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Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions

2026-04-28T18:55:10Z

Jhurley:

The U.S. Department of Defense (DoD) faces many challenges in restoring aquifers at contaminated sites, often due to back-diffusion of tetrachloroethene (PCE) and trichloroethene (TCE) from low-permeability clay zones. The uptake, storage, and subsequent long-term release of these dissolved contaminants from clays are key processes in understanding the longevity, intensity, and risks associated with many persistent chlorinated ethene groundwater plumes. Although naturally occurring abiotic and biotic dechlorination processes in clays may reduce stored contaminant mass and significantly aid natural attenuation, no standardized field method currently exists to verify or quantify these reactions. It is critical to remediation design efforts to demonstrate and validate a cost-effective ''in situ'' approach for assessing these dechlorination processes using first-order rate constants. An approach was developed and applied across eight DoD sites to support Remedial Project Managers (RPMs) and regulators in evaluating natural attenuation potential in clay-rich environments.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

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

*[[Monitored Natural Attenuation (MNA)]]
*[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]
*[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
*[[Matrix Diffusion]]
*[[REMChlor - MD]]

'''Contributors:''' Dani Tran, Dr. Charles Schaefer, Dr. Charles Werth

'''Key Resource:'''
*Schaefer, C.E, Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils<ref name="SchaeferEtAl2025"/>

==Introduction==
Cost-effective methods are needed to verify the occurrence of natural dechlorination processes and quantify their dechlorination rates in clays under ambient in situ conditions in order to reliably predict their long-term influence on plume longevity and mass discharge. However, accurately determining these rates is challenging due to slow reaction kinetics, the transient nature of transformation products, and the interplay of biotic and abiotic mechanisms within the clay matrix or at clay-sand interfaces. Tools capable of quantifying these reactions and assessing their role in mitigating plume persistence would be a significant aid for long-term site management.

For reductive abiotic dechlorination under anoxic conditions, a 1% hydrochloric acid (HCl) extraction of a sample of native clay coupled with X-ray diffraction (XRD) data can be used as a screening level tool to estimate reductive dechlorination rate constants. These rate constants can be inserted into fate and transport models such as [[REMChlor - MD]]<ref>Falta, R., and Wang, W., 2017. A semi-analytical method for simulating matrix diffusion in numerical transport models. Journal of Contaminant Hydrology, 197, pp. 39-49. [https://doi.org/10.1016/j.jconhyd.2016.12.007 doi: 10.1016/j.jconhyd.2016.12.007]  [[Media: FaltaWang2017.pdf | Open Access Manuscript]]</ref><ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., Newell, C.J., 2022. Modeling a well-charactized perfluorooctane sulfate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion. Journal of Contaminant Hydrology, 247, Article 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi: 10.1016/j.jconhyd.2022.103986]  [[Media: KulkarniEtAl2022.pdf | Open Access Manuscript]]</ref> to quantify abiotic dechlorination impacts within clay aquitards on chlorinated solvent plumes. Thus, determination of the abiotic reductive dechlorination rate constant for a particular clayey soil can be readily utilized to provide a more accurate assessment of aquifer cleanup timeframes for groundwater plumes that are being sustained by contaminant back-diffusion.

==Recommended Approach==
[[File: TranFig1.png | thumb | 500 px | Figure 1: First-order rate constants for abiotic reductive dechlorination of TCE under anaerobic conditions. Circles are data from Schaefer ''et al.'', 2021<ref>Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2021. Abiotic dechlorination in the presence of ferrous minerals. Journal of Contaminant Hydrology, 241, 103839. [https://doi.org/10.1016/j.jconhyd.2021.103839 doi: 10.1016/j.jconhyd.2021.103839]  [[Media: SchaeferEtAl2021.pdf | Open Access Manuscript]]</ref>, filled squares from Schaefer ''et al.'', 2018<ref name="SchaeferEtAl2018"/>, and Schaefer ''et al.'', 2017<ref>Schaefer, C.E., Ho., Gurr, C., Berns, E., Werth, C., 2017. Abiotic dechlorination of chlorinated ethenes in natural clayey soils: impacts of mineralogy and temperature. Journal of Contaminant Hydrology, 206, pp. 10-17. [https://doi.org/10.1016/j.jconhyd.2017.09.007 doi: 10.1016/j.jconhyd.2017.09.007]  [[Media: SchaeferEtAl2017.pdf | Open Access Manuscript]]</ref>, and open squares from Schaefer ''et al.'', 2025<ref name="SchaeferEtAl2025"/>. ]]
[[File: TranFig2.png | thumb | 600 px | Figure 2: Flowchart diagram of field screening procedures]]
The recommended approach builds upon the methodology and findings of a recent study<ref name="SchaeferEtAl2025">Schaefer, C.E., Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils. Groundwater Monitoring and Remediation, 45(2), pp. 31-39. [https://doi.org/10.1111/gwmr.12709 doi: 10.1111/gwmr.12709]</ref>, emphasizing field-based and analytical techniques to quantify abiotic first-order reductive dechlorination rate constants for PCE and TCE in clayey soils under anoxic conditions. Key components of this evaluation are listed below:
#Zone Identification: The focus of the investigation should be to delineate clayey zones adjacent to hydraulically conductive zones.
#Ferrous Mineral Quantification: Assess ferrous mineral context in clay via 1% HCl extraction at ambient temperature over a 10-minute interval.
#Mineralogical Characterization: Conduct XRD analysis with the specific intent of identifying the presence of pyrite and biotite.
#Reduced Gas Analysis: Measurement of reduced gases such as acetylene, ethene, and ethane concentrations in clay samples. Gas-tight sampling devices (e.g., En Core® soil samplers by En Novative Technologies, Inc.) should be used to ensure sample integrity during collection and transport.

