>Brown, J.B, Conder, J.M., Arblaster, J.A., Higgins, C.P., 2020. Assessing Human Health Risks from Per- and Polyfluoroalkyl Substance (PFAS)-Impacted Vegetable Consumption: A Tiered Modeling Approach. Environmental Science and Technology, 54(23), pp. 15202-15214. [https://doi.org/10.1021/acs.est.0c03411 doi: 10.1021/acs.est.0c03411]  [[Media: BrownEtAl2020.pdf | Open Access Article]]</ref>. Multiple studies have found PFAS can be taken up by plants from soil porewater<ref>Blaine, A.C., Rich, C.D., Hundal, L.S., Lau, C., Mills, M.A., Harris, K.M., Higgins, C.P., 2013. Uptake of Perfluoroalkyl Acids into Edible Crops via Land Applied Biosolids: Field and Greenhouse Studies. Environmental Science and Technology, 47(24), pp. 14062-14069. [https://doi.org/10.1021/es403094q doi: 10.1021/es403094q]  [https://www.epa.gov/sites/production/files/2019-11/documents/508_pfascropuptake.pdf Free Download from epa.gov]</ref><ref>Blaine, A.C., Rich, C.D., Sedlacko, E.M., Hyland, K.C., Stushnoff, C., Dickenson, E.R.V., Higgins, C.P., 2014. Perfluoroalkyl Acid Uptake in Lettuce (Lactuca sativa) and Strawberry (Fragaria ananassa) Irrigated with Reclaimed Water. Environmental Science and Technology, 48(24), pp. 14361-14368. [https://doi.org/10.1021/es504150h doi: 10.1021/es504150h]</ref><ref>Ghisi, R., Vamerali, T., Manzetti, S., 2019. Accumulation of perfluorinated alkyl substances (PFAS) in agricultural plants: A review. Environmental Research, 169, pp. 326-341. [https://doi.org/10.1016/j.envres.2018.10.023 doi: 10.1016/j.envres.2018.10.023]</ref>, and livestock can accumulate PFAS from drinking water and/or feed<ref>van Asselt, E.D., Kowalczyk, J., van Eijkeren, J.C.H., Zeilmaker, M.J., Ehlers, S., Furst, P., Lahrssen-Wiederhold, M., van der Fels-Klerx, H.J., 2013. Transfer of perfluorooctane sulfonic acid (PFOS) from contaminated feed to dairy milk. Food Chemistry, 141(2), pp.1489-1495. [https://doi.org/10.1016/j.foodchem.2013.04.035 doi: 10.1016/j.foodchem.2013.04.035]</ref>. Thus, when PFAS are present in surface water bodies where fishing or shellfish harvesting occurs or terrestrial areas where produce is grown or game is hunted, the bioaccumulation of PFAS into dietary items can be an important pathway for human exposure.

PFAAs such as PFOA and PFOS are not expected to volatilize from PFAS-impacted environmental media<ref name="USEPA2016a"/><ref name="USEPA2016b"/> such as soil and groundwater, which are the primary focus of most site-specific risk assessments. In contrast to non-volatile PFAAs, fluorotelomer alcohols (FTOHs) are among the more widely studied of the volatile PFAS. FTOHs are transient in the atmosphere with a lifetime of 20 days<ref>Ellis, D.A., Martin, J.W., De Silva, A.O., Mabury, S.A., Hurley, M.D., Sulbaek Andersen, M.P., Wallington, T.J., 2004. Degradation of Fluorotelomer Alcohols: A Likely Atmospheric Source of Perfluorinated Carboxylic Acids. Environmental Science and Technology, 38(12), pp. 3316-3321. [https://doi.org/10.1021/es049860w doi: 10.1021/es049860w]</ref>. At most AFFF sites under evaluation, AFFF releases have occurred many years before such that FTOH may no longer be present. As such, the current assumption is that volatile PFAS, such as FTOHs historically released at the site, will have transformed to stable, low-volatility PFAS, such as PFAAs in soil or groundwater, or will they have diffused to the outdoor atmosphere. There is no evidence that FTOHs or other volatile PFAS are persistent in groundwater or soils such that they present an indoor vapor intrusion pathway risk concern as observed for chlorinated solvents. Ongoing research continues for the vapor pathway<ref name="ITRC2023"/>.

General and site-specific human health exposure pathways and risk assessment methods as outlined by USEPA<ref>United States Environmental Protection Agency (USEPA), 1989. Risk Assessment Guidance for Superfund: Volume I, Human Health Evaluation Manual (Part A). Office of Solid Waste and Emergency Response, EPA/540/1-89/002. [https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=10001FQY.txt Free Download]  [[Media: USEPA1989.pdf | Report.pdf]]</ref><ref name="USEPA1997">United States Environmental Protection Agency (USEPA), 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments, Interim Final. Office of Solid Waste and Emergency Response, EPA 540-R-97-006. [http://semspub.epa.gov/src/document/HQ/157941 Free Download]  [[Media: EPA540-R-97-006.pdf | Report.pdf]]</ref> can be applied to PFAS risk assessments for which human health toxicity values have been developed. Additionally, for risk assessments with dietary exposures of PFAS, standard risk assessment food web modeling can be used to develop initial estimates of dietary concentrations which can be confirmed with site-specific tissue sampling programs.

==Approaches for Evaluating Exposures and Effects in AFFF Site Environmental Risk Assessment: Ecological==
Information available currently on exposures and effects of PFAS in ecological receptors indicate that the PFAS ecological risk issues at most sites are primarily associated with risks to vertebrate wildlife. Avian and mammalian wildlife are relatively sensitive to PFAS, and dietary intake via bioaccumulation in terrestrial and aquatic food webs can result in exposures that are dominated by the more accumulative PFAS<ref name="LarsonEtAl2018">Larson, E.S., Conder, J.M., Arblaster, J.A., 2018. Modeling avian exposures to perfluoroalkyl substances in aquatic habitats impacted by historical aqueous film forming foam releases. Chemosphere, 201, pp. 335-341. [https://doi.org/10.1016/j.chemosphere.2018.03.004 doi: 10.1016/j.chemosphere.2018.03.004]</ref><ref name="ConderEtAl2020"/><ref name="ZodrowEtAl2021a"/>. Direct toxicity to aquatic life (e.g., fish, pelagic life, benthic invertebrates, and aquatic plants) can occur from exposure to sediment and surface water at effected sites. For larger areas, surface water concentrations associated with adverse effects to aquatic life are generally higher than those that could result in adverse effects to aquatic-dependent wildlife. Soil invertebrates and plants are generally less sensitive, with risk-based concentrations in soil being much higher than those associated with potential effects to terrestrial wildlife<ref name="ZodrowEtAl2021a"/>.

Aquatic life are exposed to PFAS through direct exposure in surface water and sediment. Ecological risk assessment approaches for PFAS for aquatic life follow standard risk assessment approaches. The evaluation of potential risks for aquatic life with direct exposure to PFAS in environmental media relies on comparing concentrations in external exposure media to protective, media-specific benchmarks, including the aquatic life risk-based screening levels discussed above<ref name="ZodrowEtAl2021a"/><ref name="USEPA2024a">United States Environmental Protection Agency (USEPA), 2024. National Recommended Water Quality Criteria - Aquatic Life Criteria Table. [https://www.epa.gov/wqc/national-recommended-water-quality-criteria-aquatic-life-criteria-table USEPA Website]</ref>.

When an area at the point of PFAS release is an industrial setting which does not feature favorable habitats for terrestrial and aquatic-dependent wildlife, the transport mechanisms may allow PFAS to travel offsite. If offsite or downgradient areas contain ecological habitat, then PFAS transported to these areas are expected to pose the highest risk potential to wildlife, particularly those areas that feature aquatic habitat<ref>Ahrens, L., Bundschuh, M., 2014. Fate and effects of poly- and perfluoroalkyl substances in the aquatic environment: A review. Environmental Toxicology and Chemistry, 33(9), pp. 1921-1929. [https://doi.org/10.1002/etc.2663 doi: 10.1002/etc.2663]  [[Media: AhrensBundschuh2014.pdf | Open Access Article]]</ref><ref name="LarsonEtAl2018"/>.

Wildlife receptors, specifically birds and mammals, are typically exposed to PFAS through uptake from dietary sources such as plants and invertebrates, along with direct soil ingestion during foraging activities. Dietary intake modeling typical for ecological risk assessments is the recommended approach for an evaluation of potential risks to wildlife species where PFAS exposure occurs primarily via dietary uptake from bioaccumulation pathways. Dietary intake modeling uses relevant exposure factors for each receptor group (terrestrial birds, terrestrial mammals, aquatic-dependent birds, and aquatic mammals) to determine a total daily intake (TDI) of PFAS via all potential exposure pathways. This approach requires determination of concentrations of PFAS in dietary items, which can be obtained by measuring PFAS in biota at sites or by using food web models to predict concentrations in biota using measured concentrations of PFAS in soil, sediment, or surface water. Food web models use bioaccumulation metrics such as bioaccumulation factors (BAFs) and biomagnification factors (BMFs) with measurements of PFAS in abiotic media to estimate concentrations in dietary items, including plants and benthic or pelagic invertebrates, to model wildlife exposure and calculate TDI. Once site-specific TDI values are calculated, they are compared to known TRVs identified from toxicity data with exposure doses associated with a lack of adverse effects (termed no observed adverse effect level [NOAEL]) or low adverse effects (termed lowest observed adverse effect level [LOAEL]), per standard risk assessment practice<ref name="USEPA1997"/>.

Recently, Conder ''et al.''<ref name="ConderEtAl2020"/>, Gobas ''et al.''<ref name="GobasEtAl2020"/>, and Zodrow ''et al.''<ref name="ZodrowEtAl2021a"/> compiled bioaccumulation modeling parameters and approaches for terrestrial and aquatic food web modeling of a variety of commonly detected PFAS at AFFF sites. There are also several sources of TRVs which can be relied upon for estimating TDI values<ref name="ConderEtAl2020"/><ref name="GobasEtAl2020"/><ref name="ZodrowEtAl2021a"/><ref>Newsted, J.L., Jones, P.D., Coady, K., Giesy, J.P., 2005. Avian Toxicity Reference Values for Perfluorooctane Sulfonate. Environmental Science and Technology, 39(23), pp. 9357-9362. [https://doi.org/10.1021/es050989v doi: 10.1021/es050989v]</ref><ref name="Suski2020"/>. In general, the highest risk for PFAS is expected for smaller insectivore and omnivore receptors (e.g., shrews and other small rodents, small nonmigratory birds), which tend to be lower in trophic level and spend more time foraging in small areas similar to or smaller in size than the impacted area. Compared to smaller, lower-trophic level organisms, larger mammalian and avian carnivores are expected to have lower exposures from site-specific PFAS sources because they forage over larger areas that may include areas that are not impacted, as compared to small organisms with small home ranges<ref name="LarsonEtAl2018"/><ref name="ConderEtAl2020"/><ref name="GobasEtAl2020"/><ref name="Suski2020"/><ref name="ZodrowEtAl2021a"/>.

Available information regarding PFAS exposure pathways and effects in aquatic life, terrestrial invertebrates and plants, as well as aquatic and terrestrial wildlife allow ecological risk assessment methods to be applied as outlined by USEPA<ref name="USEPA1997"/> to site-specific PFAS risk assessments. Additionally, food web modeling can be used in site-specific PFAS risk assessment to develop initial estimates of dietary concentrations for aquatic and terrestrial wildlife, which can be confirmed with tissue sampling programs at a site.

==PFAS Risk Assessment Data Gaps==
There are a number of data gaps currently associated with PFAS risk assessment including the following:
*'''Unmeasured PFAS:''' There are a number of additional PFAS that we know little about and many PFAS that we are unable to quantify in the environment. The approach to dealing with the lack of information on the overwhelming number of PFAS is being debated; in the meantime, however, PFAS beyond PFOS and PFOA are being studied more, and this information will result in improved characterization of risks for other PFAS.

*'''Mixtures:''' Another major challenge in effects assessment for PFAS, for both human health risk assessments and environmental risk assessments, is understanding the potential importance of mixtures of PFAS. Considering the limited human health and ecological toxicity data available for just a few PFAS, the understanding of the relative toxicity, additivity, or synergistic effects of PFAS in mixtures is just beginning.

*'''Toxicity Data Gaps:''' For environmental risk assessments, some organisms such as reptiles and benthic invertebrates do not have toxicity data available. Benchmark or threshold concentrations of PFAS in environmental media intended to be protective of wildlife and aquatic organisms suffer from significant uncertainty in their derivation due to the limited number of species for which data are available. As species-specific data becomes available for more types of organisms, the accuracy of environmental risk assessments is likely to improve.

==References==
<references />

==See Also==
[https://www.atsdr.cdc.gov/pfas/health-studies/index.html Agency for Toxic Substances and Disease Registry (ATSDR) PFAS Health Studies]

Jennifer Arblaster

2025-10-15T14:16:39Z

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==About the Contributor==
Jennifer Arblaster has 12 years of experience in ecological and human health risk assessment, bioaccumulation modeling, and strategic planning, evaluation of toxicity, and site-specific risk assessment of emerging contaminants of concern including per and poly-fluoroalkyl substances (PFAS).

==Article Contributions==
*[[PFAS Toxicology and Risk Assessment]]

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Dr. Christopher Bellona

2025-09-24T15:07:02Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Colorado School of Mines :Department of Civil and Environmental Engineering :Golden, CO 80401 EMAIL: [mailto:cbellona..."

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WEBPAGE: [https://cee.mines.edu/project/bellona-christopher https://cee.mines.edu/project/bellona-christopher]

==About the Contributor==
Chris Bellona is an Associate Professor in the Department of Civil and Environmental Engineering at the Colorado School of Mines. His area of expertise is in the removal of contaminants by advanced treatment processes for a variety of applications including water and wastewater treatment, potable water reuse, and remediation projects. He has numerous ongoing PFAS research projects on the development and evaluation of technologies for the removal of PFAS from impacted water resources including adsorbents, membrane technologies, foam fractionation and destructive processes. Most of this research involves pilot-scale evaluations of treatment processes at impacted sites. Dr. Bellona has published more than 60 peer-reviewed publications, presented numerous times at national and international conferences, webinars and professional meetings on his research.

==Article Contributions==
*[[Reverse Osmosis and Nanofiltration Membrane Filtration Systems for PFAS Removal]]

__NOTOC__

[[Category: Contributors|Bellona]]]

Reverse Osmosis and Nanofiltration Membrane Filtration Systems for PFAS Removal

2025-09-24T15:00:50Z

Debra Tabron:

[[Wikipedia: Nanofiltration | Nanofiltration (NF)]] and [[Wikipedia: Reverse osmosis | reverse osmosis (RO)]] are engineered polymeric filters designed to remove solutes down to the atomic and molecular size scale<ref name="Wilf2019">Wilf, M., 2019. Basic Terms and Definitions, Chapter 3 in Desalination: Water from Water, 2nd Edition, J. Kucera, Editor. John Wiley & Sons. ISBN: 978-1-119-40774-4 [https://doi.org/10.1002/9781119407874.ch3 doi: 10.1002/9781119407874.ch3]</ref><ref name="BellonaEtAl2004">Bellona, C., Drewes, J., Xu, P., Amy, G., 2004. Factors affecting the rejection of organic solutes during NF/RO treatment—a literature review. Water Research, 38(12), p. 2795-2809. [https://doi.org/10.1016/j.watres.2004.03.034 doi: 10.1016/j.watres.2004.03.034]</ref><ref name="BazarganSalgado2018">Bazargan, A., Salgado, B., 2018. Fundamentals of Desalination Technology, in A Multidisciplinary Introduction to Desalination, A. Bazargan, Editor. River Publishers. p. 41-66. ISBN 9788793379541. [https://doi.org/10.1201/9781003336914 doi: 10.1201/9781003336914]</ref>. RO, and to a lesser extent NF, has been implemented in a variety of water treatment applications including seawater and brackish water desalination, surface water treatment, industrial process water separation, and purification applications<ref name="Wilf2019"/><ref name="BellonaEtAl2004"/><ref name="BazarganSalgado2018"/><ref name="TurekEtAl2017">Turek, M., Mitko, K., Piotrowski, K., Dydo, P., Laskowska, E., Jakóbik-Kolon, A., 2017. Prospects for high water recovery membrane desalination. Desalination, 401, p. 180-189. [https://doi.org/10.1016/j.desal.2016.07.047 doi: 10.1016/j.desal.2016.07.047]</ref><ref name="PanagopoulosEtAl2019">Panagopoulos, A., Haralambous, K.-J., Loizidou, M., 2019. Desalination brine disposal methods and treatment technologies - A review. Science of The Total Environment, 693, Article 133545. [https://doi.org/10.1016/j.scitotenv.2019.07.351 doi: 10.1016/j.scitotenv.2019.07.351]</ref><ref name="WarsingerEtAl2018">Warsinger, D.M., Chakraborty, S., Tow, E.W., Plumlee, M.H., Bellona, C., Loutatidou, S., Karimi, L., Mikelonis, A.M., Achilli, A., Ghassemi, A., Padhye, L.P., Snyder, S.A., Curcio, S., Vecitis, C.D., Arafat, H.A., Lienhard, J.H., 2018. A review of polymeric membranes and processes for potable water reuse. Progress in Polymer Science, 81, p. 209-237. [https://doi.org/10.1016/j.progpolymsci.2018.01.004 doi: 10.1016/j.progpolymsci.2018.01.004]</ref><ref name="Yan2017">Yan, D., 2017. Membrane Desalination Technologies, Chapter 6 in A Multidisciplinary Introduction to Desalination, A. Bazargan, Editor. River Publishers, p. 155-199. ISBN: 9788793379541</ref><ref name="Bellona2019">Bellona, C., 2019. Nanofiltration - Theory and Application, Chapter 4 in Desalination: Water from Water, 2nd Edition, J. Kucera, Editor. John Wiley & Sons. ISBN: 978-1-119-40774-4. [https://doi.org/10.1002/9781118904855.ch4 doi: 10.1002/9781118904855.ch4]</ref>. RO and NF use semi-permeable membranes that limit diffusion of solutes into the product water (''i.e.'', permeate) through [[Wikipedia: Steric effects | steric]] and electrostatic exclusion from the membrane polymer<ref name="BellonaEtAl2004"/>. Due to the molecular size and ionic character of [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]], past research has demonstrated that both RO and NF membranes can achieve a high degree of separation (''i.e.'', rejection) of PFAS<ref name="ApplemanEtAl2013">Appleman, T.D., Dickenson, E.R.V., Bellona, C., Higgins, C.P., 2013. Nanofiltration and granular activated carbon treatment of perfluoroalkyl acids. Journal of Hazardous Materials, 260, p. 740-746. [https://doi.org/10.1016/j.jhazmat.2013.06.033 doi: 10.1016/j.jhazmat.2013.06.033]</ref><ref name="Steinle-DarlingReinhard2008">Steinle-Darling, E., Reinhard, M., 2008. Nanofiltration for Trace Organic Contaminant Removal: Structure, Solution, and Membrane Fouling Effects on the Rejection of Perfluorochemicals. Environmental Science and Technology, 42(14), p. 5292-5297. [https://doi.org/10.1021/es703207s doi: 10.1021/es703207s]</ref><ref name="SafulkoEtAl2023">Safulko, A., Cath, T.Y., Li, F., Tajdini, B., Boyd, M., Huehmer, R.P., Bellona, C., 2023. Rejection of perfluoroalkyl acids by nanofiltration and reverse osmosis in a high-recovery closed-circuit membrane filtration system. Separation and Purification Technology, 326, Article 124867. [https://doi.org/10.1016/j.seppur.2023.124867 doi: 10.1016/j.seppur.2023.124867] [[Media: SafulkoEtAl2023.pdf | Open Access Manuscript]]</ref>.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Ex Situ Water Treatment]]
*[[PFAS Sources]]
*[[PFAS Transport and Fate]]

'''Contributors:''' [[Dr. Christopher Bellona]], [[Nicole Masters]], [[Dr. Stephen Richardson]]

'''Key Resource(s):'''

*[https://itrcweb.org/ Interstate Technology Regulatory Council (ITRC)], [https://pfas-1.itrcweb.org/ PFAS – Per- and Polyfluoroalkyl Substances]: [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_2 12.2 Field-Implemented Liquids Treatment Technologies] and [https://pfas-1.itrcweb.org/12-treatment-technologies/#12_5 12.5 Limited Application and Developing Liquids Treatment Technologies]

==Introduction==
[[File:RichardsonFig1.png|thumb|500px|Figure 1. Basic schematic of cross-flow operation of high-pressure membranes. The feed water flows parallel to the membrane becoming more concentrated and then leaves the system as retentate. The permeate is water forced through the membrane by applying pressure. Q is flowrate and C is concentration of the solute of interest. F is the feed, P is the permeate, and R is the retentate.]]
<onlyinclude>High-pressure membrane filtration such as nanofiltration (NF) or reverse osmosis (RO) is a filtration process that separates dissolved inorganic and organic solutes from liquid solvents, typically water</onlyinclude><ref name="Wilf2019"/><onlyinclude>. As opposed to porous and more permeable low-pressure membranes (''i.e.'', microfiltration and ultrafiltration), NF and RO membranes are widely considered semi-permeable and therefore require higher operating pressures to force water against an [[Wikipedia: Osmosis | osmotic gradient]] to produce a purified permeate stream</onlyinclude><ref name="BellonaEtAl2004"/><ref name="BazarganSalgado2018"/><onlyinclude>. </onlyinclude>The semi-permeable nature and properties of RO and NF membranes results in significantly lower solute diffusive flux across the membranes compared to water<ref name="BellonaEtAl2004"/>.

To optimize solute separation and minimize accumulation of solutes on the membrane, these systems are almost exclusively operated in a cross-flow configuration where feed water flows parallel to the membrane surface and is forced across the membrane through the application of pressure (Figure 1). In a cross-flow configuration, <onlyinclude>NF and RO systems are separation processes that yield two streams: the treated permeate and the concentrated retentate. </onlyinclude>

<onlyinclude>Typical parameters used to describe operational performance of high-pressure membrane systems include solvent ''recovery'' and solute ''rejection''. Recovery is defined as the percentage of feed water that becomes permeate</onlyinclude>, which can be calculated as:

:::[[File: RichardsonEq1.png]]

where ''QP'' is the permeate flow rate, and ''QF'' is the feed flow rate<onlyinclude>. </onlyinclude>The recovery of a high-pressure membrane system is dependent upon the RO system configuration and feed water quality. For feed waters containing relatively low [[Wikipedia: Total dissolved solids | total dissolved solids (TDS)]] concentrations, in conventional RO and NF membrane applications, recovery is typically between 75% and 85%. However, several novel membrane configurations have been developed to increase membrane recoveries to 90% and greater depending on feed water quality.

<onlyinclude>Solute rejection is defined as the percent of concentrated feed water retained by the membrane</onlyinclude> and can be calculated as:

:::[[File: RichardsonEq2.png]]

where ''Cp'' and ''Cf'' are the concentration of a solute in the permeate and feed water, respectively<onlyinclude>. </onlyinclude>Because the retentate stream contains high concentrations of all solutes rejected by the membrane, minimization of retentate volume is a focus of ongoing research and development<ref name="TurekEtAl2017"/><ref name="PanagopoulosEtAl2019"/>.

[[File:RichardsonFig2.png|thumb|650px|Figure 2. (Left) Spiral-wound membrane element with the feed side of the element and permeate collection tube in the middle visible. (Right) 1-million gallon per day membrane system with multiple pressure vessels.]]
<onlyinclude>Significant advancements in membrane material development have led to development of NF and RO membranes with varying pressure requirements and solute rejection characteristics</onlyinclude><ref name="BellonaEtAl2004"/><ref name="WarsingerEtAl2018"/><onlyinclude>. </onlyinclude>RO utilizes very tight and selective membrane material (typically [[Wikipedia: Polyamide | polyamide]]) that can achieve high rejection of most dissolved solutes but requires relatively high pressures, typically >150 psi depending on TDS concentration and RO membrane type (''e.g.'', requiring up to 1000 psi when treating seawater with RO membrane elements optimized for seawater)<ref name="Yan2017"/>. RO is used in a variety of applications where a high degree of solute separation is desired including seawater and brackish water desalination, potable water reuse applications, industrial water treatment, and separation applications<ref name="Wilf2019"/>. NF is fundamentally similar to RO; however, NF has been engineered to provide selective separation of solutes and often operate at lower pressures than RO (<150 psi). NF membranes have a range of rejection characteristics with some NF membranes being ‘tighter’ with lower permeability similar to RO (''i.e.'', high salt and organic solute rejection) and others being ‘looser’ with high permeability (''i.e.'', lower salt and organic solute rejection)<ref name="Bellona2019"/>.

High-pressure NF and RO membranes are commonly found in a spiral-wound configuration<ref name="Wilf2019"/>. Spiral-wound elements come in standardized sizes that are then loaded into a series of pressure vessels. An example of a spiral-wound element and a membrane system comprised of multiple pressure vessels is shown in Figure 2. Large-scale membrane systems are typically comprised of several membrane “stages” to increase recovery. Each stage contains multiple pressure vessels containing several individual spiral-wound elements each.

