Biotransformation of 8:2 fluorotelomer alcohol in soil and by soil bacteria isolates

Per- and polyfluoroalkyl substances (PFAS) as contaminants in groundwater resources - A comprehensive review of subsurface transport processes

Per- and polyfluorinated alkyl substances (PFAS) are persistent contaminants in the environment. An increased awareness of adverse health effects related to PFAS has further led to stricter regulations for several of these substances in e.g. drinking water in many countries. Groundwater constitutes an important source of raw water for drinking water production. A thorough understanding of PFAS subsurface fate and transport mechanisms leading to contamination of groundwater resources is therefore essential for management of raw water resources. A review of scientific literature on the subject of processes affecting subsurface PFAS fate and transport was carried out. This article compiles the current knowledge of such processes, mainly focusing on perfluoroalkyl acids (PFAA), in soil- and groundwater systems. Further, a compilation of data on transport parameters such as solubility and distribution coefficients, as well as, insight gained and conclusions drawn from the reviewed material are presented. As the use of certain fire-fighting foams has been identified as the major source of groundwater contamination in many countries, research related to this type of pollution source has been given extra focus. Uptake of PFAS in biota is outside the scope of this review. The review showed a large spread in the magnitude of distribution coefficients and solubility for individual PFAS. Also, it is clear that the influence of multiple factors makes site-specific evaluation of distribution coefficients valuable. This article aims at giving the reader a comprehensive overview of the subject, and providing a base for further work.

Analysis of Legacy and Novel Neutral Per- and Polyfluoroalkyl Substances in Soils from an Industrial Manufacturing Facility

Per- and polyfluoroalkyl substances (PFASs) have been detected in an array of environmental media due to their ubiquitous use in industrial and consumer products as well as potential release from fluorochemical manufacturing facilities. During their manufacture, many fluorotelomer (FT) facilities rely on neutral intermediates in polymer production including the FT-alcohols (FTOHs). These PFAS are known to transform to the terminal acids (perfluoro carboxylic acids; PFCAs) at rates that vary with environmental conditions. In the current study on soils from a FT facility, we employed gas chromatography coupled with conventional- and high-resolution mass spectrometry (GC-MS and GC-HRMS) to investigate the profile of these precursor compounds, the intermediary secondary alcohols (sFTOHs), FT-acrylates (FTAcr), and FT-acetates (FTAce) in soils around the former FT-production facility. Of these precursors, the general trend in detection intensity was [FTOHs] > [sFTOHs] > [FTAcrs], while for the FTOHs, homologue intensities generally were [12:2 FTOH] > [14:2 FTOH] > [16:2 FTOH] > [10:2 FTOH] > [18:2 FTOH] > [20:2 FTOH] > [8:2 FTOH] ∼ [6:2 FTOH]. The corresponding terminal acids were also detected in all soil samples and positively correlated with the precursor concentrations. GC-HRMS confirmed the presence of industrial manufacturing byproducts such as FT-ethers and FT-esters and aided in the tentative identification of previously unreported dimers and other compounds. The application of GC-HRMS to the measurement and identification of precursor PFAS is in its infancy, but the methodologies described here will help refine its use in tentatively identifying these compounds in the environment.

A review of the occurrence and microbial transformation of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF)-impacted environments

Aqueous film-forming foams (AFFFs) have been extensively used for extinguishing hydrocarbon-fuel fires at military sites, airports, and fire-training areas. Despite being a significant source of per- and polyfluoroalkyl substances (PFAS), our understanding of PFAS occurrence in AFFF formulations and AFFF-impacted environments is limited, as is the impact of microbial transformation on the environment fate of AFFF-derived PFAS. This literature review compiles PFAS concentrations in electrochemical fluorination (ECF)- and fluorotelomer (FT)-based AFFFs and provides an overview of PFAS occurrence in AFFF-impacted environments. Our analysis reveals that AFFF use is a predominant point source of PFAS contamination, including primary precursors (polyfluoroalkyl substances as AFFF components), secondary precursors (polyfluoroalkyl transformation products of primary precursors), and perfluoroalkyl acids (PFAAs). Moreover, there are discrepancies between PFAS concentration profiles in AFFFs and those measured in AFFF-impacted media. For example, primary precursors constitute 52.6 % and 99.5 % of PFAS mass in ECF- and FT-based AFFFs, respectively, whereas they represent only 0.7 % total mass in AFFF-impacted groundwater. Conversely, secondary precursors, which constitute <1 % of PFAS in AFFFs, represent 4.0-27.8 % of PFAS in AFFF-impacted environments. The observed differences in PFAS levels between AFFFs and environmental samples are likely due to in-situ biotransformation processes. Biotransformation rates and pathways reported for AFFF-derived primary and secondary precursors varied among different classes of precursors, consistent with the PFAS occurrence in AFFF-impacted environments. For example, readily biodegradable primary precursors, N-dimethyl ammonio propyl perfluoroalkane sulfonamide (AmPr-FASA) and n:2 fluorotelomer thioether amido sulfonate (n:2 FtTAoS), were rarely detected in AFFF-impacted environments. In contrast, key secondary precursors, perfluoroalkane sulfonamides (FASAs) and n:2 fluorotelomer sulfonate (n:2 FTS), were widely detected, which was attributed to their resistance to biotransformation. Key knowledge gaps and future research priorities are presented to better understand the occurrence, fate, and transport of AFFF-derived PFAS in the environment and to design more effective remediation strategies.

PFAS in Nigeria: Identifying data gaps that hinder assessments of ecotoxicological and human health impacts

This review examines the extensive use and environmental consequences of Per- and Polyfluoroalkyl Substances (PFAS) on a global scale, specifically emphasizing their potential impact in Nigeria. Recognized for their resistance to water and oil, PFAS are under increased scrutiny for their persistent nature and possible ecotoxicological risks. Here, we consolidate existing knowledge on the ecological and human health effects of PFAS in Nigeria, focusing on their neurological effects and the risks they pose to immune system health. We seek to balance the advantages of PFAS with their potential ecological and health hazards, thereby enhancing understanding of PFAS management in Nigeria and advocating for more effective policy interventions and the creation of safer alternatives. The review concludes with several recommendations: strengthening regulatory frameworks, intensifying research into the ecological and health impacts of PFAS, developing new methodologies and longitudinal studies, fostering collaborative efforts for PFAS management, and promoting public awareness and education to support sustainable environmental practices and healthier communities in Nigeria.

Using Network Analysis and Predictive Functional Analysis to Explore the Fluorotelomer Biotransformation Potential of Soil Microbial Communities

Microbial transformation of per- and polyfluoroalkyl substances (PFAS), including fluorotelomer-derived PFAS, by native microbial communities in the environment has been widely documented. However, few studies have identified the key microorganisms and their roles during the PFAS biotransformation processes. This study was undertaken to gain more insight into the structure and function of soil microbial communities that are relevant to PFAS biotransformation. We collected 16S rRNA gene sequencing data from 8:2 fluorotelomer alcohol and 6:2 fluorotelomer sulfonate biotransformation studies conducted in soil microcosms under various redox conditions. Through co-occurrence network analysis, several genera, including Variovorax, Rhodococcus, and Cupriavidus, were found to likely play important roles in the biotransformation of fluorotelomers. Additionally, a metagenomic prediction approach (PICRUSt2) identified functional genes, including 6-oxocyclohex-1-ene-carbonyl-CoA hydrolase, cyclohexa-1,5-dienecarbonyl-CoA hydratase, and a fluoride-proton antiporter gene, that may be involved in defluorination. This study pioneers the application of these bioinformatics tools in the analysis of PFAS biotransformation-related sequencing data. Our findings serve as a foundational reference for investigating enzymatic mechanisms of microbial defluorination that may facilitate the development of efficient microbial consortia and/or pure microbial strains for PFAS biotransformation.

Spatial distribution, isomer signature and air-soil exchange of legacy and emerging poly- and perfluoroalkyl substances

Widespread occurrences of various poly- and perfluoroalkyl substances (PFAS) in terrestrial environment calls for the growing interest in their transport behaviors. However, limited studies detected PFAS with structural diversity in tree barks, which reflect the long-term contamination in atmosphere and play a vital role in air-soil exchange behaviors. In this study, 26 PFAS congeners and typical branched isomers were investigated in surface soils and tree barks at 28 sites along the Taihu Lake, Taipu River, and Huangpu River. Concentrations of total PFAS in soils and tree barks were 0.991-29.4 and 7.99-188 ng/g dw, with PFPeA and PFDoA were the largest contributors in the two matrices. The highest PFAS levels were found in the Taihu Lake watershed, where textile manufacturing and metal plating activities highly prosper. With regard to the congener and isomer signatures, short-chain homologs dominated in soils (65.5%), whereas long-chain PFAS showed a major proportion in barks (41.9%). The composition of linear isomers of PFOS, PFOA and PFHxS implied that precursor degradation might be an important source of PFAS in addition to the 3M electrochemical fluorination (ECF). Additionally, the distance from the emission source, total organic carbon (TOC), logKOA and logKOW were considered potential influencing factors in PFAS distributions. Based on the multi-media fugacity model, about 71% of the fugacity fraction (ffs) values of the PFAS were below 0.3, indicating the dominant deposition from the atmosphere to the soil. The average fluxes of air-soil exchange for PFAS were -0.700 ± 11.0 ng/(m2·h). Notably, the estimated daily exposure to PFAS ranged from 9.57 × 10-2 to 8.59 × 10-1 ng/kg·bw/day for children and 3.31 × 10-2 to 3.09 × 10-1 ng/kg·bw/day for adults, suggesting low risks from outdoor inhalation and dermal uptake. Overall, results from distribution with structural diversity, air-soil exchange and preliminary risk assessment. This study provided in-depth insight of PFAS in multi-medium environment and bridged gaps between field data and policy-making for pollution control.