Clay samples should be collected within a few centimeters of the high-permeability interface, with optional additional sampling further inward. For mineralogical analysis, a defined interval may be collected and subsequently subsampled. To preserve sample integrity, exposure to air should be minimized during collection, transport, and handling. Homogenization should occur within an anaerobic chamber, and if subsamples are required for external analysis, they must be shipped in gas-tight, anaerobic containers.

Estimation of the abiotic reductive first-order rate constant for PCE and TCE is based on the “reactive” ferrous content in the clay. Reactive ferrous content (Fe(II)r) is estimated as shown in Equation 1:

::'''Equation 1:'''       <big>''Fe(II)r = DA + XRDpyr - XRDbiotite''</big>

where ''DA'' is the ferrous content from the dilute acid (1% HCl) extraction, ''XRDpyr'' is the pyrite content from XRD analysis, and ''XRDbiotite'' is the biotite content from XRD analysis<ref name="SchaeferEtAl2025"/>.

Abiotic dechlorination is unlikely to contribute to mitigating contaminant back-diffusion when reactive ferrous iron (Fe(II)r) concentrations are below 100 mg/kg (Figure 1). For Fe(II)r above 100 mg/kg, the first-order rate constant for PCE and TCE reductive dechlorination can be estimated using the correlation shown in Figure 1<ref name="SchaeferEtAl2018">Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2018. Mechanisms for abiotic dechlorination of trichloroethene by ferrous minerals under oxic and anoxic conditions in natural sediments. Environmental Science and Technology, 52(23), pp.13747-13755. [https://doi.org/10.1021/acs.est.8b04108 doi: 10.1021/acs.est.8b04108]</ref><ref>Borden, R.C., Cha, K.Y., 2021. Evaluating the impact of back diffusion on groundwater cleanup time. Journal of Contaminant Hydrology, 243, Article 103889. [https://doi.org/10.1016/j.jconhyd.2021.103889 doi: 10.1016/j.jconhyd.2021]  [[Media: BordenCha2021.pdf | Open Access Manuscript]]</ref>. The rate constant exhibits a strong positive correlation with the logarithm of reactive Fe(II) content (Pearson’s ''r'' = 0.82), with a slope of 4.7 × 10⁻⁸ L g⁻¹ d⁻¹ (log mg kg⁻¹)⁻¹.

Figure 2 presents a decision flowchart designed to evaluate the significance and extent of abiotic reductive dechlorination. By applying Equation 1 to the dilute acid extractable Fe(II) plus measured mineral species data from clay samples, the reactive ferrous iron content (Fe(II)r) can be quantified, enabling a streamlined assessment of the extent to which abiotic processes are contributing to the mitigation of contaminant back-diffusion.

If Fe(II)r is ≥ 100 mg/kg, a first-order dechlorination rate constant can be estimated and subsequently used within a contaminant fate and transport model. However, if acetylene is detected in the clay, even with Fe(II)r less than 100 mg/kg, then bench-scale testing using methods similar to those described in a recent study<ref name="SchaeferEtAl2025"/> is recommended, as such results would likely be inconsistent with those shown in Figure 1, suggesting some other mechanism might be involved, or that the system mineralogy might be more complex than anticipated. Even if Fe(II)r ≥ 100 mg/kg, confirmatory bench-scale testing may be conducted for additional verification and to refine estimation of the abiotic dechlorination rate constant.

==Summary and Recommendations==
The approach outlined above is intended to serve as a generalized guide for practitioners and site managers to cost-effectively determine the extent to which beneficial abiotic reductive dechlorination reactions are likely occurring in low permeability (e.g., clayey) zones. This approach may be contraindicated if co-contaminants are present. It is currently unclear whether other classes of potentially reactive chemicals, such as trinitrotoluene (TNT) or chlorinated ethanes, could interact competitively with PCE and TCE.

In addition, it remains unclear how other classes of compounds such as per- and polyfluoroalkyl substances (PFAS) may interact or sorb with ferrous minerals and potentially inhibit abiotic dechlorination reactions. Coupling these recommended activities with conventional site investigation tasks would provide an opportunity to perform many of the up-front screening activities with minimal additional project costs. It is important to note that the guidance proposed herein pertains to particularly low permeability media. Sites with complex or varying lithology, where the mineralogy and/or redox conditions may vary, might require evaluation of multiple samples to provide appropriate site-wide information.
 

==References==
<references />

==See Also==
*[https://serdp-estcp.mil/projects/details/a7e3f7b5-ed82-4591-adaa-6196ff33dd60 ESTCP Project ER20-5031 – In Situ Verification and Quantification of Naturally Occurring Dechlorination Rates in Clays: Demonstrating Processes that Mitigate Back-Diffusion and Plume Persistence]

Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions

2026-04-28T18:42:20Z

Jhurley: /* Summary and Recommendations */

The U.S. Department of Defense (DoD) faces many challenges in restoring aquifers at contaminated sites, often due to back-diffusion of tetrachloroethene (PCE) and trichloroethene (TCE) from low-permeability clay zones. The uptake, storage, and subsequent long-term release of these dissolved contaminants from clays are key processes in understanding the longevity, intensity, and risks associated with many persistent chlorinated ethene groundwater plumes. Although naturally occurring abiotic and biotic dechlorination processes in clays may reduce stored contaminant mass and significantly aid natural attenuation, no standardized field method currently exists to verify or quantify these reactions. It is critical to remediation design efforts to demonstrate and validate a cost-effective in situ approach for assessing these dechlorination processes using first-order rate constants. An approach was developed and applied across eight DoD sites to support Remedial Project Managers (RPMs) and regulators in evaluating natural attenuation potential in clay-rich environments.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