==Application of High-Pressure Membranes for Treatment of PFAS Contaminated Water==
[[File:RichardsonFig3.png|thumb|470px|Figure 3. Rejection of nine PFAAs by four available membrane products at the pilot-scale. Rejection data shown above was generated from permeate samples collected at 97% recovery.]]
[[File:RichardsonFig4.png|thumb|600px|Figure 4. Mobile high-pressure membrane treatment trailer (left) and pilot-scale closed-circuit membrane filtration system (right).]]
The effectiveness of RO and NF membranes for dissolved solute rejection has led to high-pressure membranes being regarded as one of the best available technologies for PFAS removal for over a decade<ref name="ApplemanEtAl2013"/><ref name="Steinle-DarlingReinhard2008"/>. Several studies have evaluated aspects of PFAS removal by NF and RO membranes including evaluating different membrane products, the impact of operating conditions and water quality, and the influence of physicochemical characteristics of PFAS<ref name="ApplemanEtAl2013"/><ref name="SafulkoEtAl2023"/><ref name="LiuStrathmannBellona2021">Liu, C.J., Strathmann, T.J., Bellona, C., 2021. Rejection of per- and polyfluoroalkyl substances (PFASs) in aqueous film-forming foam by high-pressure membranes. Water Research, 188, Article 116546. [https://doi.org/10.1016/j.watres.2020.116546 doi: 10.1016/j.watres.2020.116546]</ref><ref name="WangEtAl2018">Wang, J., Wang, L., Xu, C., Zhi, R., Miao, R., Liang, T., Yue, X., Lv, Y., Liu, T., 2018. Perfluorooctane sulfonate and perfluorobutane sulfonate removal from water by nanofiltration membrane: The roles of solute concentration, ionic strength, and macromolecular organic foulants. Chemical Engineering Journal, 332, p. 787-797. [https://doi.org/10.1016/j.cej.2017.09.061 doi: 10.1016/j.cej.2017.09.061]</ref><ref name="ZhaoEtAl2016">Zhao, C., Tang, C.Y., Li, P., Adrian, P., Hu, G., 2016. Perfluorooctane sulfonate removal by nanofiltration membrane—the effect and interaction of magnesium ion / humic acid. Journal of Membrane Science, 503, p. 31-41. [https://doi.org/10.1016/j.memsci.2015.12.049 doi: 10.1016/j.memsci.2015.12.049]</ref><ref name="ZhaoEtAl2013">Zhao, C., Zhang, J., He, G., Wang, T., Hou, D., Luan, Z., 2013. Perfluorooctane sulfonate removal by nanofiltration membrane the role of calcium ions. Chemical Engineering Journal, 233, p. 224-232. [https://doi.org/10.1016/j.cej.2013.08.027 doi: 10.1016/j.cej.2013.08.027]</ref><ref name="Steinle-DarlingEtAl2010">Steinle-Darling, E., Litwiller, E., Reinhard, M., 2010. Effects of Sorption on the Rejection of Trace Organic Contaminants During Nanofiltration. Environmental Science and Technology, 44(7), p. 2592-2598. [https://doi.org/10.1021/es902846m doi: 10.1021/es902846m]</ref>. Most studies have focused on anionic (at neutral pH) [[Perfluoroalkyl_and_Polyfluoroalkyl_Substances_(PFAS)#Nomenclature | perfluoroalkyl acid (PFAA)]] rejection and reported greater than 90% separation of PFAAs by available NF and RO membranes due to electrostatic and steric exclusion from the membrane polymer<ref name="ApplemanEtAl2013"/><ref name="Steinle-DarlingReinhard2008"/><ref name="LiuStrathmannBellona2021"/>. Water quality constituents such as organic matter and cations including calcium and magnesium have been shown to reduce rejection of PFAS<ref name="LiuStrathmannBellona2021"/>. However, little is known about how fouling and membrane aging impact rejection of PFAS by NF and RO membranes and additional data are needed. A recent Department of Defense [https://serdp-estcp.mil/ ESTCP] pilot scale project ([https://serdp-estcp.mil/projects/details/0aa2fb20-b851-4b5b-ac64-e72795986b8a ER20-5369]) conducted at Colorado School of Mines (Mines) systematically evaluated the rejection of nine PFAAs by four available NF and RO products using full scale spiral-wound membrane elements in a high recovery membrane system which achieved up to 97% recovery<ref name="SafulkoEtAl2023"/>. Tight NF and the two RO membranes evaluated exhibited greater than 98% rejection of all PFAAs evaluated even at high recovery conditions (Figure 3). The loose NF membrane product evaluated provided lower than expected (based on literature) rejection of investigated PFAAs particularly at higher recovery values. These findings indicate that tight NF and RO membranes can be effective at separating PFAAs from contaminated source waters regardless of PFAA chain length. Energy requirements modeled from these experiments varied from 0.14 kWh/m3 for loose NF to 0.57 kWh/m3 for seawater RO<ref name="SafulkoEtAl2023"/>.

Mines researchers have developed a mobile high-recovery closed-circuit membrane filtration system (Figure 4) that has been successfully deployed for treating groundwater at a fire training area of Wright-Patterson Air Force Base ([https://serdp-estcp.mil/projects/details/be0417c9-aaa4-4fd6-9007-7de0cdbffb85 ESTCP ER21-5136]), groundwater at Peterson Space Force Base (AFCEC BAA-031), and firetruck rinsate at Tyndall Air Force Base ([https://serdp-estcp.mil/projects/details/0aa2fb20-b851-4b5b-ac64-e72795986b8a ESTCP ER20-5369]) during recent ESTCP and AFCEC funded research projects. In these projects, NF or RO was implemented to produce a permeate stream containing low concentrations of PFAS and to concentrate PFAS into smaller volumes of retentate for subsequent destructive PFAS treatment. While NF and RO membranes have demonstrated effective rejection of PFAS, PFAS are subsequently concentrated in the membrane concentrate, or retentate stream. This concentrate stream is increasingly paired with PFAS destruction technologies, as PFAS destruction is often considered viable only for concentrated solutions of PFAS. Ongoing ESTCP funded projects include using high-recovery NF and RO to treat and concentrate groundwater leading to PFAS destruction using [[PFAS Treatment by Electrical Discharge Plasma | plasma based treatment]]<ref name="Richardson2021"> Richardson, S., 2021. Nanofiltration Followed by Electrical Discharge Plasma for Destruction of PFAS and Co-occurring Chemicals in Groundwater: A Treatment Train Approach. [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/be0417c9-aaa4-4fd6-9007-7de0cdbffb85/er21-5136-project-overview Project ER21-5136]</ref> or [[Hydrothermal Alkaline Treatment (HALT) | hydrothermal alkaline treatment (HALT)]]<ref name="Bellona2023">Bellona, C., 2023. Cradle to Grave PFAS Treatment Using Membrane and Foam Fractionation Concentration Followed by Hydrothermal Alkaline Treatment. [https://serdp-estcp.mil/ Environmental Security Technology Certification Program (ESTCP)], [https://serdp-estcp.mil/projects/details/5cf08cdb-b86a-45d2-98d3-f747ba97d293 Project ER23-8367]</ref>.

==Advantages and Limitations of the Technology for PFAS Removal==
Advantages:
*Robust, high throughput treatment
*Mature technology with well documented solute separation performance
*High rejection of PFAS and other contaminants
*Removes solutes at the molecular scale

Limitations:
*Complex and often expensive pretreatment requirements for certain waters
*Energy intensive
*High capital costs
*Membrane fouling requiring high chemical usage for cleaning
*Concentrated waste stream requiring disposal or destruction
*Permeate quality depends on feed water concentration
*Greater operation complexity than most water treatment processes
*Water loss due to membrane separation

==Summary==
High-pressure membranes including NF and RO are well established technologies used in a variety of water treatment fields for the purification of water resources and industrial process waste streams. Research conducted over the past decade has demonstrated that various available membrane products can achieve high rejection of PFAS, enabling compliance with state and federal PFAS regulations. As opposed to adsorbent based PFAS removal technologies (e.g., [[PFAS Ex Situ Water Treatment#Activated Carbon Adsorption | activated carbon]], [[PFAS Treatment by Anion Exchange | ion exchange]]), high-pressure membranes do not have a finite capacity for PFAS removal and do not exhibit breakthrough. High-recovery membrane systems are being implemented into ex situ treatment trains to simultaneously treat PFAS impacted water resources and concentrate PFAS into the retentate stream to enable more effective and efficient PFAS destruction.

==References==
<references />

==See Also==
[[Media: LiuEtAl2021.pdf | Pilot-Scale Demonstration of a Hybrid Nanofiltration and UV-Sulfite Treatment Train for Groundwater Contaminated by Per- and Polyfluoroalkyl Substances (PFASs)]], Liu, C.J., McKay, G., Jiang, D., Tenorio, R., Cath, J.T., Amador, C., Murray, C.C., Brown, J.B., Wright, H.B., Schaefer, C., Higgins, C.P., Bellona, C., Strathmann, T.J., 2021. Water Research, 205, Article 117677. [https://doi.org/10.1016/j.watres.2021.117677 doi: 10.1016/j.watres.2021.117677]

Nicole Masters

2025-09-24T14:59:09Z

==Work and Contact Information==

EMPLOYER:
:Colorado School of Mines 
:Department of Civil and Environmental Engineering
:Golden, CO 80401 

EMAIL: [mailto:nmasters@mines.edu nmasters@mines.edu]

WEBPAGE: [https://orcid.org/0000-0001-7908-9711 https://orcid.org/0000-0001-7908-9711]

==About the Contributor==
Nicole Masters is a PhD candidate in Environmental Engineering at the Colorado School of Mines. She holds a BS in Chemical Engineering and focused on microfluidic systems to model bleeding disorders and thrombosis. Aside from PFAS research, Nicole’s work in environmental engineering has included researching soil recovery post-wildfire, wastewater-based epidemiology, and process optimization for wastewater treatment. Her PFAS research includes evaluating the impact of microbial colonization on adsorbents, fate of PFAS in potable reuse systems and use of membranes in PFAS treatment trains. Her thesis focuses on PFAS removal during pilot-scale evaluations of membrane systems and modeling the rejection of a wide range of PFAS by nanofiltration and reverse using mass transfer models. Nicole has published in Lab on a Chip, Nature Nanotechnology, Applied and Environmental Microbiology, and Separation and Purification Technology. She was awarded the Best Student Technical Paper at the 2025 AWWA/AMTA Membrane Technology Conference for her paper and presentation on a pilot demonstration of a closed-circuit membrane system to treat AFFF-impacted groundwater.

==Article Contributions==
*[[Reverse Osmosis and Nanofiltration Membrane Filtration Systems for PFAS Removal]]

__NOTOC__

[[Category: Contributors|Masters]]]

Articles

2025-08-07T16:12:31Z

Debra Tabron:

{| class="wikitable sortable"
|-
!Title!!First Author!!Linking Phrases
|-
|[[Groundwater Sampling - No-Purge/Passive]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||passive sampling, no purge sampling, grab samplers, diffusion samplers, sorptive samplers
|-
|[[ Long-Term Monitoring (LTM)]]||[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]||long-term monitoring, LTM, LTM objectives, LTM programs, LTM challenges
|-
|[[PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)]]
|[[Dr. David Adamson, P.E. |Adamson, David, Ph.D., P.E.]]
|PFAS, MNA, natural attenuation
|-
|[[Sorption of Organic Contaminants]]||[[Richelle Allen-King|Allen-King, Richelle]]||
|-
|[[PFAS Transport and Fate]]
|[[Dr. Richard Anderson|Anderson, Richard, Ph.D.]]
|
|-
|[[Mass Flux and Mass Discharge]]||[[Dr. Michael Annable, P.E. |Annable, Michael, Ph.D., P.E.]]||source reduction
|-
|[[Metal(loid)s - Small Arms Ranges]]|| Dr. Amanda Barker |[[Dr. Amanda Barker|Barker, Amanda, Ph.D.]]
|
|-
|[[Munitions Constituents – Photolysis|Munitions Constituents - Photolysis]]
|[[Dr. Warren Kadoya|Kadoya, Warren, Ph.D.]]
|
|-
|[[Munitions Constituents - Soil Sampling]]
|[[Dr. Samuel Beal|Beal, Samuel, Ph.D.]]
|
|-
|[[Vapor Intrusion – Sewers and Utility Tunnels as Preferential Pathways|Vapor Intrusion - Sewers and Utility Tunnels as Preferential Pathways]]
|[[Lila Beckley|Beckley, Lila]]
|vapor intrusion
|-
|[[Natural Attenuation in Source Zone and Groundwater Plume - Bemidji Crude Oil Spill]]
|[[Dr. Barbara Bekins|Bekins, Barbara, Ph.D.]]||
|-
|[[Bioremediation - Anaerobic Secondary Water Quality Impacts]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||secondary impacts, water quality (in regards to anaerobic conditions)
|-
|[[Design Tool - Base Addition for ERD]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||aquifer acidity, base addition
|-
|[[Emulsified Vegetable Oil (EVO) for Anaerobic Bioremediation]]
|[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||
|-
|[[Low pH Inhibition of Reductive Dechlorination]]||[[Dr. Robert Borden, P.E. |Borden, Robert, Ph.D., P.E.]]||low pH inhibition
|-
|[[OPTically-based In-situ Characterization System (OPTICS)]]
|[[Dr. Grace Chang|Chang, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents - Electrochemical Treatment]]
|[[Dr. Brian P. Chaplin|Chaplin, Brian, Ph.D.]]
|munitions constituents remediation
|-
|[[PFAS Sources]]
|[[Dr. Dora Chiang|Chiang, Dora, Ph.D.]]
|
|-
|[[Biodegradation - Cometabolic]]||[[Dr. Kung-Hui (Bella) Chu |Chu, Kung-Hui (Bella), Ph.D]]||cometabolic biodegradation
|-
|[[Munitions Constituents - Composting]]
|[[Harry Craig|Craig, Harry]]
|
|-
|[[Chemical Oxidation (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||ISCO, chemical oxidation
|-
|[[Chemical Oxidation Oxidant Selection (In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||chemical oxidant, oxidant (in regards to ISCO)
|-
|[[Chemical Oxidation Design Considerations(In Situ - ISCO)]]||[[Dr. Michelle Crimi |Crimi, Michelle, Ph.D]]||screening, design, implementation, oxidant delivery (in regards to ISCO)
|-
|[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]||[[Dr. Rula Deeb |Deeb, Rula, Ph.D.]]||PFAS, perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS)
|-
|[[Metal and Metalloid Contaminants]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal contaminant(s), metalloid contaminant(s), metal(s), metalloid(s),
|-
|[[Metals and Metalloids - Mobility in Groundwater]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||metal mobility, aqueous speciation, adsorption, precipitation, colloidal transport (in regards to metals)
|-
|[[Monitored Natural Attenuation (MNA) of Metal and Metalloids]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||MNA, attenuation of metal(s), natural attenuation processes, attenuation (in regards to metals)
|-
|[[Metal and Metalloids - Remediation]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||remediation, in situ technologies, contaminant removal (in regards to metals)
|-
|[[pH Buffering in Aquifers]]||[[Dr. Miles Denham |Denham, Miles, Ph.D.]]||ph buffer, natural pH buffer, engineered pH buffer
|-
|[[Munitions Constituents - Sorption]]||[[Dr. Katerina Dontsova |Dontsova, Katerina, Ph.D.]]||energetics, sorption
|-
|[[Biodegradation - Hydrocarbons]]||[[Dr. Elizabeth Edwards |Edwards, Elizabeth, Ph.D.]]||hydrocarbon, biodegradation
|-
|[[Source Zone Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||source zone modeling
|-
|[[Plume Response Modeling]]||[[Dr. Ron Falta |Falta, Ron, Ph.D.]]||plume response modeling
|-
|[[REMChlor - MD]]
|[[Dr. Ron Falta|Falta, Ron, Ph.D.]]
|
|-
|[[In Situ Groundwater Treatment with Activated Carbon]]
|[[Dr. Dimin Fan|Fan, Dimin, Ph.D.]]
|
|-
|[[LNAPL Remediation Technologies]]||[[Dr. Shahla Farhat |Farhat, Shahla, Ph.D.]]||
|-
|[[Sustainable Remediation]]||[[Paul Favara |Favara, Paul]]||sustainable remediation, social, economic and environmental impacts
|-
|[[Munitions Constituents]]||[[Dr. Kevin Finneran |Finneran, Kevin, Ph.D.]]||Explosives, energetics, insensitive munitions
|-
|[[Biodegradation - Reductive Processes]]||[[Dr. David Freedman |Freedman, David, Ph.D.]]||biotic reduction, biotic reductive processes, hydrogenolysis, dihaloelimination, coupling, organohalide respiration
|-
|[[Subgrade Biogeochemical Reactor (SBGR)]]||[[Jeff Gamlin |Gamlin, Jeff]]||SBGR, subgrade biogeochemical reactor, bioreactor
|-
|[[Thermal Remediation - Smoldering]]||[[Dr. Jason Gerhard |Gerhard, Jason, Ph.D.]]||smouldering remediation, self-sustaining treatment for active remediation, STAR
|-
|[[Contaminated Sediments - Introduction]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
|
|-
|[[Contaminated Sediment Risk Assessment]]
|[[Richard Wenning|Wenning, Richard]]
|
|-
|[[In Situ Treatment of Contaminated Sediments with Activated Carbon]]
|[[Dr. Upal Ghosh|Ghosh, Upal, Ph.D.]]
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|[[PFAS Ex Situ Water Treatment]]
|[[Dr. Scott Grieco |Grieco, Scott, Ph.D.]]
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|[[Stream Restoration]]
|[[Dr. Natalie Griffiths|Griffiths, Natalie, Ph.D.]]
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|[[Passive Sampling of Sediments]]
|[[Dr. Philip M. Gschwend|Gschwend, Philip]]
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|-
|[[Phytoplankton (Algae) Blooms]]
|[[Dr. Nathan Hall|Hall, Nathan]]
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|-
|[[PFAS Soil Remediation Technologies]]||[[James_Hatton |Hatton, Jim]]||PFAS, Soil source zones
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|[[Proteomics and Proteogenomics]]
|[[Dr. Kate Kucharzyk|Kucharzyk, Kate, Ph.D.]]
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|[[N-nitrosodimethylamine (NDMA)]]
|[[Paul Hatzinger|Hatzinger, Paul, Ph.D.]]
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|[[Alternative Endpoints]]||[[Elisabeth Hawley |Hawley, Elisabeth]]||management of complex sites||
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|[[Thermal Remediation]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal remediation, in situ thermal
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|[[Thermal Remediation - Steam]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Steam Enhanced Extraction
|-
|[[Thermal Remediation - Electrical Resistance Heating]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||Electrical Resistance Heating
|-
|[[Thermal Conduction Heating (TCH)]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal Desorption
|-
|[[Thermal Remediation - Combined Remedies]]||[[Dr. Gorm Heron |Heron, Gorm, Ph.D.]]||thermal Remediation
|-
|[[Predicting Species Responses to Climate Change with Population Models]]
|[[Dr. Brian Hudgens|Hudgens, Brian, Ph.D.]]
|climate change
|-
|[[Infrastructure Resilience]]
|[[Dr. John Hummel|Hummel, John, Ph.D.]]
|
|-
|[[Munitions Constituents- TREECS™ Fate and Risk Modeling]]||[[Dr. Billy E. Johnson |Johnson, Billy, Ph.D.]]||munitions constituents fate and transport modeling, TREECS
|-
|[[Munitions Constituents - Alkaline Degradation]]
|[[Jared Johnson|Johnson, Jared]]
|
|-
|[[Assessing Vapor Intrusion (VI) Impacts in Neighborhoods with Groundwater Contaminated by Chlorinated Volatile Organic Chemicals (CVOCs)|Vapor Intrusion - Assessing VI Impacts in Neighborhoods with Groundwater Contaminated CVOCs]]
|[[Dr. Paul C. Johnson|Johnson, Paul, Ph.D.]]
|vapor intrusion
|-
|[[Munitions Constituents - IM Toxicology]]||-----||insensitive explosives, insensitive munitions, IMX-101, IMX
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|[[Landfarming]]
|[[Dr. Roopa Kamath|Kamath, Roopa, Ph.D.]]
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|[[NAPL Mobility]]
|[[Andrew Kirkman|Kirkman, Andrew]]
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|-
|[[Climate Change Primer]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Perchlorate]]||[[Thomas Krug |Krug, Thomas]]||perchlorate
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|[[Injection Techniques for Liquid Amendments]]||[[Thomas Krug |Krug, Thomas]]||amendment injection
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|[[Transition of Aqueous Film Forming Foam (AFFF) Fire Suppression Infrastructure Impacted by Per and Polyfluoroalkyl Substances (PFAS)]]
|[[Dr. Johnsie Ray Lang|Lang, Johnsie Ray, Ph.D.]]
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|[[Characterization Methods – Hydraulic Conductivity]]
|[[Dr. Gaisheng Liu|Liu, Gaisheng, Ph.D.]]
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|-
|[[Compound Specific Isotope Analysis (CSIA)]]||[[Dr. Barbara Sherwood Lollar, F.R.S.C. |Lollar, Barbara S., FRSC]]||Compound Specific Isotope Analysis (CSIA)
|-
|[[Passive Sampling of Munitions Constituents]]
|[[Dr. Guilherme Lotufo|Lotufo, Guilerme, Ph.D.]]
|
|-
|[[Vapor Intrusion (VI)]]||[[Chris Lutes |Lutes, Chris]]||vapor intrusion
|-
|[[Bioremediation - Anaerobic]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||anaerobic bioremediation
|-
|[[Bioremediation - Anaerobic Design Considerations]]||[[Leah MacKinnon, M.A.Sc., P. Eng.|MacKinnon, Leah]]||
|-
|[[Biodegradation - 1,4-Dioxane]]
|[[Dr. Shaily Mahendra|Mahendra, Shaily, Ph.D.]]
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|-
|[[Direct Push (DP) Technology]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push, DP, DP machines, DP technology
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|[[Direct Push Sampling]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push sampling, soil sampling, groundwater sampling, well installation, soil vapor sampling (in regards to DP)
|-
|[[Direct Push Logging]]||[[Wesley McCall, M.S., P.G. |McCall, Wesley, M.S., P.G.]]||direct push logging, Cone Penetration Testing, CPT, Electrical Conductivity, EC, Hydraulic Profiling Tool, HPT, Membrane Interface Probe, MIP, Optical Imaging Profiler, OIP
|-
|[[Downscaled High Resolution Datasets for Climate Change Projections]]
|[[Dr. Rao Kotamarthi|Kotamarthi, Rao, Ph.D.]]
|
|-
|[[Remediation Performance Assessment at Chlorinated Solvent Sites]]||[[Travis McGuire|McGuire, Travis]]||multi-site studies
|-
|[[LNAPL Conceptual Site Models]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
|
|-
|[[Long-Term Monitoring (LTM) - Data Analysis]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data analysis, analysis methods (in regards to LTM)
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|[[Long-Term Monitoring (LTM) - Data Variability]]||[[Dr. Thomas McHugh |McHugh, Thomas, Ph.D.]]||data variability (in regards to LTM), LTM evaluation
|-
|-
|[[Munitions Constituents - Abiotic Reduction]]||[[Dr. Jimmy Murillo-Gelvez |Murillo-Gelvez, Jimmy, Ph.D.]]
|-
|[[Supercritical Water Oxidation (SCWO)]]
|Nagar, Kobe
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|[[Matrix Diffusion]]
|[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]
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|[[Groundwater Flow and Solute Transport]]||[[Dr. Charles Newell, P.E. |Newell, Charles, Ph.D., P.E.]]||groundwater flow, advection, dispersion, diffusion, molecular diffusion, mechanical dispersion
|-
|[[Molecular Biological Tools - MBTs]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||MBT, Molecular Biological Tool(s)
|-
|[[Quantitative Polymerase Chain Reaction (qPCR)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||qPCR, Polymerase Chain Reaction
|-
|[[Sediment Capping]]
|[[Dr. Danny Reible|Reible, Danny]]
|
|-
|[[Stable Isotope Probing (SIP)]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||SIP, Stable Isotope Probing
|-
|[[Metagenomics]]||[[Dora Ogles-Taggart |Ogles-Taggart, Dora]]||Metagenomics
|-
|[[Natural Source Zone Depletion (NSZD)]]||[[Tom Palaia |Palaia, Tom]]||natural source zone depletion, NSZD
|-
|[[Climate Change Effects on Wildlife]]
|[[Dr. Breanna F. Powers|Powers, Breanna, PhD.]]
|
|-
|[[Amendment Distribution in Low Conductivity Materials]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||
|-
|[[Polycyclic Aromatic Hydrocarbons (PAHs)]]||[[Dr. Stephen Richardson |Richardson, Stephen, Ph.D.]]||Polycyclic Aromatic Hydrocarbons, PAH(s)
|-
|[[Sediment Porewater Dialysis Passive Samplers for Inorganics (Peepers)]]
|[[Florent Risacher|Risacher, Florent, M.Sc.]]
|
|-
|[[1,2,3-Trichloropropane]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||TCP, trichloropropane
|-
|[[Zerovalent Iron (ZVI) (Chemical Reduction - ISCR)]]||[[Dr. Alexandra Salter-Blanc |Salter-Blanc, Alexandra, Ph.D.]]||ZVI
|-
|[[Mercury in Sediments]]
|[[Dr. Grace Schwartz|Schwartz, Grace, Ph.D.]]
|
|-
|[[Munitions Constituents – Sample Extraction and Analytical Techniques]]
|[[Dr. Austin Scircle|Scircle, Austin]]
|
|-
|[[Geophysical Methods]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[Geophysical Methods - Case Studies]]||[[Dr. Lee Slater |Slater, Lee, Ph.D.]]||geophysics
|-
|[[PFAS Treatment by Anion Exchange]]
|[[Dr. Timothy J. Strathmann|Strathmann, Timothy, Ph.D.]]
|PFAS
|-
|[[Munitions Constituents - Dissolution]]||[[Dr. Susan Taylor |Taylor, Susan, Ph.D.]]||explosive(s), dissolution,
|-
|[[PFAS Treatment by Electrical Discharge Plasma]]
|[[Dr. Selma Mededovic Thagard|Thagard, Selma Mededovic, Ph.D.]]
|PFAS
|-
|[[Restoration of Ecological Function in Terrestrial Systems Impacted by Invasive Species]]
|Thierry, Hugo, Ph.D.
|climate change, invasive species, restoration ecology
|-
|[[Chemical Reduction (In Situ - ISCR)]]||[[Dr. Paul Tratnyek |Tratnyek, Paul, Ph.D.]]||In Situ Chemical Reduction, ISCR
|-
|[[Injection Techniques - Viscosity Modification]]||[[Michael Truex |Truex, Michael]]||viscosity, viscosity modifiers, viscosity modification
|-
|[[Soil Vapor Extraction (SVE)]]||[[Michael Truex |Truex, Michael]]||soil vapor extraction, SVE
|-
|[[Munitions Constituents - Deposition]]||[[Michael R. Walsh, P.E., M.E.|Walsh, Michael, P.E.]]||explosive deposition, energetics deposition
|-
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|[[Dr. James Weaver|Weaver, James, Ph.D.]]
|vapor intrusion
|-
|[[Zerovalent Iron Permeable Reactive Barriers]]
|[[Dr. Richard Wilkin|Wilkin, Rick, Ph.D.]]
|
|-
|[[Monitored Natural Attenuation (MNA)]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, In Situ MNA, natural attenuation, natural attenuation processes
|-
|[[Monitored Natural Attenuation (MNA) of Fuels]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to petroleum hydrocarbons and fuel components)
|-
|[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]||[[Dr. John Wilson |Wilson, John, Ph.D.]]||MNA, natural attenuation, attenuate (when used in context related to chlorinated solvents)
|-
|[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
|[[Dr. John Wilson|Wilson, John, Ph.D.]]
|MNA, natural attenuation
|-
|[[Chlorinated Solvents]]||[[Dr. Bilgen Yuncu, P.E. |Yuncu, Bilgen, Ph.D., P.E.]]||chlorinated solvents
|-
|[[Petroleum Hydrocarbons (PHCs)]]
|[[Dr. Bilgen Yuncu, P.E.|Yuncu, Bilgen, Ph.D., P.E.]]
|Petroleum Hydrocarbons (PHCs)
|-
|[[Photoactivated Reductive Defluorination - PFAS Destruction]]
|[[Dr. Suzanne Witt|Witt, Suzanne, Ph.D.]]
|PFAS
|
|-
|[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]
|[[Dr. Lee Slater|Slater, Lee, Ph.D.]]
|geophysics, hydrogeophysical methods,
|
|-
|[[Hydrothermal Alkaline Treatment (HALT)]]
|[[Dr. Brian Pinkard|Pinkard, Brian]]
|
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|[[1,4-Dioxane]]
|[[Matthew Zenker|Zenker, Matthew]]

