Discovery and Implications of C₂ and C₃ Perfluoroalkyl Sulfonates in Aqueous Film-Forming Foams and Groundwater

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C₄–C₁₀ homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11–7500 ng/L) and PFPrS in all samples (19–63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging

Per- and Polyfluoroalkyl Substances (PFASs) and Aqueous Film-Forming Foam Impacted Sites : New PFAS Discovery and Sorption of Anionic, Zwitterionic, and Cationic PFASs

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

Barzen-Hanson KristaChemistryDiscoveryImplicationsC-2 C-3PerfluoroalkylSupportingInformation.pdf

Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C₄–C₁₀ homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11–7500 ng/L) and PFPrS in all samples (19–63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging

Barzen-Hanson KristaChemistryDiscoveryImplicationsC-2 C-3Perfluoroalkyl.pdf

Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C₄–C₁₀ homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11–7500 ng/L) and PFPrS in all samples (19–63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging

Discovery and Implications of C₂ and C₃ Perfluoroalkyl Sulfonates in Aqueous Film-Forming Foams and Groundwater

Historically, 3M aqueous film-forming foams (AFFFs) were released at U.S. military and civilian sites to extinguish hydrocarbon-based fuel fires. To date, only C₄–C₁₀ homologues of the perfluoroalkyl sulfonic acids (PFSAs) are documented in 3M AFFFs. Perfluoroethanesulfonate (PFEtS) and perfluoropropanesulfonate (PFPrS), two ultra-short-chain PFSAs, were discovered by liquid chromatography (LC) quadrupole time-of-flight mass spectrometry. Once they were identified, PFEtS and PFPrS were then quantified in five 3M AFFFs and in one groundwater sample from each of 11 U.S. military bases by LC tandem mass spectrometry. Concentrations of PFEtS and PFPrS in the five AFFFs ranged from 7 to 13 mg/L and from 120 to 270 mg/L, respectively. For the groundwater, PFEtS was quantified in 8 of the 11 samples (11–7500 ng/L) and PFPrS in all samples (19–63000 ng/L). The high water solubility, mobility, and detection frequency of these ultra-short-chain PFSAs indicate that groundwater contaminant plumes may be larger than previously believed, and their removal by conventional activated carbon will be challenging

Sorption of Fluorotelomer Sulfonates, Fluorotelomer Sulfonamido Betaines, and a Fluorotelomer Sulfonamido Amine in National Foam Aqueous Film-Forming Foam to Soil

During fire-fighter training, equipment testing, and emergency responses with aqueous film-forming foams (AFFFs), milligrams per liter concentrations of anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFASs) enter the environment. Because the behavior of zwitterionic and cationic PFASs in the subsurface is unknown, batch sorption experiments were conducted using National Foam AFFF, which contains anionic fluorotelomer sulfonates (FtSs), zwitterionic fluorotelomer sulfonamido betaines (FtSaBs), and cationic 6:2 fluorotelomer sulfonamido amine (FtSaAm). Sorption of the FtSs, FtSaBs, and 6:2 FtSaAm to six soils with varying organic carbon, effective cation-exchange capacity, and anion-exchange capacity was evaluated to determine sorption mechanisms. Due to the poor recovery of the FtSaBs and 6:2 FtSaAm with published PFAS soil extraction methods, a new soil extraction method was developed to achieve good (90–100%) recoveries. The 6:2 FtSaAm was depleted from the aqueous phase in all but one soil, which is attributed to electrostatic and hydrophobic interactions. Sorption of the FtSs was driven by hydrophobic interactions, while the FtSaBs behave more like cations that strongly associate with the solid phase relative to groundwater. Thus, the sorption mechanisms of the FtSs, FtSaBs, and 6:2 FtSaAm are more complex than expected and cannot be predicted by bulk soil properties

Practical Application Guide for the Discovery of Novel PFAS in Environmental Samples Using High Resolution Mass Spectrometry

Background The intersection of the topics of high-resolution mass spectrometry (HRMS) and per- and polyfluoroalkyl substances (PFAS) bring together two disparate and complex subjects. Recently non-targeted analysis (NTA) for the discovery of novel PFAS in environmental and biological media has been shown to be valuable in multiple applications. Classical targeted analysis for PFAS using LC-MS/MS, though growing in compound coverage, is still unable to inform a holistic understanding of the PFAS burden in most samples. NTA fills at least a portion of this data gap. Objectives Entrance into the study of novel PFAS discovery requires identification techniques such as HRMS (e.g., QTOF and Orbitrap) instrumentation. This requires practical knowledge of best approaches depending on the purpose of the analyses. The utility of HRMS applications for PFAS discovery is unquestioned and will likely play a significant role in many future environmental and human exposure studies. Methods/Results PFAS have some characteristics that make them standout from most other chemicals present in samples. Through a series of tell-tale PFAS characteristics (e.g., characteristic mass defect range, homologous series and characteristic fragmentation patterns), and case studies different approaches and remaining challenges are demonstrated. Impact statement: The identification of novel PFAS via non-targeted analysis using high resolution mass spectrometry is an important and difficult endeavor. This synopsis document will hopefully make current and future efforts on this topic easier to perform for novice and experienced alike. The typical time devoted to NTA PFAS investigations (weeks to months or more) may benefit from these practical steps employed

Discovery of 40 Classes of Per- and Polyfluoroalkyl Substances in Historical Aqueous Film-Forming Foams (AFFFs) and AFFF-Impacted Groundwater

Aqueous film-forming foams (AFFFs), containing per- and polyfluoroalkyl substances (PFASs), are released into the environment during response to fire-related emergencies. Repeated historical applications of AFFF at military sites were a result of fire-fighter training exercises and equipment testing. Recent data on AFFF-impacted groundwater indicates that ∼25% of the PFASs remain unidentified. In an attempt to close the mass balance, a systematic evaluation of 3M and fluorotelomer-based AFFFs, commercial products, and AFFF-impacted groundwaters from 15 U.S. military bases was conducted to identify the remaining PFASs. Liquid chromatography quadrupole time-of-flight mass spectrometry was used for compound discovery. Nontarget analysis utilized Kendrick mass defect plots and a “nontarget” R script. Suspect screening compared masses with those of previously reported PFASs. Forty classes of novel anionic, zwitterionic, and cationic PFASs were discovered, and an additional 17 previously reported classes were observed for the first time in AFFF and/or AFFF-impacted groundwater. All 57 classes received an acronym and IUPAC-like name derived from collective author knowledge. Thirty-four of the 40 newly identified PFAS classes derive from electrochemical fluorination (ECF) processes, most of which have the same base structure. Of the newly discovered PFASs found only in AFFF-impacted groundwater, 11 of the 13 classes are ECF-derived, and the remaining two classes are fluorotelomer-derived, which suggests that both ECF- and fluorotelomer-based PFASs are persistent in the environment