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

*[[Monitored Natural Attenuation (MNA)]]
*[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]
*[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
*[[Matrix Diffusion]]
*[[REMChlor - MD]]

'''Contributors:''' Dani Tran, Dr. Charles Schaefer, Dr. Charles Werth

'''Key Resource:'''
*Schaefer, C.E, Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils<ref name="SchaeferEtAl2025"/>

==Introduction==
Cost-effective methods are needed to verify the occurrence of natural dechlorination processes and quantify their dechlorination rates in clays under ambient in situ conditions in order to reliably predict their long-term influence on plume longevity and mass discharge. However, accurately determining these rates is challenging due to slow reaction kinetics, the transient nature of transformation products, and the interplay of biotic and abiotic mechanisms within the clay matrix or at clay-sand interfaces. Tools capable of quantifying these reactions and assessing their role in mitigating plume persistence would be a significant aid for long-term site management.

For reductive abiotic dechlorination under anoxic conditions, a 1% hydrochloric acid (HCl) extraction of a sample of native clay coupled with X-ray diffraction (XRD) data can be used as a screening level tool to estimate reductive dechlorination rate constants. These rate constants can be inserted into fate and transport models such as [[REMChlor - MD]]<ref>Falta, R., and Wang, W., 2017. A semi-analytical method for simulating matrix diffusion in numerical transport models. Journal of Contaminant Hydrology, 197, pp. 39-49. [https://doi.org/10.1016/j.jconhyd.2016.12.007 doi: 10.1016/j.jconhyd.2016.12.007]  [[Media: FaltaWang2017.pdf | Open Access Manuscript]]</ref><ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., Newell, C.J., 2022. Modeling a well-charactized perfluorooctane sulfate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion. Journal of Contaminant Hydrology, 247, Article 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi: 10.1016/j.jconhyd.2022.103986]  [[Media: KulkarniEtAl2022.pdf | Open Access Manuscript]]</ref> to quantify abiotic dechlorination impacts within clay aquitards on chlorinated solvent plumes. Thus, determination of the abiotic reductive dechlorination rate constant for a particular clayey soil can be readily utilized to provide a more accurate assessment of aquifer cleanup timeframes for groundwater plumes that are being sustained by contaminant back-diffusion.

==Recommended Approach==
[[File: TranFig1.png | thumb | 500 px | Figure 1: First-order rate constants for abiotic reductive dechlorination of TCE under anaerobic conditions. Circles are data from Schaefer ''et al.'', 2021<ref>Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2021. Abiotic dechlorination in the presence of ferrous minerals. Journal of Contaminant Hydrology, 241, 103839. [https://doi.org/10.1016/j.jconhyd.2021.103839 doi: 10.1016/j.jconhyd.2021.103839]  [[Media: SchaeferEtAl2021.pdf | Open Access Manuscript]]</ref>, filled squares from Schaefer ''et al.'', 2018<ref name="SchaeferEtAl2018"/>, and Schaefer ''et al.'', 2017<ref>Schaefer, C.E., Ho., Gurr, C., Berns, E., Werth, C., 2017. Abiotic dechlorination of chlorinated ethenes in natural clayey soils: impacts of mineralogy and temperature. Journal of Contaminant Hydrology, 206, pp. 10-17. [https://doi.org/10.1016/j.jconhyd.2017.09.007 doi: 10.1016/j.jconhyd.2017.09.007]  [[Media: SchaeferEtAl2017.pdf | Open Access Manuscript]]</ref>, and open squares from Schaefer ''et al.'', 2025<ref name="SchaeferEtAl2025"/>. ]]
[[File: TranFig2.png | thumb | 600 px | Figure 2: Flowchart diagram of field screening procedures]]
The recommended approach builds upon the methodology and findings of a recent study<ref name="SchaeferEtAl2025">Schaefer, C.E., Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils. Groundwater Monitoring and Remediation, 45(2), pp. 31-39. [https://doi.org/10.1111/gwmr.12709 doi: 10.1111/gwmr.12709]</ref>, emphasizing field-based and analytical techniques to quantify abiotic first-order reductive dechlorination rate constants for PCE and TCE in clayey soils under anoxic conditions. Key components of this evaluation are listed below:
#Zone Identification: The focus of the investigation should be to delineate clayey zones adjacent to hydraulically conductive zones.
#Ferrous Mineral Quantification: Assess ferrous mineral context in clay via 1% HCl extraction at ambient temperature over a 10-minute interval.
#Mineralogical Characterization: Conduct XRD analysis with the specific intent of identifying the presence of pyrite and biotite.
#Reduced Gas Analysis: Measurement of reduced gases such as acetylene, ethene, and ethane concentrations in clay samples. Gas-tight sampling devices (e.g., En Core® soil samplers by En Novative Technologies, Inc.) should be used to ensure sample integrity during collection and transport.

Clay samples should be collected within a few centimeters of the high-permeability interface, with optional additional sampling further inward. For mineralogical analysis, a defined interval may be collected and subsequently subsampled. To preserve sample integrity, exposure to air should be minimized during collection, transport, and handling. Homogenization should occur within an anaerobic chamber, and if subsamples are required for external analysis, they must be shipped in gas-tight, anaerobic containers.