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Hydrothermal Alkaline Treatment (HALT)

2025-08-07T16:06:56Z

Debra Tabron:

Hydrothermal alkaline treatment (HALT) is a thermochemical processing technology effective at destroying and defluorinating [[Wikipedia: Halogenation | halogenated]] organic compounds such as [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]]. HALT is highly effective at destroying and defluorinating all types of PFAS that have been evaluated. The HALT technology enables end-to-end treatment and destruction of PFAS from a variety of matrices when integrated into a suitable treatment train.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Ex Situ Water Treatment]]
*[[PFAS Sources]]
*[[PFAS Transport and Fate]]

'''Contributors:''' [[Dr. Brian Pinkard]], [[Dr. Timothy J. Strathmann | Dr. Timothy Strathmann]], and [[Dr. Shilai Hao]]

'''Key Resource(s):'''

*Hydrothermal Technologies for On-Site Destruction of Site Investigation Wastes Contaminated with Per- and Polyfluoroalkyl Substances (PFAS), Phase I<ref name="Strathmann2023">Strathmann, T.J., Higgins, C., Deeb, R., 2020. Final Report: Hydrothermal Technologies for On-Site Destruction of Site Investigation Wastes Contaminated with Per- and Polyfluoroalkyl Substances (PFAS), Phase I. Strategic Environmental Research and Development Program (SERDP) Project number ER18-1501. [[Media: ER18-1501.pdf | Final Report pdf]]  [https://serdp-estcp.mil/projects/details/b34d6396-6b6d-44d0-a89e-6b22522e6e9c Project Website]</ref>

*Hydrothermal Alkaline Treatment for Destruction of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam<ref name="HaoEtAl2021">Hao, S., Choi, Y.J., Wu, B., Higgins, C.P., Deeb, R., Strathmann, T.J., 2021. Hydrothermal Alkaline Treatment for Destruction of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam. Environmental Science and Technology, 55(5), pp. 3283-3295.  [https://doi.org/10.1021/acs.est.0c06906 doi: 10.1021/acs.est.0c06906]</ref>

*[[Media: PinkardEtAl-2024a.pdf | Degradation and Defluorination of Ultra Short-, Short-, and Long-Chain PFASs in High Total Dissolved Solids Solutions by Hydrothermal Alkaline Treatment ─ Closing the Fluorine Mass Balance]]<ref name="PinkardEtAl2024a">Pinkard, B., Smith, S.M., Vorarath, P., Smrz, T., Schmick, S., Dressel, L., Bryan, C., Czerski, M., de Marne, A., Halevi, A., Thomsen, C., Woodruff, C., 2024. Degradation and Defluorination of Ultra Short-, Short-, and Long-Chain PFASs in High Total Dissolved Solids Solutions by Hydrothermal Alkaline Treatment─Closing the Fluorine Mass Balance. ACS ES&T Engineering, 4(11), pp. 2810-2818.  [https://doi.org/10.1021/acsestengg.4c00378 doi: 10.1021/acsestengg.4c00378]  [[Media: PinkardEtAl-2024a.pdf | Report pdf]]</ref>

==Introduction==
[[File:PinkardFig1.png|thumb|350px|left|Figure 1. HALT refers to the [[Wikipedia: Critical_point_(thermodynamics)#Liquid–vapor critical point | subcritical]] water region on the pressure–temperature phase diagram of water]]
<onlyinclude>Hydrothermal alkaline treatment (HALT) is a thermochemical processing technology effective at destroying and defluorinating halogenated organic compounds such as [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) | per- and polyfluoroalkyl substances (PFAS)]]. </onlyinclude>HALT is also known as “[[Wikipedia: Hydrolysis#Alkaline_hydrolysis |alkaline hydrolysis]],” and is very similar to processing technologies such as [[Wikipedia: Hydrothermal liquefaction | hydrothermal liquefaction (HTL)]] which have been developed and investigated for organic waste-to-energy applications.

<onlyinclude>HALT processing subjects PFAS in an aqueous solution to high pressure, high temperature, and high pH conditions. The required operating conditions are dependent on the specific target PFAS being destroyed, as [[Wikipedia: Perfluoroalkyl carboxylic acids | perfluorocarboxylic acids (PFCAs)]] such as [[Wikipedia: Trifluoroacetic acid |trifluoroacetic acid (TFA)]] can be destroyed under mild conditions</onlyinclude> (e.g., P ~ 2 MPa, T ~ 200 °C, pH ~ 13)<ref name="AustinEtAl2024">Austin, C., Purohit, A., Thomsen, C., Pinkard, B.R., Strathmann, T.J., Novosselov, I.V., 2024. Hydrothermal Destruction and Defluorination of Trifluoroacetic Acid (TFA). Environmental Science and Technology, 58(18), pp. 8076-8085.  [https://doi.org/10.1021/acs.est.3c09404 doi: 10.1021/acs.est.3c09404]</ref><onlyinclude>, whereas [[Wikipedia: Perfluorosulfonic acids | perfluorosulfonic acids (PFSAs)]] such as [[Wikipedia: Perfluorobutanesulfonic acid | perfluorobutanesulfonic acid (PFBS)]] require more aggressive processing conditions</onlyinclude> (e.g., P ~ 25 MPa, T ~ 350 °C, pH ~ 14.7) [5] (Figure 1)<onlyinclude>. HALT is capable of facilitating complete “mineralization” of PFAS, defined as the conversion of organic fluorine to dissolved inorganic fluoride. </onlyinclude>The treatment time for HALT is relatively shorter (<2 hours) compared to most other PFAS destructive technologies. For instance, treatment of two-fold diluted [[Wikipedia: Firefighting foam | aqueous film-forming foams (AFFFs)]] using HALT in batch mode achieved nearly complete defluorination in just 30 minutes under conditions of 350 °C and 5 M NaOH<ref name="HaoEtAl2021"/>. PFCAs can be destroyed with even faster kinetics at milder conditions; for example, >90% destruction and defluorination of [[Wikipedia: Trifluoroacetic acid | trifluoroacetic acid (TFA)]] was achieved within 40 min at 200 °C<ref name="AustinEtAl2024"/>. Kinetic rate constants for individual PFAS compounds in HALT environments have been proposed in several studies<ref name="AustinEtAl2024"/><ref name="WuEtAl2019">Wu, B., Hao, S., Choi, Y.J., Higgins, C.P., Deeb, R., Strathmann, T.J., 2019. Rapid Destruction and Defluorination of Perfluorooctanesulfonate by Alkaline Hydrothermal Reaction. Environmental Science and Technology Letters, 6(10), pp. 630-636.  [https://doi.org/10.1021/acs.estlett.9b00506 doi: 10.1021/acs.estlett.9b00506]</ref>. The fluorine mass balance during HALT processing has also been investigated, showing near-stoichiometric conversion of organic fluorine to inorganic fluoride under optimal conditions<ref name="PinkardEtAl2024a"/>.

<onlyinclude>From a practical perspective, HALT is best suited for destroying PFAS in concentrated liquids such as liquid concentrate streams produced as byproducts of other water treatment processes (e.g., [[PFAS Treatment by Anion Exchange | regenerable ion exchange]], [[Wikipedia: Foam fractionation | foam fractionation]]). </onlyinclude>Previous publications demonstrate that complex sample matrices, including high concentrations of inorganic salts (e.g., 83 g/L chloride) and dissolved organic carbon (e.g., 13 g/L), do not inhibit the degradation rate of PFAS compared to a clean matrix, such as groundwater<ref name="HaoEtAl2022">Hao, S., Choi, Y.J,. Deeb, R.A., Strathmann, T.J., Higgins, C.P., 2022. Application of Hydrothermal Alkaline Treatment for Destruction of Per- and Polyfluoroalkyl Substances in Contaminated Groundwater and Soil. Environmental Science and Technology, 56(10), pp. 6647-6657.  [https://doi.org/10.1021/acs.est.2c00654 doi: 10.1021/acs.est.2c00654]</ref><ref name="HaoEtAl2023">Hao, S., Reardon, P.N., Choi, Y.J., Zhang, C., Sanchez, J.M., Higgins, C.P., Strathmann, T.J., 2023. Hydrothermal Alkaline Treatment (HALT) of Foam Fractionation Concentrate Derived from PFAS-Contaminated Groundwater. Environmental Science and Technology 57(44), pp. 17154-17165.  [https://doi.org/10.1021/acs.est.3c05140 doi: 10.1021/acs.est.3c05140]</ref>. Moreover, several field demonstrations of HALT have been performed successfully, and the technology is scalable for commercialization.

==Reaction Mechanisms and Treatment Efficacy==
[[File:PinkardFig2.png|thumb|400px|left|Figure 2. Representative classes of PFAS structures among 148 PFASs demonstrated complete degradation during HALT<ref name="HaoEtAl2021"/>]]
[[File:PinkardFig3.png|thumb|400px|right|Figure 3. The degradation of representative classes of PFAS during HALT of 1-to-1000 diluted AFFF under conditions of 1 M NaOH, 350 °C, and a reaction time of 60 minutes<ref name="HaoEtAl2021"/>.]]
Laboratory scale batch experiments have shown that the full suite of PFAS detected in aqueous film-forming foams (AFFFs) through targeted [[Wikipedia: Liquid chromatography–mass spectrometry | LC-MS/MS and LC-HRMS]] suspect screening analysis are degraded and defluorinated by HALT<ref name="HaoEtAl2021"/>. Figure 2 presents representative classes of PFAS structures among 148 PFAS demonstrating complete degradation during HALT. Figure 3 illustrates the degradation during HALT of representative classes of PFAS detected in an AFFF. The extent of destruction for all PFAS is highly temperature dependent, but results show that some subclasses of PFAS degrade in the absence of alkali amendments (e.g., PFCAs)<ref name="AustinEtAl2024"/>, whereas other subclasses require strong alkali in addition to near-critical reaction temperatures (e.g., PFSAs)<ref name="Strathmann2023"/><ref name="HaoEtAl2021"/><ref name="WuEtAl2019"/>. This is attributed to different mechanisms that initiate the destruction of the individual PFAS subclasses. Degradation of PFCAs is initiated by thermally driven [[Wikipedia: Decarboxylation | decarboxylation reactions]]<ref name="AustinEtAl2024"/>, whereas PFSA degradation, in the temperature range of HALT reactors, is proposed to be initiated via attack by the strong nucleophile [[Wikipedia: Hydroxide | OH-]].<ref name="HaoEtAl2021"/>

A mechanistic understanding of the HALT process for PFAS destruction needs further evaluation to optimize the process and reduce the consumption of chemicals and energy. While the studies of neat compounds are relatively straightforward, one of the major challenges is to address the effect of co-contaminants and apply the process to real-world operating scenarios. Recent laboratory studies with batch reactors conducted at the Colorado School of Mines (CSM) have extended the application of HALT for the destruction of PFAS in a variety of contaminated matrices, including groundwater and soils<ref name="HaoEtAl2022"/> and foam fractionation-derived liquid concentrate<ref name="HaoEtAl2023"/>. Apparent rates for the transformation of individual PFAS have been found to be largely insensitive to the type of media<ref name="HaoEtAl2023"/>, but there is a need to account for any reactions with the media that consume OH· (e.g., OH· reactions with silica-containing soil minerals)<ref name="HaoEtAl2022"/> Notably, while alkali is not required to degrade PFCAs, it is still necessary to convert the organically bound fluorine to inorganic F-. Austin ''et. al.''<ref name="AustinEtAl2024"/> showed that TFA, a C1 PFCA, degrades at similar rates in the absence and presence of NaOH, but mineralization to F- and CO32- only occurs when NaOH is added; otherwise [[Wikipedia:Fluoroform | fluoroform (CHF3)]] is the terminal product when no NaOH is added to the reaction solution.

HALT can also be applied to destroy other fluorinated compounds, for example, [[Wikipedia:Hydrofluorocarbon | hydrofluorocarbon (HFC)]] refrigerants. HFC refrigerants are known to decompose into PFAS such as TFA in the atmosphere and thereby subsequently appear in concerning concentrations in rainwater. By themselves, HFCs are resistant to thermal degradation; however, in the presence of alkali (e.g., NaOH), alkaline hydrolysis can occur at T < 150˚C<ref name="AustinEtAl2024"/>.

==State of the Art==
[[File:PinkardFig4.png | thumb |400px| left | Figure 4: HALT field demonstration at Fairbanks International Airport (FAI) in August 2023]]
Recently, several field demonstrations of pilot-scale HALT systems were performed by commercial HALT provider Aquagga, Inc. These have focused on treating PFAS-rich liquids, including industrial wastewater at a 3M Company facility (April 2024)<ref name="PinkardEtAl2024b">Pinkard, B.R., Smith, S.M., Bryan, C., 2024. PFAS Degradation and Defluorination of High TDS Wastewater via Continuous Hydrothermal Alkaline Treatment (HALT). In: (Proceedings of the) 85th Annual International Water Conference (IWC 2024), Volume 1, pp. 359-374. Engineers Society of Western Pennsylvania. ISBN: 979-8-3313-1299-2</ref>, foam fractionate from a fire training pit in Fairbanks, AK (August 2023) (Figure 4), foam fractionate from groundwater at Beale Air Force Base, CA (May 2024), and AFFF (May 2024). For all field demonstrations, a containerized HALT system was mobilized to the site and operated for up to several weeks. The systems were typically operated at a throughput between 5 and 10 gallons per hour (gph). Since 2019, HALT has progressed from small-scale batch reactors to successful field demonstration of pilot-scale systems. This technology maturation attests to strong technical and regulatory tailwinds. Effort is still needed to demonstrate the technology at full scale and in complex treatment scenarios. Long-term operation of the systems will allow for further optimization of the systems and provide data on the applicability of HALT for the treatment of industrial and environmental PFAS-contaminated waste streams.

Scaled-up HALT systems are typically continuous flow tubular reactor systems, consisting of a single high-temperature, high-pressure fluid path. In commercial HALT systems offered by Aquagga, Inc., chemical dosing for pH adjustment is achieved via an automated chemical dosing and mixing system. The high pH feedstock is then introduced to the high-pressure reactor via a high-pressure metering pump. Pressure is controlled via a back-pressure device downstream of the high-temperature reactor zone. The pressurized reactants are brought to reaction temperatures via a recuperative heat exchanger followed by electric resistive heaters. The reactor vessel contains the reactants at the necessary temperature and pressure and for a sufficient residence time to facilitate the destruction reactions. The product stream is then cooled through a recuperative heat exchanger, before being throttled to ambient pressure through the back-pressure device. Pressure transducers, flow meters, and thermocouples are used to monitor the reactor operations at various points in the system. All reactor components are typically housed within a shipping container, for ease of system transport and to provide secondary chemical containment.

==Practical Applications==
The ideal use case for HALT is treating PFAS-rich liquid matrices. PFAS concentrations are high enough for HALT to be directly applicable primarily in the cases of AFFF treatment or industrial process water treatment. In the majority of use cases, it is more practical to apply a separation and concentration technology prior to HALT, to reduce the volume of liquid requiring HALT treatment while increasing PFAS concentrations in that liquid. These concentration technologies may include regenerable sorbents, membranes, or foam fractionation, all of which produce a liquid byproduct amenable for HALT.

===Destruction of PFAS in Ion Exchange Regeneration Brine===
One of the most promising applications of HALT is for treating PFAS-rich ion exchange (IX) regeneration brines, either in site remediation applications (e.g., groundwater treatment<ref name="Pinkard2024">Pinkard, B.R., 2024. Hydrothermal Alkaline Treatment for a Closed-Loop, On-Site PFAS Treatment Solution. Project Number ER23-8400, Environmental Security Technology Certification Program (ESTCP).  [https://serdp-estcp.mil/projects/details/a4c6918a-fe3b-43d2-95cb-fa3dfa3a50a2 Project Website]</ref>) or industrial wastewater treatment applications<ref name="PinkardEtAl2024a"/>. IX capture and regeneration involve sorbing PFAS to an IX resin, followed by chemical desorption of PFAS from the resin, typically with a solvent and/or salt wash solution. The IX regeneration technology is commercially mature and available from several vendors.

[[File:PinkardFig5.png | thumb |400px| right | Figure 5: An on-site HALT pilot demonstration at a 3M Company wastewater treatment facility]]
A treatment train of IX followed by HALT shows promise for several reasons. One reason is that the HALT process is highly compatible with the liquid matrix produced through the IX regeneration. Typically, IX regeneration brine (a.k.a. “still bottoms”) contains high levels of dissolved solids such as sodium chloride, which can cause practical processing challenges with other liquid treatment technologies. However, high levels of TDS do not appear to cause processing challenges with HALT<ref name="PinkardEtAl2024a"/>. Another reason is that IX regeneration brines often contain ultra short- and short-chain PFAS, which are amenable to destructive treatment with HALT.

In 2022, commercial HALT provider Aquagga performed a bench study in partnership with the 3M Company, demonstrating PFAS destruction performance for HALT processing of a synthetic IX regeneration brine<ref name="PinkardEtAl2024a"/>. Seven treatment conditions were tested, and fluorine mass balance closure was demonstrated for most conditions using a range of analytical techniques. In 2024, Aquagga performed an on-site demonstration in partnership with the 3M Company treating IX regeneration brine produced from active wastewater treatment activities (Figure 5)<ref name="PinkardEtAl2024b"/>.

===Foam Fractionate Treatment===
Foam fractionation is a technology that concentrates PFAS in liquids by taking advantage of the hydrophobic/interface-partitioning behavior exhibited by many types of PFAS. Foam fractionation is seeing broad adoption for challenging liquid matrices such as landfill leachate and groundwater. Long-chain PFAS are known to partition to interfaces much more readily than short-chain PFAS, and foam fractionation is correspondingly much more effective at removing long-chain PFAS from liquids. When coupled with HALT, foam fractionation can remove and destroy a high fraction of PFAS from challenging liquid matrices<ref name="HaoEtAl2023"/>.

===Destruction of PFAS in AFFF===
Legacy AFFF contains high levels of PFAS (typically 0.1 to 6 wt%) in a liquid matrix. Several studies at lab and pilot scales have demonstrated that HALT can destroy PFAS in AFFF with minimal dilution<ref name="HaoEtAl2021"/>. While the treatment is effective, the wide variety of AFFF formulations make this a challenging application.

==Advantages and Drawbacks==
===Advantages of HALT include:===
*Ability to achieve >99% destruction of all PFAS chain lengths and subtypes
*Ability to fully mineralize or defluorinate PFAS to dissolved inorganic fluoride as an end product
*Commercial systems are compact and simple to operate
*Commercial systems do not have an air emission point
*Ability to treat wastes with high TDS
*Ability to treat wastes with high TOC
*Low overall energy usage (<0.9 kWh/gal-treated)

===Drawbacks or challenges associated with HALT include:===
*Not well-suited for directly processing solid materials or slurries
*Treated effluent brine contains high TDS and must be managed accordingly
*Hard minerals (e.g., Ca2+) may precipitate and require periodic cleaning

===Safety considerations related to HALT include:===
*The use of strong bases and conjugate acids require safe chemical handling practices external to the HALT system and appropriate operator precautions
*High-pressure, high-temperature, and high-pH operating conditions are harsh and corrosive on processing equipment, and appropriate material selection, metallurgy, and corrosion control methods must be applied to ensure reactor vessel reliability

==References==
<references />

==See Also==
*[https://www.aquagga.com/ourtech Aquagga (company) website]
*[https://strathmanngroup.com/research/ Strathmann Research Group]
*[https://www.youtube.com/watch?v=UANEiMIDcZM&t=2696s SERDP Webinar Series: PFAS Fate, Transport and Treatment]
*[https://www.youtube.com/watch?v=KRVJ2S9F9qU&t=3261s SERDP Webinar Series: Developing and Demonstrating Technologies for Destruction of PFAS in Concentrated Liquid Waste Streams]

Dr. Shilai Hao

2025-08-07T16:04:42Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Department of Civil & Environmental Engineering :Colorado School of Mines :1500 Illinois Street :Golden, CO 80401 EMAIL: [mailto..."

==Work and Contact Information==
EMPLOYER:
:Department of Civil & Environmental Engineering
:Colorado School of Mines
:1500 Illinois Street
:Golden, CO 80401

EMAIL: [mailto:shao@mines.edu shao@mines.edu]

LINKEDIN: https://www.linkedin.com/in/shilai-hao-7486bb9b/

==About the Contributor==
Dr. Shilai Hao is a Research Assistant Professor in the Department of Civil and Environmental Engineering at the Colorado School of Mines, where he also earned his Ph.D. in Environmental Engineering. His research focuses on developing innovative treatment technologies for the removal of emerging contaminants—particularly per- and polyfluoroalkyl substances (PFAS)—from environmental systems. He also works on advancing analytical methodologies for detecting trace organic contaminants using high-resolution mass spectrometry (HRMS). Dr. Hao is a recipient of the ACS Graduate Student Award and currently serves on the Early Career Editorial Advisory Board for Environmental Science & Technology. His long-term goal is to promote a safe and sustainable environment by enhancing the understanding of contaminant fate and transport and by developing cost-effective, sustainable treatment strategies.

==Article Contributions==
*[[Hydrothermal Alkaline Treatment (HALT)]]

__NOTOC__

[[Category: Contributors|Hao]]

Dr. Brian Pinkard

2025-06-04T14:03:55Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Aquagga, Inc. :748 Market Street :Tacoma, WA 98402 EMAIL: [mailto:brian@aquagga.com brian@aquagga.com] WEBPA..."

==Work and Contact Information==

EMPLOYER:
:Aquagga, Inc. 
:748 Market Street 
:Tacoma, WA 98402 

EMAIL: [mailto:brian@aquagga.com brian@aquagga.com]

WEBPAGE: [http://www.aquagga.com/ http://www.aquagga.com/]

==About the Contributor==
Dr. Brian Pinkard is a subject matter expert on the hydrothermal destruction of hazardous wastes. He is the CTO and Co-Founder of Aquagga, which offers PFAS destruction equipment and services leveraging the hydrothermal alkaline treatment (HALT) process. Dr. Pinkard is also an affiliate professor at the University of Washington and has been heavily involved in research efforts to develop sub- and supercritical water processing technologies.

==Article Contributions==
*[[Hydrothermal Alkaline Treatment (HALT)]]

__NOTOC__

[[Category: Contributors|Pinkard]]

S. M. Mohaiminul Islam

2025-02-25T18:57:36Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :University of Illinois Chicago :Department of Chemical Engineering :147 Engineering Innovation Building :929 Wes..."

==Work and Contact Information==

EMPLOYER:
:University of Illinois Chicago 
:Department of Chemical Engineering 
:147 Engineering Innovation Building 
:929 West Taylor Street 
:Chicago, IL 60608

EMAIL: [mailto:sislam23@uic.edu sislam23@uic.edu]

==About the Contributor==
Mohaiminul is a graduate student in the Department of Chemical Engineering at the University of Illinois at Chicago. His research focuses on applying electrochemical methods for remediation of wide range of water contaminants. Previously, he worked on treatment of both legacy munitions and newer “insensitive” munitions. Currently, his work focuses on the electrocatalytic remediation of per- and polyfluoroalkyl substances (PFAS) compounds.

