Featured article: Sediment Capping
The use of aqueous film-forming foam (AFFF) can release PFAS into the environment during fire training, an emergency response, or as a result of leaks or spills from AFFF systems. Following AFFF releases, perfluoroalkyl acids (PFAAs), particularly PFOS, PFOA, and PFHxS, tend to be the most commonly detected PFAS in environmental media. PFAAs are relatively water-soluble and mobile in the environment, are not volatile (i.e., they do not evaporate to the atmosphere readily) and can sorb to the organic carbon present in soil or sediment. PFAS can bioaccumulate in animals and plants, and persistent PFAS, such as PFCAs and PFSAs, do not undergo significant biodegradation or biotransformation once present in a biological system. The human health issues associated with PFAS AFFF sites are primarily the exposure pathways associated with drinking water ingestion and dietary intake of PFAS. The characterization of toxicological effects in human health risk assessments is based on toxicological studies of mammalian exposures to per- and polyfluoroalkyl substances (PFAS), primarily studies involving perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). The most sensitive noncancer adverse effects involve the liver and kidney, immune system, and various developmental and reproductive endpoints. Only PFOS and PFOA (and their derivatives) have sufficient data for USEPA to characterize as Likely to Be Carcinogenic to Humans via the oral route of exposure. Epidemiological studies provided evidence of bladder, prostate, liver, kidney, and breast cancers in humans related to PFOS exposure, as well as kidney and testicular cancer in humans and limited evidence of breast cancer related to PFOA exposure.
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Enviro Wiki Highlights
 Molecular diffusion slowly transports solutes into clay-rich, lower permeability zones  Typical subgrade biogeochemical reactor (SBGR) layout. The SBGR is an in situ remediation technology for treatment of contaminated source areas and groundwater plume hot spots  An Hydraulic Profiling Tool (HPT) log with electrical conductivity (EC) on left, injection pressure in middle, and flow rate on the right  Diagram of mineral surface exchanging hydrogen ions with varying pH. The surface of most aquifer minerals carries an electrical charge that varies with pH  Comparison of the longitudinal redox zonation concept (A) and the plume fringe concept (B). Both concepts describe the spatial distribution of electron acceptors and respiration processes in a hydrocarbon contaminant plume  Schematic of an Hydraulic Profiling Tool (HPT) probe. HPT were developed to better understand formation permeability and the distribution of permeable and low permeability zones in unconsolidated formations  In situ chemical oxidation using (a) direct-push injection probes or (b) well-to-well flushing to delivery oxidants (shown in blue) into a target treatment zone of groundwater contaminated by dense nonaqueous phase liquid compounds (shown in red)  High-resolution 3D cross-borehole electrical imaging of contaminated fractured rock at the former Naval Air Warfare Center in New Jersey. Cross-borehole resistivity tomography imaging is a geophysical technique that can be used for site characterization and monitoring by observing variations in the electrical properties of subsurface materials  Stable isotope probing (SIP) in use: Loading, deployment and recovery of Bio-Trap® passive sampler with 13C-labeled benzene. Stable isotope probing (SIP) is used to conclusively determine whether in situ biodegradation of a contaminant is occurring  Summary of anticipated, primary reaction pathways for degradation of 1,2,3-Trichloropropane (TCP). TCP is a man-made chemical that was used in the past primarily as a solvent and extractive agent, a paint and varnish remover, and as a cleaning and degreasing agent  Distribution of BTEX plume lengths from 604 hydrocarbon sites. Monitored Natural Attenuation (MNA) is one of the most commonly used remediation approaches for groundwater contaminated with petroleum hydrocarbons (PHCs) and certain fuel additives such as fuel oxygenates or lead scavengers  No-purge and passive sampling methods eliminate the pre-purging step for groundwater sample collection and represent alternatives to conventional sampling methods that rely on low-flow purging of a well prior to collection. The Snap SamplerTM is an example of a passive grab sampler  Conceptualization of Vapor Transport-related Natural Source Zone Depletion (NSZD) processes at a Petroleum Release Site  Conceptual diagram of basic Soil Vapor Extraction (SVE) system for vadose zone remediation. (SVE) is a common and typically effective physical treatment process for remediation of volatile contaminants in vadose zone (unsaturated) soils  Emulsified Vegetable Oil (EVO) mixed in field during early pilot test. EVO is commonly added as a slowly fermentable substrate to stimulate the in situ anaerobic bioremediation of chlorinated solvents, explosives, perchlorate, chromate, and other contaminants  Key elements of vapor intrusion pathways  Batch reactor experiments to generate points on a sorption isotherm  Results for metagenomic analysis of a groundwater sample obtained from a site impacted with petroleum hydrocarbons  Perchlorate releases and drinking water detections  Data input screen for ESTCP Mass Flux Toolkit  Amendment addition for biobarrier  Thermal Remediation - Desorption schematic  Key exposure pathways for human health risk from contaminated sediments  The PFAS family of compounds
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