- Program Areas
Characterization of the Fate and Biotransformation of Fluorochemicals in AFFF-Contaminated Groundwater at Fire/Crash Testing Military Sites
The overall objective of this study was to fully delineate the per- and polyfluoroalkyl substances (PFASs) that persist in aqueous film-forming foam (AFFF)-contaminated groundwater, sediment, and soil and evaluate their impact on priority pollutant biotransformation. Researchers intended to characterize the composition of individual PFASs and their precursors in AFFF formulations and delineate the total organic fluorine concentrations of AFFF-contaminated groundwater, sediment, and soils. To achieve this overall goal, researchers had the following technical objectives (Tasks):
- Characterize the concentration/composition of individual PFASs and their precursors in AFFF formulations.
- Characterize the individual PFASs and total organic fluorine composition of AFFF-contaminated groundwater, sediment, and soil at military fire-training sites; determine field-based estimates of PFAS transport; and evaluate the spatial relations with priority pollutant distributions in groundwater at military fire-training sites.
- Determine the potential for the biotransformation of partially-fluorinated substances and AFFF formulations and the impact of AFFF and its components on Trichloroethene (TCE) transformation under redox conditions that are representative of groundwater at fire-training sites.
- Characterize the sorption of cationic and zwitterionic PFASs to soils and sediments.
For Task 1, the PFAS composition of 3M and fluorotelomer-based AFFFs was determined using a number of mass spectrometric approaches. The total oxidizable precursor assay was adapted for use with AFFF-contaminated groundwater, soil, and sediment. For Task 2, the developed analytical tools were applied to environmental samples from US military bases. Microcosm experiments were performed for Task 3 to determine the biotransformation pathways of polyfluoroalkyl substances in fluorotelomer-based Ansul AFFF under anaerobic and aerobic conditions. The impact on TCE reductive dechlorination was also evaluated in laboratory batch microcosm experiments. For Task 4, a series of laboratory batch sorption experiments were conducted using a fluorotelomer-based AFFF from National Foam, which contained anionic, zwitterionic, and cationic PFASs, on six soils that varied in physical properties.
Over 50 classes of PFASs, comprised of several individual homologs, were identified in AFFF formulations and groundwater over the course of this project. The composition of AFFFs was defined as either 3M or fluorotelomer-based AFFFs (Ansul, Chemguard, National Foam, Buckeye Fire Equipment, and Angus) with dates of manufacture dating back to 1989. Many of the newly-identified classes are 3M-derived and are cationic or zwitterionic. The TOP assay was modified for use with AFFF-contaminated media and precursors make up a significant fraction of total PFASs in groundwater, soil, and sediment. However, perfluoroalkyl carboxylates (PFCAs) (e.g., perfluroooctanoate, PFOA), perfluoroalkyl sulfonates (PFSAs) (e.g., perfluorooctane sulfonate, PFOS), and fluorotelomer sulfonates (FTSAs) remain the most abundant individual PFASs in AFFF-contaminated groundwater. The biotransformation of fluorotelomer thioamido sulfonates (FtTAoS) occurs under anaerobic and aerobic conditions; however, the two conditions produce different transformation products. Aerobic conditions produced FTSAs; however, they were further transformed to PFCAs. Some AFFFs and the solvent present in AFFF, diethyl glycol butyl ether (DGBE) promoted reductive dechlorination of trichloroethene when provided as the sole carbon and energy source. Low Kd values for the anionic 6:2 FTSA in sorption experiments are consistent with the detection and mobility of 6:2 SA is groundwater. Higher Kd values indicate that the anionic 8:2 FTSA, zwitterionic FTSaBs, and cationic 6:2 fluorotelomer sulfonamido amine (FTSaAm) are more likely to be associated with soil and sediment of source zones. Complete removal of the cationic FTSaAm indicates potential for strong sorption to source zone soils and sediments at some sites. The lack of correlations between the sorption of anionic FTSAs, zwitterionic FTSaBs, and cationic 6:2 FTSaAm and parameters including organic carbon content, cation exchange capacity (CEC), and anion exchange capacity (AEC), indicates that the bulk parameters do not adequately predict sorption. More information is needed on the conditions (e.g. pH and ionic strength) that promote desorption of zwitterionic and cationic PFASs in order to determine the potential for source zone soils and sediments to act as long-term PFAS sources.