==Article Contributions==
*[[Munitions Constituents - Electrochemical Treatment]]

__NOTOC__

[[Category: Contributors|Islam]]

Munitions Constituents - Electrochemical Treatment

2025-02-25T18:38:05Z

Debra Tabron:

Electrochemical treatment of [[Munitions Constituents|munitions constituents]] is an emerging technology for the remediation of explosive compounds in wastewater. This process utilizes [[wikipedia:Electro-oxidation|electrochemical oxidation]] mechanisms to degrade both legacy explosives, as well as newer [[wikipedia:Insensitive_munition|insensitive high explosives]]. The treatment relies on direct electron transfer reactions and the generation of highly reactive [[wikipedia:Hydroxyl_radical|hydroxyl radicals]] at the electrode surface. Recent research has elucidated the oxidation pathways and byproducts for various munitions constituents, demonstrating the potential of electrochemical methods as an effective and environmentally friendly alternative to traditional [[Munitions Constituents - Sorption|adsorption-based treatments]] for explosive-contaminated water.

<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Munitions Constituents]]
*[[Munitions Constituents - Abiotic Reduction]]
*[[Munitions Constituents - Alkaline Degradation]]
*[[Munitions Constituents – Photolysis]]
*[[Munitions Constituents - Sorption]]

'''Contributor(s):''' [[Dr. Brian P. Chaplin]] and [[S. M. Mohaiminul Islam]]

'''Key Resource(s):'''

*[https://pubs.acs.org/doi/10.1021/acsestengg.3c00620 Electrochemical Destruction of Insensitive High Explosives Using Magnéli Phase Titanium Oxide Reactive Electrochemical Membranes]<ref name=":0">Islam, S.M.M., and Chaplin, B.P., 2024. Electrochemical Destruction of Insensitive High Explosives Using Magnéli Phase Titanium Oxide Reactive Electrochemical Membranes. ACS ES&T Engineering, 4(5), pp. 1241-1252. [https://pubs.acs.org/doi/10.1021/acsestengg.3c00620 doi: 10.1021/acsestengg.3c00620]</ref>
*[https://pubs.acs.org/doi/10.1021/es8028878 Electrochemical Method Applicable to Treatment of Wastewater from Nitrotriazolone Production]<ref name=":1">Wallace, L., Cronin, M.P., Day, A.I., and Buck, D.P., 2009. Electrochemical Method Applicable to Treatment of Wastewater from Nitrotriazolone Production. Environmental Science & Technology, 43(6), pp. 1993-1998. [https://pubs.acs.org/doi/10.1021/es8028878 doi: 10.1021/es8028878]</ref>
*[//www.enviro.wiki/images/a/a8/Szopi%C5%84ska2024.pdf Efficient Removal of 2,4,6-Trinitrotoluene (TNT) from Industrial/Military Wastewater Using Anodic Oxidation on Boron-Doped Diamond Electrodes]<ref name=":2">Szopińska, M., Prasuła, P., Baran, P., Kaczmarzyk, I., Pierpaoli, M., Nawała, J., Szala, M., Fudała-Książek, S., Kamieńska-Duda, A., and Dettlaff, A., 2024. Efficient Removal of 2,4,6-Trinitrotoluene (TNT) from Industrial/Military Wastewater Using Anodic Oxidation on Boron-Doped Diamond Electrodes. Scientific Reports, 14, pp. 4802. [https://doi.org/10.1038/s41598-024-55573-w doi:10.1038/s41598-024-55573-w] [//www.enviro.wiki/images/a/a8/Szopi%C5%84ska2024.pdf Article pdf] </ref>
*[https://www.sciencedirect.com/science/article/abs/pii/S1385894711002002?via%3Dihub Treatment of High Explosive Production Wastewater Containing RDX by Combined Electrocatalytic Reaction and Anoxic–Oxic Biodegradation]<ref name=":3">Chen, Y., Hong, L., Han, W., Wang, L., Sun, X., and Li, J., 2011. Treatment of High Explosive Production Wastewater Containing RDX by Combined Electrocatalytic Reaction and Anoxic–Oxic Biodegradation. Chemical Engineering Journal, 168(3), pp. 1256-1262. [https://www.sciencedirect.com/science/article/abs/pii/S1385894711002002?via%3Dihub doi: 10.1016/j.cej.2011.02.032]</ref>
*[//www.enviro.wiki/images/a/ac/Qian2022.pdf Performance Optimization and Toxicity Effects of the Electrochemical Oxidation of Octogen]<ref name=":4">Qian, Y., Chen, K., Chai, G., Xi, P., Yang, H., Xie, L., Qin, L., Lin, Y., Li, X., Yan, W., and Wang, D., 2022. Performance Optimization and Toxicity Effects of the Electrochemical Oxidation of Octogen. Catalysts, 12 (8), pp. 815. [https://doi.org/10.3390/catal12080815 doi: 10.3390/catal12080815][//www.enviro.wiki/images/a/ac/Qian2022.pdf Article pdf]</ref>

==Introduction==
[[Munitions Constituents|Munitions constituents]] refer to the energetic compounds utilized in various military applications, such as propellants, artillery shells, and ballistic agents. Legacy munitions constituents typically include compounds such as [[wikipedia:TNT|2,4,6-trinitrotoluene]] (TNT), [[wikipedia:RDX|Hexahydro-1,3,5-trinitro-1,3,5-triazine]] (RDX), and [[wikipedia:HMX|1,3,5,7-tetranitro-1,3,5,7-tetrazocane]] (HMX). However, due to safety concerns, there has been a shift towards the use of [[wikipedia:Insensitive_munition|Insensitive High Explosives]] (IHEs). These compounds offer reduced susceptibility to unintended detonation, enhancing safety in military applications. One notable example of an IHE is [[wikipedia:IMX-101|IMX-101]], a standard explosive formulation containing [[wikipedia:2,4-Dinitroanisole|2,4-dinitroanisole]] (DNAN), [[wikipedia:Nitroguanidine|nitroguanidine]] (NQ), and [[wikipedia:Nitrotriazolone|3-nitro-1-2-4-triazol-5-one]] (NTO).

==Electrochemical Oxidation Mechanisms==
[[File:ChaplinFig1.png | thumb | 450px | Figure 1. Conceptual diagram of the two primary electrochemical oxidation mechanisms.]]
In [[wikipedia:Electro-oxidation|electrochemical wastewater treatment]], contaminants react either through a direct electron transfer (DET) reaction with the electrode or with a reactive species generated at the surface of the electrode (Figure 1)<ref>Comninellis, Ch., and Pulgarin, C., 1993. Electrochemical Oxidation of Phenol for Wastewater Treatment Using SnO2, Anodes. Journal of Applied Electrochemistry, 23 (2), pp. 108–112. [https://doi.org/10.1007/BF00246946 doi: 10.1007/BF00246946]</ref><ref>Borrás, C., Berzoy, C., Mostany, J., and Scharifker, B.R., 2006. Oxidation of P-Methoxyphenol on SnO2–Sb2O5 Electrodes: Effects of Electrode Potential and Concentration on the Mineralization Efficiency. Journal of Applied Electrochemistry, 36 (4), pp. 433–439. [https://doi.org/10.1007/s10800-005-9088-5 doi: 10.1007/s10800-005-9088-5]</ref><ref>Borrás, C., Rodríguez, P., Laredo, T., Mostany, J., and Scharifker, B.R., 2004. Electrooxidation of Aqueous P-Methoxyphenol on Lead Oxide Electrodes. Journal of Applied Electrochemistry, 34 (6), pp. 583–589. [https://doi.org/10.1023/B:JACH.0000021922.73582.85 doi: 10.1023/B:JACH.0000021922.73582.85]</ref><ref>Borras, C., Laredo, T., and Scharifker, B.R., 2003. Competitive Electrochemical Oxidation of p-chlorophenol and p-nitrophenol on Bi-Doped PbO2. Electrochimica Acta, 48 (19), pp. 2775–2780. [https://doi.org/10.1016/S0013-4686(03)00411-0 doi: 10.1016/S0013-4686(03)00411-0].</ref><ref>Kesselman, J. M., Weres, O., Lewis, N. S., and Hoffmann, M.R., 1997. Electrochemical Production of Hydroxyl Radical at Polycrystalline Nb-Doped TiO2 Electrodes and Estimation of the Partitioning between Hydroxyl Radical and Direct Hole Oxidation Pathways. The Journal of Physical Chemistry B, 101(14), pp. 2637–2643. [https://doi.org/10.1021/jp962669r doi: 10.1021/jp962669r].</ref><ref>Zaky, A.M., and Chaplin, B.P., 2013. Porous Substoichiometric TiO2 Anodes as Reactive Electrochemical Membranes for Water Treatment. Environmental Science & Technology, 47(12), pp. 6554–6563. [https://doi.org/10.1021/es401287e doi: 10.1021/es401287e]</ref><ref>Bejan, D., Guinea, E., and Bunce, N.J., 2012. On the Nature of the Hydroxyl Radicals Produced at Boron-Doped Diamond and Ebonex® Anodes. Electrochimica Acta, 69, pp. 275–281. [https://doi.org/10.1016/j.electacta.2012.02.097 doi: 10.1016/j.electacta.2012.02.097.] </ref>. Electrochemical advanced oxidation process (EAOP) electrodes generally have a high overpotential for the oxygen evolution reaction, which allows them to produce [[wikipedia:Hydroxyl_radical|hydroxyl radicals]] (OH•), a strong oxidant [E0(OH•/H2O) = 2.8 vs normal hydrogen electrode (NHE)]<ref>Gligorovski, S., Strekowski, R., Barbati, S., and Vione, D., 2015. Environmental Implications of Hydroxyl Radicals (•OH). Chemical Reviews, 115(24), pp. 13051–13092. [https://doi.org/10.1021/cr500310b doi: 10.1021/cr500310b].</ref>, through water oxidation according to equation (1).

H2O → OH• + H+ + e- (1)

Then the contaminants (R) react with these electrochemically generated hydroxyl radicals (OH•) to form mineralization products according to reaction (2).

R + OH• → xHNO3 + yCO2 + zH2O (2)

In equation (2), x, y, and z represent stoichiometric ratios that are dependent on the composition of species R. The other primary oxidation is through the DET mechanism, according to reaction (3).

R → (R•)+ + e- (3)

==Electrochemical Oxidation of Munitions==
[[File:ChaplinFig2.png | thumb | 350px | left | Figure 2. Proposed electrochemical oxidation pathway of NQ on Ti4O7 electrode (adapted from Islam et al., 2024)<ref name=":0" />.]]
[[File:ChaplinFig3.png | thumb | 350px | right | Figure 3. Proposed electrochemical oxidation mechanism of NTO on a glassy carbon working electrode (adapted from Wallace et al., 2009)<ref name=":1" />.]]

===Nitroguanidine (NQ)===
[[wikipedia:Electro-oxidation|Electrochemical oxidation]] of NQ has been reported recently on a porous Ti4O7 electrode. Analysis by [[wikipedia:Linear_sweep_voltammetry#:~:text=In%20analytical%20chemistry%2C%20linear%20sweep,is%20swept%20linearly%20in%20time.|linear sweep voltammetry]] (LSV) revealed that NQ undergoes oxidation via a DET reaction<ref name=":0" />. Following the initial DET step, the resulting radical reacts with as shown in the pathway in Figure 2. Analysis of oxidation byproducts showed the formation of [[wikipedia:Nitrate|nitrate]], [[wikipedia:Cyanamide|cyanamide]], [[wikipedia:Urea|urea]], and [[wikipedia:Melamine|melamine]] depending on the electrode potential. The nitrate yield was observed to be a function of the initial NQ concentration. Lower concentrations of NQ showed higher nitrate yield, whereas higher concentrations of NQ led to lower nitrate yield due to increased byproduct formation from elevated NQ concentration.

===3-Nitro-1-2-4-triazol-5-one (NTO)===
Studies from the literature showed that NTO undergoes electrochemical oxidation via a direct electron transfer mechanism, as studies conducted on a glassy carbon electrode showed an increase in current for NTO-spiked solutions<ref name=":1" />. A pathway for electrochemical oxidation of NTO has also been proposed (Figure 3). According to the proposed pathway, NTO forms 5-nitrotriazolinone in the initial step. Due to its unstable nature, it decomposes to form O2N-CN, CO and N2. The O2N-CN compound then hydrolyzes and forms [[wikipedia:Nitrous_acid|HNO2]] and [[wikipedia:Isocyanic_acid|HOCN]]. Additional hydrolysis products of nitrate and [[wikipedia:Ammonium|ammonium]] were also observed<ref name=":1" />.

===2,4-Dinitroanisole (DNAN)===
Experimental and computational work has shown that DNAN can undergo both direct and indirect electrochemical oxidation<ref name=":0" /><ref>Zhou, Y., Liu, X., Jiang, W., and Shu, Y., 2018. Theoretical Insight into Reaction Mechanisms of 2,4-Dinitroanisole with Hydroxyl Radicals for Advanced Oxidation Processes. Journal of Molecular Modeling, 24 (2), pp. 44. [https://doi.org/10.1007/s00894-018-3580-4 doi: 10.1007/s00894-018-3580-4].</ref><ref name=":5">Su, H., Christodoulatos, C., Smolinski, B., Arienti, P., O’Connor, G., and Meng, X., 2019. Advanced Oxidation Process for DNAN Using UV/H2O2. Engineering, 5(5), pp. 849–854. [https://doi.org/10.1016/j.eng.2019.08.003 doi: 10.1016/j.eng.2019.08.003][//www.enviro.wiki/images/9/9a/Su2019.pdf Article pdf]</ref>. Electrochemical oxidation of DNAN has produced nitrate, carbon dioxide, and water as the terminal byproducts<ref name=":0" />. DNAN can undergo direct oxidation on the anode as predicted by DFT calculations<ref name=":0" />. Moreover, it can also react with produced on the anode through addition and H atom abstraction mechanisms, ultimately leading to destabilization and ring-opening reactions<ref name=":0" /><ref name=":5" />. The DNAN electrochemical oxidation pathway is shown in Figure 4.

===2,4,6-Trinitrotoluene (TNT)===
Electrochemical oxidation of TNT on a boron-doped-diamond (BDD) electrode was primarily attributed to H-atom abstraction reactions by OH•<ref name=":2" />. [[wikipedia:Gas_chromatography–mass_spectrometry|Gas chromatography-mass spectrometry]] was used to identify the byproducts from TNT oxidation. Detection of compounds like trinitrobenzene and [[wikipedia:1,3-Dinitrobenzene|1,3-dinitrobenzene]] supports the proposed pathway shown in Figure 5.

===Hexahydro -1,3,5-trinitro-1,3,5-triazine (RDX)===
Electrochemical oxidation of RDX was studied on a TiO2-nantube/SnO2-Sb anode<ref name=":3" />. The proposed pathway (Figure 6) is based on synergistic electrochemical oxidation and reduction. RDX is first reduced to mono, di, and tri-nitroso RDX on the cathode based on the pathway. These intermediates are then attacked by OH• generated on the anode which leads to ring-opening reactions due to H abstraction by OH•. [[wikipedia:Formaldehyde|Formaldehyde]], [[wikipedia:Formic_acid|formic acid]], nitrate, and [[wikipedia:Nitrite|nitrite]] were detected as terminal byproducts.

===1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)===
To date there is not any experimental evidence of HMX reacting through a direct electrochemical oxidation mechanism. However, some studies proposed that HMX reacted through indirect electrochemical oxidation<ref name=":4" /><ref>Bonin, P.M.L., Bejan, D., Radovic-Hrapovic, Z., Halasz, A., Hawari, J., and Bunce, N. J., 2005. Indirect Oxidation of RDX, HMX, and CL-20 Cyclic Nitramines in Aqueous Solution at Boron-Doped Diamond Electrodes. Environmental Chemistry'','' 2(2), pp. 125–129. [https://doi.org/10.1071/EN05006 doi: 10.1071/EN05006] </ref>. The electrochemical oxidation pathway is driven by the reaction of RDX with electrochemically generated hydroxyl radicals through the addition mechanism (Figure 7). Detection of smaller compounds such as methylene dinitramine, urea, and [[wikipedia:Acetamide|acetamide]] provides support for this pathway.

==Conclusion==
Electrochemical oxidation of pollutants is a potentially effective technology using electrons as reactants, not requiring chemical dosage. It can be a viable alternative to adsorption-based methods for treating munitions constituents, eliminating the need for additional waste treatment and disposal.
[[File:ChaplinFig4.png | thumb | 650px | left | Figure 4. Proposed electrochemical oxidation pathway of DNAN on Ti4O7 electrode (adapted from Islam et al., 2024)<ref name=":0" />.]]
[[File:ChaplinFig5.png | thumb | 650px | left| Figure 5. Proposed pathway for electrochemical oxidation of TNT on boron-doped diamond (BDD) electrode (redrawn from Szopińska et al., 2024)<ref name=":2" />.]]
[[File:ChaplinFig6.png | thumb | 550px | center | Figure 6. Proposed pathway for electrochemical oxidation of RDX on TiO2 -nanotube/ SnO2-Sb electrode (redrawn from Chen et al., 2011)<ref name=":3" />.]]
[[File:ChaplinFig7.png | thumb | 550px | center | Figure 7. Proposed pathway for electrochemical oxidation of HMX on TiO2 -Pb electrode (redrawn from Qian et al., 2022)<ref name=":4" />.]]

==References==
<references />

==See Also==

Dr. Brian P. Chaplin

2025-02-25T18:36:58Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :University of Illinois Chicago :Department of Chemical Engineering :154 Engineering Innovation Building :929 West T..."

==Work and Contact Information==

EMPLOYER:
:University of Illinois Chicago 
:Department of Chemical Engineering 
:154 Engineering Innovation Building 
:929 West Taylor Street 
:Chicago, IL 60608

EMAIL: [mailto:chaplin@uic.edu chaplin@uic.edu]

WEBPAGE: [https://chaplin.lab.uic.edu https://chaplin.lab.uic.edu]

==About the Contributor==
Dr. Brian P. Chaplin is a leading researcher in the field of water treatment and environmental remediation. His work focuses on developing innovative electrochemical and catalytic processes that promote water sustainability. Dr. Chaplin's research encompasses advanced electrode and reactor design, elucidation of contaminant degradation pathways, and application of mathematical transport and molecular modeling. These interdisciplinary approaches enable Dr. Chaplin to devise effective strategies for contaminant remediation. His recent work is focused on the electrochemical destruction of munitions constituents in water and the remediation of per- and polyfluoroalkyl substances (PFAS), a group of persistent environmental pollutants. Dr. Chaplin's research contributes significantly to the development of technologies that address emerging water quality concerns, with potential far-reaching impacts on environmental protection and public health.

==Article Contributions==
*[[Munitions Constituents - Electrochemical Treatment]]

__NOTOC__

[[Category: Contributors|Chaplin]]

Contributors

2025-02-19T22:06:41Z

Debra Tabron:

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ENVIRO.wiki aims to connect users with the most current and credible science and engineering research into the design and implementation of environmental projects. Financial support for ENVIRO.wiki is provided by the US Department of Defense environmental research and demonstration programs – [https://www.serdp-estcp.org/ SERDP and ESTCP]. Articles are written by nationally and internationally recognized experts who provide a concise summary of the current State-of-Practice and relevant research results. Many of these authors have written similar articles for SERDP-ESTCP as part of the existing monograph series or for other publications. All articles are reviewed by outside technical reviewers as described in the [[Editorial_Policy|editorial policy]]. Day to day administration is provided by [https://www.trccompanies.com/ TRC].

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|''Technical Editor''
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|Jim Hurley, MS, EIT
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|TRC, Cary NC
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|''Administrative Assistant''
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|Debra Tabron
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{| style="width: 100%;margin: left; text-align:left;"
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| style="width:13.3%" |[[Dr._David_Adamson,_P.E.|David Adamson]]
| style="width:13.3%" |[[Tom_Christy,_P.E.|Tom Christy]]
| style="width:13.3%" |[[Dr. Shahla Farhat |Shahla Farhat]]
| style="width:13.3%" |[[Dr._Gorm_Heron|Gorm Heron]]
| style="width:13.3%" |[[M. Tony Lieberman|Tony Lieberman]]
| style="width:13.3%" |[[Dr. Robert Murdoch|Robert Murdoch]]
| style="width:13.3%" |[[Dr. Selma Mededovic Thagard|Selma Thagard]]
|-
|[[Richelle Allen-King]]
|[[Dr. Pei Chiu|Pei Chiu]]
|[[Paul Favara|Paul Favara]]
|[[Dr._Christopher_Higgins|Christopher Higgins]]
|[[Dr. Gaisheng Liu|Gaisheng Liu]]
|[[Kobe Nagar]]
|[[Dr._Paul_Tratnyek|Paul Tratnyek]]
|-
|[[Dr. Richard Anderson|Richard "Hunter" Anderson]]
|[[Dr._Kung-Hui_(Bella)_Chu|Bella Chu]]
|[[Dr. Jack Feminella|Jack Feminella]]
|[[Dr. Thomas Holsen|Thomas Holsen]]
|[[Dr._Barbara_Sherwood_Lollar,_F.R.S.C.|Barbara Lollar]]
|[[Dr._Charles_Newell,_P.E.|Charles Newell]]
|[[Michael_Truex|Michael Truex]]
|-
|[[Dr. Michael Annable, P.E.|Michael Annable]]
|[[Dr. Jason Conder|Jason Conder]]
|[[Dr._Jennifer_Field|Jennifer Field]]
|[[Dr. Brian Hudgens|Brian Hudgens]]
|[[Dr. Guilherme Lotufo|Guilherme Lotufo]]
|[[Dr. Dimitrios Ntarlagiannis|Dimitrios Ntarlagiannis]]
|[[Michael_R._Walsh,_P.E.,_M.E.|Michael Walsh]]
|-
|[[Dr. Sabine E. Apitz|Sabine E. Apitz]]
|[[Dr._Michelle_Crimi|Michelle Crimi]]
|[[Dr._Kevin_Finneran|Kevin Finneran]]
|[[Dr. John Hummel|John Hummel]]
|[[John Lowe|John Lowe]]
|[[Dora_Ogles-Taggart|Dora Ogles-Taggart]]
|[[Dr. Meng Wang|Meng Wang]]
|-
|[[Dr._Brett_Baldwin|Brett Baldwin]]
|[[Harry Craig]]
|[[Jeff_Fitzgibbons|Jeff Fitzgibbons]]
|[[Dr. Michael Hyman|Michael Hyman]]
|[[Dr. Loren Lund|Loren Lund]]
|[[Tom_Palaia|Tom Palaia]]
|[[Dr. James Weaver|James Weaver]]

|-
|[[Dr. Amanda Barker|Amanda Barker]]
|[[Dr. Paul Dahlen|Paul Dahlen]]
|[[Dr._David_L._Freedman|David Freedman]]
|[[Dan Isenberg]]
|[[Chris_Lutes|Chris Lutes]]
|[[Dr. Frederic Petit|Frederic Petit]]
|[[Richard Wenning]]
|-
|[[Dr. Samuel Beal|Samuel Beal]]
|[[Dr. Phillip de Blanc, P.E. |Phil de Blanc]]
|[[Jeff Gamlin, P.G.|Jeff Gamlin]]
|[[Dr._Billy_E._Johnson|Billy Johnson]]
|[[Leah_MacKinnon,_M.A.Sc.,_P._Eng.|Leah MacKinnon]]
|[[Kien Pham]]
|[[Dr. Katie van Werkhoven|Katie van Werkhoven]]
|-
|[[Lila Beckley]]
|[[Dr. Rula Deeb|Rula Deeb]]
|[[Dr._Jason_Gerhard|Jason Gerhard]]
|[[Dr. Paul C. Johnson|Paul C. Johnson]]
|[[Elisse_Magnuson|Elisse Magnuson]]
|[[Dr. Breanna F. Powers|Breanna F. Powers]]
|[[Dr. Hal White|Hal White]]
|-
|[[Dr. Barbara Bekins|Barbara Bekins]]
|[[Dr._Miles_Denham|Miles Denham]]
|[[Dr. Upal Ghosh|Upal Ghosh]]
|[[Jared Johnson]]
|[[Dr. Shaily Mahendra|Shaily Mahendra]]
|[[Dr. Danny Reible|Danny Reible]]
|[[Dr. Richard Wilkin|Rick Wilkin]]
|-
|[[Rene Bernier]]
|[[Dr. Marc A. Deshusses|Marc Deshusses]]
|[[Dr. Scott Grieco|Scott Grieco]]
|[[Dr. Warren Kadoya|Warren Kadoya]]
|[[Todd Martin]]
|[[Dr._Stephen_Richardson|Stephen Richardson]]
|[[Dr._John_Wilson|John Wilson]]
|-
|[[Sam Bickley]]
|[[William DiGuiseppi]]
|[[Dr. Natalie Griffiths|Natalie Griffiths]]
|[[Dr. Roopa Kamath|Roopa Kamath]]
|[[Wesley_McCall,_M.S.,_P.G.|Wesley McCall]]
|[[Florent Risacher]]
|[[Dr. Suzanne Witt|Suzanne Witt]]
|-
|[[Dr. Robert Borden, P.E.|Robert Borden]]
|[[Dr._Katerina_Dontsova|Katerina Dontsova]]
|[[Dr. Philip M. Gschwend|Philip M. Gschwend]]
|[[Dr. Denise Kay|Denise Kay]]
|[[Travis_McGuire|Travis McGuire]]
|[[Gunther Rosen]]
|[[Dr. Bilgen Yuncu, P.E.|Bilgen Yuncu]]
|-
|[[Dr. Treavor H. Boyer|Treavor Boyer]]
|[[Dr. Mark S. Dortch, PE, D.WRE|Mark Dortch]]
|[[Dr. Yuanming Guo|Yuanming Guo]]
|[[Andrew Kirkman]]
|[[Dr._Thomas_McHugh|Thomas McHugh]]
|[[Dr._Alexandra_Salter-Blanc|Alexandra Salter-Blanc]]
|[[Matthew Zenker]]
|-
|[[Dr. Mark Brusseau|Mark Brusseau]]
|[[Doug_Downey,_P.E.|Doug Downey]]
|[[Dr. Nathan Hall|Nathan Hall]]
|[[Deyuan Kong]]
|[[Michaye_McMaster,_M.Sc.|Michaye McMaster]]
|[[Dr. Grace Schwartz|Grace Schwartz]]
|
|-
|[[Dr. James Butler, Jr.|James Butler]]
|[[Dr. Elizabeth_Edwards|Elizabeth Edwards]]
|[[James Hatton]]
|[[Dr. Rao Kotamarthi|Rao Kotamarthi]]
|[[Sara McMillen]]
|[[Dr. Austin Scircle|Austin Scircle]]
|
|-
|[[Dr. Richard F. Carbonaro|Richard F. Carbonaro]]
|[[Dr. Anderson Ellis|Anderson Ellis]]
|[[Paul Hatzinger]]
|[[Thomas_Krug|Thomas Krug]]
|[[Dr. Jonathan Miles|Jonathan Miles]]
|[[Dr._Lee_Slater|Lee Slater]]
|
|-
|[[Paula Andrea Cárdenas-Hernández|Paula A. Cárdenas-Hernández]]
|[[Dr. Morgan Evans|Morgan Evans]]
|[[Elisabeth_Hawley|Elisabeth Hawley]]
|[[Dr. Kate Kucharzyk|Kate Kucharzyk]]
|[[Henry Moore]]
|[[Dr. Timothy J. Strathmann|Timothy Strathmann]]
|
|-
|[[Dr. Grace Chang|Grace Chang]]
|[[Dr._Ron_Falta|Ron Falta]]
|[[Dr. Julie A. Heath|Julie A. Heath]]
|[[Poonam Kulkarni|Poonam Kulkarni]]
|[[Larry Mullins]]
|[[Dr. Hans Stroo|Hans Stroo]]
|
|-
|[[Dr. Dora Chiang|Dora Chiang]]
|[[Dr._Dimin_Fan|Dimin Fan]]
|[[Dr. Brian Helms|Brian Helms]]
|[[Dr. Johnsie Ray Lang|Johnsie Ray Lang]]
|[[Dr. Fadime Murdoch|Fadime Murdoch]]
|[[Dr._Susan_Taylor|Susan Taylor]]
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|}
|}
|}

Henry Moore

2025-02-19T21:43:50Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: :Rutgers University Newark :Department of Earth & Environmental Sciences :101 Warren Street, Smith 135 :Newark, N..."