Estimation of the abiotic reductive first-order rate constant for PCE and TCE is based on the “reactive” ferrous content in the clay. Reactive ferrous content (Fe(II)r) is estimated as shown in Equation 1:

::'''Equation 1:'''       <big>''Fe(II)r = DA + XRDpyr - XRDbiotite''</big>

where ''DA'' is the ferrous content from the dilute acid (1% HCl) extraction, ''XRDpyr'' is the pyrite content from XRD analysis, and ''XRDbiotite'' is the biotite content from XRD analysis<ref name="SchaeferEtAl2025"/>.

Abiotic dechlorination is unlikely to contribute to mitigating contaminant back-diffusion when reactive ferrous iron (Fe(II)r) concentrations are below 100 mg/kg (Figure 1). For Fe(II)r above 100 mg/kg, the first-order rate constant for PCE and TCE reductive dechlorination can be estimated using the correlation shown in Figure 1<ref name="SchaeferEtAl2018">Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2018. Mechanisms for abiotic dechlorination of trichloroethene by ferrous minerals under oxic and anoxic conditions in natural sediments. Environmental Science and Technology, 52(23), pp.13747-13755. [https://doi.org/10.1021/acs.est.8b04108 doi: 10.1021/acs.est.8b04108]</ref><ref>Borden, R.C., Cha, K.Y., 2021. Evaluating the impact of back diffusion on groundwater cleanup time. Journal of Contaminant Hydrology, 243, Article 103889. [https://doi.org/10.1016/j.jconhyd.2021.103889 doi: 10.1016/j.jconhyd.2021]  [[Media: BordenCha2021.pdf | Open Access Manuscript]]</ref>. The rate constant exhibits a strong positive correlation with the logarithm of reactive Fe(II) content (Pearson’s ''r'' = 0.82), with a slope of 4.7 × 10⁻⁸ L g⁻¹ d⁻¹ (log mg kg⁻¹)⁻¹.

Figure 2 presents a decision flowchart designed to evaluate the significance and extent of abiotic reductive dechlorination. By applying Equation 1 to the dilute acid extractable Fe(II) plus measured mineral species data from clay samples, the reactive ferrous iron content (Fe(II)r) can be quantified, enabling a streamlined assessment of the extent to which abiotic processes are contributing to the mitigation of contaminant back-diffusion.

If Fe(II)r is ≥ 100 mg/kg, a first-order dechlorination rate constant can be estimated and subsequently used within a contaminant fate and transport model. However, if acetylene is detected in the clay, even with Fe(II)r less than 100 mg/kg, then bench-scale testing using methods similar to those described in a recent study<ref name="SchaeferEtAl2025"/> is recommended, as such results would likely be inconsistent with those shown in Figure 1, suggesting some other mechanism might be involved, or that the system mineralogy might be more complex than anticipated. Even if Fe(II)r ≥ 100 mg/kg, confirmatory bench-scale testing may be conducted for additional verification and to refine estimation of the abiotic dechlorination rate constant.

==Summary and Recommendations==
The approach outlined above is intended to serve as a generalized guide for practitioners and site managers to cost-effectively determine the extent to which beneficial abiotic reductive dechlorination reactions are likely occurring in low permeability (e.g., clayey) zones. This approach may be contraindicated if co-contaminants are present. It is currently unclear whether other classes of potentially reactive chemicals, such as trinitrotoluene (TNT) or chlorinated ethanes, could interact competitively with PCE and TCE.

In addition, it remains unclear how other classes of compounds such as per- and polyfluoroalkyl substances (PFAS) may interact or sorb with ferrous minerals and potentially inhibit abiotic dechlorination reactions. Coupling these recommended activities with conventional site investigation tasks would provide an opportunity to perform many of the up-front screening activities with minimal additional project costs. It is important to note that the guidance proposed herein pertains to particularly low permeability media. Sites with complex or varying lithology, where the mineralogy and/or redox conditions may vary, might require evaluation of multiple samples to provide appropriate site-wide information.
 

==References==
<references />

==See Also==
*[https://serdp-estcp.mil/projects/details/a7e3f7b5-ed82-4591-adaa-6196ff33dd60 ESTCP Project ER20-5031 – In Situ Verification and Quantification of Naturally Occurring Dechlorination Rates in Clays: Demonstrating Processes that Mitigate Back-Diffusion and Plume Persistence]

Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions

2026-04-27T19:49:40Z

Jhurley: /* Recommended Approach */

==Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions==
The U.S. Department of Defense (DoD) faces many challenges in restoring aquifers at contaminated sites, often due to back-diffusion of tetrachloroethene (PCE) and trichloroethene (TCE) from low-permeability clay zones. The uptake, storage, and subsequent long-term release of these dissolved contaminants from clays are key processes in understanding the longevity, intensity, and risks associated with many persistent chlorinated ethene groundwater plumes. Although naturally occurring abiotic and biotic dechlorination processes in clays may reduce stored contaminant mass and significantly aid natural attenuation, no standardized field method currently exists to verify or quantify these reactions. It is critical to remediation design efforts to demonstrate and validate a cost-effective in situ approach for assessing these dechlorination processes using first-order rate constants. An approach was developed and applied across eight DoD sites to support Remedial Project Managers (RPMs) and regulators in evaluating natural attenuation potential in clay-rich environments.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

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

*[[Monitored Natural Attenuation (MNA)]]
*[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]
*[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
*[[Matrix Diffusion]]
*[[REMChlor - MD]]

'''Contributors:''' Dani Tran, Dr. Charles Schaefer, Dr. Charles Werth

'''Key Resource:'''
*Schaefer, C.E, Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils (3)

==Introduction==
Cost-effective methods are needed to verify the occurrence of natural dechlorination processes and quantify their dechlorination rates in clays under ambient in situ conditions in order to reliably predict their long-term influence on plume longevity and mass discharge. However, accurately determining these rates is challenging due to slow reaction kinetics, the transient nature of transformation products, and the interplay of biotic and abiotic mechanisms within the clay matrix or at clay-sand interfaces. Tools capable of quantifying these reactions and assessing their role in mitigating plume persistence would be a significant aid for long-term site management.

