Biological and Chemical Transformation of the Six-Carbon Polyfluoroalkyl Substance N-Dimethyl Ammonio Propyl Perfluorohexane Sulfonamide (AmPr-FHxSA)

Assessment of PFAS contamination in agricultural soils: Non-target identification of precursors, fluorine mass balance and microcosm studies

Biodegradation of PFAS is examined in eight PFAS precursor-contaminated topsoil samples in order to determine generation rate constants for perfluorocarboxyl acids (PFCA) and to elucidate soil properties affecting these. PFAS were analyzed via both target (HPLC-MS/MS) and non-target (HPLC-QTOF) (semi)quantification. FTMAPs, diPAPs, and diSAmPAP were identified and accounted for > 80 % of the total PFAS burden, which ranged from ∼ 280-9700 ng g-1. These levels were confirmed by chemical oxidation of precursors (TOP assay) which allowed to close the fluorine mass balance against extractable organic fluorine (EOF). Notably, in some organic carbon rich samples, repeated oxidation was needed to achieve a complete fluorine mass balance. Batch microcosm incubations and total precursor quantification allowed to determine production rate constants of short-chain PFCA, which ranged from 0.02 to 0.50 year-1 depending on PFAS and soil physicochemical properties. Principal component analysis (PCA) indicated that both acid phosphomonoesterase and, to some extent, microbial biomass influences the production rates of short-chain PFAS in soils. This allowed to assess contamination time scales, indicating that production and thus release of PFAS from precursor decay will continue for years to decades. This bears the risk of contamination of adjacent environmental compartments such as groundwater and surface water bodies.

The effects of perfluoroalkyl substance pollution on microbial community and key metabolic pathways in the Pearl River Estuary

The extensive use of perfluoroalkyl substances (PFASs) has raised significant concerns regarding their adverse environmental implications. However, the understanding of their behaviors and biological effects in natural estuarine ecosystems remain limited. This study employed a multidisciplinary approach integrating chemical analysis, biological sequencing, and statistical modeling to comprehensively investigate the distribution of PFASs, as well as their intrinsic relationship with microbial community in the Pearl River Estuary (PRE), a rapidly urbanized area. Our findings demonstrate that the total PFAS concentrations ranged from 52-127 ng L-1 in water, and 2-70 μg kg-1 dry weight in sediment, with notably distinct compositions across habitats. Aquatic microbial communities exhibited higher sensitivity to environmental variables, including PFAS concentrations, attributed to increased stochasticity and reduced spatial turnover. Conversely, sediments harbored microbial communities with higher phylogenetic diversity, rendering them less susceptible to PFAS-induced stress. Furthermore, PFAS concentrations significantly affected microbial carbon, nitrogen, and phosphorus cycling, predominantly through indirect alterations in characteristic genus composition. Importantly, noteworthy variations in impacts were observed between perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), which might contingent upon C-F bond dissociation energies. The findings shed light on PFAS ecological roles and interaction patterns with microbial communities in human-impacted estuarine environments.

Perfluoroalkane Sulfonamides and Derivatives, a Different Class of PFAS: Sorption and Microbial Biotransformation Insights

Perfluoroalkane sulfonamides and their derivatives (FASAs), an emerging subclass of per- and polyfluoroalkyl substances (PFAS), have attracted increasing attention due to their widespread applications, environmental persistence, and potential biological toxicity. Unlike perfluoroalkyl acids (PFAAs), FASAs can be transformed by microorganisms in the environment, producing fluorinated intermediates that eventually form stable PFAAs. A key difference of FASAs is that their pKas enable them to exist as neutral species or zwitterions, unlike all other PFAS subclasses, which are all anions. Sorption processes regulate the bioavailability of FASAs to microorganisms for transformation, driving the environmental transport and fate of FASAs. In this critical review, we provide a comprehensive overview of the classification, properties, and environmental fate of FASAs, with a focus on sorption and microbial transformation. We discuss recent advancements in understanding the sorption of FASAs onto soil, sediment, and microbial biomass, including key sorption descriptors and influencing factors. Additionally, we examine the microbial biotransformation of FASAs, detailing transformation pathways, key intermediates, transformation kinetics, and enzymes involved. Finally, we identify critical research gaps and propose future directions to advance the study of the sorption and biotransformation of FASAs in environmental systems. Mechanistic understanding of these processes is crucial for managing sites impacted with FASAs.

Biotic and abiotic transformations of aqueous film-forming foam (AFFF)-derived emerging polyfluoroalkyl substances in aerobic soil slurry

The severe contamination of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF)-affected soil and groundwater has raised global concerns. Although extensive studies on the transformation of electrochemical fluorination (ECF)-based PFAS in soil exist, limited research on AFFF-derived emerging fluorotelomer (FT) compounds has been conducted. Herein, a total of 38 PFAS were identified in a composite AFFF formulation through suspect and nontarget screening using high-resolution mass spectrometry (HRMS), and emerging 6:2 FT compounds were particularly prominent. Subsequently, the composite AFFF formulation was introduced to aerobic soil slurry to investigate the transformation behaviors of nine high-abundance polyfluoroalkyl substances. After a 150-day incubation, polyfluorinated sulfonamide betaine and quaternary ammonium compounds showed significant recalcitrance. The tertiary amine- and thioether-based PFAS underwent biotic and abiotic transformations, with half-lives ranging from 2 to 56 days and from 38 to 248 days, respectively. On the basis of the products identified using HRMS, the transformation pathways of FT- and ECF-based PFAS were proposed. Notably, the hydroxylation of tertiary amines and the oxidation of thioethers were two major abiotic reactions. Toxicity prediction revealed that certain transformation products exhibited higher toxicity toward aquatic organisms compared with the parent compounds. This study provides valuable insights into the stability and transformation of emerging PFAS in aerobic soil.

Practical considerations for the optimization of in situ mineralization of perfluorocarboxylic acids and polyfluoroalkyl substances using persulfate oxidation

Military bases and airports are often contaminated by per- and polyfluoroalkyl substances (PFAS) due to the repeated use of aqueous film forming foams (AFFFs) from decades of training exercises, equipment testing, and extinguishing of fuel- and solvent-based fires. Pump-and-treat systems combined with sorption processes are common ex situ remediation strategies; however, they can be expensive and may require decades of operation, particularly at sites where long-term diffusion and desorption of contaminants are the primary release processes. Alternatively, in situ chemical oxidation is an effective remediation strategy in which oxidants (e.g., persulfate, hydrogen peroxide) are injected into an aquifer to react with contaminants on site, and is competitive with alternative remediation techniques, such as pump-and-treat and ex situ treatment options. Specifically, heat-activated persulfate oxidation (HAPO) creates highly reactive sulfate radicals that under sufficiently acid conditions can mineralize perfluoroalkyl carboxylic acids (PFCAs) and many of the polyfluoroalkyl substances in AFFF. Sulfate radicals, however, can be scavenged by solutes present in groundwater, reducing the efficiency of PFCA transformation. To assess the application of HAPO, we conducted experiments under conditions typical of source zones where remediation is likely to be employed. We found that repeated treatment of aquifer solids with modest amounts of persulfate (50-300 mM) at low temperature activation (40 °C) could reduce the concentrations of precursors and PFCAs with chain lengths greater than three carbons by over 95 %. Following treatment, addition of strong base (i.e., NaOH) was needed to neutralize acidity and convert dissolved metals back into less mobile forms.