==Work and Contact Information==

EMPLOYER:
:Rutgers University Newark 
:Department of Earth & Environmental Sciences 
:101 Warren Street, Smith 135 
:Newark, NJ 07102

EMAIL: [mailto:hem62@newark.rutgers.edu hem62@newark.rutgers.edu]

==About the Contributor==
Henry E. Moore is a Ph.D. candidate at Rutgers University-Newark specializing in paired temperature sensing and electrical geophysical methods to characterize, monitor, and quantify groundwater-surface water exchanges in a variety of hydrological environments. He is further exploring these linkages to determine the effects of groundwater on surface ecology and biogeochemical processes.

==Article Contributions==
*[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]

__NOTOC__

[[Category: Contributors|Moore]]

Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges

2025-02-19T21:37:04Z

Debra Tabron:

Hydrogeophysical methods can be used to cost-effectively locate and characterize regions of
enhanced groundwater/surface-water exchange (GWSWE) and to guide effective follow up investigations based on more traditional invasive methods. The most established methods exploit the contrasts in temperature and/or specific conductance that commonly exist between groundwater and surface water.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s):'''

*[[Geophysical Methods]]
*[[Geophysical Methods - Case Studies]]

'''Contributor(s):''' [[Dr. Lee Slater]], Dr. Ramona Iery, [[Dr. Dimitrios Ntarlagiannis]], [[Henry Moore]] and Dr. Martin Briggs

'''Key Resource(s):'''

*USGS Method Selection Tool: https://code.usgs.gov/water/espd/hgb/gw-sw-mst
*USGS Water Resources: https://www.usgs.gov/mission-areas/water-resources/science/groundwatersurface-water-interaction

==Introduction==
Discharges of contaminated groundwater (GW) to surface water (SW) threaten ecosystems and degrade the quality of surface-water resources. Subsurface heterogeneity associated with geological structure and stratigraphy often results in such discharges occurring as localized zones (or seeps) of contaminated GW. Traditional methods for investigating groundwater-surface water exchanges (GWSWE) include [https://books.gw-project.org/groundwater-surface-water-exchange/chapter/seepage-meters/#:~:text=Seepage%20meters%20measure%20the%20flux,that%20it%20isolates%20water%20exchange. seepage meters]<ref>Rosenberry, D.O., Duque, C., and Lee, D.R., 2020. History and Evolution of Seepage Meters for Quantifying Flow between Groundwater and Surface Water: Part 1 – Freshwater Settings. Earth-Science Reviews, 204(103167). [https://doi.org/10.1016/j.earscirev.2020.103167 doi: 10.1016/j.earscirev.2020.103167].</ref><ref>Duque, C., Russoniello, C.J., Rosenberry, D.O., 2020. History and Evolution of Seepage Meters for Quantifying Flow between Groundwater and Surface Water: Part 2 – Marine Settings and Submarine Groundwater Discharge. Earth-Science Reviews, 204, Article 103168. [https://doi.org/10.1016/j.earscirev.2020.103168 doi: 10.1016/j.earscirev.2020.103168].</ref>, which directly quantify the volumetric flux crossing the bed of a surface-water body (i.e, a lake, river or wetland) and point probes that locally measure key water quality parameters (e.g., temperature, pore water velocity, specific conductance, dissolved oxygen, pH). Seepage meters provide direct estimates of seepage fluxes between groundwater and surface water but are time consuming and can be difficult to deploy in high energy surface-water environments and along armored bed sediments. Manual seepage meters rely on quantifying volume changes in a bag of water that is hydraulically connected to the bed. Although automated seepage meters such as the [https://clu-in.org/programs/21m2/navytools/gsw/#ultraseep Ultraseep system] have been developed, they are generally not suitable for long-term deployment (weeks to months). The United States (US) Navy has developed the [https://clu-in.org/programs/21m2/navytools/gsw/#trident Trident probe] for more rapid (relative to seepage meters) sampling, whereby the probe is inserted into the bed and point-in-time pore-water quality and sediment parameters are directly recorded (note that the Trident probe does not measure seepage flux). Such direct probe-based measurements are still relatively time consuming to acquire, particularly when reconnaissance information is required over large areas to determine the location of discrete seeps for further, more quantitative analysis.

Over the last few decades, a broader [https://www.usgs.gov/mission-areas/water-resources/science/geophysics-usgs-groundwatersurface-water-exchange-studies toolbox of hydrogeophysical technologies] has been developed to rapidly and non-invasively evaluate zones of GWSWE in a variety of SW settings, spanning from freshwater bodies to saline coastal environments. Many of these technologies are currently being deployed under a Department of Defense Environmental Security Technology Certification Program ([https://serdp-estcp.mil/ ESTCP]) project ([https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ER21-5237]) to demonstrate the value of the toolbox to remedial program managers (RPMs) dealing with the challenge of characterizing surface-water contamination via groundwater from facilities proximal to surface-water bodies. This article summarizes these technologies and provides references to key resources, mostly provided by the [https://www.usgs.gov/mission-areas/water-resources Water Resources Mission Area] of the US Geological Survey (USGS) that describes the technologies in further detail.

==Hydrogeophysical Technologies for Understanding Groundwater-Surface Water Exchanges==
[[Wikipedia: Hydrogeophysics |Hydrogeophysical technologies]] exploit contrasts in the physical properties between groundwater and surface water to detect and monitor zones of pronounced GWSWE. The two most valuable properties to measure are temperature and electrical conductivity (EC). Temperature has been used for decades as an indicator of GWSWE<ref>Constantz, J., 2008. Heat as a Tracer to Determine Streambed Water Exchanges. Water Resources Research, 44 (4). [https://doi.org/https://doi.org/10.1029/2008WR006996 doi: 10.1029/2008WR006996]. [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2008WR006996 Open Access Article]</ref> with early uses including pushing a thermistor into the bed of a surface-water body to assess zones of SW downwelling and GW upwelling. Today, a variety of novel technologies that measure temperature over a wide range of spatial and temporal scales are being used to investigate GWSWE. The evaluation of EC measurements using point probes and geophysical imaging is also well established. However, new technologies are now available to exploit EC contrasts from GWSWE occurring over a range of spatial and temporal scales.

===Temperature-Based Technologies===
Several temperature-based GWSWE methodologies exploit the gradient in temperature between surface water and groundwater that exists during certain times of day or seasons of the year. The thermal insulation provided by the Earth’s land surface means that GW is warmer than SW in winter months, but colder than SW in summer months away from the equator. Therefore, in temperate climates, localized (or ‘preferential’) groundwater discharge into surface-water bodies is often observed as cold temperature anomalies in the summer and warm temperature anomalies in the winter. However, there are times of the year such as fall and spring when contrasts in the temperature between GW and SW will be minimal, or even undetectable. These seasonal-driven points in time correspond to the switch in the polarity of the temperature contrast between GW and SW. Consequently, SW to GW temperature gradient based methods are most effective when deployed at times of the year when the temperature contrasts between GW and SW are greatest. Other time-series temperature monitoring methods depend more on natural daily signals measured at the bed interface and in bed sediments, and those signals may exist year-round except where strongly muted by ice cover or surface water stratification. A variety of sensing technologies now exist within the GWSWE toolbox, including techniques that rapidly characterize temperature contrasts over large areas as well as powerful monitoring methods that can continuously quantify GWSWE fluxes at discrete locations identified as hotspots.

====Characterization Methods====
The primary use of the characterization methods is to rapidly determine precise locations of GW upwelling over large areas in order to pinpoint locations for subsequent ground-based observations. A common limitation of these methods is that they can only detect GW fluxes into SW. Methods applied at the water surface and in the surface-water column generally cannot identify localized regions of surface-water transfer to groundwater, for which temperature measurements collected within the bed sediments are needed. This is a more challenging characterization task that may in some cases be addressed using electrical conductivity-based methods described later in this article.

=====''Unoccupied Aerial Vehicle Infrared (UAV-IR)''=====
[[File:IeryFig1.png | thumb |600px|Figure 1. UAV-IR orthomosaics with estimated scale of (a) a wetland in winter (modified from Briggs ''et al.''<ref>Briggs, M.A., Jackson, K.E., Liu, F., Moore, E.M., Bisson, A., Helton, A.M., 2022. Exploring Local Riverbank Sediment Controls on the Occurrence of Preferential Groundwater Discharge Points. Water, 14(1). [https://doi.org/10.3390/w14010011 doi: 10.3390/w14010011]  [https://www.mdpi.com/2073-4441/14/1/11 Open Access Article].</ref>) and (b) a mountain stream in summer (modified from Briggs ''et al.''<ref>Briggs, M.A., Wang, C., Day-Lewis, F.D., Williams, K.H., Dong, W., Lane, J.W., 2019. Return Flows from Beaver Ponds Enhance Floodplain-to-River Metals Exchange in Alluvial Mountain Catchments. Science of the Total Environment, 685, pp. 357–369. [https://doi.org/10.1016/j.scitotenv.2019.05.371 doi: 10.1016/j.scitotenv.2019.05.371].  [//www.enviro.wiki/images/6/63/BriggsEtAl2019.pdf Open Access Manuscript]</ref>) that both capture multiscale groundwater discharge processes. Figure reproduced from Mangel ''et al.''<ref>Mangel, A.R., Dawson, C.B., Rey, D.M., Briggs, M.A., 2022. Drone Applications in Hydrogeophysics: Recent Examples and a Vision for the Future. The Leading Edge, 41 (8), pp. 540–547. [https://doi.org/10.1190/tle41080540.1 doi: 10.1190/tle41080540].</ref>]]
[[Wikipedia: Unmanned aerial vehicle | Unoccupied aerial vehicles (UAVs)]] equipped with infrared (IR) cameras can provide a very powerful tool for rapidly determining zones of pronounced upwelling of GW into SW. Large areas can be covered with high spatial resolution. The information obtained can be used to rapidly define locations of focused GW upwelling and prioritize these for more intensive surface-based observations (Figure 1). As with all thermal methods, flights must be performed when adequate contrasts in temperature between SW and GW are expected to exist. Not just time of year but, because of the effect of the diurnal temperature signal on surface water bodies, time of day might need to be considered in order to maximize the chance of success. Calibration of UAV-IR camera measurements against simultaneously acquired direct measurements of temperature is recommended to optimize the value of these datasets. UAV-IR methods will not work in all situations. One major limitation of the technology is that the temperature expression of groundwater upwelling must be manifested at the surface of the surface-water body. Consequently, the technology will not detect relatively small discharges occurring beneath a relatively deep surface-water layer, and thermal imaging over the water surface can be complicated by thermal IR reflection. The chances of success with UAV-IR will be strongest in regions of exposed banks or shallow water where there are no strong currents causing mixing (and thus dilution) of the upwelling GW temperature signals. UAV-IR methods will therefore likely be most successful close to shorelines of lakes and ponds, over shallow, low-flow streams and rivers, and in wetland environments. UAV-IR methods require a licensed pilot, and restrictions on the use of airspace may limit the application of this technology.

=====''Handheld Thermal Infrared (TIR) Cameras''=====
[[File:IeryFig2.png | thumb|left |600px|Figure 2. (a) A TIR camera set up to image groundwater discharges to surface water (b) TIR data inset on a visible light photograph. Cooler (blue) bank seepage groundwater is discharging into warmer (red) stream water (temperature scale in degrees). Both photographs courtesy of Martin Briggs, USGS.]]
Hand-held thermal infrared (TIR) cameras are powerful tools for visual identification of localized seeps of upwelling groundwater. TIR cameras may be used to follow up on UAV-IR surveys to better characterize local seeps identified from the air using UAV-IR. Alternatively, a TIR camera is a valuable tool when performing initial walks of prospective study sites as they may quickly confirm the presence of suspected seeps. TIR cameras provide high resolution images that can define the structure of localized seeps and may provide valuable insights into the role of discrete features (e.g., fractures in rocks or pipes in soil) in determining seep morphology (Figure 2). Like UAV-IR, TIR provides primarily qualitative information (location, extent) of seeps, and it only succeeds when there are adequate contrasts between GW and SW that are expressed at the surface of the investigated water body or along bank sediments. The USGS has made extensive use of TIR cameras for studying GWSWE.

=====''Continuous Near-bed Temperature Sensing''=====
When performing surveys from a boat, a simple yet often powerful technology is continuous
near-bed temperature sensing, whereby a temperature probe is strategically suspended to float in the water column just above the bed or dragged along it. Compared to UAV-IR, this approach does not rely on upwelling groundwater being expressed as a temperature anomaly at the surface. The utility of the method can be enhanced when a specific conductance (SC) probe is co-located with the temperature probe so that anomalies in both temperature and SC can be investigated.

====Monitoring Methods====
Monitoring methods allow temperature signals to be recorded with high temporal resolution along the bed interface or within bank or bed sediments. These methods can capture temporal trends in GWSWE driven by variations in the hydraulic gradients around surface water bodies, as well as changes in [[Wikipedia: Hydraulic conductivity | hydraulic conductivity]] due to sedimentation, clogging, scour or microbial mass. If vertical profiles of bed temperature are collected, a range of analytical and numerical models can be applied to infer the vertical water flux rate and direction, similar to a seepage meter. These fluxes may vary as a function of season, rainfall events (enhanced during storm activity), tidal variability in coastal settings and due to engineered controls such as dam discharges. The methods can capture evidence of GWSWE that may not be detected during a single ‘characterization’ survey if the local hydraulic conditions at that point in time result in relatively weak hydraulic gradients.

=====''Fiber-optic Distributed Temperature Sensing (FO-DTS)''=====
[[File:IeryFig3.png | thumb|600px|Figure 3. (a) Basic concept of FO-DTS based on backscattering of light transmitted down a fiber optic cable (b) Example of riverbed temperature data acquired over time and space in relation to variation in river stage (black line) modified from Mwakanyamale ''et al.''<ref>Mwakanyamale, K., Slater, L., Day-Lewis, F., Elwaseif, M., Johnson, C., 2012. Spatially Variable Stage-Driven Groundwater-Surface Water Interaction Inferred from Time-Frequency Analysis of Distributed Temperature Sensing Data. Geophysical Research Letters, 39(6). [https://doi.org/10.1029/2011GL050824 doi: 10.1029/2011GL050824].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011GL050824 Open Access Article]</ref> (c) spatial distribution of riverbed temperature and correlation coefficient (CC) between riverbed temperature and river stage for a 1.5 km stretch along the Hanford 300 Area adjacent to the Columbia River (modified from Slater ''et al.''<ref name="Slater2010" />). Data are shown for winter and summer. Orange contours show uranium concentrations (μg/L) in groundwater measured in boreholes.]]
Fiber-optic distributed temperature sensing (FO-DTS) is a powerful monitoring technology used in fire detection, industrial process monitoring, and petroleum reservoir monitoring. The method is also used to obtain [https://www.usgs.gov/mission-areas/water-resources/science/fiber-optic-distributed-temperature-sensing-technology spatially rich datasets for monitoring GWSWE]<ref name="Selker2006">Selker, J.S., Thévenaz, L., Huwald, H., Mallet, A., Luxemburg, W., van de Giesen, N., Stejskal, M., Zeman, J., Westhoff, M., Parlange, M.B., 2006. Distributed Fiber-Optic Temperature Sensing for Hydrologic Systems. Water Resources Research, 42 (12). [https://doi.org/10.1029/2006WR005326 doi: 10.1029/2006WR005326].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2006WR005326 Open Access Article]</ref><ref name="Tyler2009">Tyler, S.W., Selker, J.S., Hausner, M.B., Hatch, C.E., Torgersen, T., Thodal, C.E., Schladow, S.G., 2009. Environmental Temperature Sensing Using Raman Spectra DTS Fiber-Optic Methods. Water Resources Research, 45(4). [https://doi.org/https://doi.org/10.1029/2008WR007052 doi: 10.1029/2008WR007052].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2008WR007052 Open Access Article]</ref>. The FO-DTS sensor consists of standard telecommunications optical fiber typically housed in an armored cable. The physics underlying FO-DTS measurements is based on temperature-dependent backscatter mechanisms including [[Wikipedia: Brillouin scattering | Brillouin]] and [[Wikipedia: Raman scattering | Raman backscatter]]<ref name="Selker2006" />. Most commercially available systems are based on analysis of Raman scatter. As laser light is transmitted down the fiber-optic cable, light scatters continuously back toward the instrument from all along the fiber, with some of the scattered light at frequencies above and below the frequency of incident light, i.e., [[Wikipedia: Raman scattering#Raman scattering | anti-Stokes and Stokes-Raman backscatter]], respectively. The ratio of anti-Stokes to Stokes energy provides the basis for FO-DTS measurements. Measurements are localized to a section of cable according to a time-of-flight calculation (i.e., [[Wikipedia: Optical time-domain reflectometer | optical time-domain reflectometry]]). Assuming the speed of light within the fiber is constant, scatter collected over a specific time window corresponds to a specific spatial interval of the fiber. Although there are tradeoffs between spatial resolution, thermal precision, and sampling time, in practice it is possible to achieve sub meter-scale spatial resolution and approximately 0.1°C thermal precision for measurement cycle times on the order of minutes and cables extending several kilometers<ref name="Tyler2009" />; thus, thousands of temperature measurements can be made simultaneously along a single cable. The method allows the visualization of a large amount of temperature data and rapid identification of major trends in GWSWE. Figure 3 illustrates the use of FO-DTS to detect and monitor zones of focused GW discharge along a 1.5 km reach of the Columbia River that is threatened by contaminated groundwater<ref name="Slater2010">Slater, L.D., Ntarlagiannis, D., Day-Lewis, F.D., Mwakanyamale, K., Versteeg, R.J., Ward, A., Strickland, C., Johnson, C.D., Lane Jr., J.W., 2010. Use of Electrical Imaging and Distributed Temperature Sensing Methods to Characterize Surface Water-Groundwater Exchange Regulating Uranium Transport at the Hanford 300 Area, Washington. Water Resources Research, 46(10). [https://doi.org/10.1029/2010WR009110 doi: 10.1029/2010WR009110].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2010WR009110 Open Access Article]</ref>. As temperature is only sensed at the location of the cable on the bed, FO-DTS can only detect GW inputs to SW. It cannot detect losses of surface water to groundwater. The USGS public domain software tool [https://www.usgs.gov/software/dtsgui DTSGUI] allows a user to import, manage, visualize and analyze FO-DTS datasets.

=====''Vertical Temperature Profilers (VTPs)''=====
Analysis methods now allow for the accurate quantification of groundwater fluxes over time based on temperature measurements. Vertical temperature profilers (VTPs) are sensors applied for diurnal temperature data collection within saturated geologic matrices (Figure 4). Extensive experience with VTPs indicates that the methodology is equal to traditional seepage meters in terms of flux accuracy<ref>Hare, D.K., Briggs, M.A., Rosenberry, D.O., Boutt, D.F., Lane Jr., J.W., 2015. A Comparison of Thermal Infrared to Fiber-Optic Distributed Temperature Sensing for Evaluation of Groundwater Discharge to Surface Water. Journal of Hydrology, 530, pp. 153–166. [https://doi.org/10.1016/j.jhydrol.2015.09.059 doi: 10.1016/j.jhydrol.2015.09.059].</ref>. However, VTPs have the advantage of measuring continuous temporal variations in flux rates while such information is impractical to obtain with traditional seepage meters.
[[File:IeryFig4.png |thumb|600px|left|Figure 4. (a) Schematic of different VTP setups including (from left to right) thermistors in a piezometer, thermistors embedded in a solid rod and wrapped FO-DTS cable modified from Irvine et al.<ref name="Irvine2017a">Irvine, D.J., Briggs, M.A., Cartwright, I., Scruggs, C.R., Lautz, L.K., 2016. Improved Vertical Streambed Flux Estimation Using Multiple Diurnal Temperature Methods in Series. Groundwater, 55(1), pp. 73-80. [https://doi.org/10.1111/gwat.12436 doi: 10.1111/gwat.12436].</ref>; (b) construction of VTPs showing thermistors embedded in rods and subsequent insulation; (c) example dataset plotted in 1DTempPro showing 5 days of streambed temperature at 6 streambed depths<ref>Koch, F.W., Voytek, E.B., Day-Lewis, F.D., Healy, R., Briggs, M.A., Lane Jr., J.W., Werkema, D., 2016. 1DTempPro V2: New Features for Inferring Groundwater/Surface-Water Exchange. Groundwater, 54(3), pp. 434–439. [https://doi.org/10.1111/gwat.12369 doi: 10.1111/gwat.12369].</ref>.]]

The low-cost design, ease of data collection, and straightforward interpretation of the data using open-source software make VTP sensors increasingly attractive for quantifying flux rates. These sensors typically consist of at least two temperature loggers installed within a steel or plastic pipe filled with foam insulation<ref name="Irvine2017a" /> although the use of loggers installed in well screens or FO-DTS cable wrapped around a piezometer casing (for high vertical resolution data) are also possible (Figure 4a). Loggers are inserted into the insulated housing at different depths, typically starting from one centimeter within the geologic matrix of interest<ref name="Irvine2017b"> Irvine, D.J., Briggs, M.A., Lautz, L.K., Gordon, R.P., McKenzie, J.M., Cartwright, I., 2017. Using Diurnal Temperature Signals to Infer Vertical Groundwater-Surface Water Exchange. Groundwater, 55(1), pp. 10–26. [https://doi.org/10.1111/gwat.12459 doi: 10.1111/gwat.12459].  [https://ngwa.onlinelibrary.wiley.com/doi/am-pdf/10.1111/gwat.12459 Open Access Manuscript]</ref>. Temperature loggers usually remain within the first 0.2 meters of the geologic matrix based on the observed limits of diurnal signal influence<ref>Briggs, M.A., Lautz, L.K., Buckley, S.F., Lane Jr., J.W., 2014. Practical Limitations on the Use of Diurnal Temperature Signals to Quantify Groundwater Upwelling. Journal of Hydrology, 519(B), pp. 1739–1751. [https://doi.org/10.1016/j.jhydrol.2014.09.030 doi: 10.1016/j.jhydrol.2014.09.030].</ref>, though zones of strong surface-water downwelling may necessitate deeper temperature data collection. Reliability of flux values generated from the temperature signal analysis is dependent in part on the temperature logger precision, VTP placement, sediment heterogeneity, flow direction, flow magnitude<ref name="Irvine2017b" />, and absence of macropore flow. Application of single dimension temperature-based fluid flux models assumes that all flow is vertical, and therefore lateral flow within upwelling systems cannot be quantified using VTPs, emphasizing the importance of installing the VTP directly over the active area of exchange<ref name="Irvine2017b" /> at shallow depths. Thermal parameters of the geologic matrix where the VTP is installed can be measured using a thermal properties analyzer to record heat capacity and thermal conductivity for later analytical and numerical modeling.