The analytical tools developed for this project, including methods for quantifying individual PFASs as well as precursors by the total oxidizable precursor (TOP) assay, researchers have provided analytical advances for more complete characterization of AFFF-contaminated media. Using these tools, researchers have generated information that has significantly improved the understanding of the PFASs present in groundwater, sediment, and soil at AFFF-contaminated sites. Having identified precursors at AFFF-contaminated sites, efforts now focus on understanding the process that retain PFASs in source zones and the conditions that may mobilize them. Identifying precursors will lead to a better of understanding of the effectiveness of treatment technologies, such as the use of granulated activated carbon and other sorbents for their removal. The biotransformation pathway of the polyfluoroalkyl substances in Ansul AFFF provides a framework for understanding the fate of the precursor and insight into the conditions (anaerobic) that lead to high concentrations of persistent FTSAs and the potential for intermediates to be ultimately transformed to persistent PFCAs.
Researchers worked closely with Wellington Laboratories to identify and name new PFASs and to advocate for the synthesis of high quality authentic standards for perfluoroethane sulfonate (PFEtS). They participated in a number of webinars with Department of Defense (DoD) participants. Information gained from this project was used to inform current SERDP and ESTCP projects including SERDP ER-2720 and ESTCP ER-201633.
Place, B., and J.A. Field. 2012. Identification of Novel Fluorochemicals in Aqueous Film-Forming Foams (AFFF) Used by the US military. Environmental Science and Technology, 46 (13): 7120-7127.
Backe, W.J. and J.A. Field. 2012.. Is SPE Necessary for Environmental Analysis? A Quantitative Comparison of Matrix Effects From Large-Volume Injection and Solid-Phase Extraction Based Methods. Environmental Science and Technology, 46 (10): 6750–6758.
Houtz, E., Higgins, C., Field, J. and D. Sedlak. 2013. Persistence of Perfluoroalkyl Acid Precursors in AFFF-Impacted Groundwater and Soil. Environmental Science and Technology, 47 (15): 9342-9349.
Backe, W.J., Christensen, K.E., and J.A. Field. 2013. Newly-Identified Cationic, Anionic, and Zwitterionic Fluorinated Chemicals in Groundwater at US military Bases by Large Volume Injection HPLC – MS/MS. Environmental Science and Technology, 47 (10): 5226-5234.
McGuire, M.E., Schaefer, C., Richards, T., Backe, W.J., Field, J.A., Houtz, E., Sedlak, D.S., Guelfo, J.L., Wunsch, A., and C.P. Higgins. 2014. Evidence of Remediation-Induced Alteration of Subsurface Poly- and Perfluoroalkyl Substance Distribution at a Former Firefighter Training Area. Environmental Science and Technology, 48 (12): 6644-6652.
Harding-Marjanovic, K., Houtz, E., Yi, S., Field, J., Sedlak, D., and L. Alvarez-Cohen. 2015. Aerobic Biotransformation of Fluorotelomer Thioamido Sulfonate (Lodyne™) in AFFF-Amended Microcosms. Environmental Science and Technology, 49 (13), 7666–7674.
Barzen-Hanson, K., and J.A. Field. 2015. Discovery and Implications of C2 and C3 Perfluoroalkyl Sulfonates in Aqueous Film Forming Foams (AFFF) and Groundwater. Environmental Science and Technology Letters, 2 (4): 95-99. Selected for Editor’s Choice, granting free open access for one year, and Environmental Science and Technology Letters Paper of the Year in 2015.
Harding-Marjanovic, K.C., Yi, S., Weathers, T.S., Sharp, J.O., Sedlak, D.L., and L. Alvarez-CohenL. 2016. Effects of Aqueous Film-Forming Foams (AFFFs) on Trichloroethene (TCE) Dechlorination by a Dehalococcoides Mccartiyi-Containing Microbial community. Environmental Science and Technology, 50 (7): 3352-3361.
Barzen-Hanson, K., Simon, R., Choyke, S., Oetjen, K., McAlees, A., Riddell, N., McCrindle, R., Ferguson, P., Higgins, C., and J.A. Field. 2017. Discovery of 40 Classes of Per- and Polyfluoroalkyl Substances in Historical Aqueous Film-Forming Foams (AFFF) and AFFF-Impacted Groundwater. Environmental Science and Technology, 51 (4): 2047-2057.
Barzen-Hanson, K.A., S.E. Davis, M. Kleber, J.A. Field. 2017. Sorption of the Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil. Environmental Science & Technology, http://dx.doi.org/10.1021/acs.est.7b03452.