Harnessing the power of microbial consortia for the biodegradation of per- and polyfluoroalkyl substances: Challenges and opportunities

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants that pose significant risks to human health and ecosystems owing to their widespread use and resistance to degradation. This study examines the potential of microbial consortia as a sustainable and effective strategy for biodegrading PFAS. It highlights how these complex communities interact with various PFAS, including perfluorocarboxylic acids, perfluorosulfonic acids, fluorotelomer alcohols, and fluorotelomer-based precursors. Despite the potential of microbial consortia, several challenges impede their application in PFAS remediation, including effective microbial species identification, inherent toxicity of PFAS compounds, co-contaminants, complications from biofilm formation, diversity of environmental matrices, and competition with native microbial populations. Future research should focus on refining characterization techniques to enhance our understanding of microbial interactions and functions within consortia. Integrating bioinformatics and system biology will enable a comprehensive understanding of microbial dynamics and facilitate the design of tailored consortia for specific PFAS compounds. Furthermore, field applications and pilot studies are essential for assessing the real-world effectiveness of microbial remediation strategies. Ultimately, advancing our understanding and methodologies will lead to efficient biodegradation processes and positioning microbial consortia as viable solutions for PFAS-contaminated environments.

Biotransforming the "Forever Chemicals": Trends and Insights from Microbiological Studies on PFAS

Per- and polyfluoroalkyl substances (PFAS) are recalcitrant contaminants of emerging concern. Research efforts have been dedicated to PFAS microbial biotransformation in the hopes of developing treatment technologies using microorganisms as catalysts. Here, we performed a meta-analysis by extracting and standardizing quantitative data from 97 microbial PFAS biotransformation studies and comparing outcomes via statistical tests. This meta-analysis indicated that the likelihood of PFAS biotransformation was higher under aerobic conditions, in experiments with defined or axenic cultures, when high concentrations of PFAS were used, and when PFAS contained fewer fluorine atoms in the molecule. This meta-analysis also documented that PFAS biotransformation depends on chain length, chain branching geometries, and headgroup chemistry. We found that the literature is scarce or lacking in (i) anaerobic PFAS biotransformation experiments with well-defined electron acceptors, electron donors, carbon sources, and oxidation-reduction potentials, (ii) analyses of PFAS biotransformation products, and (iii) analyses to identify microorganisms and enzymes responsible for PFAS biotransformation. To date, most biotransformation research emphasis has been on 8:2 fluorotelomer alcohol (8:2 FTOH), 6:2 fluorotelomer alcohol (6:2 FTOH), perfluorooctanesulfonic acid (PFOS), and perfluorooctanoic acid (PFOA). A wide array of PFAS remains to be tested for their potential to biotransform.

Assessing the efficacy of the Plasma Spinning Disc Reactor (PSDR) in treating undiluted Aqueous Film Forming Foams (AFFFs)

This work used pulsed electrical discharge plasma to treat undiluted Aqueous Film Forming Foam (AFFF) solution that contained significant quantities of per- and polyfluoroalkyl substances (PFAS). The plasma was generated within a plasma spinning disc reactor (PSDR), which utilizes the electric breakdown of argon gas to create plasma over a thin liquid film generated on a spinning disc. The PSDR performance toward degradation of AFFF constituents such as fluorotelomers, perfluorinated C2-C7 alkyl acids, and unidentified precursors was investigated. The PSDR performance sensitivity to the process parameters, such as reactor electrode design, disc rotational speed, liquid flowrate across the disc, and discharge voltage, was explored. The results indicate degradation of all quantified PFAS with chain length ≥ 4 to below detection limit within a 250 mL sample after 86 h of treatment on a 6.5 cm disc rotating at 200 rpm. The overall PSDR performance was insensitive to the tested process parameters. A direct comparison with a UV/H2O2 process revealed the superior performance of the plasma-based treatment toward degradation of perfluorinated compounds, evidenced by higher precursor removal rates and lower energy consumption. The energy efficiency of the UV/H2O2 system was approximately 100 times lower than that of the plasma process under all conditions. This study confirms that PSDR is a promising technology for effectively remediating PFAS in undiluted AFFF.

Selective Quantification of Charged and Neutral Polyfluoroalkyl Substances Using the Total Oxidizable Precursor (TOP) Assay

Perfluoroalkyl acid (PFAA) precursors are a diverse subclass of per- and polyfluoroalkyl substances (PFASs) that can be transformed into PFAAs of public health concern. Unlike strongly acidic PFAAs, precursors can be anionic, cationic, neutral, or zwitterionic. Precursor charge affects the environmental fate, but existing quantification techniques struggle to ascertain the abundance of compounds within each charge group. To fill this gap, we developed and validated a solid-phase extraction procedure that separates precursors by charge and quantifies the sum of the precursors in each fraction with the total oxidizable precursor (TOP) assay. Method performance was demonstrated by spiking known concentrations of ten precursors into aqueous film-forming foam (AFFF)-impacted groundwater, municipal wastewater, and soil samples. Precursor fractionation and recovery were greater in groundwater and soil samples than in wastewater. Use of the method provided results that were consistent with expectations based on precursor transport properties. In surficial soils near an AFFF source zone, anionic precursors with five or fewer perfluorinated carbons accounted for about 95% of PFASs, but less than half of PFASs in the underlying groundwater. In municipal wastewater influent, the sum of precursors exceeded the sum of PFAAs and was approximately equally distributed among all charge fractions.