Aerobic biotransformation of 6:2 fluorotelomer sulfonate in soils from two aqueous film-forming foam (AFFF)-impacted sites

Although 6:2 fluorotelomer sulfonate (6:2 FTS) is a common ingredient in aqueous film-forming foam (AFFF) formulations, its environmental fate at AFFF-impacted sites remains poorly understood. This study investigated the biotransformation of 6:2 FTS in microcosms prepared with soils collected from two AFFF-impacted sites; the former Loring Air Force Base (AFB) and Robins AFB. The half-life of 6:2 FTS in Loring soil was 43.3 days; while >60 mol% of initially spiked 6:2 FTS remained in Robins soil microcosms after a 224-day incubation. Differences in initial sulfate concentrations and the depletion of sulfate over the incubation likely contributed to the different 6:2 FTS biotransformation rates between the two soils. At day 224, stable transformation products, i.e., C4C7 perfluoroalkyl carboxylates, were formed with combined molar yields of 13.8 mol% and 1.2 mol% in Loring and Robins soils, respectively. Based on all detected transformation products, the biotransformation pathways of 6:2 FTS in the two soils were proposed. Microbial community analysis suggests that Desulfobacterota microorganisms may promote 6:2 FTS biotransformation via more efficient desulfonation. In addition, species from the genus Sphingomonas, which exhibited higher tolerance to elevated concentrations of 6:2 FTS and its biotransformation products, are likely to have contributed to 6:2 FTS biotransformation. This study demonstrates the potential role of biotransformation processes on the fate of 6:2 FTS at AFFF-impacted sites and highlights the need to characterize site biogeochemical properties for improved assessment of 6:2 FTS biotransformation behavior.

Degradation of 8:2 fluorotelomer carboxylic acid (8:2 FTCA) by plants and their co-existing microorganisms

8:2 fluorotelomer carboxylic acid (8:2 FTCA), an important precursor of perfluorocarboxylic acids (PFCAs), is widely detected in environment and biotas. Hydroponic exposures were conducted to investigate the accumulation and metabolism of 8:2 FTCA in wheat (Triticum aestivum L.) and pumpkin (Cucurbita maxima L.). Endophytic and rhizospheric microorganisms co-existing with the plants were isolated to investigate their contributions to degrade 8:2 FTCA. Wheat and pumpkin roots could take up 8:2 FTCA efficiently with the root concentration factor (RCF) as 5.78 and 8.93, respectively. 8:2 FTCA could be biotransformed to 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA), 7:3 fluorotelomer carboxylic acid (7:3 FTCA), and seven PFCAs with 2-8 carbon chain length in plant roots and shoots. Cytochromes P450 (CYP450) and glutathione-S-transferase (GST) activities in plants were significantly increased, while flavin-dependent monooxygenases (FMOs) activities were not changed, suggesting that CYP 450 and GST were involved in the transformation of 8:2 FTCA in plant tissues. Twelve 8:2 FTCA-degrading endophytic (8 strains) and rhizospheric (4 strains) bacterial strains were isolated from root interior, shoot interior and rhizosphere of plants, respectively. These bacteria were identified as Klebsiella sp. based on the morphology and 16S rDNA sequence, and they could biodegrade 8:2 FTCA to intermediates and stable PFCAs.

A Review: Per- and Polyfluoroalkyl Substances-Biological Degradation

Per- and polyfluoroalkyl substances (PFASs), highly stable synthetic organic compounds with multiple carbon-fluorine bonds, are emerging as environmental contaminants, toxic, bioaccumulative, and environmentally persistent. PFASs are strongly resistant to biological and chemical degradation, and therefore PFASs present a challenge to researchers and scientists for a better understanding and application of remediation methods and biodegradation of PFASs and have become subject to strict government regulations. The review summarizes the recent knowledge of bacterial and fungal degradation of PFASs, as well as the enzymes involved in the processes of transformation/degradation of PFASs.

Assessing aerobic biotransformation of 8:2 fluorotelomer alcohol in aqueous film-forming foam (AFFF)-impacted soils: Pathways and microbial community dynamics

Production of 8:2 fluorotelomer alcohol (8:2 FTOH) for industrial and consumer products, including aqueous film-forming foams (AFFFs) used for firefighting, has resulted in its widespread occurrence in the environment. However, the fate of 8:2 FTOH at AFFF-impacted sites remains largely unknown. Using AFFF-impacted soils from two United States Air Force Bases, microcosm experiments evaluated the aerobic biotransformation of 8:2 FTOH (extent and byproduct formation) and the dose-response on microbial communities due to 8:2 FTOH exposure. Despite different microbial communities, rapid transformation of 8:2 FTOH was observed during a 90-day incubation in the two soils, and 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were detected as major transformation products. Novel transformation products, including perfluoroalkane-like compounds (1H-perfluoroheptane, 1H-perfluorohexane, and perfluoroheptanal) were identified by liquid chromatography-high resolution mass spectrometry (LC-HRMS) and used to develop aerobic 8:2 FTOH biotransformation pathways. Microbial community analysis suggests that species from genus Sphingomonas are potential 8:2 FTOH degraders based on increased abundance in both soils after exposure, and the genus Afipia may be more tolerant to and/or involved in the transformation of 8:2 FTOH at elevated concentrations. These findings demonstrate the potential role of biological processes on PFAS fate at AFFF-impacted sites through fluorotelomer biotransformation.

A review of microbial degradation of per- and polyfluoroalkyl substances (PFAS): Biotransformation routes and enzymes

Since the 1950s, copious amounts of per- and polyfluoroalkyl substances (PFAS) (dubbed "forever chemicals") have been dumped into the environment, causing heavy contamination of soil, surface water, and groundwater sources. Humans, animals, and the environment are frequently exposed to PFAS through food, water, consumer products, as well as waste streams from PFAS-manufacturing industries. PFAS are a large group of synthetic organic fluorinated compounds with widely diverse chemical structures that are extremely resistant to microbial degradation. Their persistence, toxicity to life on earth, bioaccumulation tendencies, and adverse health and ecological effects have earned them a "top priority pollutant" designation by regulatory bodies. Despite that a number of physicochemical methods exist for PFAS treatment, they suffer from major drawbacks regarding high costs, use of high energy and incomplete mineralization (destruction of the CF bond). Consequently, microbial degradation and enzymatic treatment of PFAS are highly sought after as they offer a complete, cheaper, sustainable, and environmentally friendly alternative. In this critical review, we provide an overview of the classification, properties, and interaction of PFAS within the environment relevant to microbial degradation. We discuss latest developments in the biodegradation of PFAS by microbes, transformation routes, transformation products and degradative enzymes. Finally, we highlight the existing challenges, limitations, and prospects of bioremediation approaches in treating PFAS and proffer possible solutions and future research directions.

Biotransformation of 8:2 Fluorotelomer Alcohol in Soil from Aqueous Film-Forming Foams (AFFFs)-Impacted Sites under Nitrate-, Sulfate-, and Iron-Reducing Conditions

The environmental fate of per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFFs) remains largely unknown, especially under the conditions representative of natural subsurface systems. In this study, the biotransformation of 8:2 fluorotelomer alcohol (8:2 FTOH), a component of new-generation AFFF formulations and a byproduct in fluorotelomer-based AFFFs, was investigated under nitrate-, iron-, and sulfate-reducing conditions in microcosms prepared with AFFF-impacted soils. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-resolution mass spectrometry (HRMS) were employed to identify biotransformation products. The biotransformation was much slower under sulfate- and iron-reducing conditions with >60 mol % of initial 8:2 FTOH remaining after ∼400 days compared to a half-life ranging from 12.5 to 36.5 days under nitrate-reducing conditions. Transformation products 8:2 fluorotelomer saturated and unsaturated carboxylic acids (8:2 FTCA and 8:2 FTUA) were detected under all redox conditions, while 7:2 secondary fluorotelomer alcohol (7:2 sFTOH) and perfluorooctanoic acid (PFOA) were only observed as transformation products under nitrate-reducing conditions. In addition, 1H-perfluoroheptane (F(CF₂)₆CF₂H) and 3-F-7:3 acid (F(CF₂)₇CFHCH₂COOH) were identified for the first time during 8:2 FTOH biotransformation. Comprehensive biotransformation pathways for 8:2 FTOH are presented, which highlight the importance of accounting for redox condition and the related microbial community in the assessment of PFAS transformations in natural environments.

