Biodegradation of per- and polyfluoroalkyl substances (PFAS): A review

Constructed wetlands as nature-based solutions in managing per-and poly-fluoroalkyl substances (PFAS): Evidence, mechanisms, and modelling

Per- and poly-fluoroalkyl substances (PFAS) have emerged as newly regulated micropollutants, characterised by extreme recalcitrance and environmental toxicity. Constructed wetlands (CWs), as a nature-based solution, have gained widespread application in sustainable water and wastewater treatment and offer multiple environmental and societal benefits. Despite CWs potential, knowledge gaps persist in their PFAS removal capacities, associated mechanisms, and modelling of PFAS fate. This study carried out a systematic literature review, supplemented by unpublished experimental data, demonstrating the promise of CWs for PFAS removal from the influents of varying sources and characteristics. Median removal performances of 64, 46, and 0 % were observed in five free water surface (FWS), four horizontal subsurface flow (HF), and 18 vertical flow (VF) wetlands, respectively. PFAS adsorption by the substrate or plant root/rhizosphere was deemed as a key removal mechanism. Nevertheless, the available dataset resulted unsuitable for a quantitative analysis. Data-driven models, including multiple regression models and machine learning-based Artificial Neural Networks (ANN), were employed to predict PFAS removal. These models showed better predictive performance compared to various mechanistic models, which include two adsorption isotherms. The results affirmed that artificial intelligence is an efficient tool for modelling the removal of emerging contaminants with limited knowledge of chemical properties. In summary, this study consolidated evidence supporting the use of CWs for mitigating new legacy PFAS contaminants. Further research, especially long-term monitoring of full-scale CWs treating real wastewater, is crucial to obtain additional data for model development and validation.

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.

A data-driven analysis to discover research hotspots and trends of technologies for PFAS removal

The frequent detection of persistent per- and polyfluoroalkyl substances (PFAS) in organisms and environment coupled with surging evidence for potential detrimental impacts, have attracted widespread attention throughout the world. In order to reveal research hotspots and trends of technologies for PFAS removal, herein, we performed a data-driven analysis of 3975 papers and 436 patents from Web of Science Core Collection and Derwent Innovation Index databases up to 2023. The results showed that China and the USA led the way in the research of PFAS removal with outstanding contributions to publications. The progression generally transitioned from accidental discovery of decomposition, to experimentation with removal effects and mechanisms of existing methods, and finally to enhanced defluorination and mechanism-driven design approaches. The keywords co-occurrence network and technology classification together revealed the main knowledge framework, which was constructed and correlated through contaminants, substrates, materials, processes and properties. Moreover, adsorption was demonstrated to be the dominant removal process among the current studies. Subsequently, we concluded the principles, advances and drawbacks of enrichment and separation, biological methods, advanced oxidation and reduction processes. Further exploration indicated the hotspots such as alternatives and precursors for PFAS ("genx": 1.258, "f-53b": 0.337), degradable mineralization technologies ("photocatalytic degrad": 0.529, "hydrated electron": 0.374), environment-friendly remediation technologies ("phytoremedi": 0.939, "constructed wetland": 0.462) and combination with novel materials ("metal-organic framework": 1.115, "layered double hydroxid": 0.559) as well as computer science ("molecular dynamics simul": 0.559, "machine learn"). Furthermore, the future direction of technological innovation might lie in high-performance processes that minimize secondary pollution, the development of recyclable and renewable treatment agents, and collaborative control strategies for multiple pollutants. Overall, this study offers comprehensive and objective review for researchers and industry professionals in this field, enabling rapid access to knowledge guidance and insights into research frontiers.

Per-and polyfluoroalkyl (PFAS) eternal pollutants: Sources, environmental impacts and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have become a growing environmental concern due to their tangible impacts on human health. However, due to the large number of PFAS compounds and the analytical difficulty to identify all of them, there are still some knowledge gaps not only on their impact on human health, but also on how to manage them and achieve their effective degradation. PFAS compounds originate from man-made chemicals that are resistant to degradation because of the presence of the strong carbon-fluorine bonds in their chemical structure. This review consists of two parts. In the first part, the environmental effects of fluorinated compound contamination in water are covered with the objective to highlight how their presence in the environment adversely impacts the human health. In the second part, the focus is put on the different techniques available for the degradation and/or separation of PFAS compounds in different types of waters. Examples of removal/treatment of PFAS present in either surface or ground water are presented.