Zwitterionic, cationic, and anionic PFAS in freshwater sediments from AFFF-impacted and non-impacted sites of Eastern Canada

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFAS) were investigated in freshwater sediments of Canada, including sites impacted by aqueous film-forming foams (AFFFs). The first step of the project involved optimizing the extraction method with equilibrated sediment-water-AFFF samples. The analytical method had acceptable linearity, accuracy, and precision in the sediment matrix, and was further validated with NIST SRM 1936. In the second step of the project, the method was applied to determine over 70 target PFAS in field-collected sediments (n = 102). At federal contaminated sites of Ontario, Newfoundland, and Québec (ditches and creeks at international airports with fire training or fire equipment testing areas), summed PFAS averaged 30 ng/g (maximum of 160 ng/g) with molecular patterns dominated by perfluorooctane sulfonate (maximum PFOS: 84 ng/g). Based on maximum observed concentrations >10 ng/g, other key PFAS at these AFFF-impacted sites included negative ion mode perfluorohexane sulfonate, perfluorohexane sulfonamide, fluorotelomer sulfonates (6:2 FTS and 8:2 FTS) and 5:3 fluorotelomer acid, and positive ion mode N-dimethylammoniopropyl perfluorohexane sulfonamide and 5:1:2 fluorotelomer betaine. In contrast, environmental sediment samples collected at a larger spatial scale (province-wide survey) were characterized by low ΣPFAS (generally <1 ng/g), with PFOS/PFOA below chronic toxicity thresholds for aquatic life.

Investigation of Transformation Pathways of Polyfluoroalkyl Substances during Chlorine Disinfection

Recent regulations on perfluorinated compounds in drinking water underscore the need for a deeper understanding of the formation of perfluorinated compounds from polyfluoroalkyl substances during chlorine disinfection. Among the compounds investigated in this study, N-(3-(dimethylaminopropan-1-yl)perfluoro-1-hexanesulfonamide (N-AP-FHxSA) underwent rapid transformation during chlorination. Within an hour, it produced quantitative yields of various poly- and per-fluorinated products, including perfluorohexanoic acid (PFHxA). Sixteen reactions involving chlorine with N-AP-FHxSA and its quaternary ammonium analog were investigated; seven were confirmed, while the remainder were either disproved or found to be insignificant. The quaternary ammonium moiety did not determine a polyfluoroalkyl substance's reactivity toward chlorine. For example, while 6:2 fluorotelomer sulfonamide betaine transformed rapidly to PFHxA, other quaternary-ammonium-containing polyfluoroalkyl substances, such as 5:1:2 and 5:3 fluorotelomer betaines, showed significant resistance to chlorination. Further investigation identified potential sites for electrophilic attacks near the amine region by examining the highest occupied molecular orbitals of the polyfluoroalkyl substances. Visualization techniques helped pinpoint electron-deficient and electron-rich sites as potential targets for nucleophilic and electrophilic attacks, respectively. Increasing the solution pH from 6 to 10 did not diminish the apparent degradation of the studied polyfluoroalkyl substances, likely due to the greater reactivity of the deprotonated forms compared to the conjugate acids. Finally, we also examined the hydrolysis of polyfluoroalkyl substances at pH 6 to 11 in the absence of chlorine.

Cascading Pathways Regulate the Biotransformations of Eight Fluorotelomer Acids Performed by Wastewater Microbial Communities

Polyfluoroalkyl substances can be biotransformed in natural or engineered environmental systems to generate perfluoroalkyl acids (PFAAs). Data are needed to support the development of biotransformation pathway prediction tools that simulate biotransformation pathways of polyfluoroalkyl substances in specific environmental systems. The goal of this study was to experimentally evaluate the biotransformation of eight structurally similar fluorotelomer acids to identify biotransformation products and propose biotransformation pathways. We selected six fluorotelomer carboxylic acids and two fluorotelomer sulfonic acids and employed a biotransformation test system in which batch reactors are seeded with aerobic wastewater microbial communities. We identified 111 biotransformation products among the eight parent compounds, 58 of which represent unique chemical structures. Many of the biotransformation products are the result of apparent dehydrogenation, monohydroxylation, alcohol oxidation, decarboxylation, HF-elimination, and reductive defluorination biotransformations. We use these data to propose cascading biotransformation pathways that are regulated by integrated and synergistic α-oxidation-like, β-oxidation-like, and defluorination biotransformations that result in the formation of terminal PFAAs of varying chain length. Our data provide a comprehensive view on the aerobic biotransformation of fluorotelomer acids and our results can be used to support the ongoing development of biotransformation pathway prediction tools.

Fate and Transformation of 15 Classes of Per- and Polyfluoroalkyl Substances in Aqueous Film-Forming Foam (AFFF)-Amended Soil Microcosms

The environmental fate of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFFs), especially those synthesized by electrochemical fluorination (ECF) processes, remains largely unknown. This study evaluated the transformation of AFFF-derived ECF-based precursors in aerobic soil microcosms amended with a historically used AFFF formulation (3M Light WaterTM). Fifteen classes of PFAS, including AFFF components and transformation products, were identified or tentatively identified by suspect screening/nontargeted analysis (SSA/NTA) throughout a 308-day incubation. This study demonstrates that AFFF-derived ECF-based precursors serve as sources of perfluoroalkane sulfonamides (FASAs) and perfluoroalkyl acids (PFAAs), which are commonly detected at AFFF-impacted sites. Temporal sampling provided evidence for biotransformation of multiple precursors including tri- or dimethyl ammonio propyl perfluoroalkane sulfonamides. Additionally, the environmental stability (i.e., resistance to transformation) of ECF-based precursors was found to depend upon structural characteristics, including perfluoroalkyl chain length, presence of sulfonamide or carboxamide groups, and functional groups (e.g., a branch of carboxyalkyl group) attached to the nitrogen atoms. These findings provide insights into the transformation pathways of AFFF-derived PFAS and other structurally similar ECF-based PFAS, which will support the management and remediation of PFAS contamination at legacy AFFF-impacted sites.

Assessing strategies to measure hidden per- and polyfluoroalkyl substances (PFAS) in groundwater and to evaluate adsorption remediation efficiencies

The widespread presence of per- and polyfluoroalkyl substances (PFAS) in the environment, driven by extensive industrial use, has raised global concerns due to their persistence and adverse health effects. Despite the increased regulatory focus on a sub-set of well-known PFAS, over 12,000 compounds exist, many poorly characterized. Our study assessed hidden PFAS concentrations, undetectable by standard LC-MS/MS analysis, in contaminated groundwater. We analyzed total oxidizable precursors (TOP) via TOP assay followed by LC-MS/MS, and total organic fluorine (TOF) via combustion ion chromatography (CIC). Results were compared with those from LC-MS/MS analysis of 25 individual PFAS (∑PFAS25), representing the non-hidden PFAS fraction. We also evaluated the removal of hidden PFAS employing conventional and novel adsorbents. Groundwater samples from drinking water sources and contaminated military sites in the USA showed varying PFAS contamination levels as indicated by TOF values ranging from non-detect (<0.7 μg L-1) to 40.2 μg L-1. ∑PFAS25 was a major fraction of the TOF (41.7 - 92.8%) in some samples, whereas in others it only accounted for 5.1 - 20.4% of the TOF. The remaining percentages consisted of hidden PFAS not detected by conventional LC-MS/MS, but detectable as TOF by CIC. Organic fluorine content of oxidizable precursors accounted for 0.0-39.0% of TOF content, depending on the sample. Selected samples underwent adsorption with activated carbon (AC), anion exchange resin (IX), polyaniline (PANI), and poly-o-toluidine (POT). All adsorbents removed the hidden PFAS less effectively than the PFAS quantified by direct LC-MS/MS techniques. This is likely because PFAS adsorbents investigated to date primarily target anionic per- and polyfluoroalkyl acids, not effectively removing cationic, neutral, or zwitterionic hidden PFAS. AC exhibited the best overall performance among the investigated adsorbents. The results demonstrate that measuring TOP and TOF concentrations is effective for evaluating the removal of hidden PFAS in groundwater remediation.