For reductive abiotic dechlorination under anoxic conditions, a 1% hydrochloric acid (HCl) extraction of a sample of native clay coupled with X-ray diffraction (XRD) data can be used as a screening level tool to estimate reductive dechlorination rate constants. These rate constants can be inserted into fate and transport models such as [[REMChlor - MD]]<ref>Falta, R., and Wang, W., 2017. A semi-analytical method for simulating matrix diffusion in numerical transport models. Journal of Contaminant Hydrology, 197, pp. 39-49. [https://doi.org/10.1016/j.jconhyd.2016.12.007 doi: 10.1016/j.jconhyd.2016.12.007]  [[Media: FaltaWang2017.pdf | Open Access Manuscript]]</ref><ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., Newell, C.J., 2022. Modeling a well-charactized perfluorooctane sulfate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion. Journal of Contaminant Hydrology, 247, Article 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi: 10.1016/j.jconhyd.2022.103986]  [[Media: KulkarniEtAl2022.pdf | Open Access Manuscript]]</ref> to quantify abiotic dechlorination impacts within clay aquitards on chlorinated solvent plumes. Thus, determination of the abiotic reductive dechlorination rate constant for a particular clayey soil can be readily utilized to provide a more accurate assessment of aquifer cleanup timeframes for groundwater plumes that are being sustained by contaminant back-diffusion.

==Recommended Approach==
[[File: TranFig1.png | thumb | 600 px | Figure 1: First-order rate constants for abiotic reductive dechlorination of TCE under anaerobic conditions (data from this study and prior research)]]
[[File: TranFig2.png | thumb | 600 px | Figure 2: Flowchart diagram of field screening procedures]]
The recommended approach builds upon the methodology and findings of a recent study<ref name="SchaeferEtAl2025">Schaefer, C.E., Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils. Groundwater Monitoring and Remediation, 45(2), pp. 31-39. [https://doi.org/10.1111/gwmr.12709 doi: 10.1111/gwmr.12709]</ref>, emphasizing field-based and analytical techniques to quantify abiotic first-order reductive dechlorination rate constants for PCE and TCE in clayey soils under anoxic conditions. Key components of this evaluation are listed below:
#Zone Identification: The focus of the investigation should be to delineate clayey zones adjacent to hydraulically conductive zones.
#Ferrous Mineral Quantification: Assess ferrous mineral context in clay via 1% HCl extraction at ambient temperature over a 10-minute interval.
#Mineralogical Characterization: Conduct XRD analysis with the specific intent of identifying the presence of pyrite and biotite.
#Reduced Gas Analysis: Measurement of reduced gases such as acetylene, ethene, and ethane concentrations in clay samples. Gas-tight sampling devices (e.g., En Core® soil samplers by En Novative Technologies, Inc.) should be used to ensure sample integrity during collection and transport.

Clay samples should be collected within a few centimeters of the high-permeability interface, with optional additional sampling further inward. For mineralogical analysis, a defined interval may be collected and subsequently subsampled. To preserve sample integrity, exposure to air should be minimized during collection, transport, and handling. Homogenization should occur within an anaerobic chamber, and if subsamples are required for external analysis, they must be shipped in gas-tight, anaerobic containers.

Estimation of the abiotic reductive first-order rate constant for PCE and TCE is based on the “reactive” ferrous content in the clay. Reactive ferrous content (Fe(II)r) is estimated as shown in Equation 1:

::'''Equation 1:'''       <big>''Fe(II)r = DA + XRDpyr - XRDbiotite''</big>

where ''DA'' is the ferrous content from the dilute acid (1% HCl) extraction, ''XRDpyr'' is the pyrite content from XRD analysis, and ''XRDbiotite'' is the biotite content from XRD analysis<ref name="SchaeferEtAl2025"/>.

Abiotic dechlorination is unlikely to contribute to mitigating contaminant back-diffusion when reactive ferrous iron (Fe(II)r) concentrations are below 100 mg/kg (Figure 1). For Fe(II)r above 100 mg/kg, the first-order rate constant for PCE and TCE reductive dechlorination can be estimated using the correlation shown in Figure 1<ref name="SchaeferEtAl2018">Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2018. Mechanisms for abiotic dechlorination of trichloroethene by ferrous minerals under oxic and anoxic conditions in natural sediments. Environmental Science and Technology, 52(23), pp.13747-13755. [https://doi.org/10.1021/acs.est.8b04108 doi: 10.1021/acs.est.8b04108]</ref><ref>Borden, R.C., Cha, K.Y., 2021. Evaluating the impact of back diffusion on groundwater cleanup time. Journal of Contaminant Hydrology, 243, Article 103889. [https://doi.org/10.1016/j.jconhyd.2021.103889 doi: 10.1016/j.jconhyd.2021]  [[Media: BordenCha2021.pdf | Open Access Manuscript]]</ref>. The rate constant exhibits a strong positive correlation with the logarithm of reactive Fe(II) content (Pearson’s ''r'' = 0.82), with a slope of 4.7 × 10⁻⁸ L g⁻¹ d⁻¹ (log mg kg⁻¹)⁻¹.