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.

The link between ancient microbial fluoride resistance mechanisms and bioengineering organofluorine degradation or synthesis

Fluorinated organic chemicals, such as per- and polyfluorinated alkyl substances (PFAS) and fluorinated pesticides, are both broadly useful and unusually long-lived. To combat problems related to the accumulation of these compounds, microbial PFAS and organofluorine degradation and biosynthesis of less-fluorinated replacement chemicals are under intense study. Both efforts are undermined by the substantial toxicity of fluoride, an anion that powerfully inhibits metabolism. Microorganisms have contended with environmental mineral fluoride over evolutionary time, evolving a suite of detoxification mechanisms. In this perspective, we synthesize emerging ideas on microbial defluorination/fluorination and fluoride resistance mechanisms and identify best approaches for bioengineering new approaches for degrading and making organofluorine compounds.

PFAS fate using lysimeters during degraded soil reclamation using biosolids

Carbon- and nutrient-rich biosolids are used in agriculture and land reclamation. However, per- and polyfluoroalkyl substances (PFAS) typically present in biosolids raise concerns of PFAS leaching to groundwater and plant uptake. Here, we investigated PFAS persistence and leaching from biosolids applied to a site constructed artificially to mimic degraded soils. Treatments included biosolids and biosolids blended with mulch applied at different rates to attain either one and five times the agronomic N rate for vegetable crops and a control treatment with synthetic urea and triple superphosphate fertilizer. Leachates were collected for a 2-year period from 15-cm depth zero-tension drainage lysimeters. Soils were analyzed post biosolids application. PFAS were quantified using isotope-dilution, solid-phase extraction and liquid chromatography tandem mass spectrometry. Leachate profiles exemplified an initial high total PFAS concentration, followed by a sharp decline and subsequent small fluctuations attributed to pre-existing soil conditions and rainfall patterns. Quantifiable PFAS in leachate were proportional to biosolids application rates. Short-chain perfluoroalkyl acids (CF2 < 6) were dominant in leachate, while the percentage of longer chains homologues was higher in soils. A 43% biosolids blend with mulch resulted in 21% lower PFAS leachate concentrations even with the blend application rate being 1.5 times higher than biosolids due to the blend's lower N-content. The blending effect was more pronounced for long-chain perfluoroalkyl sulfonic acids that have a greater retention by soils and the air-water interface. Biosolids blending as a pragmatic strategy for reducing PFAS leachate concentrations may aid in the sustainable beneficial reuse of biosolids.

Perspectives on Genetically Engineered Microorganisms and Their Regulation in the United States

Genetically engineered microorganisms (GEMs) represent a new paradigm in our ability to address the needs of a growing, changing world. GEMs are being used in agriculture, food production and additives, manufacturing, commodity and noncommodity products, environmental remediation, etc., with even more applications in the pipeline. Along with modern advances in genome-manipulating technologies, new manufacturing processes, markets, and attitudes are driving a boom in more products that contain or are derived from GEMs. Consequentially, researchers and developers are poised to interact with biotechnology regulatory policies that have been in effect for decades, but which are out of pace with rapidly changing scientific advances and knowledge. In the United States, biotechnology is regulated by multiple agencies with overlapping responsibilities. This poses a challenge for both developers and regulators to simultaneously allow new innovation and products into the market while also ensuring their safety and efficacy for the public and environment. This article attempts to highlight the various factors that interact between regulatory policy and development of GEMs in the United States, with perspectives from both regulators and developers. We present insights from a 2022 workshop hosted at the University of California, Berkeley that convened regulators from U.S. regulatory agencies and industry developers of various GEMs and GEM-derived products. We highlight several new biotechnologies and applications that are driving innovation in this space, and how regulatory agencies evaluate and assess these products according to current policies. Additionally, we describe recent updates to regulations that incorporate new technology and knowledge and how they can adapt further to effectively continue regulating for the future.

