Levels and Seasonal Trends of C1-C4 Perfluoroalkyl Acids and the Discovery of Trifluoromethane Sulfonic Acid in Surface Snow in the Arctic

Interspecies comparison of metabolism of two novel prototype PFAS

As a result of proposed global restrictions and regulations on current-use per-and polyfluoroalkyl substances (PFAS), research on possible alternatives is highly required. In this study, phase I in vitro metabolism of two novel prototype PFAS in human and rat was investigated. These prototype chemicals are intended to be safer-by-design and expected to mineralize completely, and thus be less persistent in the environment compared to the PFAS available on the market. Following incubation with rat liver S9 (RL-S9) fractions, two main metabolites per initial substance were produced, namely an alcohol and a short-chain carboxylic acid. While with human liver S9 (HL-S9) fractions, only the short-chain carboxylic acid was detected. Beyond these major metabolites, two and five additional metabolites were identified at very low levels by non-targeted screening for the ether- and thioether-linked prototype chemicals, respectively. Overall, complete mineralization during the in vitro hepatic metabolism of these novel PFAS by HL-S9 and RL-S9 fractions was not observed. The reaction kinetics of the surfactants was determined by using the metabolite formation, rather than the substrate depletion approach. With rat liver enzymes, the formation rates of primary metabolite alcohols were at least two orders of magnitude higher than those of secondary metabolite carboxylic acids. When incubating with human liver enzymes, the formation rates of single metabolite carboxylic acids, were similar or smaller than those experienced in rat. It also indicates that the overall metabolic rate and clearance of surfactants are significantly higher in rat liver than in human liver. The maximum formation rate of the thioether congener exceeded 10-fold that of the ether in humans but were similar in rats. Overall, the results suggest that metabolism of the prototype chemicals followed a similar trend to those reported in studies of fluorotelomer alcohols.

Taking a look at the surface: μ-XRF mapping and fluorine K-edge μ-XANES spectroscopy of organofluorinated compounds in environmental samples and consumer products

For the first time, μ-X-ray fluorescence (μ-XRF) mapping combined with fluorine K-edge μ-X-ray absorption near-edge structure (μ-XANES) spectroscopy was applied to depict per- and polyfluoroalkyl substance (PFAS) contamination and inorganic fluoride in sample concentrations down to 100 μg kg^-1 fluoride. To demonstrate the matrix tolerance of the method, several PFAS contaminated soil and sludge samples as well as selected consumer product samples (textiles, food contact paper and permanent baking sheets) were investigated. μ-XRF mapping allows for a unique element-specific visualization at the sample surface and enables localization of fluorine containing compounds to a depth of 1 μm. Manually selected fluorine rich spots were subsequently analyzed via fluorine K-edge μ-XANES spectroscopy. To support spectral interpretation with respect to inorganic and organic chemical distribution and compound class determination, linear combination (LC) fitting was applied to all recorded μ-XANES spectra. Complementarily, solvent extracts of all samples were target-analyzed via LC-MS/MS spectrometry. The detected PFAS sum values range from 20 to 1136 μg kg^-1 dry weight (dw). All environmentally exposed samples revealed a higher concentration of PFAS with a chain length > C₈ (e.g. 580 μg kg^-1 dw PFOS for Soil1), whereas the consumer product samples showed a more uniform distribution with regard to chain lengths from C₄ to C₈. Independent of quantified PFAS amounts via target analysis, μ-XRF mapping combined with μ-XANES spectroscopy was successfully applied to detect both point-specific concentration maxima and evenly distributed surface coatings of fluorinated organic contaminants in the corresponding samples.

Is adsorption onto activated carbon a feasible drinking water treatment option for persistent and mobile substances?

Persistent and mobile (PM) substances among the organic micropollutants have gained increasing interest since their inherent properties enable them to enrich in water cycles. This study set out to investigate the potential of adsorption onto activated carbon as a drinking water treatment option for 19 PM candidates in batch experiments in a drinking water matrix using a microporous and a mesoporous activated carbon. Overall, adsorption of PM candidates proved to be very variable and the extent of removal could not be directly related to molecular properties. At an activated carbon dose of 10 mg/L and 48 h contact time, five (out of 19) substances were readily removed (≥ 80%), among them N-(3-(dimethylamino)-propyl)methacrylamide, which was investigated for the first time. For five other substances, no or negligible removal (< 20%) was observed, including 2-methyl-2-propene-1-sulfonic acid and 4‑hydroxy-1-(2-hydroxyethyl)-2,2,6,6,-tetramethylpiperidine. For the former, current state of the art adsorption processes may pose a sufficient barrier. Additionally, substance specific surrogate correlations between removals and UVA₂₅₄ abatements were established to provide a cheap and fast estimate for PM candidate elimination. Adsorption onto activated carbon could contribute significantly to PM substance elimination as part of multi barrier approaches, but assessments for individual substances still require clarification, as demonstrated for the investigated PM candidates.