Figure 2 presents a decision flowchart designed to evaluate the significance and extent of abiotic reductive dechlorination. By applying Equation 1 to the dilute acid extractable Fe(II) plus measured mineral species data from clay samples, the reactive ferrous iron content (Fe(II)r) can be quantified, enabling a streamlined assessment of the extent to which abiotic processes are contributing to the mitigation of contaminant back-diffusion.

If Fe(II)r is ≥ 100 mg/kg, a first-order dechlorination rate constant can be estimated and subsequently used within a contaminant fate and transport model. However, if acetylene is detected in the clay, even with Fe(II)r less than 100 mg/kg, then bench-scale testing using methods similar to those described in a recent study<ref name="SchaeferEtAl2025"/> is recommended, as such results would likely be inconsistent with those shown in Figure 1, suggesting some other mechanism might be involved, or that the system mineralogy might be more complex than anticipated. Even if Fe(II)r ≥ 100 mg/kg, confirmatory bench-scale testing may be conducted for additional verification and to refine estimation of the abiotic dechlorination rate constant.

==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 | Open Access Article]]</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==

User:Jhurley/sandbox

2026-04-14T19:58:21Z

Jhurley: /* Recommended Approach */

==Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions==
The U.S. Department of Defense (DoD) faces many challenges in restoring aquifers at contaminated sites, often due to back-diffusion of tetrachloroethene (PCE) and trichloroethene (TCE) from low-permeability clay zones. The uptake, storage, and subsequent long-term release of these dissolved contaminants from clays are key processes in understanding the longevity, intensity, and risks associated with many persistent chlorinated ethene groundwater plumes. Although naturally occurring abiotic and biotic dechlorination processes in clays may reduce stored contaminant mass and significantly aid natural attenuation, no standardized field method currently exists to verify or quantify these reactions. It is critical to remediation design efforts to demonstrate and validate a cost-effective in situ approach for assessing these dechlorination processes using first-order rate constants. An approach was developed and applied across eight DoD sites to support Remedial Project Managers (RPMs) and regulators in evaluating natural attenuation potential in clay-rich environments.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

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

*[[Monitored Natural Attenuation (MNA)]]
*[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]
*[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
*[[Matrix Diffusion]]
*[[REMChlor - MD]]

'''Contributors:''' Dani Tran, Dr. Charles Schaefer, Dr. Charles Werth

'''Key Resource:'''
*Schaefer, C.E, Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils (3)

==Introduction==
Cost-effective methods are needed to verify the occurrence of natural dechlorination processes and quantify their dechlorination rates in clays under ambient in situ conditions in order to reliably predict their long-term influence on plume longevity and mass discharge. However, accurately determining these rates is challenging due to slow reaction kinetics, the transient nature of transformation products, and the interplay of biotic and abiotic mechanisms within the clay matrix or at clay-sand interfaces. Tools capable of quantifying these reactions and assessing their role in mitigating plume persistence would be a significant aid for long-term site management.

For reductive abiotic dechlorination under anoxic conditions, a 1% hydrochloric acid (HCl) extraction of a sample of native clay coupled with X-ray diffraction (XRD) data can be used as a screening level tool to estimate reductive dechlorination rate constants. These rate constants can be inserted into fate and transport models such as [[REMChlor - MD]]<ref>Falta, R., and Wang, W., 2017. A semi-analytical method for simulating matrix diffusion in numerical transport models. Journal of Contaminant Hydrology, 197, pp. 39-49. [https://doi.org/10.1016/j.jconhyd.2016.12.007 doi: 10.1016/j.jconhyd.2016.12.007]  [[Media: FaltaWang2017.pdf | Open Access Manuscript]]</ref><ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., Newell, C.J., 2022. Modeling a well-charactized perfluorooctane sulfate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion. Journal of Contaminant Hydrology, 247, Article 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi: 10.1016/j.jconhyd.2022.103986]  [[Media: KulkarniEtAl2022.pdf | Open Access Manuscript]]</ref> to quantify abiotic dechlorination impacts within clay aquitards on chlorinated solvent plumes. Thus, determination of the abiotic reductive dechlorination rate constant for a particular clayey soil can be readily utilized to provide a more accurate assessment of aquifer cleanup timeframes for groundwater plumes that are being sustained by contaminant back-diffusion.

==Recommended Approach==
[[File: TranFig1.png | thumb | 600 px | Figure 1: First-order rate constants for abiotic reductive dechlorination of TCE under anaerobic conditions (data from this study and prior research)]]
[[File: TranFig2.png | thumb | 600 px | Figure 2: Flowchart diagram of field screening procedures]]
The recommended approach builds upon the methodology and findings of a recent study<ref name="SchaeferEtAl2025">Schaefer, C.E., Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils. Groundwater Monitoring and Remediation, 45(2), pp. 31-39. [https://doi.org/10.1111/gwmr.12709 doi: 10.1111/gwmr.12709]</ref>, emphasizing field-based and analytical techniques to quantify abiotic first-order reductive dechlorination rate constants for PCE and TCE in clayey soils under anoxic conditions. Key components of this evaluation are listed below:
#Zone Identification: The focus of the investigation should be to delineate clayey zones adjacent to hydraulically conductive zones.
#Ferrous Mineral Quantification: Assess ferrous mineral context in clay via 1% HCl extraction at ambient temperature over a 10-minute interval.
#Mineralogical Characterization: Conduct XRD analysis with the specific intent of identifying the presence of pyrite and biotite.
#Reduced Gas Analysis: Measurement of reduced gases such as acetylene, ethene, and ethane concentrations in clay samples. Gas-tight sampling devices (e.g., En Core® soil samplers by En Novative Technologies, Inc.) should be used to ensure sample integrity during collection and transport.