Leaching and Transformation of Perfluoroalkyl Acids and Polyfluoroalkyl Phosphate Diesters in Unsaturated Soil Column Studies

Per- and polyfluoroalkyl substances (PFAS) are environmentally ubiquitous, anthropogenic substances with adverse effects on organisms, which shows the need to study their environmental fate and leaching behavior. In the present soil columns study, the leaching behavior and fate of nontransformable and transformable (precursors) were investigated. Ten nontransformable PFAS in two different soils, two precursors and two field soils, which were already contaminated with a mixture of PFAS, and two uncontaminated controls, were set up for a time span of 2 years. At the end of the study, the molecular balance could not be closed for nontransformable PFAS. This effect was positively correlated to the fluorinated carbon chain length. The precursors, which were both polyfluoroalkyl phosphate diesters (diPAP), had different transformation products and transformation rates, with a higher rate for 6:2 diPAP than 8:2 diPAP. After 2 years, amounts of diPAP were still found in the soil with no significant vertical movement, showing high adsorption to soils. Transformation products were estimated to be simultaneously formed. They were predominantly found in the percolation water; the amounts left in soil were negligible. Up to half of the initial precursor amounts could not be balanced and were considered missing amounts. The results of contaminated field soil experiments showed the challenge to estimate PFAS leaching without knowing all occurring precursors and complex transformation dynamics. For this purpose, it was shown that a broad examination of contaminated soil with different analytical methods can help with qualitative estimations of leaching risks. For a better quantitative estimation, analytical determination of more PFAS and a quantification of the missing amounts are needed. Environ Toxicol Chem 2022;41:2065-2077. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Occurrence, distribution, and input pathways of per- and polyfluoroalkyl substances in soils near different sources in Shanghai

Per- and polyfluoroalkyl substances (PFAS) are complex emerging pollutants that are widely distributed in soils. The compositions of PFAS vary according to the emission sources. However, the soil distributions of PFAS from different sources are still poorly understood. In this study, the concentrations and compositions of 18 PFAS in soils close to potential sources (industrial areas, airports, landfills, fire stations and agricultural areas) were investigated in Shanghai. The total PFAS concentrations varied from 0.64 to 294 μg kg^-1_d.w.. Among the sites, the highest PFAS concentration was found near the fire station (average = 57.9 μg kg^-1_d.w.), followed by the industrial area (average = 8.53 μg kg^-1_d.w.). The detection frequencies of the 18 PFAS ranged from 47.5% to 100%. Perfluorooctanoic acid (PFOA) and perfluoroheptanoic acid (PFHpA) were detected in all samples. The detection frequencies of PFAS near the fire station were higher than those near other sources. The PFAS in soils were mainly composed of short-chain perfluoroalkyl carboxylic acids (C ≤ 8). Elevated concentrations of long-chain perfluoroalkyl carboxylic acids (C > 12) were found in industrial area. Principal component analysis revealed that long-chain PFAS had different factor loadings compared to short-chain PFAS. With the exception of agricultural soils, the correlations between individual PFAS were more positive than negative. Strong positive correlations were found within three groups of perfluoroalkyl carboxylic acids (C5-C7, C9-C12, and C14-C18), suggesting their similar inputs and transportation pathways. The PFAS in soils around the fire station were likely directly emitted from a point source. In contrast, the PFAS in soils near the other sites had multiple input pathways, including both direct emission and precursor degradation.

Neutral Per- and Polyfluoroalkyl Substances, Butyl Carbitol, and Organic Corrosion Inhibitors in Aqueous Film-Forming Foams: Implications for Vapor Intrusion and the Environment

Per- and polyfluoroalkyl substances (PFAS), butyl carbitol, and corrosion inhibitors are components of aqueous film-forming foams (AFFFs). Volatile (neutral) fluorotelomerization (FT)- and electrochemical fluorination (ECF)-based PFAS, butyl carbitol, and organic corrosion inhibitors were quantified in 39 military specification (MilSpec), non-MilSpec, and alcohol resistant-AFFF concentrates (undiluted) from 1974 to 2010. Fluorotelomer alcohols were found only in FT-based AFFFs and N-methyl- and N-ethyl-perfluoroalkyl sulfonamides, and sulfonamido ethanols were found only in ECF-based AFFFs. Neutral PFAS and benzotriazole, 4-methylbenzotriazole, and 5-methybenzotriazole occurred at mg/L levels in the AFFFs, while butyl carbitol occurred at g/L levels. Neutral PFAS concentrations in indoor air due to vapor intrusion of a nearby undiluted AFFF release are estimated to be anywhere from 2 to >10 orders of magnitude higher than documented background indoor air concentrations. Estimated butyl carbitol and organic corrosion inhibitor concentrations were lower than and comparable to indoor concentrations recently measured, respectively. The wide range of neutral PFAS concentrations and Henry's law constants indicate that field, soil-gas measurements are needed to validate the estimations. Co-discharged butyl carbitol likely contributes to oxygen depletion in AFFF-impacted aquifers and may hinder the natural PFAS aerobic biotransformation. Organic corrosion inhibitors in AFFFs indicate that these are another source of corrosion inhibitors in the environment.

Foliar uptake overweighs root uptake for 8:2 fluorotelomer alcohol in ryegrass (Lolium perenne L.): A closed exposure chamber study

Fluorotelomer alcohols (FTOHs) are a kind of volatile monomers that can be released from FTOH-based products and their ubiquitous occurrence raises concerns for their plant uptake. To study plant uptake pathway, translocation, and transformation characteristics of 8:2 FTOH, ryegrass (Lolium perenne L.) was selected as a model plant for 8:2 FTOH exposure via air and/or soil uptake for 4 weeks in custom-built closed exposure chambers. The bio-degradation of spiked 8:2 FTOH in the soil led to the production of C6-C8 perfluoroalkyl carboxylic acids (PFCAs) and other intermediates, and perfluorooctanoic acid (PFOA) was the main product (54.9%-88.9%). In the ryegrass, foliar uptake of 8:2 FTOH contributed 78.1% ± 3.4% to the total shoot accumulation while PFOA in shoot was mainly from root uptake of PFOA and the further biotransformation of other unmonitored intermediates biodegraded from 8:2 FTOH in the soil (83.7% ± 7.3%). The results in this study provides the first laboratory evidences that foliar uptake of airborne 8:2 FTOH can be a major pathway over root uptake and its subsequent biotransformation contribute to the burden of PFCA accumulation in plants.

Development of a PFAS reaction library: identifying plausible transformation pathways in environmental and biological systems

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are used in many consumer applications due to their stain repellency, surfactant properties, ability to form water-proof coatings and use in fire suppression. The production, application, transport, use and disposal of PFAS and PFAS-treated products have resulted in their wide-spread occurrence in environmental and biological systems. Concern over exposure to PFAS and their transformation products and metabolites has necessitated the development of tools to predict the transformation of PFAS in environmental systems and metabolism in biological systems. We have developed reaction libraries for predicting transformation products and metabolites in a variety of environmental and biological reaction systems. These reaction libraries are based on generalized reaction schemes that encode the process science of PFAS reported in the peer-reviewed literature. The PFAS reaction libraries will be executed through the Chemical Transformation Simulator, a web-based tool that is available to the public. These reaction libraries are intended for predicting the environmental transformation and metabolism of PFAS only.

Fate of Per- and Polyfluoroalkyl Substances from Durable Water-Repellent Clothing during Use

To make outdoor clothing water- or dirt-repellent, durable water-repellent (DWR) coatings based on side-chain fluorinated polymers (SFPs) are used. During use of outdoor clothing, per- and polyfluoroalkyl substances (PFASs) can be emitted from the DWR to the environment. In this study, the effects of aging, washing, and tumble drying on the concentration of extractable PFASs in the DWR of perfluorohexane-based short-chain SFPs (FC-6 chemistry) and of perfluorooctane-based long-chain SFPs (FC-8 chemistry) were assessed. For this purpose, polyamide (PA) and polyester (PES) fabrics were coated with FC-6- and FC-8-based DWRs. Results show that aging of the coated fabrics causes an increase in concentration and formation of perfluoroalkyl acids (PFAAs). The effect of aging on the volatile PFASs depends on the type of fabric. Washing causes a decrease in PFAA concentrations, and in general, volatile PFASs are partly washed out of the textiles. However, washing can also increase the extractable concentration of volatile PFASs in the fabrics. This effect becomes stronger by a combination of aging and washing. Tumble drying does not affect the PFAS concentrations in textiles. In conclusion, aging and washing of fabrics coated with the DWR based on SFPs release PFASs to the environment.

Global performance and trends of research on per- and polyfluoroalkyl substances (PFASs) between 2001 and 2018 using bibliometric analysis

Per- and polyfluoroalkyl substances (PFASs) are widely used in food packaging, non-stick pots, and surfactants. However, their persistence in the environment, hazardous nature, and potential for bioaccumulation and long-range transport have alarmed an increasing number of scholars and research institutions. Although several literature reviews on PFASs research exist, only a few of them have considered bibliometric indices. In this study, 3,373 PFASs-related articles published between 2001 and 2018 were analyzed using a bibliometric analysis method based on the Science Citation Index (SCI) Expanded. The software tools for mapping knowledge domain (MKD) (VOSviewer and Science of Science (Sci2)) were used to analyze the performance of contributors and PFASs research topics, hotspots, and trends. Our results reveal that the number of PFASs-related articles published annually has increased significantly, with most originating from the United States (followed by those from China). The Chinese Academy of Sciences has published the most articles. A comprehensive analysis of title, keywords, and keywords plus showed that PFASs research hotspots include humans, precursors, and detection methods, with the main focuses being environmental science, toxicology, and environmental engineering. The four main research topics of PFASs were identified, and a literature review was carried out for each one. Overall, this study can supply researchers with a deeper understanding of the development of PFASs studies and provide a comprehensive data reference for researchers to further grasp the research direction in this field.