One-dimensional (1D) analytical and numerical solutions, used to solve or estimate the advection-conduction equation within the geologic matrix (bed sediments), continue to evolve to better quantify flux values over time. Analytical solutions to the heat transport equation are used to solve for flux values between sensor pairs from VTP datasets<ref name="Gordon2012">Gordon, R.P., Lautz, L.K., Briggs, M.A., McKenzie, J.M., 2012. Automated Calculation of Vertical Pore-Water Flux from Field Temperature Time Series Using the VFLUX Method and Computer Program. Journal of Hydrology, 420–421, pp. 142–158. [https://doi.org/10.1016/j.jhydrol.2011.11.053 doi: 10.1016/j.jhydrol.2011.11.053].</ref><ref name="Irvine2015">Irvine, D.J., Lautz, L.K., Briggs, M.A., Gordon, R.P., McKenzie, J.M., 2015. Experimental Evaluation of the Applicability of Phase, Amplitude, and Combined Methods to Determine Water Flux and Thermal Diffusivity from Temperature Time Series Using VFLUX 2. Journal of Hydrology, 531(3), pp. 728–737. [https://doi.org/10.1016/j.jhydrol.2015.10.054 doi: 10.1016/j.jhydrol.2015.10.054].</ref>. [https://data.usgs.gov/modelcatalog/model/a54608c5-ea6c-4d61-afc4-1ae851f46744 VFLUX] is an open-source [https://www.mathworks.com/products/matlab.html MATLAB] package that allows the user to solve for flux values from a VTP dataset using a variety of analytical solutions<ref name="Gordon2012" /><ref name="Irvine2015" /> based on the vertical propagation of diurnal temperature signals. Other emerging ‘spectral’ methods make use of a wide range of natural temperature signals to estimate vertical flux and bed sediment thermal diffusivity<ref>Sohn, R.A., Harris, R.N., 2021. Spectral Analysis of Vertical Temperature Profile Time-Series Data in Yellowstone Lake Sediments. Water Resources Research, 57(4), e2020WR028430. [https://doi.org/10.1029/2020WR028430 doi: 10.1029/2020WR028430].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020WR028430 Open Access Article]</ref>. VFLUX analytical solutions are limited by subsurface heterogeneity and diurnal temperature signal strength<ref name="Irvine2017b" />. [https://data.usgs.gov/modelcatalog/model/82fe0c15-97f5-4f6a-b389-b90f9bad615e 1DTempPro] (Figure 4c), a free open-source program available from USGS, provides a graphical user interface (GUI) for numerical solutions to heat transport<ref>Koch, F.W., Voytek, E.B., Day-Lewis, F.D., Healy, R., Briggs, M.A., Werkema, D., Lane Jr., J.W., 2015. 1DTempPro: A Program for Analysis of Vertical One-Dimensional (1D) Temperature Profiles v2.0. U.S. Geological Survey Software Release. [http://dx.doi.org/10.5066/F76T0JQS doi: 10.5066/F76T0JQS].  [https://data.usgs.gov/modelcatalog/model/82fe0c15-97f5-4f6a-b389-b90f9bad615e Free Download from USGS]</ref> and does not depend on diurnal signals. Numerical models can produce more accurate flux estimates in the case of complex boundary conditions, significant heterogeneity, or abrupt changes in flux rates, but require significant user calibration efforts for longer time series<ref name="McAliley2022"> McAliley, W.A., Day-Lewis, F.D., Rey, D., Briggs, M.A., Shapiro, A.M., Werkema, D., 2022. Application of Recursive Estimation to Heat Tracing for Groundwater/Surface-Water Exchange. Water Resources Research, 58(6), Article e2021WR030443. [https://doi.org/10.1029/2021WR030443 doi: 10.1029/2021WR030443].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2021WR030443 Open Access Article]</ref>. A hybrid approach between the analytical and numerical solutions, known as [https://www.sciencebase.gov/catalog/item/60a55c71d34ea221ce48b9e7 Tempest1d]<ref name="McAliley2022" /> improves flux modeling with enhanced computational efficiency, resolution of abrupt changes, evaluation of complex boundary conditions, and uncertainty estimations with each step. This new state-space modeling approach uses recursive estimation techniques to automatically estimate highly dynamic vertical flux patterns ranging from sub-daily to seasonal time scales<ref name="McAliley2022" />.

===Electrical Conductivity (EC) Based Technologies===
Electrical conductivity (EC)-based technologies exploit contrasts in EC between surface water and groundwater<ref>Cox, M.H., Su, G.W., Constantz, J., 2007. Heat, Chloride, and Specific Conductance as Ground Water Tracers near Streams. Groundwater, 45(2), pp. 187–195. [https://doi.org/10.1111/j.1745-6584.2006.00276.x doi: 10.1111/j.1745-6584.2006.00276.x].</ref>. EC-based technologies are mostly applied as characterization tools, although the opportunity to monitor GWSWE dynamics with one of these technologies does exist. With the exception of specific conductance probes, the technologies measure the bulk EC of sediments, which will often (but not always) reveal evidence of GWSWE.

Electrical conduction (i.e., the transport of charges) in SW occurs via dissolved ions. Electrical conduction in soils similarly occurs via the ions dissolved in groundwater, with an additional contribution from ions in the electrical double layer that exists at mineral-pore fluid interfaces (known as surface conduction)<ref name="Binley2020">Binley, A., Slater, L., 2020. Resistivity and Induced Polarization: Theory and Applications to the Near-Surface Earth. Cambridge University Press. [https://doi.org/10.1017/9781108685955 doi: 10.1017/9781108685955].</ref>. In relatively fresh surface-water environments, GW is typically more electrically conductive than SW due to the higher ionic concentrations in GW. In these settings, GW inputs to SW may be identified as zones of higher bulk EC beneath the bed. In coastal settings where SW is saline, inputs of relatively fresh GW will give rise to zones of lower conductivity. Whereas the temperature-based methods rely on point measurements at the location of the sensor, EC-based technologies (with the exception of specific conductance measurements at localized points) incorporate inverse modeling to estimate distributions of EC away from the sensors and beneath the bed. Consequently, these technologies may also image losses of SW to GW<ref>Johnson, T.C., Slater, L.D., Ntarlagiannis, D., Day-Lewis, F.D., Elwaseif, M., 2012. Monitoring Groundwater-Surface Water Interaction Using Time-Series and Time-Frequency Analysis of Transient Three-Dimensional Electrical Resistivity Changes. Water Resources Research, 48(7). [https://doi.org/10.1029/2012WR011893 doi: 10.1029/2012WR011893].  [https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2012WR011893 Open Access Article]</ref>. Another advantage is that they may provide information on structural controls on zones of focused GWSWE expressed at the surface. However, interpretation of EC patterns from these technologies is inherently uncertain due to the fact that (with the exception of specific conductance probes) the bulk EC of the sediments is measured. Variations in lithology (e.g., porosity, grain size distribution, which determine the strength of surface conduction) can be misinterpreted as variations in the ionic composition of water.

====Characterization Methods====

=====''Specific Conductance Probes''=====
The simplest EC-based technology is a specific conductance probe, which measures the specific conductance of water between a small pair of metal plates at the end of the sensor probe. Many commercially available water quality sensors have a specific conductance sensor and a temperature sensor integrated into a single probe (they often also measure other water quality parameters, including pH and dissolved oxygen (DO) content). These are direct sensing measurements with a small footprint (the size of the sensor), so this is usually a time-consuming, inefficient method for observing GWSWE dynamics. Furthermore, the sampling volume of the measurement is small (on the order of a cubic centimeter or less), so the degree to which the spot measurement is representative of larger-scale hydrological exchanges is often uncertain. However, specific conductance sensors remain popular, especially when integrated with a point temperature sensor, such as in the [https://clu-in.org/programs/21m2/navytools/gsw/#trident Trident Probe].

=====''Frequency Domain Electromagnetic (EM) Sensing Systems''=====
[[File:IeryFig5.png |thumb|600px|Figure 5. (a) FDEM survey path within a stream and drainage channel network bisecting a wetland complex experiencing localized upwelling of contaminated groundwater (b) operation of an FDEM sensor (Dualem 421S, Dualem, CA) in this shallow stream environment (c) resulting imaging of EC structure in the upper 6 m of streambed sediments. In this case, variations in EC may result from changes in sediment texture that determine the location of focused GWSWE. Dataset acquired under [https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ESTCP project ER21-5237].]]
Electromagnetic (EM) sensors non-invasively measure the bulk EC of sediments (a function of both fluid composition and lithology as mentioned above) by measuring eddy currents induced in conductors using time varying electric and magnetic fields based on the physics of electromagnetic induction. Modern EM systems can simultaneously image across a range of depths. Frequency domain EM (FDEM) instruments generate a current that varies sinusoidally with time at a fixed frequency that is selected on the basis of desired exploration depth and resolution. Modern FDEM sensors use a combination of different coil separations and/or frequencies to resolve conductivity structure over a range of depths. These instruments typically provide high-resolution (sub-meter) information on the bulk EC structure in the upper 5 m of the subsurface (approximately, depending on subsurface EC). Measurements are non-invasively and continuously made, meaning that large areas can be quickly surveyed on foot (e.g., along a shoreline) or from a boat in shallow water (1 m or less deep), for example when pulled along a river or stream channel. The method can also be deployed in wetlands (Figure 5). FDEM data are often presented in terms of variations in the raw measurements because apparent EC values do not represent the true EC of the subsurface. However, with the increasing popularity of sensors with combinations of coil separations, the datasets can be inverted to obtain a model of the distribution of the true EC of the subsurface on land or below a water layer. Inversion of FDEM datasets is usually performed as a series of 1D models, constrained to have a limited variance from each other, to generate a pseudo-2D model of the subsurface. Open-source software, such as [https://hkex.gitlab.io/emagpy/ EMagPy]<ref>McLachlan, P., Blanchy, G., Binley, A., 2021. EMagPy: Open-Source Standalone Software for Processing, Forward Modeling and Inversion of Electromagnetic Induction Data. Computers and Geosciences, 146, 104561. [https://doi.org/10.1016/j.cageo.2020.104561 doi: 10.1016/j.cageo.2020.104561].</ref>, is freely available to manage, visualize and interpret FDEM datasets.

=====''Time Domain EM Sensing Systems''=====
Time domain EM (TEM) systems transmit a current that is abruptly shut off (reduced to zero), resulting in a transient current flow that propagates (with decaying amplitude) into the earth. The time-decaying voltage recorded in a receiver coil contains information on the EC variation with depth below the instrument. TEM systems specifically designed for waterborne surveys provide investigation depths of up to 70 m (again depending on bulk EC structure)<ref>Lane Jr., J.W., Briggs, M.A., Maurya, P.K., White, E.A., Pedersen, J.B., Auken, E., Terry, N., Minsley, B., Kress, W., LeBlanc, D.R., Adams, R., Johnson, C.D., 2020. Characterizing the Diverse Hydrogeology Underlying Rivers and Estuaries Using New Floating Transient Electromagnetic Methodology. Science of the Total Environment, 740, 140074. [https://doi.org/10.1016/j.scitotenv.2020.140074 doi: 10.1016/j.scitotenv.2020.140074].  [//www.enviro.wiki/images/4/4d/LaneEtAl2020.pdf Open Access Manuscript]</ref>. Airborne TEM systems can also be deployed to look at large-scale surface-water/groundwater dynamics, for example submarine discharge or saline intrusion along coastlines<ref>d’Ozouville, N., Auken, E., Sorensen, K., Violette, S., de Marsily, G., Deffontaines, B., Merlen, G., 2008. Extensive Perched Aquifer and Structural Implications Revealed by 3D Resistivity Mapping in a Galapagos Volcano. Earth and Planetary Science Letters, 269(3–4), pp. 518–522. [https://doi.org/10.1016/j.epsl.2008.03.011 doi: 10.1016/j.epsl.2008.03.011].</ref>. Inverse modelling methods are employed to convert the raw measurements obtained along a transect into a distribution of conductivity.

=====''Waterborne Electrical Imaging''=====
[[File:IeryFig6.png |thumb|600px|left|Figure 6. Waterborne electrical imaging in a coastal setting with expected zones of upwelling groundwater (a) typical operation with floating electrode cable pulled behind boat (b) inverted 2D cross section of electrical resistivity along the survey path with possible zones of fresh groundwater discharges indicated from relatively high resistivity sediments. Dataset acquired under [https://serdp-estcp.mil/projects/details/e4a12396-4b56-4318-b9e5-143c3011b8ff ESTCP project ER21-5237].]]
Direct current (DC) electrical imaging techniques are based on galvanic (direct) contact between electrodes used to inject currents (and measure voltages) and the subsurface<ref name="Binley2020" />. Relative to EM methods, this can be a disadvantage when surveying on land. However, when making measurements from a water body, the electrodes used to acquire the data can be deployed as a floating array that is pulled behind a vessel. Waterborne electrical imaging relies on acquiring measurements of electrical potential differences between different pairs of electrodes on the array while current is passed between one pair of electrodes<ref>Day-Lewis, F.D., White, E.A., Johnson, C.D., Lane Jr, J.W., Belaval, M., 2006. Continuous Resistivity Profiling to Delineate Submarine Groundwater Discharge—Examples and Limitations. The Leading Edge, 25(6), pp. 724–728. [https://doi.org/10.1190/1.2210056 doi: 10.1190/1.2210056]</ref>. As the array is pulled behind the boat, thousands of measurements are made along a survey transect. Similar to the EM methods, inverse methods are used to process these datasets and generate a 2D image of the variation in the conductivity of the sediments below the bed. Open-source software such as [https://hkex.gitlab.io/resipy/ ResIPy] support 2D or 3D inversion of waterborne datasets. Figure 6 shows results of a waterborne electrical imaging survey conducted to locate regions where relative fresh (low EC) groundwater is discharging into the near shore environment in a coastal setting. Beneath the saline (high EC) water layer, spatial variability in bulk EC may partly be related to variations in conductivity of the pore-filling fluid, with localized low bulk EC zones possibly indicating upwelling of fresh groundwater. However, the variation in bulk EC in the sediments below the water layer may reflect variations in lithology. An extension of the electrical imaging method involves collecting induced polarization (IP) data<ref name="Binley2020" /> in addition to bulk EC data. IP measurements capture the temporary charge storage characteristics of the subsurface, which are strongly controlled by lithology, with finer-grained (e.g. clay rich) sediments being more chargeable than coarser grained sediments. The method can be particularly useful for differentiating between EC variations resulting from variations in pore fluid specific conductance and those conductivity variations associated with lithology. For example, based on electrical imaging methods alone (or the EM method alone), it may not be possible to distinguish a zone of high EC groundwater entering into freshwater from a region of relatively finer-grained sediments without additional supporting data (e.g. a core). IP measurements may be able to resolve this ambiguity as the region of finer-grained sediments will be more chargeable than the surrounding areas.

====Monitoring Methods====

=====''Land-based Electrical Monitoring''=====
There is increasing interest in the use of electrical imaging methods as monitoring systems. Semi-permanent arrays of electrodes can be installed to monitor GWSWE dynamics over periods of days to years. Low-power prototype instrumentation has been developed to specifically address the needs for long-term monitoring, although such instrumentation is not yet commercially available. Consequently, electrical monitoring of GWSWE currently remains in the realm of research-driven specialists.

===Considerations for Using Waterborne EM and Electrical Imaging Methods===
The waterborne EM and electrical imaging methods both provide a way to determine variations in bulk electrical conductivity associated with GWSWE. However, each method has some advantages and some disadvantages. One consideration is maneuverability, particularly in shallow water environments. FDEM instruments are the most maneuverable, although they offer only limited investigation depths. Although bigger than the shallow-sensing FDEM systems, TEM systems are still relatively maneuverable on water bodies. Whereas FDEM systems can be operated from a single small vessel, the TEM deployments require the use of pontoons as the transmitter and receiver coils need to be separated 9 m apart. This still equates to good maneuverability compared to waterborne electrical imaging where a floating electrode cable, typically 30-50 m long, is pulled behind a vessel.

In all three methods, variations in the water layer depth and the specific conductance of the water can significantly affect the data, especially in deeper water. Therefore, it is common to continuously record these parameters with an echo depth sounder and a specific conductance probe suspended in the water layer, with a GPS receiver to record continuous spatial data.

===Other Hydrogeophysical Technologies===
A number of other hydrogeophysical technologies exist, with proven applications to the characterization of settings where GWSWE occurs. Seismic [[Wikipedia:Reflection seismology | reflection]] and [[Wikipedia:Seismic refraction | refraction]] methods are used to image the depositional environments along coastlines. [[Wikipedia:Ground-penetrating radar | Ground penetrating radar]] has been effectively used to image depositional environments around freshwater lake shorelines, and across streams and rivers. Such information may help to identify depositional features that promote GWSWE but, unlike the temperature- and conductivity-based methods, do not sense changes in physical properties associated with the exchanging water itself.

One promising technique for detecting GWSWE is known as the [https://www.epa.gov/environmental-geophysics/self-potential-sp self-potential (SP)] method. This simple to deploy geophysical technique is based on mapping voltage differences caused by natural sources of electric current in the Earth that are generated through a number of coupled flow processes, one being the coupling of pore fluid flow and transport of electric charge. Zones of enhanced seepage within a porous medium can result in a significant ‘streaming potential’ due to charge transport induced by fluid flow. This phenomenon has been effectively used to locate zones of leakage through dams and embankments<ref>Panthulu, T.V, Krishnaiah, C., Shirke, J.M., 2001. Detection of Seepage Paths in Earth Dams Using Self-Potential and Electrical Resistivity Methods. Engineering Geology, 59(3-4), pp. 281–295. [https://doi.org/10.1016/S0013-7952(00)00082-X doi: 10.1016/S0013-7952(00)00082-X].</ref>. Recently, floating SP measurements have been used to define gaining and losing portions of streams and to identify evidence of focused exchange<ref>Ikard, S.J., Teeple, A.P., Payne, J.D., Stanton, G.P., Banta, J.R., 2018. New Insights On Scale-Dependent Surface-Groundwater Exchange from a Floating Self-Potential Dipole. Journal of Environmental and Engineering Geophysics, 23(2), pp. 261–287. [https://doi.org/10.2113/JEEG23.2.261 doi: 10.2113/JEEG23.2.261].</ref>. Although the data acquisition is simple, consisting of a pair of non-polarizing electrodes and a voltmeter, the interpretation of SP measurements requires expert knowledge to filter out confounding contributions to the recorded signals.

==Guidelines for Implementing Hydrogeophysical Methods into GWSWE Studies==
A number of factors will affect the success of individual hydrogeophysical methods at a specific
site of GWSWE. Depending on site conditions and the objective, some methods may be inappropriate to deploy. For example, temperature-based methods will most likely succeed at times of the year and times of day when contrasts between upwelling groundwater and surface water are greatest. In contrast, it is quite possible that some sites of GWSWE will have an insufficient contrast in the specific conductance of the GW versus the SW to make techniques based on EC measurements effective. A groundwater-surface water method selection tool ([https://water.usgs.gov/water-resources/software/GW-SW-MST/ GW/SW-MST]<ref>Hammett, S., Day-Lewis, F.D., Trottier, B., Barlow, P.M., Briggs, M.A., Delin, G., Harvey, J.W., Johnson, C.D., Lane Jr., J.W., Rosenberry, D.O., Werkema, D.D., 2022. GW/SW-MST: A Groundwater/Surface-Water Method Selection Tool. Groundwater, 60(6), pp. 784-791. [https://doi.org/10.1111/gwat.13194 doi: 10.1111/gwat.13194].  [https://ngwa.onlinelibrary.wiley.com/doi/am-pdf/10.1111/gwat.13194 Open Access Manuscript]</ref>) has recently been developed to assist practitioners in the informed selection of the methods that will be most effective for a particular site at a particular time. The tool guides the user through a series of questions that consider both the specific conditions at the site and the primary objectives of the investigation. The methods selection tool covers the application of a number of additional technologies besides those included in this article. The selection tool is recommended as the starting point for any practitioner needing to investigate potential GWSWE.

==Summary==
A number of temperature-based and electrical conductivity-based technologies exist for monitoring GWSWE over a range of spatial scales. Many of these technologies are most powerful when used as reconnaissance tools to rapidly identify probable locations of GWSWE to be verified with a limited campaign of direct sensing measurements (traditionally seepage meters). Vertical temperature profilers (VTPs) offer direct quantification of fluxes at sites identified by the reconnaissance tools, and some studies show that these methods are more reliable than traditional seepage meters. Given the number of sites across the globe where contaminated groundwater is impacting surface water resources, use of these technologies for both characterization and monitoring is expected to become more common.

==References==
<references />

==See Also==
USGS Water Resources:

*https://www.usgs.gov/mission-areas/water-resources/science/geophysics-usgs-groundwatersurface-water-exchange-studies

*https://www.usgs.gov/mission-areas/water-resources/science/thermal-imaging-cameras-studying-groundwatersurface-water

*https://www.usgs.gov/mission-areas/water-resources/science/fiber-optic-distributed-temperature-sensing-technology

*https://www.usgs.gov/mission-areas/water-resources/science/integration-suas-hydrogeophysical-studies

Dr. Dimitrios Ntarlagiannis

2025-02-19T21:35:36Z

==Work and Contact Information==

EMPLOYER:
:Rutgers University Newark 
:Department of Earth & Environmental Sciences 
:101 Warren Street, Smith 135 
:Newark, NJ 07102

EMAIL: [mailto:dimntar@newark.rutgers.edu dimntar@newark.rutgers.edu]

==About the Contributor==
Dr. Ntarlagiannis is a geophysicist with expertise in electrical methods. His research is focused on the use of geophysical methods for environmental, hydrological and geological applications. He is also very interested in the geophysical signatures of biogeochemical processes, and how we can use them as a characterization and monitoring tool.

==Article Contributions==
*[[Hydrogeophysical Methods for Characterization and Monitoring of Groundwater-Surface Water Exchanges]]

__NOTOC__

[[Category: Contributors|Ntarlagiannis]]

Contributors

2025-02-06T19:03:03Z

Debra Tabron:

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|'''Executive Editor'''
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|[[Dr. Bilgen Yuncu, P.E. | Bilgen Yuncu, PhD, PE]]
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|TRC, Cary NC
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|''Technical Editor''
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|Jim Hurley, MS, EIT
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|TRC, Cary NC
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|''Administrative Assistant''
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|Debra Tabron
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|TRC, Cary NC
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__NOTOC__

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|-
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{| style="width: 100%;margin: left; text-align:left;"
|-
| style="width:13.3%" |[[Dr._David_Adamson,_P.E.|David Adamson]]
| style="width:13.3%" |[[Dr. Dora Chiang|Dora Chiang]]
| style="width:13.3%" |[[Dr._Ron_Falta|Ron Falta]]
| style="width:13.3%" |[[Elisabeth_Hawley|Elisabeth Hawley]]
| style="width:13.3%" |[[Thomas_Krug|Thomas Krug]]
| style="width:13.3%" |[[Sara McMillen]]
| style="width:13.3%" |[[Dr._Lee_Slater|Lee Slater]]
|-
|[[Richelle Allen-King]]
|[[Tom_Christy,_P.E.|Tom Christy]]
|[[Dr._Dimin_Fan|Dimin Fan]]
|[[Dr. Julie A. Heath|Julie A. Heath]]
|[[Dr. Kate Kucharzyk|Kate Kucharzyk]]
|[[Dr. Jonathan Miles|Jonathan Miles]]
|[[Dr. Timothy J. Strathmann|Timothy Strathmann]]
|-
|[[Dr. Richard Anderson|Richard "Hunter" Anderson]]
|[[Dr. Pei Chiu|Pei Chiu]]
|[[Dr. Shahla Farhat |Shahla Farhat]]
|[[Dr. Brian Helms|Brian Helms]]
|[[Poonam Kulkarni|Poonam Kulkarni]]
|[[Larry Mullins]]
|[[Dr. Hans Stroo|Hans Stroo]]
|-
|[[Dr. Michael Annable, P.E.|Michael Annable]]
|[[Dr._Kung-Hui_(Bella)_Chu|Bella Chu]]
|[[Paul Favara|Paul Favara]]
|[[Dr._Gorm_Heron|Gorm Heron]]
|[[Dr. Johnsie Ray Lang|Johnsie Ray Lang]]
|[[Dr. Fadime Murdoch|Fadime Murdoch]]
|[[Dr._Susan_Taylor|Susan Taylor]]
|-
|[[Dr. Sabine E. Apitz|Sabine E. Apitz]]
|[[Dr. Jason Conder|Jason Conder]]
|[[Dr. Jack Feminella|Jack Feminella]]
|[[Dr._Christopher_Higgins|Christopher Higgins]]
|[[M. Tony Lieberman|Tony Lieberman]]
|[[Dr. Robert Murdoch|Robert Murdoch]]
|[[Dr. Selma Mededovic Thagard|Selma Thagard]]
|-
|[[Dr._Brett_Baldwin|Brett Baldwin]]
|[[Dr._Michelle_Crimi|Michelle Crimi]]
|[[Dr._Jennifer_Field|Jennifer Field]]
|[[Dr. Thomas Holsen|Thomas Holsen]]
|[[Dr. Gaisheng Liu|Gaisheng Liu]]
|[[Kobe Nagar]]
|[[Dr._Paul_Tratnyek|Paul Tratnyek]]