N-glucuronidation and Excretion of Perfluoroalkyl Sulfonamides in Mice Following Ingestion of Aqueous Film-Forming Foam

Perfluoroalkyl sulfonamides (FASAs) and other FASA-based per- and polyfluoroalkyl substances (PFASs) can transform into recalcitrant perfluoroalkyl sulfonates in vivo. We conducted high-resolution mass spectrometry suspect screening of urine and tissues (kidney and liver) from mice dosed with an electrochemically fluorinated aqueous film-forming foam (AFFF) to better understand the biological fate of AFFF-associated precursors. The B6C3F1 mice were dosed at five levels (0, 0.05, 0.5, 1, and 5 mg kg-1 day-1) based on perfluorooctane sulfonate and perfluorooctanoate content of the AFFF mixture. Dosing continued for 10 days followed by a 6-day depuration. Total oxidizable precursor assay of the AFFF suggested significant contributions from precursors with three to six perfluorinated carbons. We identified C4 to C6 FASAs and N-glucuronidated FASAs (FASA-N-glus) excreted in urine collected throughout dosing and depuration. Based on normalized relative abundance, FASA-N-glus accounted for up to 33% of the total excreted FASAs in mouse urine, highlighting the importance of phase II metabolic conjugation as a route of excretion. High-resolution mass spectrometry screening of liver and kidney tissue revealed accumulation of longer-chain (C7 and C8) FASAs not detected in urine. Chain-length-dependent conjugation of FASAs was also observed by incubating FASAs with mouse liver S9 fractions. Shorter-chain (C4) FASAs conjugated to a much greater extent over a 120-min incubation than longer-chain (C8) FASAs. Overall, this study highlights the significance of N-glucuronidation as an excretion mechanism for short-chain FASAs and suggests that monitoring urine for FASA-N-glus could contribute to a better understanding of PFAS exposure, as FASAs and their conjugates are often overlooked by traditional biomonitoring studies. Environ Toxicol Chem 2024;43:2274-2284. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Characterizing the Areal Extent of PFAS Contamination in Fish Species Downgradient of AFFF Source Zones

Most monitoring programs next to large per- and polyfluoroalkyl substances (PFAS) sources focus on drinking water contamination near source zones. However, less is understood about how these sources affect downgradient hydrological systems and food webs. Here, we report paired PFAS measurements in water, sediment, and aquatic biota along a hydrological gradient away from source zones contaminated by the use of legacy aqueous film-forming foam (AFFF) manufactured using electrochemical fluorination. Clustering analysis indicates that the PFAS composition characteristic of AFFF is detectable in water and fishes >8 km from the source. Concentrations of 38 targeted PFAS and extractable organofluorine (EOF) decreased in fishes downgradient of the AFFF-contaminated source zones. However, PFAS concentrations remained above consumption limits at all locations within the affected watershed. Perfluoroalkyl sulfonamide precursors accounted for approximately half of targeted PFAS in fish tissues, which explain >90% of EOF across all sampling locations. Suspect screening analyses revealed the presence of a polyfluoroketone pharmaceutical in fish species, and a fluorinated agrochemical in water that likely does not accumulate in biological tissues, suggesting the presence of diffuse sources such as septic system and agrochemical inputs throughout the watershed in addition to AFFF contamination. Based on these results, monitoring programs that consider all hydrologically connected regions within watersheds affected by large PFAS sources would help ensure public health protection.

Non-target screening reveals 124 PFAS at an AFFF-impacted field site in Germany specified by novel systematic terminology

The uncontrolled release of aqueous film-forming foam (AFFF) ingredients during a major fire incident in Reilingen, Germany, in 2008 led to significant soil and groundwater contamination. As the identity of fluorochemical surfactants in AFFF are often veiled due to company secrets, it is important to characterize AFFF contaminations and their impact on the environment comprehensively. In this study, we adapted a systematic approach combining a suitable extraction method with liquid chromatography high-resolution quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) for an extensive non-targeted analysis. Our analysis identified 124 per- and polyfluoroalkyl substances (PFAS) from 42 subclasses in the contaminated soil (confidence levels of identification between 1 and 3). Typical for AFFF-impacted field sites, these included anionic, cationic, and zwitterionic substances with perfluoroalkyl chains spanning from 3 to 14 carbon atoms. Furthermore, we identified 1 previously unreported substance, and detected 9 PFAS subclasses for the first time in soil. AFFFs have long been employed to extinguish large hydrocarbon fires, yet their environmental consequences remain a concern. This study sheds light on the complex composition of AFFFs at this particularly contaminated area, emphasizing the necessity for extensive contaminant characterization as sound basis for informed management strategies to mitigate their adverse effects. AFFF PFAS are often named differently in the literature, leading to inconsistency in terminology. To address this issue, we introduced partially new terminology for AFFF-related PFAS to establish consistent terminology, to facilitate communication of identified compounds, and to ensure that the chemical structure can be directly derived from acronyms.

Fluorotelomer betaines and sulfonic acid in aerobic wetland soil: Stability, biotransformation, and bacterial community response

The microbial degradation of 6:2 fluorotelomer sulfonic acid (6:2 FTSA), fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), and fluorotelomer betaines (5:3 and 5:1:2 FTB) in aerobic wetland soil was investigated during a 100-day incubation. The half-lives of 6:2 FTSA in the treatments with diethylene glycol butyl ether as the sole carbon source (NA treatment) and with additional supplementation of sodium acetate (ED treatment) were determined to be 26.2 and 16.7 days, respectively. By day 100, ∼20 mol% of 6:2 FTAB was degraded in the NA and ED treatments. The potential transformation products of 6:2 FTSA and 6:2 FTAB were identified using liquid/gas chromatography-high resolution mass spectrometry, and their biotransformation pathways were proposed. In contrast, 5:3 and 5:1:2 FTB exhibited high persistence under two carbon source conditions. There was no intense alteration in the diversity of soil bacterial communities under the stress of fluorotelomer compounds at the level of ∼150 μg/L. The supplementation of sodium acetate led to an enrichment of bacterial species within the genera Hydrogenophaga (phylum Proteobacteria) and Rhodococcus (phylum Actinobacteria), promoting the biodegradation of 6:2 FTSA and 6:2 FTAB and the formation of transformation products. Species from the genus Rhodococcus were potentially crucial functional microorganisms involved in the degradation of 6:2 FTSA.