Characterization of Per- and Polyfluorinated Alkyl Substances Present in Commercial Anti-fog Products and Their In Vitro Adipogenic Activity

Anti-fog sprays and solutions are used on eyeglasses to minimize the condensation of water vapor, particularly while wearing a mask. Given their water-repellent properties, we sought to characterize per- and polyfluorinated alkyl substance (PFAS) compounds in four anti-fog spray products, five anti-fog cloth products, and two commercial fluorosurfactant formulations suspected to be used in preparing anti-fog products. Fluorotelomer alcohols (FTOHs) and fluorotelomer ethoxylates (FTEOs) were detected in all products and formulations. While 6:2 FTOH and the 6:2 FTEO polymeric series were predominant, one anti-fog cloth and one formulation contained 8:2, 10:2, 12:2, 14:2, and 16:2 FTOH and FTEO polymeric series. PFAS concentrations varied in samples and were detected at levels up to 25,000 μg/mL in anti-fog sprays and 185,000 μg (g cloth)^-1 in anti-fog cloth products. The total organic fluorine (TOF) measurements of anti-fog products ranged from 190 to 20,700 μg/mL in sprays and 44,200 to 131,500 μg (g cloth)^-1 in cloths. Quantified FTOHs and FTEOs accounted for 1-99% of TOF mass. In addition, all four anti-fog sprays and both commercial formulations exhibited significant cytotoxicity and adipogenic activity (either triglyceride accumulation and/or pre-adipocyte proliferation) in murine 3T3-L1 cells. Results suggest that FTEOs are a significant contributor to the adipogenic activity exhibited by the anti-fog sprays. Altogether, these results suggest that FTEOs are present in commercial products at toxicologically relevant levels, and more research is needed to fully understand the health risks from using these PFAS-containing products.

Environmental Sources, Chemistry, Fate, and Transport of Per- and Polyfluoroalkyl Substances: State of the Science, Key Knowledge Gaps, and Recommendations Presented at the August 2019 SETAC Focus Topic Meeting

A Society of Environmental Toxicology and Chemistry (SETAC) Focused Topic Meeting (FTM) on the environmental management of per- and polyfluoroalkyl substances (PFAS) convened during August 2019 in Durham, North Carolina (USA). Experts from around the globe were brought together to critically evaluate new and emerging information on PFAS including chemistry, fate, transport, exposure, and toxicity. After plenary presentations, breakout groups were established and tasked to identify and adjudicate via panel discussions overarching conclusions and relevant data gaps. The present review is one in a series and summarizes outcomes of presentations and breakout discussions related to (1) primary sources and pathways in the environment, (2) sorption and transport in porous media, (3) precursor transformation, (4) practical approaches to the assessment of source zones, (5) standard and novel analytical methods with implications for environmental forensics and site management, and (6) classification and grouping from multiple perspectives. Outcomes illustrate that PFAS classification will continue to be a challenge, and additional pressing needs include increased availability of analytical standards and methods for assessment of PFAS and fate and transport, including precursor transformation. Although the state of the science is sufficient to support a degree of site-specific and flexible risk management, effective source prioritization tools, predictive fate and transport models, and improved and standardized analytical methods are needed to guide broader policies and best management practices. Environ Toxicol Chem 2021;40:3234-3260. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Structure-Specific Aerobic Defluorination of Short-Chain Fluorinated Carboxylic Acids by Activated Sludge Communities

Per- and polyfluoroalkyl substances (PFAS) are a large group of manmade chemicals that impose emerging environmental concerns. Among them, short-chain per- and polyfluorinated carboxylic acids represent an important subgroup used as building blocks of biologically active chemicals and functional materials. Some are also considered PFAS alternatives, and some could be byproducts of the physicochemical treatment of PFAS. However, little is known about the environmental fate of short-chain fluorinated carboxylic acids (FCAs) and their defluorination/transformation by microorganisms. To fill the knowledge gap, we investigated the structure-reactivity relationships in the aerobic defluorination of C₃-C₅ FCAs by activated sludge communities. Four structures exhibited greater than 20% defluorination, with 3,3,3-trifluoropropionic acid being almost completely defluorinated. We further analyzed the defluorination/transformation pathways and inferred the structures susceptible to aerobic microbial defluorination. We also demonstrated that the defluorination was via cometabolism. The findings advance the fundamental understanding of aerobic microbial defluorination and help assess the environmental fate of PFAS. Since some short-chain PFAS, such as 3,3,3-trifluoropropionic acid, are the incomplete defluorination byproducts of advanced reduction processes, their defluorination by activated sludge communities sheds light on the development of cost-effective chemical-biological PFAS treatment train systems.

Investigation of distribution, sources and flux of perfluorinated compounds in major southern Indian rivers and their risk assessment

Perfluorinated compounds (PFCs) are a group of emerging contaminants still less reported in rivers, particularly southern India. Therefore, we investigated the fate of 13 PFCs in three major rivers in southern India during post-monsoon and summer seasons. Twelve PFCs were detected, with an average total PFCs of 1853 ± 1463 pg/l. However, the total PFCs recorded in ppost-monsoon and summer seasons ranged from ND (none detected) to 10,545 pg/l and ND to 4960 pg/l, respectively. Among the individual congeners, perfluoro-n-hexanoic acid (PFHxA) had the highest detection average (929 ± 710 pg/l). The higher detection of short chain PFCs signifies their increasing wide usage as an alternative to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). Higher levels of PFCs were observed in summer than post-monsoon season in the river Kaveri, which is mainly attributed to the decrease in river flow. A multidimensional source identification revealed domestic and commercial wastewater as the major source. A correlation analysis showed that most of the detected PFCs share the common source and undergo co-migration into rivers. The flux of PFCs into the Bay of Bengal, loaded by the Kaveri (15 kg/yr) and the Tamiraparani (2.2 kg/yr) rivers, signifies lower per capita emissions than other rivers in India and other countries. Further, the PFC levels found in the rivers can be considered safe for human consumption and aquatic organisms based on international guidelines. Being the first hand report in southern Indian rivers, the results warrant further investigation to understand the exact sources, fate and removal in detail.

Occurrence and seasonal distribution of legacy and emerging per- and polyfluoroalkyl substances (PFASs) in different environmental compartments from areas around ski resorts in northern China

Skiing is an important direct input route of per- and polyfluoroalkyl substances (PFASs) to the environment. However, there has been no study on the occurrence of PFASs in Chinese ski area. In this study, 27 neutral PFASs (n-PFASs) and ionic PFASs (i-PFASs), including 4 emerging PFASs, were analyzed in the multimedia samples collected from areas around six ski resorts in Zhangjiakou and Shenyang to investigate the occurrence and seasonal distribution of PFASs. Both i-PFASs and n-PFASs were found in the air (13.2 ± 9.5 pg/m³ and 167 ± 173 pg/m³, respectively) and pine needles [1.44 ± 0.96 ng/g dry weight (dw) and 0.983 ± 0.590 ng/g dw], whereas only i-PFASs were found in the soil (0.755 ± 0.281 ng/g dw) and snow (3.30 ± 2.66 ng/kg). i-PFASs were significantly higher in samples collected around ski resorts than those from rural sites (n = 105, p < 0.05). Significantly higher perfluorooctanoate concentrations were found in the air around the ski resorts in winter (n = 33, p < 0.05). The i-PFASs were stable in the needle, and the short-chain PFASs in the needle could be ascribed to both air and root uptake. More attention should be paid to PFASs emissions in Zhangjiakou with the approaching 2022 Winter Olympic Games.

Remediation of poly- and perfluoroalkyl substances (PFAS) contaminated soils - To mobilize or to immobilize or to degrade?

Poly- and perfluoroalkyl substances (PFASs) are synthetic chemicals, which are introduced to the environment through anthropogenic activities. Aqueous film forming foam used in firefighting, wastewater effluent, landfill leachate, and biosolids are major sources of PFAS input to soil and groundwater. Remediation of PFAS contaminated solid and aqueous media is challenging, which is attributed to the chemical and thermal stability of PFAS and the complexity of PFAS mixtures. In this review, remediation of PFAS contaminated soils through manipulation of their bioavailability and destruction is presented. While the mobilizing amendments (e.g., surfactants) enhance the mobility and bioavailability of PFAS, the immobilizing amendments (e.g., activated carbon) decrease their bioavailability and mobility. Mobilizing amendments can be applied to facilitate the removal of PFAS though soil washing, phytoremediation, and complete destruction through thermal and chemical redox reactions. Immobilizing amendments are likely to reduce the transfer of PFAS to food chain through plant and biota (e.g., earthworm) uptake, and leaching to potable water sources. Future studies should focus on quantifying the potential leaching of the mobilized PFAS in the absence of removal by plant and biota uptake or soil washing, and regular monitoring of the long-term stability of the immobilized PFAS.