Clay samples should be collected within a few centimeters of the high-permeability interface, with optional additional sampling further inward. For mineralogical analysis, a defined interval may be collected and subsequently subsampled. To preserve sample integrity, exposure to air should be minimized during collection, transport, and handling. Homogenization should occur within an anaerobic chamber, and if subsamples are required for external analysis, they must be shipped in gas-tight, anaerobic containers.

Estimation of the abiotic reductive first-order rate constant for PCE and TCE is based on the “reactive” ferrous content in the clay. Reactive ferrous content (Fe(II)r) is estimated as shown in Equation 1:

::'''Equation 1:'''       <big>''Fe(II)r = DA + XRDpyr - XRDbiotite''</big>

where ''DA'' is the ferrous content from the dilute acid (1% HCl) extraction, ''XRDpyr'' is the pyrite content from XRD analysis, and ''XRDbiotite'' is the biotite content from XRD analysis<ref name="SchaeferEtAl2025"/>.

Abiotic dechlorination is unlikely to contribute to mitigating contaminant back-diffusion when reactive ferrous iron (Fe(II)r) concentrations are below 100 mg/kg (Figure 1). For Fe(II)r above 100 mg/kg, the first-order rate constant for PCE and TCE reductive dechlorination can be estimated using the correlation shown in Figure 1<ref name="SchaeferEtAl2018">Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2018. Mechanisms for abiotic dechlorination of trichloroethene by ferrous minerals under oxic and anoxic conditions in natural sediments. Environmental Science and Technology, 52(23), pp.13747-13755. [https://doi.org/10.1021/acs.est.8b04108 doi: 10.1021/acs.est.8b04108]</ref><ref>Borden, R.C., Cha, K.Y., 2021. Evaluating the impact of back diffusion on groundwater cleanup time. Journal of Contaminant Hydrology, 243, Article 103889. [https://doi.org/10.1016/j.jconhyd.2021.103889 doi: 10.1016/j.jconhyd.2021]  [[Media: BordenCha2021.pdf | Open Access Manuscript]]</ref>. The rate constant exhibits a strong positive correlation with the logarithm of reactive Fe(II) content (Pearson’s ''r'' = 0.82), with a slope of 4.7 × 10⁻⁸ L g⁻¹ d⁻¹ (log mg kg⁻¹)⁻¹.

Figure 2 presents a decision flowchart designed to evaluate the significance and extent of abiotic reductive dechlorination. By applying Equation 1 to the dilute acid extractable Fe(II) plus measured mineral species data from clay samples, the reactive ferrous iron content (Fe(II)r) can be quantified, enabling a streamlined assessment of the extent to which abiotic processes are contributing to the mitigation of contaminant back-diffusion.

==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 | Open Access Article]]</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==

User:Jhurley/sandbox

2026-04-13T22:30:42Z

Jhurley: /* Recommended Approach */

==Estimating PCE/TCE Abiotic First-Order Reductive Dechlorination Rate Constants in Clayey Soils Under Anoxic Conditions==
The U.S. Department of Defense (DoD) faces many challenges in restoring aquifers at contaminated sites, often due to back-diffusion of tetrachloroethene (PCE) and trichloroethene (TCE) from low-permeability clay zones. The uptake, storage, and subsequent long-term release of these dissolved contaminants from clays are key processes in understanding the longevity, intensity, and risks associated with many persistent chlorinated ethene groundwater plumes. Although naturally occurring abiotic and biotic dechlorination processes in clays may reduce stored contaminant mass and significantly aid natural attenuation, no standardized field method currently exists to verify or quantify these reactions. It is critical to remediation design efforts to demonstrate and validate a cost-effective in situ approach for assessing these dechlorination processes using first-order rate constants. An approach was developed and applied across eight DoD sites to support Remedial Project Managers (RPMs) and regulators in evaluating natural attenuation potential in clay-rich environments.
<div style="float:right;margin:0 0 2em 2em;">__TOC__</div>

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

*[[Monitored Natural Attenuation (MNA)]]
*[[Monitored Natural Attenuation (MNA) of Chlorinated Solvents]]
*[[Monitored Natural Attenuation - Transitioning from Active Remedies]]
*[[Matrix Diffusion]]
*[[REMChlor - MD]]

'''Contributors:''' Dani Tran, Dr. Charles Schaefer, Dr. Charles Werth

'''Key Resource:'''
*Schaefer, C.E, Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils (3)

==Introduction==
Cost-effective methods are needed to verify the occurrence of natural dechlorination processes and quantify their dechlorination rates in clays under ambient in situ conditions in order to reliably predict their long-term influence on plume longevity and mass discharge. However, accurately determining these rates is challenging due to slow reaction kinetics, the transient nature of transformation products, and the interplay of biotic and abiotic mechanisms within the clay matrix or at clay-sand interfaces. Tools capable of quantifying these reactions and assessing their role in mitigating plume persistence would be a significant aid for long-term site management.