Levels and distribution profiles of Per- and Polyfluoroalkyl Substances (PFAS) in a high Arctic Svalbard ice core

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent organic contaminants of which some are toxic and bioaccumulative. Several PFAS can be formed from the atmospheric degradation of precursors such as fluorotelomer alcohols (FTOHs) as well as hydrochlorofluorocarbons (HFCs) and other ozone-depleting chlorofluorocarbon (CFC) replacement compounds. Svalbard ice cores have been shown to provide a valuable record of long-range atmospheric transport of contaminants to the Arctic. This study uses a 12.3 m ice core from the remote Lomonosovfonna ice cap on Svalbard to understand the atmospheric deposition of PFAS in the Arctic. A total of 45 PFAS were targeted, of which 26 were detected, using supercritical fluid chromatography (SFC) tandem mass spectrometry (MS/MS) and ultra-performance liquid chromatography (UPLC) MS/MS. C₂ to C₁₁ perfluoroalkyl carboxylic acids (PFCAs) were detected continuously in the ice core and their fluxes ranged from 2.5 to 8200 ng m^-2 yr^-1 (9.51-16,500 pg L^-1). Trifluoroacetic acid (TFA) represented 71 % of the total mass of C₂ - C₁₁ PFCAs in the ice core and had increasing temporal trends in deposition. The distribution profile of PFCAs suggested that FTOHs were likely the atmospheric precursor to C₈ - C₁₁ PFCAs, whereas C₂ - C₆ PFCAs had alternative sources, such as HFCs and other CFC replacement compounds. Perfluorooctanesulfonic acid (PFOS) was also widely detected in 82 % of ice core subsections, and its isomer profile (81 % linear) indicated an electrochemical fluorination manufacturing source. Comparisons of PFAS concentrations with a marine aerosol proxy showed that marine aerosols were insignificant for the deposition of PFAS on Lomonosovfonna. Comparisons with a melt proxy showed that TFA and PFOS were mobile during meltwater percolation. This indicates that seasonal snowmelt and runoff from post-industrial accumulation on glaciers could be a significant seasonal source of PFAS to ecosystems in Arctic fjords.

Analyzing Organofluorine Compounds in the Environment Using Combustion Ion Chromatography (CIC) and Other Methods

Organofluorine compounds are potential contaminants in the environment, particularly in natural water sources. Leo W. Y. Yeung, PhD, is a Senior Lecturer in the School of Science and Technology of the Man-Technology-Environment Research Centre (MTM) at Örebro University in Örebro, Sweden. His research has involved the analysis of organofluorine compounds of concern in the natural environment. We recently spoke to him about his work using combustion ion chromatography (CIC) and other methods to analyze organofluorine and specific perfluoroalkyl and polyfluoroalkyl substances (PFAS) compounds in environmental samples.

Occurrence, spatial heterogeneity, and risk assessment of perfluoroalkyl acids (PFAAs) in the major rivers of the Tibetan Plateau

The Tibetan Plateau (TP) is home to the headwaters of major rivers in Asia, yet their water quality security on a large spatial scale is scarcely studied, especially in regard to emerging organic pollutants. In this study, a systematic field campaign was carried out along Yarlung Tsangpo River, Nu River, Lancang River and Jinsha River, and 13 perfluoroalkyl acids (PFAAs) were analyzed. The total concentrations of PFAAs in the river waters of the TP were in the range of 0.58-7.46 ng/L, containing a high proportion of perfluorobutanoic acid (PFBA) and perfluorobutane sulfonate (PFBS) with average values of 56.7 %. Elevated PFAA loadings were found for the midstream of Yarlung Tsangpo River in central Tibet. Geodetector results indicated that precipitation, solar radiation and vegetation type were the top three influential factors contributing to the observed spatial heterogeneity. When interactions with human activities were taken into account, the explanatory power was significantly enhanced and rose above 0.70, highlighting the increased risks for TP rivers from the combined effects of natural environments and anthropogenic activities. Risk assessments suggest a low risk is posed to the alpine aquatic ecosystems and human health. The discharge fluxes of PFAAs via riverine export were estimated at 94-425 kg/year, which is one to two orders of magnitude lower than their mass loadings in major rivers worldwide. Our study underlined the need for further attention to the increased risk of water resource quality on the central TP in the context of long-range transport, increased cryosphere melting and local emission.