Review on perfluoroalkyl and polyfluoroalkyl substances (PFASs) in the Chinese atmospheric environment

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been manufactured and used for over 50 years, and now are worldwide distributed in the environment. The atmospheric environment is the main compartment for PFASs to be transported and transformed, and relevant research has highlighted the global occurrence and impacts of atmospheric PFASs in ecosystems and human health. With the phasing-out and restriction of eight‑carbon chain-length (C8) PFASs in developed countries, China has become the largest producer of C8 PFASs since 2004. Subsequently, a number of studies on PFASs in the Chinese atmospheric environment have been conducted in the recent decade. This review documented twenty-eight studies on PFASs in Chinese outdoor air published to date. Methods of sampling, extraction, cleanup, and instrumental analysis were summarized for both ionic and neutral PFASs. Levels, compositions, and spatial distribution of PFASs from different areas in China (i.e. source, urban, and remote regions, and north versus south China) were compared and discussed. Leaves and tree barks were proposed as effective bioindicators to reflect the contamination status of atmospheric PFASs. Special attention can be given to non-target screening for future research directions.

Fluorochemicals biodegradation as a potential source of trifluoroacetic acid (TFA) to the environment

The anthropogenic release of trifluoroacetic acid (TFA) into the environmental media is not limited to photochemical oxidation of CFC alternatives and industrial emissions. Biological degradation of some fluorochemicals is expected to be a potential TFA source. For the first time, we assess if the potential precursors [6:2 fluorotelomer alcohol (6:2 FTOH), 4:2 fluorotelomer alcohol (4:2 FTOH), acrinathrin, trifluralin, and 2-(trifluoromethyl)acrylic acid (TFMAA)] can be biologically degraded to TFA. Results show that 6:2 FTOH was terminally transformed to 5:3 polyfluorinated acid (5:3 FTCA; 12.5 mol%), perfluorohexanoic acid (PFHxA; 2.0 mol%), perfluoropentanoic acid (PFPeA; 1.6 mol%), perfluorobutyric acid (PFBA; 1.7 mol%), and TFA (2.3 mol%) by day 32 in the landfill soil microbial culture system. 4:2 FTOH could remove multiple -CF₂ groups by microorganisms and produce PFPeA (2.6 mol%), PFBA (17.4 mol%), TFA (7.8 mol%). We also quantified the degradation products of TFMAA as PFBA (1.3 mol%) and TFA (6.3 mol%). Furthermore, we basically analyzed the biodegradation contribution of short-chain FTOH as raw material residuals in commercial products to the TFA burden in the environmental media. We estimate global emission of 3.9-47.3 tonnes of TFA in the period from 1961 to 2019, and project 3.8-46.4 tonnes to be emitted from 2020 to 2040 via the pathway of 4:2 and 6:2 FTOH biodegradation (0.6-7.1 and 0.6-7.0 tonnes in China, respectively). Direct evidence of the experiments indicates that biodegradation of fluorochemicals is an overlooked source of TFA and there are still some unspecified mechanisms of TFA production pathways.

Novel and legacy per- and polyfluoroalkyl substances (PFASs) in a farmland environment: Soil distribution and biomonitoring with plant leaves and locusts

The occurrence of legacy and novel per- and polyfluoroalkyl substances (PFASs) in multiple matrices from a farmland environment was investigated in the Beijing-Tianjin-Hebei core area of northern China. PFASs were ubiquitously detected in farmland soils, and the detection frequency of 6:2 chlorinated polyfluoroalkyl ether sulfonic acid (6:2 Cl-PFESA) was higher than that of perfluorooctane sulfonic acid (98% vs. 83%). Long-chain PFASs, including 6:2 Cl-PFESA, showed a centered distribution pattern around the metropolis of Tianjin, probably due to the local intensive industrial activity, while trifluoroacetic acid (TFA) showed a decreasing trend from the coast to the inland area. Other than soil, TFA was also found at higher levels than other longer-chain PFASs in dust, maize (Zea mays), poplar (Populus alba) leaf and locust (Locusta migratoria manilens) samples. Both poplar leaves and locusts can be used as promising biomonitoring targets for PFASs in farmland environments, and their accumulation potential corresponds with protein and lipid contents. Apart from being exposed to PFASs via food intake, locusts were likely exposed via uptake from soil and precipitated dust in farmland environments. The biomonitoring of locusts may be more relevant to insectivores, which is important to conducting a comprehensive ecological risk assessment of farmland environments.

The effect of weathering on per- and polyfluoroalkyl substances (PFASs) from durable water repellent (DWR) clothing

To assess the effects of weathering on per- and polyfluoroalkyl substances (PFASs) from durable water repellent (DWR) clothing, thirteen commercial textile samples were exposed to elevated ultra violet (UV) radiation, humidity, and temperature in an aging device for 300 h, which mimics the lifespan of outdoor clothing. Before and after aging, the textile samples were extracted and analysed for the ionic PFASs (perfluoroalkyl acids (PFAAs), perfluorooctane sulfonamide (FOSA)) and volatile PFASs (fluorotelomer alcohols (FTOHs), acrylates (FTACs) and methacrylates (FTMACs)). Results showed that weathering can have an effect on PFASs used in DWR of outdoor clothing, both on the PFAS profile and on the measured concentrations. In most weathered samples the PFAA concentrations increased by 5- to more than 100-fold, while PFAAs not detected in the original textiles were detected in the weathered samples. DWR chemistries are based on side-chain fluorinated polymers. A possible explanation for the increase in concentration of the PFAAs is hydrolysis of the fluorotelomer based polymers (FTPs), or degradation of the FTOHs, which are used in the manufacturing of the FTPs. The concentrations of volatile PFASs also increased, by a factor up to 20. Suggested explanations are the degradation of the DWR polymers, making non-extractable fluorines extractable, or the transformation or degradation of unknown precursors. Further research is needed to unravel the details of these processes and to determine the transformation routes. This study shows that setting maximum tolerance limits only for a few individual PFASs is not sufficient to control these harmful substances in outdoor clothing.

Aerobic biotransformation of fluorotelomer compounds in landfill leachate-sediment

Consumer products containing fluorotelomer polymers are a source of fluorotelomer compounds to the environment following their disposal at landfills. The fate and transformation of fluorotelomer compounds are unknown in landfill leachates. This study investigates the aerobic biotransformation of 8:2 fluorotelomer alcohol (FTOH) and 6:2 fluorotelomer sulfonate (FTS) in landfill leachate-sediment microcosms using batch tests. Spiked 8:2 FTOH, 6:2 FTS and their known biotransformation products were quantified in sediment-leachate and headspace over 90 days under aerobic conditions. 8:2 FTOH and 6:2 FTS biotransformation was slow (half-life >>30 d) in landfill leachate-sediment microcosm, suggesting persistence of fluorotelomer compounds under the conditions investigated. Significant volatilization (>20%) of 8:2 FTOH was observed in the microcosm headspace after 90 days. C6 - C8 and C4 - C6 perfluorocarboxylic acids (PFCAs) were the most abundant products for 8:2 FTOH and 6:2 FTS, respectively. PFCAs accounted for 4-9 mol% of the initially spiked parent compounds at 90 days. Perfluorooctanoic acid (PFOA) was the single most abundant product of 8:2 FTOH (>2.8 mol% at 90 days). The unaccounted mass (20 to 35 mol%) of the initially spiked parent compounds indicated formation of fluorotelomer intermediates and sediment-bound residue. Overall the findings suggest that aerobic biotransformation of fluorotelomer compounds acts as a secondary source of long- and short-chain (≤C7) PFCAs in the environment. Partitioning of semi-volatile fluorotelomer compounds (e.g., 8:2 FTOH) to the gas-phase indicates possible long-range transport and subsequent release of PFCAs in pristine environments. Short-chain fluorotelomer replacements (e.g., 6:2 FTS) result in a higher abundance of short-chain PFCAs in landfill leachate. Future research is needed to understand the long-term exposure effects of short-chain PFCAs to humans, aquatic life and biota.

Formation of perfluorocarboxylic acids from 6:2 fluorotelomer sulfonate (6:2 FTS) in landfill leachate: Role of microbial communities

Fluorotelomer compounds in landfill leachate can undergo biotransformation under aerobic conditions and act as a secondary source of perfluorocarboxylic acids (PFCAs) to the environment. Very little is known about the role of various microbial communities towards fluorotelomer compounds biotransformation. Using an inoculum prepared from the sediment of a leachate collection ditch, 6:2 fluorotelomer sulfonate (6:2 FTS) biotransformation experiments were carried out. Specific substrates (i.e., glucose, ammonia) and ammonia-oxidizing inhibitor (allylthiourea) were used to produce two experimental runs with heterotrophic (HET) growth only and heterotrophic with ammonia-oxidizing and nitrite- oxidizing bacteria (HET + AOB + NOB). After 10 days, ∼20% of the spiked 6:2 FTS removal was observed in HET + AOB + NOB, compared to ∼7% under HET condition. Higher 6:2 FTS removal in HET + AOB + NOB likely resulted from ammonia monooxygenase enzyme that catalyzes the first step of ammonia oxidation. The HET + AOB + NOB condition also showed higher PFCA (C4-C6) formation (∼2% of initially spiked 6:2 FTS), possibly due to higher overall bioactivity. Microbial community analysis through 16s rRNA sequencing confirmed that Proteobacteria and Bacteroidetes were the most abundant phyla (>75% relative abundance) under all experimental conditions. High abundance of Actinobacteria (>17%) was observed under the HET + AOB + NOB condition on day 7. Since Actinobacteria can synthesize a wide range of enzymes including monooxygenases, they likely play an important role in 6:2 FTS biotransformation and PFCA production.