Biotransformation of PFAA Precursors by Oxygenase-Expressing Bacteria in AFFF-Impacted Groundwater and in Pure-Compound Studies with 6:2 FTS and EtFOSE

Numerous US drinking water aquifers have been contaminated with per- and polyfluoroalkyl substances (PFAS) from fire-fighting and fire-training activities using aqueous film-forming foam (AFFF). These sites often contain other organic compounds, such as fuel hydrocarbons and methane, which may serve as primary substrates for cometabolic (i.e., nongrowth-linked) biotransformation reactions. This work investigates the abilities of AFFF site relevant bacteria (methanotrophs, propanotrophs, octane, pentane, isobutane, toluene, and ammonia oxidizers), known to express oxygenase enzymes when degrading their primary substrates, to biotransform perfluoroalkyl acid (PFAA) precursors to terminal PFAAs. Microcosms containing AFFF-impacted groundwater, 6:2 fluorotelomer sulfonate (6:2 FTS), or N-ethylperfluorooctane sulfonamidoethanol (EtFOSE) were inoculated with the aerobic cultures above and incubated for 4 and 8 weeks at 22 °C. Bottles were sacrificed, extracted, and subjected to target, nontarget, and suspect screening for PFAS. The PFAA precursors 6:2 FTS, N-sulfopropyldimethyl ammoniopropyl perfluorohexane sulfonamide (SPrAmPr-FHxSA), and EtFOSE transformed up to 99, 71, and 93%, respectively, and relevant daughter products, such as the 6:1 fluorotelomer ketone sulfonate (6:1 FTKS), were identified in quantities previously not observed, implicating oxygenase enzymes. This is the first report of a suite of site relevant PFAA precursors being transformed in AFFF-impacted groundwater by bacteria grown on substrates known to induce specific oxygenase enzymes. The data provide crucial insights into the microbial transformation of these compounds in the subsurface.

High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site

The long-term leaching of polyfluoroalkyl substances (PFAS) within the vadose zone of an AFFF application site for which the depth to groundwater is approximately 100 m was investigated by characterizing the vertical distribution of PFAS in a high spatial resolution. The great majority (99%) of PFAS mass resides in the upper 3 m of the vadose zone. The depths to which each PFAS migrated, quantified by moment analysis, is an inverse function of molar volume, demonstrating chromatographic separation. The PFAS were operationally categorized into three chain-length groups based on the three general patterns of retention observed. The longest-chain (>∼335 cm3/mol molar volume) PFAS remained within the uppermost section of the core, exhibiting minimal leaching. Conversely, the shortest-chain (<∼220 cm3/mol) PFAS accumulated at the bottom of the interval, which coincides with the onset of a calcic horizon. PFAS with intermediate-chain lengths were distributed along the length of the core, exhibiting differential magnitudes of leaching. The minimal or differential leaching observed for the longest- and intermediate-chain-length PFAS, respectively, demonstrates that retention processes significantly impacted migration. The accumulation of shorter-chain PFAS at the bottom of the core is hypothesized to result from limited deep infiltration and potential-enhanced retention associated with the calcic horizon.

Sulfonamide Per- and Polyfluoroalkyl Substances Can Impact Microorganisms Used in Aromatic Hydrocarbon and Trichloroethene Bioremediation

Per- and polyfluoroalkyl substances (PFASs) from aqueous film forming foams (AFFFs) can hinder bioremediation of co-contaminants such as trichloroethene (TCE) and benzene, toluene, ethylbenzene, and xylene (BTEX). Anaerobic dechlorination can require bioaugmentation of Dehalococcoides, and for BTEX, oxygen is often sparged to stimulate in situ aerobic biodegradation. We tested PFAS inhibition to TCE and BTEX bioremediation by exposing an anaerobic TCE-dechlorinating coculture, an aerobic BTEX-degrading enrichment culture, and an anaerobic toluene-degrading enrichment culture to n-dimethyl perfluorohexane sulfonamido amine (AmPr-FHxSA), perfluorohexane sulfonamide (FHxSA), perfluorohexanesulfonic acid (PFHxS), or nonfluorinated surfactant sodium dodecyl sulfate (SDS). The anaerobic TCE-dechlorinating coculture was resistant to individual PFAS exposures but was inhibited by >1000× diluted AFFF. FHxSA and AmPr-FHxSA inhibited the aerobic BTEX-degrading enrichment. The anaerobic toluene-degrading enrichment was not inhibited by AFFF or individual PFASs. Increases in amino acids in the anaerobic TCE-dechlorinating coculture compared to the control indicated stress response, whereas the BTEX culture exhibited lower concentrations of all amino acids upon exposure to most surfactants (both fluorinated and nonfluorinated) compared to the control. These data suggest the main mechanisms of microbial toxicity are related to interactions with cell membrane synthesis as well as protein stress signaling.

PFAS Porewater concentrations in unsaturated soil: Field and laboratory comparisons inform on PFAS accumulation at air-water interfaces

Poly- and perfluoroalkyl substance (PFAS) leaching from unsaturated soils impacted with aqueous film-forming foams (AFFFs) is an environmental challenge that remains difficult to measure and predict. Complicating measurements and predictions of this process is a lack of understanding between the PFAS concentrations measured in a collected environmental unsaturated soil sample, and the PFAS concentrations measured in the corresponding porewater using field-deployed lysimeters. The applicability of bench-scale batch testing to assess this relationship also remains uncertain. In this study, field-deployed porous cup suction lysimeters were used to measure PFAS porewater concentrations in unsaturated soils at 5 AFFF-impacted sites. Field-measured PFAS porewater concentrations were compared to those measured in porewater extracted in the laboratory from collected unsaturated soil cores, and from PFAS concentrations measured in the laboratory using batch soil slurries. Results showed that, despite several years since the last AFFF release at most of the test sites, precursors were abundant in 3 out of the 5 sites. Comparison of field lysimeter results to laboratory testing suggested that the local equilibrium assumption was valid for at least 3 of the sites and conditions of this study. Surprisingly, PFAS accumulation at the air-water interface was orders of magnitude less than expected at two of the test sites, suggesting potential gaps in the understanding of PFAS accumulation at the air-water interface at AFFF-impacted sites. Finally, results herein suggest that bench-scale testing on unsaturated soils can in some cases be used to inform on PFAS in situ porewater concentrations.