Widespread Occurrence of Non-Extractable Fluorine in Artificial Turfs from Stockholm, Sweden

Per- and polyfluoroalkyl substances (PFAS) are frequently used in the production of rubber and plastic, but little is known about the identity, concentration, or prevalence of PFAS in these products. In this study, a representative sample of plastic- and rubber-containing artificial turf (AT) fields from Stockholm, Sweden, was subjected to total fluorine (TF), extractable organic fluorine (EOF), and target PFAS analysis. TF was observed in all 51 AT samples (ranges of 16-313, 12-310, and 24-661 μg of F/g in backing, filling, and blades, respectively), while EOF and target PFAS occurred in <42% of all samples (<200 and <1 ng of F/g, respectively). A subset of samples extracted with water confirmed the absence of fluoride. Moreover, application of the total oxidizable precursor assay revealed negligible perfluoroalkyl acid (PFAA) formation across all three sample types, indicating that the fluorinated substances in AT are not low-molecular weight PFAA precursors. Collectively, these results point toward polymeric organofluorine (e.g., fluoroelastomer, polytetrafluoroethylene, and polyvinylidene fluoride), consistent with patent literature. The combination of poor extractability and recalcitrance toward advanced oxidation suggests that the fluorine in AT does not pose an imminent risk to users. However, concerns surrounding the production and end of life of AT, as well as the contribution of filling and blades to environmental microplastic contamination, remain.

Rapid quantitative analysis and suspect screening of per-and polyfluorinated alkyl substances (PFASs) in aqueous film-forming foams (AFFFs) and municipal wastewater samples by Nano-ESI-HRMS

A rapid analytical method for per- and polyfluoroalkyl substances (PFASs) combining nano-electrospray ionization and high-resolution mass spectrometry (Nano-ESI-HRMS) was developed and applied to aqueous film-forming foams (AFFFs) and wastewater samples collected from three local wastewater treatment plants (WWTPs). This method exhibited high sensitivity with lower limits of detection (LODs) of 3.2∼36.2 ng/L for 22 target PFAS analytes. In AFFF formulations, Nano-ESI-HRMS enabled the first-time detection of trifluoromethanesulfonic acid (TFMS), perfluoroethyl cyclohexanesulfonate (PFECHS), 6:2 fluorotelomer sulfonyl amido sulfonic acid (6:2 FTSAS-SO2), N-ammoniopropyl perfluoroalkanesulfonamidopropylsulfonate (N-AmP-FASAPS, n = 3-6), ketone-perfluorooctanesulfonic acid (Keto-PFOS), fluorotelomer unsaturated amide sulfonic acid (FTUAmS, n = 7), and 6:2 fluorotelomer amide (6:2 FTAm). Their structures were verified by the tandem MS analysis using collision-induced dissociation. Further, the combination of absolute and semi-quantification results revealed 16 PFASs from 9 PFAS classes as dominant AFFF constituents, accounting for 88.2∼96.5% of the total detected anionic and zwitterionic PFASs, including perfluorinated sulfonic acids (PFSAs, n = 1,4∼8), 6:2 fluorotelomer sulfonates (6:2 FTS), fluorotelomer thioether amido sulfonic acid (FTSAS, n = 6,8), fluorotelomer sulfinyl amido sulfonic acid (FTSAS-SO, n = 6,8), N-AmP-FASAPS (n = 6), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), perfluoroalkylsulfonamido amino carboxylate (PFASAC, n = 6), 2-((perfluorooctyl)thio)acetatic acid (Thio-8:2 FTCA), and 6:2 FTAm. At WWTPs, aerobic and anaerobic biotransformation of PFAS precursors at the aeration tanks and secondary clarifiers were evident by the generation of mid/short-chain perfluoroalkyl acids, such as perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), as well as the emergence of ultrashort trifluoroacetic acid (TFA) and TFMS and several novel fluorotelomer carboxylic acids (FTCAs). Overall, Nano-ESI-HRMS enabled comprehensive PFAS quantitative analysis and suspect screening, applicable for rapid investigation and assessment of PFAS-related exposure and treatment in environmental matrixes. Our results also revealed that AFFFs and municipal wastewaters are two key sources contributing to the prevalent detection of ultrashort-chain PFASs (e.g., TFMS and TFA) in water.