On the Ability of Perfluorohexane Sulfonate (PFHxS) Bioaccumulation by Two Pseudomonas sp. Strains Isolated from PFAS-Contaminated Environmental Matrices

PFASs (perfluoroalkyl and polyfluoroalkyl substances) are highly fluorinated, aliphatic, synthetic compounds with high thermal and chemical stability as well as unique amphiphilic properties which make them ingredients in a range of industrial processes. PFASs have attracted consideration due to their persistence, toxicity and bioaccumulation tendency in the environment. Recently, attention has begun to be addressed to shorter-chain PFASs, such as perfluorohexane sulfonate [PFHxS], apparently less toxic to and more easily eliminated from lab animals. However, short-chain PFASs represent end-products from the transformation of fluorotelomers whose biotic breakdown reactions have not been identified to date. This means that such emergent pollutants will tend to accumulate and persist in ecosystems. Since we are just learning about the interaction between short-chain PFASs and microorganisms, this study reports on the response to PFHxS of two Pseudomonas sp. strains isolated from environmental matrices contaminated by PFASs. The PFHxS bioaccumulation potential of these strains was unveiled by exploiting different physiological conditions as either axenic or mixed cultures under alkanothrofic settings. Moreover, electron microscopy revealed nonorthodox features of the bacterial cells, as a consequence of the stress caused by both organic solvents and PFHxS in the culturing substrate.

Per- and polyfluoroalkyl substances in commercially available biosolid-based products: The effect of treatment processes

Per- and polyfluoroalkyl substances (PFAS) have been used in a variety of consumer and industrial products and are known to accumulate in sewage sludge due to sorption and their recalcitrant nature. Treatment processes ensure safe and high-quality biosolids by reducing the potential for adverse environmental impacts such as pathogen levels; however, they have yet to be evaluated for their impact on the fate of PFAS. The objective of this study was to compare PFAS concentrations in four commercially available biosolid-based products that received different types of treatments: heat treatment, composting, blending, and thermal hydrolysis. Seventeen perfluoroalkyl acids (PFAAs) were quantified using liquid chromatography with tandem quadrupole time-of-flight mass spectrometry followed by screening for 30 PFAA precursors. Treatment processes did not reduce PFAA loads except for blending, which served only to dilute concentrations. Several PFAA precursors were identified with 6:2 and 8:2 fluorotelomer phosphate diesters in all samples pre- and post-treatment. PRACTITIONER POINTS: Heat treatment and composting increased perfluoroalkyl acid (PFAA) concentrations. Only dilution from blending with non-PFAS material decreased PFAA concentrations. Thermal hydrolysis process had no apparent effect on PFAA concentrations. PFAS sources are a greater driver of PFAS loads in biosolid-based products than treatment processes.

Occurrence, sources and health risk of polyfluoroalkyl substances (PFASs) in soil, water and sediment from a drinking water source area

Polyfluoroalkyl substances (PFASs) enter into environmental metric via various pathways in the process of manufacturing and consuming the products containing PFASs. Yuqiao reservoir (YQR) is a major drinking water source in Tianjin of China, where little attention was given to PFASs. To explore the occurrence, source and risk of 17 PFASs, multi-media environmental including soil, water, and sediment were sampled from this water source area. The ∑PFASs concentrations of surface water, groundwater, soil and sediment ranged from 5.839 to 120.885 ng/L, 1.426 to 17.138 ng/L, 0.622 to 5.089 μg/kg dw, and 0.240 to 1.210 μg/kg dw respectively. Some short-chained (C4-C8) PFASs were detected widely such as PFOA, PFBA, PFHxA, PFBS, PFHpA and PFPeA in surface water and groundwater, with the detection frequency of ＞78%, and PFBA and PFOA dominated in the 17 PFASs. In addition, the correlations between total PFASs and TOC were significant at 0.05 level, especially in surface water with R² = 0.9165 (p = 0.011). In terms of vertical distribution characteristics of ∑PFASs, the ∑PFASs in four sediment cores showed a decreasing trend at first, and then an increasing trend from the bottom to the top associated with TOC. PFBA/PFOA and PFHpA/PFOA showed better linear correlations with R² of 0.5541 (p = 0.039), and for PFNA/PFOA and PFHpA/PFOA with R² of 0.6312 (p = 0.032) at the 0.05 level in the surface water, which indicated that sewage and atmospheric precipitation were the major sources. Though the RQ results based on the measured concentrations and reference values in environmental media revealed lower risks, the potential hazard may occur due to accumulation characteristics and long-distance transmission capability of PFASs. Hence, the corresponding management strategies should be taken, such as control over emission at source, product substitution and strengthening legislation, to eliminate potential risks to human health.

Isomer-specific biotransformation of perfluoroalkyl sulfonamide compounds in aerobic soil

As an important reservoir of pollutants, soil may play a critical role in altering isomer ratios of perfluorooctane sulfonate (PFOS) or PFOS precursors (PrePFOS) via microbial processes, but this possibility has not yet been investigated, as well as the feasibility of using PFOS isomer ratio for source tracking in PFOS contaminated sites. In the present study, N‑ethyl perfluorooctane sulfonamide ethanol (EtFOSE) of the technical grade was incubated in soil microcosms for 105 days to examine isomer-specific transformation processes. Experimental data combined with a mathematical model suggest new biotransformation pathways leading to PFOS, including a direct pathway to produce PFOS via hydrolysis of the sulfonamide bond. A similar rate of biotransformation was observed for EtFOSE with an estimated half-life of 8.7 and 9.6 days for the branched and linear isomers, respectively, without statistical difference. Two transformation intermediates, N‑ethyl perfluorooctanoic acid (EtFOSAA) and perfluorooctane sulfonamide (FOSA), also showed preferential biotransformation of branched isomers. On the contrary, one intermediate N‑ethyl perfluorooctane sulfonamide (EtFOSA) showed the preferred transformation of the linear isomer with an estimated half-life of 80.8 and 11.2 days for the branched and linear isomers, respectively. As PFOS is likely to be generated through more than one pathway or one precursor, its final isomer ratio is collectively determined by several upstream reactions, each having specific isomer-specific transformation kinetics. Though the soil showed enrichment of branched PFOS isomers during the 4-month incubation, compared to PFOS standards, some uncertainty arises in concluding preferential generation of branched PFOS from its precursors, due to the lack of standards for branched PreFOS. The complexity of isomer-specific biotransformation only reinforced the challenge of applying the PFOS isomer ratio for source tracking in environmental microbial systems.

In-Vial Extraction Large Volume Gas Chromatography Mass Spectrometry for Analysis of Volatile PFASs on Papers and Textiles

Volatile per- and polyfluorinated alkyl substances (PFASs) are found in consumer goods that contribute to human exposure to PFASs. Volatile PFAS precursors transform to perfluorinated carboxylates (PFCAs) and sulfonates (PFSAs) in both humans and the environment. Established methods for volatile PFASs in consumer goods exist, but higher sample throughput and greener sample preparation methods are needed to minimize analyte loss, while maintaining sensitivity. New analytical methodology was developed where a 1.5 × 1.5 cm piece of paper or textile is placed into an autosampler vial with solvent and mass-labeled internal standards, sonicated for 30 min, and directly injected without removal of material from the autosampler vial. Large volume injection (20 μL) gas chromatography mass spectrometry was applied for the quantification for 21 individual PFASs from five classes: fluorotelomer alcohols (FTOHs), fluorinated sulfonamides (N-MeFASA, N-EtFASA), and fluorinated sulfonamidoethanols (N-MeFASE, N-EtFASE). Nontargeted analysis revealed additional C₂-C₇ homologues of N-MeFASE and N-EtFASE, which accounted for 14-18% of the total volatile PFASs on three textiles. Overlooking short-chain (≤C₇) N-MeFASE, N-EtFASE, and long-chained (10:2-14:2) FTOHs on older textiles from the 1980s leads to an underestimation of human and environmental exposure to volatile PFAS.

Sorption, Aerobic Biodegradation, and Oxidation Potential of PFOS Alternatives Chlorinated Polyfluoroalkyl Ether Sulfonic Acids

Global phase out of perfluorooctanesulfonic acid (PFOS) has led to increasing production of alternatives such as the chlorinated polyfluoroalkyl ether sulfonic acids (Cl-PFESAs) for which little is known on their environmental fate. In this study, sorption by soils, aerobic soil biodegradation, and oxidation potential of 6:2 Cl-PFESA (9-chlorohexadecafluoro-3-oxanonane-1-sulfonate) and 8:2 Cl-PFESA (9-chlorooctadecafluoro-3-oxanonane-1-sulfonate) were evaluated. 6:2 Cl-PFESA sorption was quantified for aqueous and acetone/water solutions, whereas 8:2 PFESA could only be accurately measured in acetone/water solutions. The log-linear cosolvency model was applied and validated to estimate sorption of 8:2 Cl-PFESA. Only soil organic carbon (OC, 0.76-4.30%) was highly and positively correlated to sorption of the Cl-PFESAs ( R² > 0.96). The resulting log K_oc values (OC-normalized sorption coefficients) are 4.01 ± 0.09 ( n = 6) and 5.54 ± 0.05 ( n = 4) L kg^-1 for 6:2 Cl-PFESA and 8:2 Cl-PFESA, respectively. Aerobic biodegradation in a loam soil at 24 ± 0.5 °C showed negligible degradation of both Cl-PFESAs. Cl-PFESAs also remained unchanged in an unbuffered heat (50 °C)-activated 42 mM persulfate oxidation treatment. Therefore, Cl-PFESAs are equally recalcitrant as PFOS in addition to being more sorptive, thus with a higher bioaccumulation potential for a similar alkyl chain length.