Maximum desorption of perfluoroalkyl substances adsorbed on granular activated carbon used in full-scale drinking water treatment plants

Activated carbon adsorption is an effective method for removing perfluoroalkyl substances (PFAS) from water. However, the observation that higher concentrations of PFAS are observed after treatment than before (i.e., desorption) is an important, unsolved issue. In this study, to elucidate PFAS desorption and its relationship with PFAS properties, we conducted solvent extraction and long-term desorption experiments using granular activated carbon (GAC) that had been loaded with PFAS in two actual drinking water treatment plants. The amount of PFAS extracted from GAC depended on the depth in the GAC filter; longer-chain and hydrophobic PFAS were present in relatively higher amounts in the shallow part compared to the deep part of the GAC filter, whereas shorter-chain and hydrophilic PFAS were present in relatively higher amounts in the deep part compared to the shallow part. This pattern was probably due to a chromatographic effect by which hydrophilic PFAS adsorbed once, subsequently desorbed, and migrated from the shallow part of the GAC filter to the deeper part. The desorption potential of PFAS to water (i.e., the maximum amount of PFAS desorbed to water per unit mass of GAC) was estimated by conducting long-term bottle-point desorption tests and analyzing the relationship between the equilibrium water-phase concentration of PFAS in a bottle containing GAC and the amount of PFAS desorbed to water per unit GAC mass. The desorption ratio (ratio of desorption potential to loading) was the highest for PFAS for which the logarithm of the octanol/water distribution coefficient (Log DOW) ranged from -1 to 1. The implication was that most of those PFAS removed by GAC were likely to return to the water as the external water-phase concentrations dropped. The decrease of the desorption ratio to 20 % as Log DOW increased suggested irreversible adsorption due to hydrophobic affinity.

Poly- and perfluoroalkyl substances (PFASs) in amphibians and reptiles - exposure and health effects

Poly- and perfluoroalkyl substances (PFASs) are commonly used in various industries and everyday products, including clothing, electronics, furniture, paints, and many others. PFASs are primarily found in aquatic environments, but also present in soil, air and plants, making them one of the most important and dangerous pollutants of the natural environment. PFASs bioaccumulate in living organisms and are especially dangerous to aquatic and semi-aquatic animals. As endocrine disruptors, PFASs affect many internal organs and systems, including reproductive, endocrine, nervous, cardiovascular, and immune systems. This manuscript represents the first comprehensive review exclusively focusing on PFASs in amphibians and reptiles. Both groups of animals are highly vulnerable to PFASs in the natural habitats. Amphibians and reptiles, renowned for their sensitivity to environmental changes, are often used as crucial bioindicators to monitor ecosystem health and environmental pollution levels. Furthermore, the decline in amphibian and reptile populations worldwide may be related to increasing environmental pollution. Therefore, studies investigating the exposure of amphibians and reptiles to PFASs, as well as their impacts on these organisms are essential in modern toxicology. Summarizing the current knowledge on PFASs in amphibians and reptiles in a single manuscript will facilitate the exploration of new research topics in this field. Such a comprehensive review will aid researchers in understanding the implications of PFASs exposure on amphibians and reptiles, guiding future investigations to mitigate their adverse effects of these vital components of ecosystems.

PFAS occurrence and distribution in yard waste compost indicate potential volatile loss, downward migration, and transformation

We discovered high concentrations of PFAS (18.53 ± 1.5 μg kg-1) in yard waste compost, a compost type widely acceptable to the public. Seventeen out of forty targeted PFAS, belonging to six PFAS classes were detected in yard waste compost, with PFCAs (13.51 ± 0.99 μg kg-1) and PFSAs (4.13 ± 0.19 μg kg-1) being the dominant classes, comprising approximately 72.5% and 22.1% of the total measured PFAS. Both short-chain PFAS, such as PFBA, PFHxA, and PFBS, and long-chain PFAS, such as PFOA and PFOS, were prevalent in all the tested yard waste compost samples. We also discovered the co-occurrence of PFAS with low-density polyethylene (LDPE) and polyethylene terephthalate (PET) plastics. Total PFAS concentrations in LDPE and PET separated from incoming yard waste were 7.41 ± 0.41 μg kg-1 and 1.35 ± 0.1 μg kg-1, which increased to 8.66 ± 0.81 μg kg-1 in LDPE and 5.44 ± 0.56 μg kg-1 in PET separated from compost. An idle mature compost pile revealed a clear vertical distribution of PFAS, with the total PFAS concentrations at the surface level approximately 58.9-63.2% lower than the 2 ft level. This difference might be attributed to the volatile loss of short-chain PFCAs, PFAS's downward movement with moisture, and aerobic transformations of precursor PFAS at the surface.