Hunting the missing fluorine in aqueous film-forming foams containing per- and polyfluoroalkyl substances

Since aqueous film-forming foams (AFFFs) are major sources of per- and polyfluoroalkyl substances (PFAS), understanding the quantity and type of PFAS present in AFFFs is crucial for assessing environmental risk and remediation. We characterized 25 foams from Canada and Europe, including two non-AFFFs and two fluorine-free AFFFs. We used liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) to identify novel PFAS, as well as total oxidizable precursor assays (TOP) and total organofluorine (TOF) measurements for comparison. LC-HRMS showed that the two non-AFFF foams and two PFAS-free AFFFs contained little or no PFAS, confirmed by TOF measurement using combustion ion chromatography (CIC). The PFAS-containing AFFFs, however, spanned a wide concentration range of TOF (2200-45,000 mg F/L) and contained 22 new classes of polyfluoroalkyl substances not previously reported. As a result of identifying new compounds, LC-HRMS was fully able to capture the oxidizable precursors determined by TOP assay in all tested fluorotelomer (FT) AFFFs, while unknown compounds still constituted a significant fraction (19-53 mol%) in most electrochemical fluorination (ECF) AFFFs. A fluorine mass balance was achieved by comparing the amounts of compounds identified by LC-HRMS with those detected by CIC, although LC-HRMS overestimated TOF with a recovery of 127 ± 36%.

Stability and Biotransformation of 6:2 Fluorotelomer Sulfonic Acid, Sulfonamide Amine Oxide, and Sulfonamide Alkylbetaine in Aerobic Sludge

The 6:2 fluorotelomer sulfonamide (6:2 FTSAm)-based compounds signify a prominent group of per- and polyfluoroalkyl substances (PFAS) widely used in contemporary aqueous film-forming foam (AFFF) formulations. Despite their widespread presence, the biotransformation behavior of these compounds in wastewater treatment plants remains uncertain. This study investigated the biotransformation of 6:2 FTSAm-based amine oxide (6:2 FTNO), alkylbetaine (6:2 FTAB), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA) in aerobic sludge over a 100-day incubation period. The biotransformation of 6:2 fluorotelomer sulfonamide alkylamine (6:2 FTAA), a primary intermediate product of 6:2 FTNO, was indirectly assessed. Their stability was ranked based on the estimated half-lives (t1/2): 6:2 FTAB (no obvious products were detected) ≫ 6:2 FTSA (t1/2 ≈28.8 days) > 6:2 FTAA (t1/2 ≈11.5 days) > 6:2 FTNO (t1/2 ≈1.2 days). Seven transformation products of 6:2 FTSA and 15 products of 6:2 FTNO were identified through nontarget and suspect screening using high-resolution mass spectrometry. The transformation pathways of 6:2 FTNO and 6:2 FTSA in aerobic sludge were proposed. Interestingly, 6:2 FTSAm was hardly hydrolyzed to 6:2 FTSA and further biotransformed to perfluoroalkyl carboxylic acids (PFCAs). Furthermore, the novel pathways for the generation of perfluoroheptanoic acid (PFHpA) from 6:2 FTSA were revealed.

New PFASs Identified in AFFF Impacted Groundwater by Passive Sampling and Nontarget Analysis

Monitoring contamination from per- and polyfluoroalkyl substances (PFASs) in water systems impacted by aqueous film-forming foams (AFFFs) typically addresses a few known PFAS groups. Given the diversity of PFASs present in AFFFs, current analytical approaches do not comprehensively address the range of PFASs present in these systems. A suspect-screening and nontarget analysis (NTA) approach was developed and applied to identify novel PFASs in groundwater samples contaminated from historic AFFF use. A total of 88 PFASs were identified in both passive samplers and grab samples, and these were dominated by sulfonate derivatives and sulfonamide-derived precursors. Several ultrashort-chain (USC) PFASs (≤C3) were detected, 11 reported for the first time in Australian groundwater. Several transformation products were identified, including perfluoroalkane sulfonamides (FASAs) and perfluoroalkane sulfinates (PFASis). Two new PFASs were reported (((perfluorohexyl)sulfonyl)sulfamic acid; m/z 477.9068 and (E)-1,1,2,2,3,3,4,5,6,7,8,8,8-tridecafluorooct-6-ene-1-sulfonic acid; m/z 424.9482). This study highlights that several PFASs are overlooked using standard target analysis, and therefore, the potential risk from all PFASs present is likely to be underestimated.

Target and suspect per- and polyfluoroalkyl substances in fish from an AFFF-impacted waterway

A major source of toxic per- and polyfluoroalkyl substances (PFAS) is aqueous film-forming foams (AFFF) used in firefighting and training at airports and military installations, however, PFAS have many additional sources in consumer products and industrial processes. A field study was conducted on fish tissues from three reaches of the Columbia Slough, located near Portland International Airport, OR, that are affected by AFFF and other PFAS sources. Fishes including largescale sucker (Catostomus macrocheilus), goldfish (Carassius auratus), and largemouth bass (Micropterus salmoides) were collected in 2019 and 2020. Fish blood, liver, and fillet (muscle) were analyzed for target and suspect PFAS by liquid chromatography high resolution mass spectrometry (LC-HRMS). Data were analyzed for patterns by fish species, tissue type, and river reach. Thirty-three out of 50 target PFAS and additional suspect compounds were detected at least once during the study, at concentrations up to 856 ng/g. Seven carboxylic acids (PFOA, PFNA, PFDA, PFUdA, PFDoA, PFTrDA, PFTeDA), three sulfonates (PFHxS, PFOS, PFDS), three electrofluorination-based compounds (FBSA, FHxSA, FOSA), and two fluorotelomer-based compounds (8:2 FTS, 10:2 FTS) were the most frequently detected compounds in all tissue types. The C6 (PFHxS) to C10 (PFDS) homologs were detected with PFOS and FHxSA at concentrations 1-3 orders of magnitude greater than the other PFAS detected. This is the first report of Cl-PFOS, FPeSA, and FHpSA detected in fish tissue. In all fish samples, fillet concentrations of PFAS were the lowest, followed by liver, and blood concentrations of PFAS were the highest. Differences in PFAS concentrations were driven primarily by tissue types and to a lesser extent fish species, but weakly by river reach. The Oregon Health Authority modified an existing fish consumption advisory on the Columbia Slough to recommend no whole-body consumption of most fish to avoid elevated levels of PFOS in fish liver. Measured PFAS concentrations in fish tissues indicate the potential for adverse ecological effects.