Anaerobic biodegradation of 8:2 fluorotelomer alcohol in anaerobic activated sludge: Metabolic products and pathways

The anaerobic biodegradability and metabolic pathways of 8:2 fluorotelomer alcohol (8:2 FTOH) were investigated in anaerobic activated sludge. The biodegradation was well described by a double exponential decay model. 8:2 FTOH was biodegraded to poly- and perfluorinated metabolites with the release of fluoride ion. All polyfluorinated metabolites were intermediate metabolic products and could be further transformed to other metabolites, while perfluorinated metabolites were terminal products. 2H-perfluoro-2-decenoic acid (8:2 FTUA) and perfluorooctanoic acid (PFOA) were verified as the most abundant poly- and perfluorinated metabolites, respectively. Two shorter-chain perfluorinated metabolites, perfluoropentanoic acid (PFPeA) and perfluorobutyric acid (PFBA), were first reported in the biodegradation of 8:2 FTOH. However, the total molar recovery of 8:2 FTOH decreased with increasing incubation time, indicating that there might be some unknown metabolites. Thus, the anaerobic biodegradation pathways were proposed as follows: 8:2 FTOH was oxidized to 8:2 FTUA and 2-perfluorooctyl ethanoic acid (8:2 FTCA) via 2-perfluorooctyl acetaldehyde (8:2 FTAL), and then 8:2 FTUA and 8:2 FTCA were further transformed to 1-perfluoroheptyl ethanol (7:2 sFTOH) via 3-perfluoroheptyl propionic acid (7:3 acid) or/and 3-perfluoroheptyl acrylic acid (7:3 Uacid), and eventually 7:2 sFTOH was further biodegraded to PFOA and other perfluorocarboxylates containing less than eight carbons.

Enhanced generation of perfluoroalkyl carboxylic acids (PFCAs) from fluorotelomer alcohols (FTOHs) via ammonia-oxidation process

With the phase-out of persistent, bioaccumalative, and toxic perfluoroalkyl carboxylic acids (PFCAs), it is needed to explore the potential release of PFCAs from precursors being emitted into the environment. Biotransformation of fluorotelomer alcohols (FTOHs) via biological processes in wastewater treatment plants (WWTPs) leads to discharge of PFCAs into receiving waters. However, the commonly existed microbial activity that can impact on FTOHs biodegradation in WWTPs remains unclear. The objective of present research was to explore the relationship between ammonia-oxidation process and the enhanced PFCAs generation from FTOHs biodegradation under aerobic activated sludge. The obtained results indicate that the cometabolism process performed by nitrifying microorganisms (NMs) was responsible for enhanced PFCAs generation. Among NMs, the ammonia-oxidation bacteria that can express non-specific enzyme of ammonia monooxygenases resulted in the enhanced PFCAs generation from FTOHs. Meanwhile, the different addition amount of ammonia contributed to different defluorination efficiency of FTOHs. The present study further correlated the enhanced PFCAs generation from FTOHs biodegradation with ammonia-oxidation process, which can provide practical information on effective management of PFCAs generation in WWTPs.

Effects of microbial activity on perfluorinated carboxylic acids (PFCAs) generation during aerobic biotransformation of fluorotelomer alcohols in activated sludge

Biotransformation of fluorotelomer alcohols (FTOHs) in wastewater treatment plants (WWTPs) can release toxic intermediates and perfluorinated carboxylic acids (PFCAs) to the aqueous environment. However, little information is known about the role of relevant microbial activity (i.e., autotrophs and/or heterotrophs) in biotransformation of FTOHs. Additionally, the dynamics of microbial community in sludge after exposure to FTOHs remain unclear. In the present research, using domestic and industrial WWTP sludge, we performed lab-scale batch experiments to characterize the FTOHs biodegradation property under aerobic condition. Both heterotrophs and the autotrophs were associated with FTOHs biotransformation. However, the microbial activity influenced PFCAs generation efficiency. Autotrophs based on ammonia oxidation (50mgN/L) resulted in more effective generation of PFCAs than heterotrophs based on glucose (200mgC/L) metabolism. Moreover, autotrophs generated more amounts of short-chain PFCAs (carbon number ≤7) than the heterotrophs. The ammonia monooxygenase (AMO) in ammonia oxidizing microorganisms (AOMs) are suggested as responsible for the enhanced generation of PFCAs during FTOHs biotransformation. In the sludge that had been exposed to poly- and perfluorinated alkyl substances in an industrial WWTP, Chlorobi was the predominant microorganisms (36.9%), followed by Proteobacteria (20.2%), Bacteroidetes (11.1%), Chloroflexi (6.2%), Crenarchaeota (5.6%), Planctomycetes (4.2%), and Acidobacteria (3.5%). In the present research, the dosed 8:2 FTOH (12.1mg/L) and its biotransformation products (intermediates and PFCAs) could force a shift in microbial community composition in the sludge. After 192h, Proteobacteria significantly increased and dominated. These results provide knowledge for comprehending the effects of microbial activity on FTOHs biodegradation and the information about interaction between microbial community and the exposure to FTOHs in activated sludge.

Perfluoroalkyl and polyfluoroalkyl substances removal in a full-scale tropical constructed wetland system treating landfill leachate

Landfill leachate is often an important source of emerging organic contaminants including perfluoroalkyl and polyfluoroalkyl substances (PFASs) requiring proper treatment to protect surface water and groundwater resources. This study investigated the occurrence of PFASs in the leachate of a capped landfill site in Singapore and the efficacy of PFASs removal during flow through a constructed wetland (CW) treatment system. The CW treatment system consists of equalization tank, aeration lagoons, sedimentation tank, reed beds and polishing ponds. Target compounds included 11 perfluoroalkyl acids (PFAAs) (7 perfluoroalkyl carboxylic acids (PFCAs) and 4 perfluoroalkane sulfonates (PFSAs)) and 7 PFAA precursors. Although total PFASs concentrations in the leachate varied widely (1269 to 7661 ng/L) over the one-year sampling period, the PFASs composition remained relatively stable with PFCAs consistently being predominant (64.0 ± 3.8%). Perfluorobutane sulfonate (PFBS) concentrations were highly correlated with total PFASs concentrations and could be an indicator for the release of PFASs from this landfill. The release of short-chain PFAAs strongly depended on precipitation whereas concentrations of the other PFASs appeared to be controlled by partitioning. Overall, the CW treatment system removed 61% of total PFASs and 50-96% of individual PFASs. PFAAs were removed most efficiently in the reed bed (42-49%), likely due to the combination of sorption to soils and sediments and plant uptake, whereas most of the PFAA precursors (i.e. 5:3 fluorotelomer carboxylate (5:3 acid), N-substituted perfluorooctane sulfonamides (N-MeFOSAA and N-EtFOSAA)) were removed in the aeration lagoon (>55%) by biodegradation. The sedimentation tank and polishing ponds were relatively inefficient, with only 7% PFASs removal.

Quantitative and time-course analysis of microbial degradation of 1H,1H,2H,2H,8H,8H-perfluorododecanol in activated sludge

A methylene group in the fluorinated carbon backbone of 1H,1H,2H,2H,8H,8H-perfluorododecanol (degradable telomer fluoroalcohol, DTFA) renders the molecule cleavable by microbial degradation into two fluorinated carboxylic acids. Several biodegradation products of DTFA are known, but their rates of conversion and fates in the environment have not been determined. We used liquid chromatography coupled with tandem mass spectrometry (LC/MS/MS) to quantitatively investigate DTFA biodegradation by the microbial community in activated sludge in polyethylene terephthalate (PET) flasks, which we also determined here showed least adsorption of DTFA. A reduction in DTFA concentration in the medium was accompanied by rapid increases in the concentrations of 2H,2H,8H,8H-perfluorododecanoic acid (2H,2H,8H,8H-PFDoA), 2H,8H,8H-2-perfluorododecenoic acid (2H,8H,8H-2-PFUDoA), and 2H,2H,8H-7-perfluorododecenoic acid and 2H,2H,8H-8-perfluorododecenoic acid (2H,2H,8H-7-PFUDoA/2H,2H,8H-8-PFUDoA), which were in turn followed by an increase in 6H,6H-perfluorodecanoic acid (6H,6H-PFDeA) concentration, and decreases in 2H,2H,8H,8H-PFDoA, 2H,8H,8H-2-PFUDoA, and 2H,2H,8H-7-PFUDoA/2H,2H,8H-8-PFUDoA concentrations. Accumulation of perfluorobutanoic acid (PFBA), a presumed end product of DTFA degradation, was also detected. Our quantitative and time-course study of the concentrations of these compounds reveals main routes of DTFA biodegradation, and the presence of new biodegradation pathways.