Toward the development of a molecular toolkit for the microbial remediation of per-and polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFAS) are highly fluorinated synthetic organic compounds that have been used extensively in various industries owing to their unique properties. The PFAS family encompasses diverse classes, with only a fraction being commercially relevant. These substances are found in the environment, including in water sources, soil, and wildlife, leading to human exposure and fueling concerns about potential human health impacts. Although PFAS degradation is challenging, biodegradation offers a promising, eco-friendly solution. Biodegradation has been effective for a variety of organic contaminants but is yet to be successful for PFAS due to a paucity of identified microbial species capable of transforming these compounds. Recent studies have investigated PFAS biotransformation and fluoride release; however, the number of specific microorganisms and enzymes with demonstrable activity with PFAS remains limited. This review discusses enzymes that could be used in PFAS metabolism, including haloacid dehalogenases, reductive dehalogenases, cytochromes P450, alkane and butane monooxygenases, peroxidases, laccases, desulfonases, and the mechanisms of microbial resistance to intracellular fluoride. Finally, we emphasize the potential of enzyme and microbial engineering to advance PFAS degradation strategies and provide insights for future research in this field.

Deciphering behaviors of 6:2 chlorinated polyfluorinated ether sulfonate (alternative-PFOS) on anammox processes: Nitrogen removal efficiency and microbial adaptability

This study investigates the behaviors and effects of F-53B, an alternative to perfluorooctane sulfonate on anaerobic ammonium oxidation (anammox) processes. Results showed that the nitrogen removal efficiency (NRE) reached 83.8 % at a F-53B concentration of 0.5 mg·L-1, while NRE decreased to 66.9 % with 5 mg·L-1 of F-53B. The defluorination rates of 17.8 % (0.5 mg·L-1) and 9.3 % (5 mg·L-1) were observed, respectively, suggesting the occurrence of F-53B degradation. The relative abundance of Ca. Kuenenia decreased from 26.1 % to 16.2 % with the F-53B concentration increasing from 0.5 mg·L-1 to 5 mg·L-1. Meanwhile, Denitratisoma was selectively enriched with a relative abundance of 40.7 % at an F-53B concentration of 0.5 mg·L-1. Ca. Kuenenia could reduce reactive oxygen species induced by F-53B to maintain the balance of oxidative stress. This study gains insight into the behaviors and metabolic mechanisms of F-53B in anammox consortia, suggesting the feasibility of anammox processes for industrial wastewater.

Distribution characteristics and transformation mechanism of per- and polyfluoroalkyl substances in drinking water sources: A review

Per- and polyfluoroalkyl substances (PFASs) have raised significant concerns within the realm of drinking water due to their widespread presence in various water sources. This prevalence poses potential risks to human health, ecosystems, and the safety of drinking water. However, there is currently a lack of comprehensive reviews that systematically categorize the distribution characteristics and transformation mechanisms of PFASs in drinking water sources. This review aims to address this gap by concentrating on the specific sources of PFASs contamination in Chinese drinking water supplies. It seeks to elucidate the migration and transformation processes of PFASs within each source, summarize the distribution patterns of PFASs in surface and subsurface drinking water sources, and analyze how PFASs molecular structure, solubility, and sediment physicochemical parameters influence their presence in both the water phase and sediment. Furthermore, this review assesses two natural pathways for PFASs degradation, namely photolysis and biodegradation. It places particular emphasis on understanding the degradation mechanisms and the factors that affect the breakdown of PFASs by microorganisms. The ultimate goal is to provide valuable insights for the prevention and control of PFAS contamination and the assurance of drinking water quality.