Novel Per- and Polyfluoroalkyl Substances Discovered in Cattle Exposed to AFFF-Impacted Groundwater

The leaching of per- and polyfluoroalkyl substances (PFASs) from Australian firefighting training grounds has resulted in extensive contamination of groundwater and nearby farmlands. Humans, farm animals, and wildlife in these areas may have been exposed to complex mixtures of PFASs from aqueous film-forming foams (AFFFs). This study aimed to identify PFAS classes in pooled whole blood (n = 4) and serum (n = 4) from cattle exposed to AFFF-impacted groundwater and potentially discover new PFASs in blood. Thirty PFASs were identified at various levels of confidence (levels 1a-5a), including three novel compounds: (i) perfluorohexanesulfonamido 2-hydroxypropanoic acid (FHxSA-HOPrA), (ii) methyl((perfluorohexyl)sulfonyl)sulfuramidous acid, and (iii) methyl((perfluorooctyl)sulfonyl)sulfuramidous acid, belonging to two different classes. Biotransformation intermediate, perfluorohexanesulfonamido propanoic acid (FHxSA-PrA), hitherto unreported in biological samples, was detected in both whole blood and serum. Furthermore, perfluoroalkyl sulfonamides, including perfluoropropane sulfonamide (FPrSA), perfluorobutane sulfonamide (FBSA), and perfluorohexane sulfonamide (FHxSA) were predominantly detected in whole blood, suggesting that these accumulate in the cell fraction of blood. The suspect screening revealed several fluoroalkyl chain-substituted PFAS. The results suggest that targeting only the major PFASs in the plasma or serum of AFFF-exposed mammals likely underestimates the toxicological risks associated with exposure. Future studies of AFFF-exposed populations should include whole-blood analysis with high-resolution mass spectrometry to understand the true extent of PFAS exposure.

Legacy perfluoroalkyl acids and their oxidizable precursors in plasma samples of Norwegian women

Humans are exposed to perfluoroalkyl acids (PFAA) mainly through direct pathways, such as diet and drinking water, but indirect exposure also occurs when PFAA precursors break down to form legacy PFAA. Exposure to PFAA precursors raises particular concern, as neither the exposure nor the precursors themselves have been well described. In the present study, we aimed to assess the indirect contribution of oxidizable PFAA precursors to the total per- and polyfluoroalkyl substances (PFAS) burden in human plasma following the voluntary phase-out of production of long-chain PFAS. In addition, multiple logistic regression was used to explore associations between selected lifestyle and dietary factors and the oxidizable PFAA precursors fraction. This study included 302 cancer-free participants of the Norwegian Women and Cancer postgenome cohort. PFAS analyses were performed in plasma samples to determine PFAS concentrations before and after oxidation with the Total Oxidizable Precursor (TOP) assay. In pre-TOP analyses, perfluorooctane sulfonic acid (PFOS) was the dominant compound, followed by perfluorooctanoic acid (PFOA).The vast majority (98%) of the study population had increased post-TOP concentrations for at least one PFAA. The formation of PFAA accounted for 12% of the total PFAS burden, with seven PFAA observed post-TOP in at least 30% of study participants. PFHpA, br- PFOA, and PFDA were only detected in post-TOP analyses and showed the highest increase in concentrations. Of the PFAA with increased concentrations, we noted significant associations for year of birth, parity, BMI, and some dietary factors, although they were not consistent between the different PFAA. These results indicate that while the TOP assay might not provide a complete assessment of total PFAS burden in humans, it offers comprehensive assessment of unknown PFAA precursors that might be present in plasma, and it could therefore be implemented as an auxiliary tool in this regard.

PFAS in fish from AFFF-impacted environments: Analytical method development and field application at a Canadian international civilian airport

Methods targeting anionic per- and polyfluoroalkyl substances (PFAS) in aquatic biota are well established, but commonly overlook many PFAS classes present in aqueous film-forming foams (AFFFs). Here, we developed an analytical method for the expanded analysis of negative and positive ion mode PFAS in fish tissues. Eight variations of extraction solvents and clean-up protocols were first tested to recover 70 AFFF-derived PFAS from the fish matrix. Anionic, zwitterionic, and cationic PFAS displayed the best responses with methanol-based ultrasonication methods. The response of long-chain PFAS was improved for extracts submitted to graphite filtration alone compared with those involving solid-phase extraction. The validation included an assessment of linearity, absolute recovery, matrix effects, accuracy, intraday/interday precision, and trueness. The method was applied to a set of freshwater fish samples collected in 2020 in the immediate vicinity (creek, n = 15) and downstream (river, n = 15) of an active fire-training area at an international civilian airport in Ontario, Canada. While zwitterionic fluorotelomer betaines were major components of the subsurface AFFF source zone, they were rarely detected in fish, suggesting limited bioaccumulation potential. PFOS largely dominated the PFAS profile, with record-high concentrations in brook sticklebacks (Culaea inconstans) from the creek (16000-110,000 ng/g wet weight whole-body). These levels exceeded the Canadian Federal Environmental Quality Guidelines (FEQG) for PFOS pertaining to the Federal Fish Tissue Guideline (FFTG) for fish protection and Federal Wildlife Diet Guidelines (FWiDG) for the protection of mammalian and avian consumers of aquatic biota. Perfluorohexane sulfonamide and 6:2 fluorotelomer sulfonate were among the precursors detected at the highest levels (maximum of ∼340 ng/g and ∼1100 ng/g, respectively), likely reflecting extensive degradation and/or biotransformation of C6 precursors originally present in AFFF formulations.

High Persistence of Novel Polyfluoroalkyl Betaines in Aerobic Soils

Some contemporary aqueous film-forming foams (AFFFs) contain n:3 and n:1:2 fluorotelomer betaines (FTBs), which are often detected at sites impacted by AFFFs. As new chemical replacements, little is known about their environmental fate. For the first time, we investigated the biotransformation potential of 5:3 and 5:1:2 FTBs and a commercial AFFF that mainly contains n:3 and n:1:2 FTBs (n = 5, 7, 9, 11, and 13). Although some polyfluoroalkyl compounds are precursors to perfluoroalkyl acids, 5:3 and 5:1:2 FTBs exhibited high persistence, with no significant changes even after 120 days of incubation. While the degradation of 5:3 FTB into suspected products such as fluorotelomer acids or perfluoroalkyl carboxylic acids (PFCAs) could not be conclusively confirmed, we did identify a potential biotransformation product, 5:3 fluorotelomer methylamine. Similarly, 5:1:2 FTB did not break down or produce short-chain hydrogen-substituted polyfluoroalkyl acids (n:2 H-FTCA), hydrogen-substituted PFCA (2H-PFCA), or any other products. Incubating the AFFF in four soils with differing properties and microbial communities resulted in 0.023-0.25 mol % PFCAs by day 120. Most of the products are believed to be derived from n:2 fluorotelomers, minor components of the AFFF. Therefore, the findings of the study cannot be fully explained by the current understanding of structure-biodegradability relationships.