Kinetic analysis of aerobic biotransformation pathways of a perfluorooctane sulfonate (PFOS) precursor in distinctly different soils

With the phaseout of perfluorooctane sulfonate (PFOS) production in most countries and its well known recalcitrance, there is a need to quantify the potential release of PFOS from precursors previously or currently being emitted into the environment. Aerobic biodegradation of N-ethyl perfluorooctane sulfonamidoethanol (EtFOSE) was monitored in two soils from Indiana, USA: an acidic forest silt loam (FRST-48, pH = 5.5) and a high pH agricultural loam (PSF-49, pH = 7.8) with similar organic carbon contents (2.4 and 2.6%) for 210 d and 180 d, respectively. At designated times, triplicate samples were sacrificed for which headspace samples were taken followed by three sequential extractions. Extracts were analyzed using HPLC-tandem mass spectrometry. Measured profiles of EtFOSE degradation and generation/degradation of subsequent metabolites were fitted to the Indiana soils data as well as to a previously published data set for a Canadian soil using an R-based model (KinGUII) to explore pathways and estimate half-lives (t_1/2) for EtFOSE and metabolites. EtFOSE degradation ranged from a few days to up to a month. PFOS yields ranged form 1.06-5.49 mol% with the alkaline soils being four to five times higher than the acidic soil. In addition, a direct pathway to PFOS had to be invoked to describe the early generation of PFOS in the Canadian soil. Of all metabolites, the sulfonamidoacetic acids were the most persistent (t_1/2 ≥ 3 months) in all soils. We hypothesized that while pH-pK_a dependent speciation may have impacted rates, differences in microbial communities between the 3 soils arising from varied soil properties including pH, nutrient levels, soil management, and climatic regions are likely the major factors affecting pathways, rates, and PFOS yields.

Detection, Occurrence, and Fate of Fluorotelomer Alcohols in Municipal Wastewater Treatment Plants

Fluorotelomer alcohols (FTOHs) are the most well-known precursors of perfluoroalkyl carboxylic acids (PFCAs), but limited information is available on their occurrence and fate in municipal wastewater treatment plants (WWTPs). The occurrence of FTOHs was investigated in influent, secondary effluent, and sludge of 12 municipal WWTPs in nine cities of China. FTOHs were detected in all WWTPs, and 8:2 FTOH was the predominant congener, with concentrations of 2.10-11.0 ng/L, 3.05-12.4 ng/L, and 0.36-1.91 ng/g dry weight in the influent, secondary effluent, and sludge, respectively. Relatively high proportions of long-chain FTOHs (C_10-16) were mainly detected in sludge samples. The mass balance of FTOHs and PFCAs in one of the WWTPs with an anaerobic-anoxic-oxic process was further explored. The decrease of mass loads was observed for 4:2 FTOH (mass change percentage: 21 ± 3.3%), 8:2 FTOH (22 ± 1.5%), and 10:2 FTOH (29 ± 7.3%) through aerobic treatment, while the increase of mass loads was observed for 12 PFCAs from 18 ± 16% (perfluorononanoic acid) to 165 ± 15% (perfluorobutyric acid)), suggesting the potential biotransformation of FTOHs to PFCAs in the aerobic unit. This work provides the first report on the occurrence of FTOHs in sludge samples of municipal WWTPs and their mass balance and highlights a new emission route to environment via WWTPs.

Uptake and metabolism of 10:2 fluorotelomer alcohol in soil-earthworm (Eisenia fetida) and soil-wheat (Triticum aestivum L.) systems

The behavior of 10:2 fluorotelomer alcohol (10:2 FTOH) in the systems of soil-earthworm (Eisenia fetida), soil-wheat (Triticum aestivum L.) and soil-earthworm-wheat, including degradation in soil, uptake and metabolism in wheat and earthworms were investigated. Several perfluorocarboxylic acids (PFCAs) as degradation products of 10:2 FTOH were identified in the soil, plant and earthworms. 10:2 FTOH could be biodegraded to perfluorooctanoate (PFOA), perfluorononanate (PFNA) and perfluorodecanoate (PFDA) in soil in the absence or presence of wheat/earthworms, and PFDA was the predominant metabolite. Accumulation of initial 10:2 FTOH and its metabolites were observed in the wheat and earthworms, suggesting that 10:2 FTOH could be bioaccumulated in wheat and earthworms and biotransformed to the highly stable PFCAs. Perfluoropentanoic acid (PFPeA), perfluorohexanoic (PFHxA) and PFDA were detected in wheat root, while PFDA and perfluoroundecanoic acid (PFUnDA) were detected in shoot. PFNA and PFDA were determined in earthworms and the concentration of PFDA was much higher. The presence of earthworms and/or plant stimulated the microbial degradation of 10:2 FTOH in soil. The results supplied important evidence that degradation of 10:2 FTOH was an important potential source of PFCAs in the environment and in biota.

Uptake, Translocation, and Metabolism of 8:2 Fluorotelomer Alcohol in Soybean (Glycine max L. Merrill)

Biotransformation of fluorotelomer alcohols (FTOHs) is widely considered as an additional source of perfluorocarboxylic acids (PFCAs) in environmental biota. Compared with the extensive studies conducted in animals and microbes, biotransformation pathways of FTOHs in plants are still unclear. In this study, a hydroponic experiment was conducted to investigate the uptake, translocation and metabolism of 8:2 FTOH in soybean (Glycine max L. Merrill) over 144 h. 8:2 FTOH and its metabolites were found in all parts of soybean plants. At the end of the exposure, 7:3 FTCA [F(CF2)7CH2CH2COOH] was the primary metabolite in roots and stems, while PFOA [F(CF2)7COOH] was predominant in leaves. PFOA and 7:3 FTCA in the soybean-solution system accounted for 6.01 and 5.57 mol % of the initially applied 8:2 FTOH, respectively. Low levels of PFHpA [F(CF2)6COOH] and PFHxA [F(CF2)5COOH] in solutions and soybean roots resulted from microbial metabolism and plant root uptake. Glutathione-conjugated metabolites in soybean tissues were also identified. The activities of alcohol dehydrogenase, aldehyde dehydrogenase, and glutathione S-transferase in soybean roots increased during the exposure, suggesting their roles in 8:2 FTOH metabolism in soybean. This study provides important information for a better understanding of the uptake and metabolism of FTOHs and fluorotelomer-based compounds in plants.

Biotransformation of 6:2 polyfluoroalkyl phosphates (6:2 PAPs): Effects of degradative bacteria and co-substrates

Polyfluoroalkyl phosphates (PAPs), a group of fluorotelomer alcohol (FTOH)-based surfactants commonly used in water- and grease-proof food contact paper, have been suggested as a direct source of human exposure to health-concerned perfluoroalkyl carboxylic acids (PFCAs). This study investigated factors affecting biotranformation of 6:2 polyfluoroalkyl phosphates (6:2 PAPs) by three known FTOH-degrading Pseudomonas strains (Pseudomonas butanovora, P. oleovorans, and P. fluorescens DSM 8341) under different co-substrate conditions and compared to that by activated sludge samples. The three pure strains transformed 6:2 PAPs into eight different per- and poly-fluoroalkyl carboxylic acids (PFCAs) and/or PFCA precursors. P. fluorescens DSM 8341 produced 5:2 sFTOH [CF₃(CF₂)₄CH(OH)CH₃] and P. oleovorans produced 5:2 ketone [CF₃(CF₂)₄C(O)CH₃] as the primary transformation product, respectively, with citrate having a minimal impact on the transformation. P. butanovora with lactate produced more diverse transformation products than those by any two strains. Activated sludge was more efficient at transforming 6:2 PAPs and produced more transformation products including PFHpA [CF₃(CF₂)₅COOH] and PFPeA [CF₃(CF₂)₃COOH], with 5:2 sFTOH as the most abundant product on day 30. The abundance of the alkane hydroxylase (alkB) gene related to alkane oxidation, the changes of total microbial population as well as their community structure in activated sludge during 6:2 PAPs biotransformation were also investigated.

Engineering artificial communities for enhanced FTOH degradation

Fluorotelomer alcohols (FTOHs, [F(CF₂)_nCH₂CH₂OH]) are concerned environmental pollutants with perfluorinated carbon chains. FTOHs can be biotransformed; however, the extent, the pace of the defluorination, and types of metabolites produced vary depending on degradative microorganisms under different environment. In this study, we examined ways to increase the effectiveness of the FTOH defluorination process to less persistent major metabolites. Defined mixed cultures and bioaugmented microbial cultures were engineered to study their ability to biotransform 6:2 fluorotelomer alcohol [F(CF₂)₆CH₂CH₂OH]. The effects of carbon sources and the concentration of carbon sources were also examined. All experiments resulted in 5:2 sFTOH [F(CF₂)₅CH(OH)CH₃] as the primary metabolite at the end point. The carbon sources resulted in different amounts of pathway utilization as well as overall changes in effectiveness. The best overall effectiveness was observed when cosubstrate carbon was kept at low concentrations. Pathway II was best utilized by the P. butanovora+P. fluorescens mixed culture, with lactate having a slight negative impact on pathway II utilization. Additional carbon to augmented activated sludge resulted in decreased 6:2 FTOH biotransformation by 60%. Enrichment cultures showed that shorter chain FTOHs are easier to degrade, with the n-octane enriched culture transforming 20% of 8:2 FTOH, 60% of 6:2 FTOH and 70% of 4:2 FTOH. The microbial communities of the enrichment cultures and the alkane hydroxylase gene were also examined to help understand FTOH biotransformation mechanisms.