Emergence of per- and poly-fluoroalkyl substances (PFAS) and advances in the remediation strategies

A group of fluorinated organic molecules known as per- and poly-fluoroalkyl substances (PFAS) have been commonly produced and circulated in the environment. PFAS, owing to multiple strong CF bonds, exhibit exceptional stability and possess a high level of resistance against biological or chemical degradation. Recently, PFAS have been identified to cause numerous hazardous effects on the biotic ecosystem. As a result, extensive efforts have been made in recent years to develop effective methods to remove PFAS. Adsorption, filtration, heat treatment, chemical oxidation/reduction, and soil washing are a few of the physicochemical techniques that have shown their ability to remove PFAS from contaminated matrixes. However these methods also carry significant drawbacks, including the fact that they are expensive, energy-intensive, unsuitable for in-situ treatment, and requirement to be carried under dormant conditions. The metabolic products released upon PFAS degradation are largely unknown, despite the fact that thermal disintegration methods are widely used. In contrast to physical and chemical methods, biological degradation of PFAS has been regarded as efficient method. However, PFAS are difficult to instantly and completely metabolize through biological methods due to the limitations of biocatalytic mechanisms. Nevertheless, cost, easy-to-operate and environmentally safe are some of the advantages over its counterpart. The present review comprehensively discusses the occurrence of PFAS, the state-of-the science of remediation technologies and approaches applied, and the remediation challenges. The article also focuses on the future research directions toward the development of effective methods for PFAS-contaminated site in-situ treatment.

Occurrence, behaviors, and fate of per- and polyfluoroalkyl substances (PFASs) in typical municipal solid waste disposal sites

Per- and polyfluoroalkyl substances (PFASs) have become a crucial environmental concern owing to their exceptional persistence, ability to bioaccumulate within ecosystems, and potential to adversely affect biota. Products and materials containing PFASs are usually discarded into municipal solid waste (MSW) at the end of their life cycle, and the fate of PFASs may differ when different disposal methods of MSWs are employed. To date, limited research has focus on the occurrence, behaviors, and fate of PFASs emitted from various MSW disposal sites. This knowledge gap may lead to an underestimation of the contribution of MSW disposal sites as a source of PFASs in the environment. In this review, we collated publications concerning PFASs from typical MSW disposal sites (i.e., landfills, incineration plants, and composting facilities) and explored the occurrence patterns and behaviors of PFASs across various media (e.g., landfill leachate/ambient air, incineration plant leachate/ash, and compost products) in these typical MSW disposal sites. In particular, this review highlighted ultrashort-chain perfluoroalkyl acids and "unknown"/emerging PFASs. Additionally, it meticulously elucidated the use of non-specific techniques and non-target analysis for screening and identifying these overlooked PFASs. Furthermore, the composition profiles, mass loads, and ecological risks of PFASs were compared across the three typical disposal methods. To the best of our knowledge, this is the first review regarding the occurrence, behaviors, and fate of PFASs in typical MSW disposal sites on a global scale, which can help shed light on the potential environmental impacts of PFASs harbored in MSWs and guide future waste management practices.

Recent advances in the application of magnetic materials for the management of perfluoroalkyl substances in aqueous phases

Perfluoroalkyl substances (PFASs) are a class of artificially synthesised organic compounds extensively used in both industrial and consumer products owing to their unique characteristics. However, their persistence in the environment and potential risk to health have raised serious global concerns. Therefore, developing effective techniques to identify, eliminate, and degrade these pollutants in water are crucial. Owing to their high surface area, magnetic responsiveness, redox sensitivity, and ease of separation, magnetic materials have been considered for the treatment of PFASs from water in recent years. This review provides a comprehensive overview of the recent use of magnetic materials for the detection, removal, and degradation of PFASs in aqueous solutions. First, the use of magnetic materials for sensitive and precise detection of PFASs is addressed. Second, the adsorption of PFASs using magnetic materials is discussed. Several magnetic materials, including iron oxides, ferrites, and magnetic carbon composites, have been explored as efficient adsorbents for PFASs removal from water. Surface modification, functionalization, and composite fabrication have been employed to improve the adsorption effectiveness and selectivity of magnetic materials for PFASs. The final section of this review focuses on the advanced oxidation for PFASs using magnetic materials. This review suggests that magnetic materials have demonstrated considerable potential for use in various environmental remediation applications, as well as in the treatment of PFASs-contaminated water.