|-
|[[Dr. Amanda Barker|Amanda Barker]]
|[[Harry Craig]]
|[[Dr._Kevin_Finneran|Kevin Finneran]]
|[[Dr. Brian Hudgens|Brian Hudgens]]
|[[Dr._Barbara_Sherwood_Lollar,_F.R.S.C.|Barbara Lollar]]
|[[Dr._Charles_Newell,_P.E.|Charles Newell]]
|[[Michael_Truex|Michael Truex]]
|-
|[[Dr. Samuel Beal|Samuel Beal]]
|[[Dr. Paul Dahlen|Paul Dahlen]]
|[[Jeff_Fitzgibbons|Jeff Fitzgibbons]]
|[[Dr. John Hummel|John Hummel]]
|[[Dr. Guilherme Lotufo|Guilherme Lotufo]]
|[[Dora_Ogles-Taggart|Dora Ogles-Taggart]]
|[[Michael_R._Walsh,_P.E.,_M.E.|Michael Walsh]]
|-
|[[Lila Beckley]]
|[[Dr. Phillip de Blanc, P.E. |Phil de Blanc]]
|[[Dr._David_L._Freedman|David Freedman]]
|[[Dr. Michael Hyman|Michael Hyman]]
|[[John Lowe|John Lowe]]
|[[Tom_Palaia|Tom Palaia]]
|[[Dr. Meng Wang|Meng Wang]]
|-
|[[Dr. Barbara Bekins|Barbara Bekins]]
|[[Dr. Rula Deeb|Rula Deeb]]
|[[Jeff Gamlin, P.G.|Jeff Gamlin]]
|[[Dan Isenberg]]
|[[Dr. Loren Lund|Loren Lund]]
|[[Dr. Frederic Petit|Frederic Petit]]
|[[Dr. James Weaver|James Weaver]]
|-
|[[Rene Bernier]]
|[[Dr._Miles_Denham|Miles Denham]]
|[[Dr._Jason_Gerhard|Jason Gerhard]]
|[[Dr._Billy_E._Johnson|Billy Johnson]]
|[[Chris_Lutes|Chris Lutes]]
|[[Kien Pham]]
|[[Richard Wenning]]
|-
|[[Sam Bickley]]
|[[Dr. Marc A. Deshusses|Marc Deshusses]]
|[[Dr. Upal Ghosh|Upal Ghosh]]
|[[Dr. Paul C. Johnson|Paul C. Johnson]]
|[[Leah_MacKinnon,_M.A.Sc.,_P._Eng.|Leah MacKinnon]]
|[[Dr. Breanna F. Powers|Breanna F. Powers]]
|[[Dr. Katie van Werkhoven|Katie van Werkhoven]]
|-
|[[Dr. Robert Borden, P.E.|Robert Borden]]
|[[William DiGuiseppi]]
|[[Dr. Scott Grieco|Scott Grieco]]
|[[Jared Johnson]]
|[[Elisse_Magnuson|Elisse Magnuson]]
|[[Dr. Danny Reible|Danny Reible]]
|[[Dr. Hal White|Hal White]]
|-
|[[Dr. Treavor H. Boyer|Treavor Boyer]]
|[[Dr._Katerina_Dontsova|Katerina Dontsova]]
|[[Dr. Natalie Griffiths|Natalie Griffiths]]
|[[Dr. Warren Kadoya|Warren Kadoya]]
|[[Dr. Shaily Mahendra|Shaily Mahendra]]
|[[Dr._Stephen_Richardson|Stephen Richardson]]
|[[Dr. Richard Wilkin|Rick Wilkin]]
|-
|[[Dr. Mark Brusseau|Mark Brusseau]]
|[[Dr. Mark S. Dortch, PE, D.WRE|Mark Dortch]]
|[[Dr. Philip M. Gschwend|Philip M. Gschwend]]
|[[Dr. Roopa Kamath|Roopa Kamath]]
|[[Todd Martin]]
|[[Florent Risacher]]
|[[Dr._John_Wilson|John Wilson]]
|-
|[[Dr. James Butler, Jr.|James Butler]]
|[[Doug_Downey,_P.E.|Doug Downey]]
|[[Dr. Yuanming Guo|Yuanming Guo]]
|[[Dr. Denise Kay|Denise Kay]]
|[[Wesley_McCall,_M.S.,_P.G.|Wesley McCall]]
|[[Gunther Rosen]]
|[[Dr. Suzanne Witt|Suzanne Witt]]
|-
|[[Dr. Richard F. Carbonaro|Richard F. Carbonaro]]
|[[Dr. Elizabeth_Edwards|Elizabeth Edwards]]
|[[Dr. Nathan Hall|Nathan Hall]]
|[[Andrew Kirkman]]
|[[Travis_McGuire|Travis McGuire]]
|[[Dr._Alexandra_Salter-Blanc|Alexandra Salter-Blanc]]
|[[Dr. Bilgen Yuncu, P.E.|Bilgen Yuncu]]
|-
|[[Paula Andrea Cárdenas-Hernández|Paula A. Cárdenas-Hernández]]
|[[Dr. Anderson Ellis|Anderson Ellis]]
|[[James Hatton]]
|[[Deyuan Kong]]
|[[Dr._Thomas_McHugh|Thomas McHugh]]
|[[Dr. Grace Schwartz|Grace Schwartz]]
|[[Matthew Zenker]]
|-
|[[Dr. Grace Chang|Grace Chang]]
|[[Dr. Morgan Evans|Morgan Evans]]
|[[Paul Hatzinger]]
|[[Dr. Rao Kotamarthi|Rao Kotamarthi]]
|[[Michaye_McMaster,_M.Sc.|Michaye McMaster]]
|[[Dr. Austin Scircle|Austin Scircle]]
|
|}
|}
|}

PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)

2025-02-06T18:59:29Z

Debra Tabron:

[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]] Monitored Retention (PMR) is an approach for managing PFAS-affected sites that relies on natural retention processes that can lessen the migration and maximum concentrations of many PFAS at impacted sites. Because PFAS have not yet been shown to degrade to harmless end products by natural abiotic or biological actions, these retention processes (e.g., [[Sorption of Organic Contaminants|sorption]], [[Matrix Diffusion|matrix diffusion]]) are expected to be the primary factors that dictate how PFAS behave and move in the environment <ref>Interstate Technology and Regulatory Council (ITRC) PFAS Team, 2023. Technical/Regulatory Guidance: Per- and Polyfluoroalkyl Substances. [https://pfas-1.itrcweb.org/ ITRC PFAS Home Page] [//www.enviro.wiki/images/3/37/Full-PFAS-Guidance-12.11.2023.pdf Report pdf]</ref><ref name=":0">Newell, C.J., Adamson, D.T., Kulkarni, P.R., Nzeribe, B.N., Connor, J.A., Popovic, J., and Stroo, H.F., 2021a. Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis. Groundwater Monitoring and Remediation, 41(4), pp.76–89. [https://doi.org/10.1111/gwmr.12486 doi: 10.1111/gwmr.12486] [//www.enviro.wiki/images/d/d0/NewellEtAl2021a.pdf Article pdf]</ref><ref name=":1">Newell, C.J., Adamson, D.T., Kulkarni, P.R., Nzeribe, B.N., Connor, J.A., Popovic, J., and Stroo, H.F., 2021b. Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Potential Guidelines. Remediation Journal, 31(4), pp. 7–17. [https://doi.org/10.1002/rem.21697 doi: 10.1002/rem.21697] [//www.enviro.wiki/images/e/e5/NewellEtAl2021b.pdf Article pdf]</ref><ref name=":3">Adamson, D.T., Kulkarni, P.R., Nickerson, A., Higgins, C.P., Field, J., Schwichtenberg, T., Newell, C., and Kornuc, J.J., 2022. Characterization of relevant site-specific PFAS fate and transport processes at multiple AFFF sites. Environmental Advances, 7, p. 100167. [https://doi.org/10.1016/j.envadv.2022.100167 doi: 10.1016/j.envadv.2022.100167] [//www.enviro.wiki/images/a/aa/AdamsonEtAl2022.pdf Article pdf] </ref><ref>Brusseau, M.L., 2018. Assessing the Potential Contributions of Additional Retention Processes to PFAS Retardation in the Subsurface. Science of The Total Environment, 613–614, pp. 176–185. [https://doi.org/10.1016/j.scitotenv.2017.09.065 doi:10.1016/j.scitotenv.2017.09.065.] [//www.enviro.wiki/images/d/de/Brusseau2018manuscript.pdf Article pdf]</ref><ref>Guelfo, J.L., Korzeniowski, S., Mills, M.A., Anderson, J., Anderson, R.H., Arblaster, J.A., Conder, J.M., Cousins, I.T., Dasu, K., Henry, B.J., Lee, L.S., Liu, J., McKenzie, E.R., and Willey, J., 2021. Environmental Sources, Chemistry, Fate, and Transport of Per- and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting. Environmental Toxicology and Chemistry, 40(12), pp. 3234-3260. [https://doi.org/10.1002/etc.5182 doi: 10.1002/etc.5182] [//www.enviro.wiki/images/c/c5/GuelfoEtAl2021.pdf Article pdf] </ref><ref>Guo, B., Zeng, J., and Brusseau, M.L., 2020. A Mathematical Model for the Release, Transport, and Retention of Per‐ and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone. Water Resources Research, 56(2), e2019WR026667. [https://doi.org/10.1029/2019WR026667 doi:10.1029/2019WR026667] [//www.enviro.wiki/images/0/09/GuoEtAl2020.pdf Article pdf]</ref>, and they form the basis for PMR. The PMR concept has been incorporated into a framework (the “PMR Framework”) that can help users determine the suitability of PMR at a specific site or identify the highest priorities among a portfolio of PFAS-affected groundwater sites. The Framework provides guidance on collecting different types of data (lines of evidence) to support a PMR evaluation. It also describes enhanced retention strategies known as PFAS Enhanced Retention (PER) that may be applicable for management of sites where natural retention is insufficient on its own to protect downgradient receptors.

<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

'''Related Article(s): '''

*[[Monitored Natural Attenuation (MNA)]]
*[[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)]]
*[[PFAS Transport and Fate]]

'''Contributor(s): ''' [[Dr. David Adamson, P.E.]], [[Dr. Charles Newell, P.E.]] and [[Dr. Hans Stroo]]

'''Key Resource(s):'''

*[https://serdp-estcp.mil/projects/details/5f0b9092-8c9f-42c4-bf7d-958b963f907e Framework for Evaluating PFAS Monitored Retention at PFAS Groundwater Sites]
*[//www.enviro.wiki/images/d/d0/NewellEtAl2021a.pdf Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis]<ref name=":0" />
*[//www.enviro.wiki/images/e/e5/NewellEtAl2021b.pdf Monitored natural attenuation to manage PFAS impacts to groundwater: Potential guidelines]<ref name=":1" />
*[https://www.enviro.wiki/images/8/8d/NewellEtAl2022.pdf Enhanced Attenuation (EA) Processes to Manage PFAS Plumes in Groundwater]<ref name=":2">Newell, C.J., Javed, H., Li, Y., Johnson, N.W., Richardson, S.D., Connor, J.A., and Adamson, D.T., 2022. Enhanced Attenuation (EA) to Manage PFAS Plumes in Groundwater. Remediation Journal 32(4), pp. 239–257. [https://doi.org/10.1002/rem.21731 doi: 10.1002/rem.21731][//www.enviro.wiki/images/8/8d/NewellEtAl2022.pdf Article pdf]</ref>

==Introduction==
Groundwater sites contaminated with PFAS are difficult to investigate and remediate due to strict cleanup goals, lack of natural degradation mechanisms for some PFAS, and the high mobility and persistence of several PFAS. Several factors contribute to the urgency of developing cost-effective strategies to manage PFAS sites:

*The number of groundwater sites with PFAS that will require some type of management could be in the tens of thousands<ref name=":2" /><ref name=":4">Newell, C.J., Adamson, D.T., Kulkarni, P.R., Nzeribe, B.N., and Stroo, H., 2020. Comparing PFAS to other groundwater contaminants: Implications for remediation. Remediation Journal, 30(3), pp. 7-26. [https://doi.org/10.1002/rem.21645 doi: 10.1002/rem.21645] [//www.enviro.wiki/images/5/51/NewellEtAl2020.pdf Article pdf]</ref>. Recent estimates suggest that there are 50,000 to 60,000 potential PFAS sites in the U.S<ref>Environmental Business Journal (EBJ), 2022. Markets and Technology in Remediation and PFAS, 35 (7/8). </ref><ref>Salvatore, D., Mok, K., Garrett, K.K., Poudrier, G., Brown, P., Birnbaum, L.S., Goldenman, G., Miller, M.F., Patton, S., Poehlein, M., Varshavsky, J., and Cordner, A., 2022. Presumptive Contamination: A New Approach to PFAS Contamination Based on Likely Sources. Environmental Science and Technology Letters, 9(11), pp.983-990. [https://doi.org/10.1021/acs.estlett.2c00502 doi: 10.1021/acs.estlett.2c00502][//www.enviro.wiki/images/d/df/SalvatoreEtAl2022.pdf Article pdf] </ref>.
*No technologies currently exist that are capable of effectively and efficiently destroying PFAS in situ. Furthermore, the remediation industry is unlikely to be able to practically manage the large number of PFAS groundwater plumes using the only two technologies that are currently viable, groundwater pump and treat and in situ sorbents<ref name=":2" />.
*Despite a lack of natural processes that permanently sequester PFAS, there are natural processes can potentially retain PFAS in the subsurface for extended periods, limiting contaminant migration.
*Consequently, retention could be an important factor in reducing the near-term risk associated with PFAS groundwater plumes at some sites and open up approaches for managing PFAS plumes based on retention<ref name=":0" /><ref name=":1" /><ref name=":2" />.
*Even after active remediation, it is likely that low residual concentrations of PFAS will remain in soils and groundwater, and these may also be effectively controlled by retention.

As a result, understanding and potentially relying on processes that reduce PFAS migration rates and mass discharge rates is of considerable interest to site managers. This includes a variety of chemical and geochemical retention processes that have been incorporated into the '''PFAS Monitored Retention (PMR)''' approach that site owners, their consultants, and environmental regulators can use to prioritize and manage their portfolios of PFAS sites.

==PMR versus MNA==
[[File:AdamsonFig1.png | thumb | 600px | Figure 1. Development timeline and key attenuation processes associated with various monitored natural attenuation approaches. Years are approximately when key publications first appeared for each MNA approach.]]
PMR is a similar concept to [[Monitored Natural Attenuation (MNA)|monitored natural attenuation (MNA)]], and the term has recently been adopted in place of MNA to avoid potential confusion with destructive and/or permanent attenuation processes that are part of the MNA strategies for other constituents of concern (COCs). However, many of the processes remain the same, and they are expected to reduce PFAS concentrations and mass discharge during transport from source areas.

The use of management based remedial approaches like MNA to control PFAS plumes poses several challenges, including that traditional MNA applications typically deal with petroleum hydrocarbons and chlorinated solvents, which can naturally break down to harmless end products at many sites. However, MNA as a remedy or site management strategy has been approved by regulators for some non-degrading metals, metalloids, and radionuclides (e.g., chromium, arsenic, and uranium) if the local geochemical conditions can sequester or immobilize these contaminants. This implies that even if some PFAS do not naturally degrade, passive management strategies may be feasible for PFAS plumes in groundwater because PFAS retention processes can help reduce their concentrations. Figure 1 shows how PMR fits into the development timeline for MNA-type approaches for different contaminant classes.

A key concept of PMR is that ''retention'' processes can provide a credible scientific basis for attenuation of PFAS concentrations or mass discharge over time (or distance) at some PFAS sites. The concept of using these processes in a manner similar to MNA to manage PFAS sites was first proposed by Newell ''et al.''<ref name=":0" /><ref name=":1" />, which identified several retention processes, including various sorption mechanisms, geologic matrix diffusion, geochemical conditions that limit the biotransformation of precursors, and dispersion of migrating PFAS plumes. A subsequent paper<ref name=":2" /> distinguished between sequestration/immobilization and retention, noting that while permanent sequestration of PFAS compounds has not been confirmed, significant long term retention processes are likely present. These papers discussed how retention processes vary between different types of specific PFAS and PFAS classes, as well as the critical differences between the terms “retention” and “sequestration” in the context of managing groundwater plumes<ref name=":2" />. These two concepts may be summarized as:

*'''Sequestration (or immobilization):''' The permanent trapping and isolation of a chemical in the environment in a natural or artificial storage compartment, such that the chemical does not impact potential receptors.
*'''Retention:''' The storage of a chemical in the environment so that the chemical is isolated from potential receptors for a certain amount of time.

This distinction is important because permanent sequestration processes for individual PFAS in the subsurface have yet to be established. Conversely, the MNA approach designed for metals and radionuclides uses the term ''immobilization'' as a key process for implementing MNA<ref>U.S. Environmental Protection Agency, 2007. Monitored natural attenuation of inorganic contaminants in groundwater, Volume 2 Assessment for Non-Radionuclides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium, Edited by R.G. Ford, R.T. Wilkin, and R.W. Puls. [https://nepis.epa.gov/Exe/ZyNET.exe/60000N76.txt?ZyActionD=ZyDocument&Client=EPA&Index=2006%20Thru%202010&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5CZYFILES%5CINDEX%20DATA%5C06THRU10%5CTXT%5C00000002%5C60000N76.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=hpfr&DefSeekPage=&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=4# EPA/600/R-07/140]. [//www.enviro.wiki/images/3/3a/USEPA-2007-MNA_of_Inorganic_Contaminants_in_GW%2C_Vol_2.pdf Report pdf]</ref>. In the case of PMR, the focus is on ''retention'' processes that reduce the mobility and risk associated with PFAS in the subsurface.

==PFAS Retention Processes==
[[File:AdamsonFig2.png | thumb | 800px | left | Figure 2. Overview of PFAS fate and transport processes that can contribute to retention in different subsurface compartments (adapted from Newell et al., 2021a<ref name=":0" />).]]
Key retention processes for PFAS in the subsurface (shown in Figure 2) include:

'''Sorption''' of PFAS to solid phases like soil particles has been well documented. It depends on mechanisms like [[wikipedia:Hydrophobic_effect|hydrophobic]] sorption and electrostatic interactions which are a function of the physical-chemical properties of the PFAS and the environmental matrices<ref name=":0" />. In addition, air-water interfacial sorption of PFAS can be an important retention process in the unsaturated zone due to the presence of porewater and air-filled pore space in that soil compartment. In general, these can be considered “geologic retention” processes because they directly relate to interactions between PFAS and the surrounding porous media.

[[Matrix Diffusion|'''Matrix Diffusion''']] refers to the diffusion of chemicals into and out of low-permeability soils (e.g., clays, silts) that are present in heterogeneous geologic settings. Previous studies with non-PFAS contaminants have shown that the mass retained in low-permeability units can serve as a persistent source of contaminants in groundwater<ref>Chapman, S.W., and Parker, B.L., 2005. Plume persistence due to aquitard back diffusion following dense nonaqueous phase liquid source removal or isolation. Water Resources Research, 41(12), p. W12411. [https://doi.org/10.1029/2005WR004224 doi: 10.1029/2005WR004224] [//www.enviro.wiki/images/a/a0/Chapman2005.pdf Article pdf] </ref>. Recent research has shown that matrix diffusion can also play a significant role in attenuating the expansion of groundwater plumes for non-degrading or highly recalcitrant compounds like [[wikipedia:Perfluorooctanesulfonic_acid|perfluorooctanesulfonic acid (PFOS)]]<ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., and Newell, C.J., 2022. Modeling a Well-Characterized Perfluorooctane Sulfonate (PFOS) Source and Plume Using the REMChlor-MD Model to Account for Matrix Diffusion. Journal of Contaminant Hydrology, 247, p. 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi:10.1016/j.jconhyd.2022.103986][//www.enviro.wiki/images/a/a5/KulkarniEtAl2022.pdf Article pdf] </ref>.

'''Chemical Retention''' refers to the retention of polyfluoroalkyl substances in their “precursor” state. The mobility of these polyfluorinated precursors may be more limited because the head group increases the size of the molecule and may include positive charges that increase sorption to particles. Precursors can be transformed to [[Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)#Nomenclature|perfluoroalkyl acids (PFAAs)]], which are generally more mobile in groundwater but not subject to further degradation under natural conditions. Therefore, precursors can be seen as "chemically retained" PFAS mass. This distinct characteristic means that biotransformation acts as a sink for solvents and hydrocarbons but as a source of PFAAs at PFAS sites. These PFAS precursor transformations appear to occur more rapidly through aerobic biological processes (or after introducing chemical oxidants to remediate other constituents)<ref>Choi, Y.J., Helbling, D.E., Liu, J., Olivares, C.I., and Higgins, C.P., 2022. Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances. Science of the Total Environment, 824, p. 153711. [https://doi.org/10.1016/j.scitotenv.2022.153711 doi: 10.1016/j.scitotenv.2022.153711] [//www.enviro.wiki/images/5/53/ChoiEtAl2022.pdf Article pdf]</ref>, such that chemical retention is more likely under anaerobic conditions.

'''Dispersion''' describes the process by which a groundwater plume spreads out as it moves through porous media. While this process can contribute to natural attenuation of contaminants over time, recent advances in modeling dispersion have shown that it may not be as significant for groundwater plumes as previously assumed<ref>Payne, F.C., Quinnan, J.A. and Potter, S.T., 2008. ''Remediation hydraulics''. CRC Press. ISBN-13: 9780849372490/ ISBN-10: 0849372496</ref>. When a plume reaches a certain length (which can be hundreds or thousands of meters), the weak natural mixing that happens because of transverse dispersion (the dispersion perpendicular to the primary direction of contaminant transport) may limit further movement of the plume.

Because PFAS is a class of compounds, it is important to note that not all PFAS are retained identically. For instance, longer-chained PFAS are generally less mobile and more strongly retained than shorter-chain PFAS. This same relationship applies to various other sorption processes. [[wikipedia:Perfluorosulfonic_acids|Perfluorinated sulfonic acids (PFSAs)]] tend to be more strongly retained than [[wikipedia:Perfluoroalkyl_carboxylic_acids|perfluorinated carboxylic acids (PFCAs)]] of equivalent chain length. As described above, polyfluorinated precursors are generally more strongly retained than their PFAA transformation products due to their size and/or charged head groups that promote sorption.

==Benefits==
Retention processes have the potential to reduce the rate that PFAS plumes advance relative to groundwater flow, which can increase the time before receptors are affected. In addition, some retention processes render the plume susceptible to "hysteretic" retention processes<ref>Costanza, J., Arshadi, M., Abriola, L.M., and Pennell, K.D., 2019. Accumulation of PFOA and PFOS at the Air–Water Interface. Environmental Science and Technology Letters, 6(8), pp. 487–91. [https://doi.org/10.1021/acs.estlett.9b00355 doi: 10.1021/acs.estlett.9b00355]</ref><ref>Sima, M.W., and Jaffé, P.R., 2021. A Critical Review of Modeling Poly- and Perfluoroalkyl Substances (PFAS) in the Soil-Water Environment. Science of The Total Environment, 757, p. 143793. [https://doi.org/10.1016/j.scitotenv.2020.143793 doi: 10.1016/j.scitotenv.2020.143793]</ref><ref>Zeng, J., and Guo, B., 2023. Reduced Accessible Air–Water Interfacial Area Accelerates PFAS Leaching in Heterogeneous Vadose Zones. Geophysical Research Letters, 50(8), e2022GL102655. [https://doi.org/10.1029/2022GL102655 doi: 10.1029/2022GL102655][//www.enviro.wiki/images/7/71/ZengGuo2023.pdf Article pdf]</ref><ref>Schaefer, C.E., Nguyen, D., Christie, E., Shea, S., Higgins, C.P., and Field, J.A., 2021. Desorption of poly-and perfluoroalkyl substances from soil historically impacted with aqueous film-forming foam. Journal of Environmental Engineering, 147(2), p. 06020006. [https://doi.org/10.1061/(ASCE)EE.1943-7870.0001846 doi: 10.1061/(ASCE)EE.1943-7870.0001846] </ref>, such as when desorption occurs at a slower rate than sorption or when matrix diffusion loading occurs more rapidly than back-diffusion. At sites where retention capacity is substantial, hysteretic processes attenuate the mass discharge of the plume by reducing the peak mass discharge and concentration (“peak dampening”), extending the plume discharge over a longer timeframe. Finally, at some sites, retention processes coupled with dispersion could be substantial enough to stabilize the PFAS plume, thereby hindering further expansion. If the source of the plume has been removed or isolated, the PFAS plume will eventually diminish under such conditions.

PMR can offer several additional benefits for both site managers, regulatory authorities, and the public, such as:

*Reducing the environmental footprint and impacts of PFAS management
*Reducing the costs and complexities of PFAS management
*Providing time and flexibility for future decision making at sites with significant retention

==PMR/PER Framework==

==='''Lines of Evidence'''===
[[File:AdamsonFig3.png | thumb | 500px | Figure 3. Qualitative plume management framework for application of PFAS Monitored Retention (PMR), PFAS Enhanced Retention (PER), and other remediation strategies. Both Plume Mass Discharge and Plume Travel Time to Nearest Receptor are the First Lines of Evidence for evaluating PMR.]]
For PFAS sites, the three Lines of Evidence (LOE) originally developed for MNA of other COCs (see [[Monitored Natural Attenuation (MNA)]])<ref>United States Environmental Protection Agency (USEPA), 1999. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites. Office of Solid Waste and Emergency Response (OSWER) [https://www.epa.gov/sites/default/files/2014-02/documents/d9200.4-17.pdf Directive 9200.4-17P]. [//www.enviro.wiki/images/4/40/USEPA1999.pdf Report pdf]</ref> have been heavily modified to develop lines of evidence as part of the PMR Framework. Because there are no known processes that destroy the fully fluorinated PFAA class of PFAS in the environment, the demonstrated mass loss requirement for MNA Line of Evidence 1 has been modified to demonstrate that PFAS plumes have enough retention to pose no near-term risk to receptors. Therefore, for PMR projects:

The '''First Line of Evidence''' is to determine where a site fits into a PFAS Plume Management Scenario based on two key retention metrics: mass discharge (Line of Evidence-1A) and travel time to potential receptors (Line of Evidence-1B) (Figure 3). Sites that are most amenable for PMR will be sites with 1) relatively lower PFAS Mass Discharge; and 2) stable or shrinking PFAS plumes, or alternatively long travel times before the closest receptors are impacted (''e.g.'', 10 years or more). Note that ongoing groundwater monitoring (and likely land use controls) would be required as an additional safety factor to ensure that receptors are protected.