Nitrifying Microorganisms Linked to Biotransformation of Perfluoroalkyl Sulfonamido Precursors from Legacy Aqueous Film-Forming Foams

Drinking water supplies across the United States have been contaminated by firefighting and fire-training activities that use aqueous film-forming foams (AFFF) containing per- and polyfluoroalkyl substances (PFAS). Much of the AFFF is manufactured using electrochemical fluorination by 3M. Precursors with six perfluorinated carbons (C6) and non-fluorinated amine substituents make up approximately one-third of the PFAS in 3M AFFF. C6 precursors can be transformed through nitrification (microbial oxidation) of amine moieties into perfluorohexane sulfonate (PFHxS), a compound of regulatory concern. Here, we report biotransformation of the most abundant C6 sulfonamido precursors in 3M AFFF with available commercial standards (FHxSA, PFHxSAm, and PFHxSAmS) in microcosms representative of the groundwater/surface water boundary. Results show rapid (<1 day) biosorption to living cells by precursors but slow biotransformation into PFHxS (1-100 pM day^-1). The transformation pathway includes one or two nitrification steps and is supported by the detection of key intermediates using high-resolution mass spectrometry. Increasing nitrate concentrations and total abundance of nitrifying taxa occur in parallel with precursor biotransformation. Together, these data provide multiple lines of evidence supporting microbially limited biotransformation of C6 sulfonamido precursors involving ammonia-oxidizing archaea (Nitrososphaeria) and nitrite-oxidizing bacteria (Nitrospina). Further elucidation of interrelationships between precursor biotransformation and nitrogen cycling in ecosystems would help inform site remediation efforts.

Uptake of Per- and Polyfluoroalkyl Substances by Fish, Mussel, and Passive Samplers in Mobile-Laboratory Exposures Using Groundwater from a Contamination Plume at a Historical Fire Training Area, Cape Cod, Massachusetts

Aqueous film-forming foams historically were used during fire training activities on Joint Base Cape Cod, Massachusetts, and created an extensive per- and polyfluoroalkyl substances (PFAS) groundwater contamination plume. The potential for PFAS bioconcentration from exposure to the contaminated groundwater, which discharges to surface water bodies, was assessed with mobile-laboratory experiments using groundwater from the contamination plume and a nearby reference location. The on-site continuous-flow 21-day exposures used male and female fathead minnows, freshwater mussels, polar organic chemical integrative samplers (POCIS), and polyethylene tube samplers (PETS) to evaluate biotic and abiotic uptake. The composition of the PFAS-contaminated groundwater was complex and 9 PFAS were detected in the reference groundwater and 17 PFAS were detected in the contaminated groundwater. The summed PFAS concentrations ranged from 120 to 140 ng L-1 in reference groundwater and 6100 to 15,000 ng L-1 in contaminated groundwater. Biotic concentration factors (CFb) for individual PFAS were species, sex, source, and compound-specific and ranged from 2.9 to 1000 L kg-1 in whole-body male fish exposed to contaminated groundwater for 21 days. The fish and mussel CFb generally increased with increasing fluorocarbon chain length and were greater for sulfonates than for carboxylates. The exception was perfluorohexane sulfonate, which deviated from the linear trend and had a 10-fold difference in CFb between sites, possibly because of biotransformation of precursors such as perfluorohexane sulfonamide. Uptake for most PFAS in male fish was linear over time, whereas female fish had bilinear uptake indicated by an initial increase in tissue concentrations followed by a decrease. Uptake of PFAS was less for mussels (maximum CFb = 200) than for fish, and mussel uptake of most PFAS also was bilinear. Although abiotic concentration factors were greater than CFb, and values for POCIS were greater than for PETS, passive samplers were useful for assessing PFAS that potentially bioconcentrate in fish but are present at concentrations below method quantitation limits in water. Passive samplers also accumulate short-chain PFAS that are not bioconcentrated.

Influence of microbial weathering on the partitioning of per- and polyfluoroalkyl substances (PFAS) in biosolids

Per- and polyfluoroalkyl substances (PFAS) are a large group of man-made fluorinated organic chemicals that can accumulate in the environment. In water resource recovery facilities (WRRFs), some commonly detected PFAS tend to partition to and concentrate in biosolids where they can act as a source to ecological receptors and may leach to groundwater when land-applied. Although biosolids undergo some stabilization to reduce pathogens before land application, they still contain many microorganisms, contributing to the eventual decomposition of different components of the biosolids. This work demonstrates ways in which microbial weathering can influence biosolids decomposition, degrade PFAS, and impact PFAS partitioning in small-scale, controlled laboratory experiments. In the microbial weathering experiments, compound-specific PFAS biosolids-water partitioning coefficients (K_d) were demonstrated to decrease, on average, 0.4 logs over the course of the 91 day study, with the most rapid changes occurring during the first 10 days. Additionally, the highest rates of lipid, protein, and organic matter removal occurred during the same time. Among the evaluated independent variables, statistical analyses demonstrated that the most significant solids characteristics that impacted PFAS partitioning were organic matter, proteins, lipids, and molecular weight of organics. A multiple linear regression model was built to predict PFAS partitioning behavior in biosolids based on solid characteristics of the biosolids and PFAS characteristics with a R² value of 0.7391 when plotting predicted and measured log K_d. The findings from this work reveal that microbial weathering can play a significant role in the eventual fate and transport of PFAS and their precursors from biosolids.

Total Oxidizable Precursor (TOP) Assay-Best Practices, Capabilities and Limitations for PFAS Site Investigation and Remediation

The comprehensive characterization of per- and polyfluoroalkyl substances (PFASs) is necessary for the effective assessment and management of risk at contaminated sites. While current analytical methods are capable of quantitatively measuring a number of specific PFASs, they do not provide a complete picture of the thousands of PFASs that are utilized in commercial products and potentially released into the environment. These unmeasured PFASs include many PFAS precursors, which may be converted into related PFAS chemicals through oxidation. The total oxidizable precursor (TOP) assay offers a means of bridging this gap by oxidizing unknown PFAS precursors and intermediates and converting them into stable PFASs with established analytical standards. The application of the TOP assay to samples from PFAS-contaminated sites has generated several new insights, but it has also presented various technical challenges for laboratories. Despite the increased number of literature studies that include the TOP assay, there is a critical and growing gap in the application of this method beyond researchers in academia. This article outlines the benefits and challenges of using the TOP assay with aqueous samples for site assessments and suggests ways to address some of its limitations.