For reductive abiotic dechlorination under anoxic conditions, a 1% hydrochloric acid (HCl) extraction of a sample of native clay coupled with X-ray diffraction (XRD) data can be used as a screening level tool to estimate reductive dechlorination rate constants. These rate constants can be inserted into fate and transport models such as [[REMChlor - MD]]<ref>Falta, R., and Wang, W., 2017. A semi-analytical method for simulating matrix diffusion in numerical transport models. Journal of Contaminant Hydrology, 197, pp. 39-49. [https://doi.org/10.1016/j.jconhyd.2016.12.007 doi: 10.1016/j.jconhyd.2016.12.007]  [[Media: FaltaWang2017.pdf | Open Access Manuscript]]</ref><ref>Kulkarni, P.R., Adamson, D.T., Popovic, J., Newell, C.J., 2022. Modeling a well-charactized perfluorooctane sulfate (PFOS) source and plume using the REMChlor-MD model to account for matrix diffusion. Journal of Contaminant Hydrology, 247, Article 103986. [https://doi.org/10.1016/j.jconhyd.2022.103986 doi: 10.1016/j.jconhyd.2022.103986]  [[Media: KulkarniEtAl2022.pdf | Open Access Manuscript]]</ref> to quantify abiotic dechlorination impacts within clay aquitards on chlorinated solvent plumes. Thus, determination of the abiotic reductive dechlorination rate constant for a particular clayey soil can be readily utilized to provide a more accurate assessment of aquifer cleanup timeframes for groundwater plumes that are being sustained by contaminant back-diffusion.

==Recommended Approach==
[[File: TranFig1.png | thumb | 600 px | Figure 1: First-order rate constants for abiotic reductive dechlorination of TCE under anaerobic conditions (data from this study and prior research)]]
[[File: TranFig2.png | thumb | 600 px | Figure 2: Flowchart diagram of field screening procedures]]
The recommended approach builds upon the methodology and findings of a recent study<ref name="SchaeferEtAl2025">Schaefer, C.E., Tran, D., Nguyen, D., Latta, D.E., Werth, C.J., 2025. Evaluating Mineral and In Situ Indicators of Abiotic Dechlorination in Clayey Soils. Groundwater Monitoring and Remediation, 45(2), pp. 31-39. [https://doi.org/10.1111/gwmr.12709 doi: 10.1111/gwmr.12709]</ref>, emphasizing field-based and analytical techniques to quantify abiotic first-order reductive dechlorination rate constants for PCE and TCE in clayey soils under anoxic conditions. Key components of this evaluation are listed below:
#Zone Identification: The focus of the investigation should be to delineate clayey zones adjacent to hydraulically conductive zones.
#Ferrous Mineral Quantification: Assess ferrous mineral context in clay via 1% HCl extraction at ambient temperature over a 10-minute interval.
#Mineralogical Characterization: Conduct XRD analysis with the specific intent of identifying the presence of pyrite and biotite.
#Reduced Gas Analysis: Measurement of reduced gases such as acetylene, ethene, and ethane concentrations in clay samples. Gas-tight sampling devices (e.g., En Core® soil samplers by En Novative Technologies, Inc.) should be used to ensure sample integrity during collection and transport.

Clay samples should be collected within a few centimeters of the high-permeability interface, with optional additional sampling further inward. For mineralogical analysis, a defined interval may be collected and subsequently subsampled. To preserve sample integrity, exposure to air should be minimized during collection, transport, and handling. Homogenization should occur within an anaerobic chamber, and if subsamples are required for external analysis, they must be shipped in gas-tight, anaerobic containers.

Estimation of the abiotic reductive first-order rate constant for PCE and TCE is based on the “reactive” ferrous content in the clay. Reactive ferrous content (Fe(II)r) is estimated as shown in Equation 1:

::'''Equation 1:'''       <big>''Fe(II)r = DA + XRDpyr - XRDbiotite''</big>

where ''DA'' is the ferrous content from the dilute acid (1% HCl) extraction, ''XRDpyr'' is the pyrite content from XRD analysis, and ''XRDbiotite'' is the biotite content from XRD analysis<ref name="SchaeferEtAl2025"/>.

Abiotic dechlorination is unlikely to contribute to mitigating contaminant back-diffusion when reactive ferrous iron (Fe(II)r) concentrations are below 100 mg/kg (Figure 1). For Fe(II)r above 100 mg/kg, the first-order rate constant for PCE and TCE reductive dechlorination can be estimated using the correlation shown in Figure 1<ref name="SchaeferEtAl2018">Schaefer, C.E., Ho, P., Berns, E., Werth, C., 2018. Mechanisms for abiotic dechlorination of trichloroethene by ferrous minerals under oxic and anoxic conditions in natural sediments. Environmental Science and Technology, 52(23), pp.13747-13755. [https://doi.org/10.1021/acs.est.8b04108 doi: 10.1021/acs.est.8b04108]</ref><ref>Borden, R.C., Cha, K.Y., 2021. Evaluating the impact of back diffusion on groundwater cleanup time. Journal of Contaminant Hydrology, 243, Article 103889. [https://doi.org/10.1016/j.jconhyd.2021.103889 doi: 10.1016/j.jconhyd.2021]  [[Media: BordenCha2021.pdf | Open Access Manuscript]]</ref>. The rate constant exhibits a strong positive correlation with the logarithm of reactive Fe(II) content (Pearson’s r = 0.82), with a slope of 4.7 × 10⁻⁸ L g⁻¹ d⁻¹ (log mg kg⁻¹)⁻¹.

==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 | Open Access Article]]</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==

User:Jhurley/sandbox

2026-04-13T22:27:59Z

Jhurley: /* Recommended Approach */

2026-04-06T19:11:59Z

Jhurley: Undo revision 18091 by Jhurley (talk)

{| 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
|
|-
|}

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2026-04-06T19:09:30Z

2026-04-06T18:49:56Z

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