The '''Second Line of Evidence''' involves collecting site specific field data that help establish that specific retention processes are active at the site. This includes documenting matrix diffusion (e.g., significant geologic heterogeneity) in unconsolidated settings by collecting samples in low-permeability zones (e.g., silts, clays) and analyzing these for PFAS and soil organic carbon. The PFAS concentrations or mass can be compared to the concentrations or mass of PFAS in soils in the transmissive zones containing the PFAS plume. Co-located groundwater and soil samples can be collected to demonstrate significant ongoing sorption processes in key compartments and to estimate field-based partition coefficients (''Kd'') to help estimate retardation factors for PFAS. For chemical retention, field sampling can be performed to establish geochemical conditions and the total mass present as precursors versus PFAAs in various portions of the site. Another option for the Second Line of Evidence includes quantifying the mass discharge of PFAS from the vadose zone that is entering groundwater. This can be attempted using direct porewater measurements ([[wikipedia:Lysimeter|lysimeters]]), partitioning calculations, or leaching tests<ref>Anderson, R.H., Feild, J.B., Dieffenbach-Carle, H., Elsharnouby, O. and Krebs, and R.K., 2022. Assessment of PFAS in collocated soil and porewater samples at an AFFF-impacted source zone: Field-scale validation of suction lysimeters. Chemosphere, 308, p.136247. [https://doi.org/10.1016/j.chemosphere.2022.136247 doi: 10.1016/j.chemosphere.2022.136247]</ref><ref>Brusseau, M.L., and Guo, B., 2023. Revising the EPA dilution-attenuation soil screening model for PFAS. Journal of Hazardous Materials Letters, 4, p. 100077. [https://doi.org/10.1016/j.hazl.2023.100077 doi: 10.1016/j.hazl.2023.1000777][//www.enviro.wiki/images/7/78/BrusseauGuomanuscript2023.pdf Article pdf]</ref><ref>Navarro, D.A., Kabiri, S.S., Bowles, K., Knight, E.R., Braeunig, J., Srivastava, P., Boxall, N.J., Douglas, G., Mueller, J., McLaughlin, M.J., and Williams, M., 2024. Review on Methods for Assessing and Predicting Leaching of PFAS from Solid Matrices. Current Pollution Reports, 10(4), pp. 628-647. [https://doi.org/10.1007/s40726-024-00326-6 doi: 10.1007/s40726-024-00326-6] [[Special:FilePath/NavarroEtAl2024.pdf| Article pdf]]</ref>. A primary goal of quantifying the mass discharge from the vadose zone is to evaluate if its contributions to groundwater are insufficient to necessitate soil cleanup.

The '''Third Line of Evidence''' uses special field measurements or modeling studies to better establish how ongoing retention processes influence PFAS transport to potential receptors.

The first two Lines of Evidence for PMR described above have been incorporated into a qualitative framework for managing PFAS sites (Figure 3) to help determine the suitability of PMR at a specific site. Establishing relevant (site specific) values for these two key retention factors is discussed below.

==='''Evaluation Tiers'''===
[[File:AdamsonFig4.png | thumb | left | 700px | Figure 4. Overview of a Tiered Approach for Collecting Lines of Evidence for PMR Evaluations. The selection of the appropriate tier to pursue can be initially based on the level of effort and/or available resources. Tier 1 methods are the simplest approaches that require lower levels of effort, but they provide lower-resolution results that make them appropriate for planning-level assessments. Tier 2 and Tier 3 methods require more time and resources but can provide more accurate results if needed. In part, these tiers can also depend on the site’s complexity and/or the availability of existing characterization data; more complex sites are likely to require more data to fully characterize retention processes.]]
The PMR Framework relies heavily on site characterization data, with fate and transport modeling as a complementary option to support the various Lines of Evidence. The Framework contains protocols for collecting these data to support a PMR evaluation, but not all methods may be necessary at every site. Specifically, the complexity and widely varying characteristics of PFAS sites, as well as the resources that can be involved in obtaining data, necessitate differing degrees of effort for their appropriate management. Factors such as the source and plume size, proximity to receptors, and groundwater concentrations will markedly influence the required actions. Consequently, a stratified, three-tiered approach (Tier 1, Tier 2, Tier 3) has been proposed for potential PMR evaluation, with the goal of implementing the appropriate level of investigational effort and complexity for a particular site:

'''Tier 1 Evaluation:''' A limited number of conventional groundwater samples and soil samples may be sufficient for assessing PMR efficacy at less complex PFAS sites and/or sites with no or low immediate risk. A Tier 1 evaluation may also be appropriate as an initial screening step in evaluating a portfolio of sites as a basis for making decisions about performing further (higher tier) investigations. The data gathered for the First and Second Lines of Evidence can be based on this limited sampling. Simple data analysis techniques, such as calculating the PFAS plume advancement rate and then extrapolating from the current PFAS plume length to estimate the length of the plume in the future, can be employed to get a conservative estimate of potential plume growth.

'''Tier 2 Evaluation''': A more detailed evaluation may be necessary at sites with increased complexity and risk, or where the existing data are limited or less certain. In these cases, a more rigorous documentation of the First and Second Lines of Evidence should be undertaken to better understand the critical site specific retention processes. This could also include a basic Tier 2 groundwater modeling study that incorporates matrix diffusion effects within a straightforward groundwater flow regime (e.g., the ESTCP [[REMChlor - MD|REMChlor-MD]] model or the ESTCP REMFluor model that is now being developed as part of ESTCP project ER24-8200). The goal in this case would be to estimate how much further plume expansion might be expected in the future.

'''Tier 3 Evaluation:''' The most complex sites with more immediate risk may require high resolution site characterization techniques akin to those utilized by Adamson ''et al''.<ref name=":3" /><ref>Adamson, D.T., Nickerson, A., Kulkarni, P.R., Higgins, C.P., Popovic, J., Field, J., Rodowa, A., Newell, C., Deblanc, P., and Kornuc, J.J., 2020. Mass-Based, Field-Scale Demonstration of PFAS Retention within AFFF-Associated Source Areas. Environmental Science and Technology, 54(24), pp. 15768–15777. [https://doi.org/10.1021/acs.est.0c04472 doi: 10.1021/acs.est.0c04472]</ref>. These techniques augment the First and Second LOEs, enhancing comprehension of mass distribution across different environmental compartments, the extent of chemical retention onsite, and the mass flux relative to the distance from the source. A sophisticated three dimensional model that can better manage complex groundwater flow patterns and geological heterogeneity could be considered at this tier. This is because conventional finite-difference groundwater flow and transport models exhibit substantial limitations when modeling matrix diffusion<ref>Farhat, S.K., Adamson, D.T., Gavaskar, A.R., Lee, S.A., Falta, R.W., and Newell, C.J., 2020. Vertical Discretization Impact in Numerical Modeling of Matrix Diffusion in Contaminated Groundwater. Groundwater Monitoring and Remediation, 40(2), pp. 52–64. [https://doi.org/10.1111/gwmr.12373 doi: 10.1111/gwmr.12373]</ref>.

There is some subjectivity to determining whether a site is a Tier 1, Tier 2, or Tier 3 based on risk and/or complexity, but the key metrics of mass discharge and travel time to receptors can play a role in determining which Tier is initially best suited for a particular site. Figure 4 shows examples of how the Tiered approach can be used to collect data for the various Lines of Evidence for PMR.

==Applications and Relevance to Managing PFAS-Affected Sites==
PMR can be used for different purposes. It may have applicability as a sole remedy at low-risk sites, but it could also help control low levels of remaining contamination after active treatment. It may also serve as a temporary remedy at sites with no proximate receptors, giving time for the development of more cost effective technologies than the current pump-and-treat methods. Finally, it can be part of a treatment train at more complex sites where risk-based approaches are acceptable. The use of PMR as part of a site remedy would be expected to result in cost savings, particularly given the large number of PFAS sites and the high costs of current PFAS remedies<ref name=":4" /><ref>Abrams, S., McGregor, R., Burns, M., Galasso, J., Havranek, T., Hesemann, J., Longsworth, J., McDonough, J., and Mora, R., 2022. PFAS Experts Symposium 2: Statements on available in situ remediation technologies. Remediation Journal, 32(1-2), pp. 45-53. [https://doi.org/10.1002/rem.21714 doi: 10.1002/rem.21714]</ref><ref>Divine, C., Heintz, M., Dunn, S., and Pennington, A., 2023. Medical Analogue Framework for Natural Remedies and Passive Risk‐Mitigation Measures in Environmental Remediation. Groundwater Monitoring and Remediation, 43(2), pp. 13-25. [https://doi.org/10.1111/gwmr.12579 doi: 10.1111/gwmr.12579]</ref>.

PMR is most suitable for sites where: 1) the natural retention processes alone can protect receptors in the short-term, allowing PMR to be used as a temporary remediation measure for several years or decades; 2) very low concentrations (or mass discharge) of PFAS are present and/or PFAS plumes are stable, making them suitable for using PMR as the only remedy; or 3) as a polishing technology for low levels of remaining contamination that will often be present after active remediation. Because many PFAS plumes may be expanding, there may be some reluctance to use PMR as the final remedy under the [[wikipedia:Superfund|CERCLA]] regulatory program. If so, sites could apply the PMR Framework to determine if PMR could be used in an Interim Record of Decision (ROD) with a Contingency Remedy; as a polishing step after initial remediation step(s); within a Groundwater Management Zone where some plume expansion is allowed; or as a resource allocation tool for PFAS site characterization.

PMR as a sole remedy is more suitable for sites with small, low-level sources that release PFAS slowly into groundwater that moves slowly or has a long travel time to important receptors and a high capacity to retain PFAS mass in the chemical and geological environment. Sites where PMR is part of a treatment train or a risk-based approach may have different characteristics, but a long travel time to a receptor is likely to be a key factor in any case. Also, PFAS retention may be higher in hydrogeologic settings that are not uniform because of the diffusion of PFAS into the matrix. Sites where most of the PFAS mass is in the form of polyfluorinated precursors (determined by using the [[wikipedia:TOP_Assay|Total Oxidizable Precursor (TOP)]] Assay or non-target analyses such as Total Organic Fluorine) may also be more favorable for PMR because these precursors tend to move slower than PFAAs. Sites where the groundwater is mostly anaerobic are also more favorable for PMR because these conditions should slow down the conversion of precursors to PFAAs.

Site specific PMR evaluations can be performed using numerical criteria for the two primary Lines of Evidence that are developed based on the expected constraints at the site. These can then be combined with other site specific data to evaluate the secondary and tertiary Lines of Evidence for retention. For example, if the nearest downgradient receptor was a drinking water supply, then the acceptable mass discharge for PMR would be based on not causing an exceedance of any applicable drinking water criteria (e.g., PFOS proposed MCL of 4 ng/L). This can be back-calculated by knowing the mixing ratio in a receiving stream (in the case of groundwater discharge to a surface water source of drinking water) or the pumping rate of a production well (in the case of groundwater source of drinking water with compliance measured at the wellhead)<ref>Einarson, M.D., and Mackay, D.M., 2001 . Predicting impacts of ground water contamination. Environmental Science and Technology, 35(3), pp. 66A – 73A. [https://doi.org/10.1021/es0122647 doi: 10.1021/es0122647][//www.enviro.wiki/images/1/1a/2001-Einarson-Predicting_impacts_of_gw_contamination.pdf Article pdf]</ref>. The travel time of key PFAS to the receptor would also be calculated and then compared to acceptable site specific values (e.g., travel times of >10 years).

Initial estimates of these metrics may be uncertain given the limitations in available site data to fully delineate the plume boundaries and/or the relevant concentrations for mass discharge. The level of uncertainty should help guide how much additional characterization data might be needed at a site to improve the estimates. For a simple Tier 1 evaluation, the mass discharge at the source is used for evaluating Line of Evidence 1A because it is typically conservative (i.e., it assumes that the highest concentrations at the site will eventually reach the downgradient receptor). A site with limited existing data might not seem favorable for PMR based on this type of planning-level evaluation, but this outcome may signal the need to collect additional data to reduce uncertainty. This could motivate moving to a Tier 2 or Tier 3 evaluation, where the assumption is that additional data will provide a better basis for projecting travel time and mass discharge (as well as helping to establish if retention processes are active).

An alternative application of the Framework is for multi-site evaluations where generic criteria for Line of Evidence 1A (plume mass discharge) and Line of Evidence 1B (travel time to receptor) are developed and then applied to a wide range of sites. These criteria are used to build a generic framework, and then individual sites are plotted on the Framework to help visualize priorities for cleanup (i.e., those that fall in the upper right of Figure 3).

==PFAS Enhanced Retention (PER)==
[[File:AdamsonFig5.png | thumb | 650px | left | Figure 5. PER is identified as a most viable option during site screening using the PMR Framework (Panel A); Implementing PER reduces mass discharge and/or increases travel time so that site can be managed using PMR during the post-implementation period (Panel B).]]
PFAS Enhanced Retention (PER) approaches are designed to help manage those sites where natural retention mechanisms alone are insufficient to ensure that the primary Lines of Evidence (low PFAS mass discharge, long PFAS travel time to nearest receptor) for PFAS Monitored Retention (PMR) can be met. At these sites, one of more of the key PFAS retention mechanisms may be active, but site-specific data suggest that some type of intervention will be necessary (now or in the near future). These sites represent a higher priority for an action within the context of the PMR Framework (Figure 5, Panel A), but the conditions do not require the immediate implementation of an active source remediation (e.g., the installation of a pump-and-treat system, or a point-of-use treatment to protect downgradient receptors. For PER, the overall goal is to reduce loading from the source and/or increase the retention capacity within the PFAS source area or plume (Figure 5, Panel B).

For PFAS sites, multiple different PER approaches were proposed by Newell ''et al.''<ref name=":2" />, including several that are currently in use or in active development including: (1) injecting particulate sorbents such as carbon into the subsurface to enhance retention (e.g. Permeable Sorption Barrier); (2) capping to retain PFAS in the vadose zone by preventing infiltration of water from the surface which could otherwise cause leaching of PFAS into groundwater; (3) gas sparging in unconfined aquifers to potentially concentrate and retain PFAS in the capillary fringe above the water table; (4) retaining PFAS via salting out processes in coastal environments where a fresh water plume may mix with saline groundwater causing increased adsorption of PFAS to solids; (5) emplacing particulate sorbents and/or ion exchange resins and/or coagulants in closely spaced permeable columns or trenches using geotechnical equipment; (6) injection of emulsified vegetable oil (EVO) to promote sorption, exhaust available oxygen, and create an anaerobic environment which retards the aerobic biodegradation of long-chain precursors into the short-chain PFAAs which are associated with greater mobility and health risks.

 

==Implementation Issues==
PMR and PER can be evaluated as a remediation technology for PFAS-impacted sites under any regulatory jurisdiction. By adapting the Framework to the specific requirements of each site, project managers can develop targeted and effective strategies for managing PFAS contamination. In terms of its broader applications within the CERCLA process, the concept of a PFAS plume expanding indefinitely might limit the use of PMR as a single final remedy in a Final Record of Decision. Mass retention of PFAS (as opposed to remediation that involves permanent removal, destruction, or sequestration of the PFAS mass) may be less favored by some regulatory authorities. However, the PMR Framework can be utilized in other ways to help manage and remediate PFAS in groundwater (as described in the Applications and Relevance to Managing PFAS-Affected Sites section above)
PMR requires long-term monitoring and maintenance to ensure its effectiveness and reliability. Sites may also need land use restrictions or institutional controls to prevent exposure and further mass loading. PMR involves the long-term storage of PFAS-affected materials onsite, which may represent uncertainties and liabilities for site managers. PMR may also require increased engagement and risk communication with the stakeholders and the public, to explain the rationale, effectiveness, impacts, and future plans of PMR. It is important to communicate with the stakeholders and the public in a transparent and proactive manner, and to address their concerns and questions adequately. The implementation of PMR (or PER) as a management strategy may require that a site have a Plume Assimilative Capacity Zone (PACZ) downgradient of the source to accommodate plume expansion (typically still within the property boundary). In that case, the rate of plume expansion should be estimated (using the methods outlined in the Framework), and then it should be established that there are no current or reasonably foreseeable receptors that would be impacted by this predicted plume expansion.
==References==
<references />

==See Also==

Dr. Hans Stroo

2025-02-06T18:58:12Z

Debra Tabron: Created page with "==Work and Contact Information== EMPLOYER: : : : : EMAIL: WEBPAGE: ==About the Contributor== Dr. Stroo has over 30 years of experience in groundwater remediation. H..."

==Work and Contact Information==

EMPLOYER:
: 
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EMAIL:

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==About the Contributor==
Dr. Stroo has over 30 years of experience in groundwater remediation. He was a principal consultant with Remediation Technologies Inc. (RETEC) and HydroGeoLogic Inc. (HGL) before opening his own company (Stroo Consulting LLC). For over 20 years, he was a senior technical advisor to DoD’s Strategic Environmental Research and Development Program (SERDP). Dr. Stroo served as the technical expert on some of the largest remediation cost cap insurance projects ever placed, including several over $1 billion. He has edited four books on in situ remediation and authored 12 book chapters and over 30 journal articles (including several on natural attenuation of a range of contaminants, and several on technical issues related to PFAS contamination).”

==Article Contributions==
*[[PFAS Monitored Retention (PMR) and PFAS Enhanced Retention (PER)]]

__NOTOC__

[[Category: Contributors|Stroo]]

Contributors

2024-10-16T21:02:45Z

Debra Tabron:

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ENVIRO.wiki aims to connect users with the most current and credible science and engineering research into the design and implementation of environmental projects. Financial support for ENVIRO.wiki is provided by the US Department of Defense environmental research and demonstration programs – [https://www.serdp-estcp.org/ SERDP and ESTCP]. Articles are written by nationally and internationally recognized experts who provide a concise summary of the current State-of-Practice and relevant research results. Many of these authors have written similar articles for SERDP-ESTCP as part of the existing monograph series or for other publications. All articles are reviewed by outside technical reviewers as described in the [[Editorial_Policy|editorial policy]]. Day to day administration is provided by [https://www.trccompanies.com/ TRC].

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| style="width:13.3%" |[[Dr._David_Adamson,_P.E.|David Adamson]]
| style="width:13.3%" |[[Dr. Dora Chiang|Dora Chiang]]
| style="width:13.3%" |[[Dr._Ron_Falta|Ron Falta]]
| style="width:13.3%" |[[Elisabeth_Hawley|Elisabeth Hawley]]
| style="width:13.3%" |[[Thomas_Krug|Thomas Krug]]
| style="width:13.3%" |[[Sara McMillen]]
| style="width:13.3%" |[[Dr._Lee_Slater|Lee Slater]]
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|[[Richelle Allen-King]]
|[[Tom_Christy,_P.E.|Tom Christy]]
|[[Dr._Dimin_Fan|Dimin Fan]]
|[[Dr. Julie A. Heath|Julie A. Heath]]
|[[Dr. Kate Kucharzyk|Kate Kucharzyk]]
|[[Dr. Jonathan Miles|Jonathan Miles]]
|[[Dr. Timothy J. Strathmann|Timothy Strathmann]]
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|[[Dr. Richard Anderson|Richard "Hunter" Anderson]]
|[[Dr. Pei Chiu|Pei Chiu]]
|[[Dr. Shahla Farhat |Shahla Farhat]]
|[[Dr. Brian Helms|Brian Helms]]
|[[Poonam Kulkarni|Poonam Kulkarni]]
|[[Larry Mullins]]
|[[Dr._Susan_Taylor|Susan Taylor]]
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|[[Dr. Michael Annable, P.E.|Michael Annable]]
|[[Dr._Kung-Hui_(Bella)_Chu|Bella Chu]]
|[[Paul Favara|Paul Favara]]
|[[Dr._Gorm_Heron|Gorm Heron]]
|[[Dr. Johnsie Ray Lang|Johnsie Ray Lang]]
|[[Dr. Fadime Murdoch|Fadime Murdoch]]
|[[Dr. Selma Mededovic Thagard|Selma Thagard]]
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|[[Dr. Sabine E. Apitz|Sabine E. Apitz]]
|[[Dr. Jason Conder|Jason Conder]]
|[[Dr. Jack Feminella|Jack Feminella]]
|[[Dr._Christopher_Higgins|Christopher Higgins]]
|[[M. Tony Lieberman|Tony Lieberman]]
|[[Dr. Robert Murdoch|Robert Murdoch]]
|[[Dr._Paul_Tratnyek|Paul Tratnyek]]
|-
|[[Dr._Brett_Baldwin|Brett Baldwin]]
|[[Dr._Michelle_Crimi|Michelle Crimi]]
|[[Dr._Jennifer_Field|Jennifer Field]]
|[[Dr. Thomas Holsen|Thomas Holsen]]
|[[Dr. Gaisheng Liu|Gaisheng Liu]]
|[[Kobe Nagar]]
|[[Michael_Truex|Michael Truex]]

|-
|[[Dr. Amanda Barker|Amanda Barker]]
|[[Harry Craig]]
|[[Dr._Kevin_Finneran|Kevin Finneran]]
|[[Dr. Brian Hudgens|Brian Hudgens]]
|[[Dr._Barbara_Sherwood_Lollar,_F.R.S.C.|Barbara Lollar]]
|[[Dr._Charles_Newell,_P.E.|Charles Newell]]
|[[Michael_R._Walsh,_P.E.,_M.E.|Michael Walsh]]
|-
|[[Dr. Samuel Beal|Samuel Beal]]
|[[Dr. Paul Dahlen|Paul Dahlen]]
|[[Jeff_Fitzgibbons|Jeff Fitzgibbons]]
|[[Dr. John Hummel|John Hummel]]
|[[Dr. Guilherme Lotufo|Guilherme Lotufo]]
|[[Dora_Ogles-Taggart|Dora Ogles-Taggart]]
|[[Dr. Meng Wang|Meng Wang]]
|-
|[[Lila Beckley]]
|[[Dr. Phillip de Blanc, P.E. |Phil de Blanc]]
|[[Dr._David_L._Freedman|David Freedman]]
|[[Dr. Michael Hyman|Michael Hyman]]
|[[John Lowe|John Lowe]]
|[[Tom_Palaia|Tom Palaia]]
|[[Dr. James Weaver|James Weaver]]
|-
|[[Dr. Barbara Bekins|Barbara Bekins]]
|[[Dr. Rula Deeb|Rula Deeb]]
|[[Jeff Gamlin, P.G.|Jeff Gamlin]]
|[[Dan Isenberg]]
|[[Dr. Loren Lund|Loren Lund]]
|[[Dr. Frederic Petit|Frederic Petit]]
|[[Richard Wenning]]
|-
|[[Rene Bernier]]
|[[Dr._Miles_Denham|Miles Denham]]
|[[Dr._Jason_Gerhard|Jason Gerhard]]
|[[Dr._Billy_E._Johnson|Billy Johnson]]
|[[Chris_Lutes|Chris Lutes]]
|[[Kien Pham]]
|[[Dr. Katie van Werkhoven|Katie van Werkhoven]]
|-
|[[Sam Bickley]]
|[[Dr. Marc A. Deshusses|Marc Deshusses]]
|[[Dr. Upal Ghosh|Upal Ghosh]]
|[[Dr. Paul C. Johnson|Paul C. Johnson]]
|[[Leah_MacKinnon,_M.A.Sc.,_P._Eng.|Leah MacKinnon]]
|[[Dr. Breanna F. Powers|Breanna F. Powers]]
|[[Dr. Hal White|Hal White]]
|-
|[[Dr. Robert Borden, P.E.|Robert Borden]]
|[[William DiGuiseppi]]
|[[Dr. Scott Grieco|Scott Grieco]]
|[[Jared Johnson]]
|[[Elisse_Magnuson|Elisse Magnuson]]
|[[Dr. Danny Reible|Danny Reible]]
|[[Dr. Richard Wilkin|Rick Wilkin]]
|-
|[[Dr. Treavor H. Boyer|Treavor Boyer]]
|[[Dr._Katerina_Dontsova|Katerina Dontsova]]
|[[Dr. Natalie Griffiths|Natalie Griffiths]]
|[[Dr. Warren Kadoya|Warren Kadoya]]
|[[Dr. Shaily Mahendra|Shaily Mahendra]]
|[[Dr._Stephen_Richardson|Stephen Richardson]]
|[[Dr._John_Wilson|John Wilson]]
|-
|[[Dr. Mark Brusseau|Mark Brusseau]]
|[[Dr. Mark S. Dortch, PE, D.WRE|Mark Dortch]]
|[[Dr. Philip M. Gschwend|Philip M. Gschwend]]
|[[Dr. Roopa Kamath|Roopa Kamath]]
|[[Todd Martin]]
|[[Florent Risacher]]
|[[Dr. Suzanne Witt|Suzanne Witt]]
|-
|[[Dr. James Butler, Jr.|James Butler]]
|[[Doug_Downey,_P.E.|Doug Downey]]
|[[Dr. Yuanming Guo|Yuanming Guo]]
|[[Dr. Denise Kay|Denise Kay]]
|[[Wesley_McCall,_M.S.,_P.G.|Wesley McCall]]
|[[Gunther Rosen]]
|[[Dr. Bilgen Yuncu, P.E.|Bilgen Yuncu]]
|-
|[[Dr. Richard F. Carbonaro|Richard F. Carbonaro]]
|[[Dr. Elizabeth_Edwards|Elizabeth Edwards]]
|[[Dr. Nathan Hall|Nathan Hall]]
|[[Andrew Kirkman]]
|[[Travis_McGuire|Travis McGuire]]
|[[Dr._Alexandra_Salter-Blanc|Alexandra Salter-Blanc]]
|[[Matthew Zenker]]
|-
|[[Paula Andrea Cárdenas-Hernández|Paula A. Cárdenas-Hernández]]
|[[Dr. Anderson Ellis|Anderson Ellis]]
|[[James Hatton]]
|[[Deyuan Kong]]
|[[Dr._Thomas_McHugh|Thomas McHugh]]
|[[Dr. Grace Schwartz|Grace Schwartz]]
|
|-
|[[Dr. Grace Chang|Grace Chang]]
|[[Dr. Morgan Evans|Morgan Evans]]
|[[Paul Hatzinger]]
|[[Dr. Rao Kotamarthi|Rao Kotamarthi]]
|[[Michaye_McMaster,_M.Sc.|Michaye McMaster]]
|[[Dr. Austin Scircle|Austin Scircle]]
|
|}
|}
|}