|Abstract or Summary
- Public attention and concern about per- and polyfluoroalkyl substances (PFASs) are increasing due to detection of PFASs in drinking water supplies
- Public attention and concern about per- and polyfluoroalkyl substances (PFASs) are increasing due to detection of PFASs in drinking water supplies, the environment, including remote locations, and wildlife and to the lowering of the federal health advisory levels of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in drinking water. Aqueous film-forming foams (AFFFs), which typically contain anionic, zwitterionic, and cationic PFASs, are one route of environmental entry for PFASs. AFFFs were routinely applied since the 1960s to extinguish hydrocarbon-based fuel fires during emergencies and fire fighter training. Routine releases of AFFF into the environment have resulted in high concentrations (mg L) of PFASs in groundwater. Attention typically focuses on the well-known homologs of the perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates (PFSAs), including PFOA and PFOS, and other anionic, zwitterionic, and cationic PFASs receive little attention. Recent data on AFFF-impacted groundwater indicates that ~ 25% of the PFASs are currently unidentified. A complete understanding of the composition of PFASs in AFFF-impacted groundwater is needed in order to investigate biodegradation pathways and to develop effective remediation techniques that capture PFASs with a wide range of water solubilities and subsurface mobilities. Zwitterionic and cationic PFASs present in groundwater, soil, and sediment have not been characterized with respect to partitioning (sorption) behavior. Sorption studies typically focus on a select number of well-known PFCAs and or PFSAs, and a limited number of studies simulate AFFF discharge field conditions. By enhancing understanding of zwitterionic and cationic PFAS sorption, transport and likely subsurface location (i.e. predominantly in groundwater or sorbed to soil) can better direct subsurface remediation efforts and mitigate off-site migration. Chapter 2 discusses a data analysis test for non-target analysis and the subsequent serendipitous discovery of two ultrashort chained PFSAs. Select 3M AFFFs and AFFF-impacted groundwater samples, each from 11 different U.S. military bases were analyzed using quadrupole time-of-flight mass spectrometry (qTOF-MS). Kendrick mass defect plots were used to identify known homologs within a homologous series. Careful inspection of the PFSA homologous series led to the serendipitous discovery of the C₂ and C₃ PFSAs in 3M AFFF and AFFF-impacted groundwater. The C₂ and C₃ PFSAs were quantified using liquid chromatograph tandem mass spectrometry. Chapter 3 uses the developed non-target data analysis strategy to attempt to close the mass balance of PFASs in AFFF-impacted groundwater. Select 3M and fluorotelomer AFFFs, commercial products, and AFFF-impacted groundwater samples from 15 different sites were used to identify the remaining PFASs. Liquid chromatography qTOF-MS was used for compound discovery. Nontarget analysis and suspect screening were conducted. For nontarget analysis, a ‘nontarget’ R script in combination with Kendrick mass defect plots aided in compound identification. Suspect screening compared detected masses against a list of previously reported PFASs. Forty novel classes of anionic, zwitterionic, and cationic PFASs were discovered, and an additional 17 classes of previously reported PFASs were observed for the first time in AFFF and or AFFF-impacted groundwater. All 57 classes received an acronym and IUPAC-like name. Overall, of the newly discovered PFASs, ~ 68% were zwitterionic or cationic PFASs. Chapter 4 selects the representative National Foam AFFF to determine the soil properties influencing the sorption of model anionic fluorotelomer sulfonates (FtSs), zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and the cationic 6:2 fluorotelomer sulfonamido amine (FtSaAm). Batch sorption experiments were conducted using the whole National Foam AFFF, with initial aqueous phase concentrations of the 6:2 FtSaB ranging from 1,000 to 138,000,000 ng L, which represent concentrations of dilute groundwater plumes up to the application of 3% AFFF used in fire fighter training and emergency responses. Six blank soils with varying organic carbon, cation exchange capacity (CEC) and anion exchange capacity as well as a select soil buffered to pH 4 and 7 were used to determine the factors predominantly impacting sorption. A new, aggressive soil extraction method was developed due to incomplete mass balance of the FtSaBs and the 6:2 FtSaAm using published extraction methods. Hydrophobic interactions drove the sorption of the anionic FtSs, while the FtSaBs were influenced primarily by CEC. The 6:2 FtSaAm was depleted from the aqueous phase in all but one soil, and therefore, sorption is likely driven by a combination of CEC and organic carbon.