Detection, Quantification, and Isomer Differentiation of Per- and Polyfluoroalkyl Substances (PFAS) Using MALDI-TOF with Trapped Ion Mobility

Per- and polyfluoroalkyl substances (PFAS) are a class of organic compounds that have attracted global attention for their persistence in the environment, exposure to biological organisms, and their adverse health effects. There is an urgent need to develop analytical methodologies for the characterization of PFAS in various sample matrices. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) represents a chromatography-free MS method that performs laser-based ionization and in situ analysis on samples. In this study, we present PFAS analysis by MALDI-time-of-flight (TOF) MS with trapped ion mobility spectrometry (TIMS), which provides an additional dimension of gas phase separation based on the size-to-charge ratios. MALDI matrix composition and key instrument parameters were optimized to produce different ranges of calibration curves. Parts per billion (ppb) range of calibration curves were achieved for a list of legacy and alternative perfluorosulfonic acids (PFSAs) and perfluorocarboxylic acids (PFCAs), while ion mobility spectrum filtering enabled parts per trillion (ppt) range of calibration curves for PFSAs. We also successfully demonstrated the separation of three perfluorooctanesulfonic acid (PFOS) structural isomers in the gas phase using TIMS. Our results demonstrated the new development of utilizing MALDI-TOF-MS coupled with TIMS for fast, quantitative, and sensitive analysis of PFAS, paving ways to future high-throughput and in situ analysis of PFAS such as MS imaging applications.

Emerging and legacy per- and polyfluoroalkyl substances in Daling River and its estuary, Northern China

Strict restriction on legacy per- and polyfluoroalkyl substances (PFASs) has caused a dramatic increase in production and usage of emerging PFASs over the last decades. However, the environmental behaviors of emerging PFASs is largely unknown in Daling River, Northern China. In this study, the potential sources, sediment-water partitioning and substitution trends of PFASs were investigated in overlying water and sediments from Daling River and its estuary. Perfluorooctane sulfonate and 6:2 fluorotelomer sulfonic acid were major compounds, and sodium p-perfluorous nonenoxybenzene sulfonate was first detected. Firefighting foam manufacturing and fluoropolymer production were the main sources of PFASs. Compared to legacy PFASs (C8), the emerging PFASs (C6 - C9) were more incline to distribute into overlying water. Substitution trends indicated 6:2 fluorotelomer sulfonic acid and hexafluoropropylene oxide trimer acid as the important alternatives of perfluorooctane sulfonate and perfluorooctanoic acid, respectively. The results were meaningful for understanding the environmental behaviors of emerging PFASs.

Effects of perfluorooctanoic acid and perfluorooctane sulfonic acid on microbial community structure during anaerobic digestion

Per- and polyfluoroalkyl substances (PFASs) are recalcitrant organic pollutants, which accumulate widely in aquatic and solid matrices. Anaerobic digestion (AD) is one of possible options to manage organic wastes containing PFASs, however, the impacts of different types of PFAS on AD remains unclear. This study aimed to critically investigate the effects of two representative PFAS compounds, i.e., perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), on the AD performance and microbial community structure. 100 mg/L of both PFOA and PFOS considerably inhibited the AD performance and changed the microbial community structure. Especially, PFOA was more toxic to bacterial and archaeal activity than PFOS, which was reflected in AD performance. In addition, the sulfonic acid group in PFOS affected the changes in microbial community structure by inducing abundant sulfate reducing bacteria (i.e., Desulfobacterota). This study provides a significant reference to the response of AD system on different PFAS types and dosage.

Removal of PFAS from water by aquatic plants

We have found that aquatic plants can reduce the content of perfluorinated alkyl substances (PFAS) within a short period of time. The aim of this study was to determine the variation in the uptake of PFAS from contaminated water by various wetland plant species, investigate the effect of biomass on PFAS removal, and determine whether laccases and peroxidases are involved in the removal and degradation of PFAS. Seventeen emergent and one submerged wetland plant species were screened for PFAS uptake from highly contaminated lake water. The screening showed that Eriophorum angustifolium, Carex rostrata, and Elodea canadensis accumulated the highest levels of all PFAS. These species were thereafter used to investigate the effect of biomass on PFAS removal from water and for the enzyme studies. The results showed that the greater the biomass per volume, the greater the PFAS removal effect. The plant-based removal of PFAS from water is mainly due to plant absorption, although degradation also occurs. In the beginning, most of the PFAS accumulated in the roots; over time, more was translocated to the shoots, resulting in a higher concentration in the shoots than in the roots. Most PFAS degradation occurred in the water; the metabolites were thereafter taken up by the plants and were accumulated in the roots and shoots. Both peroxidases and laccases were able to degrade PFAS. We conclude that wetland plants can be used for the purification of PFAS-contaminated water. For effective purification, a high biomass per volume of water is required.

The role of helicity in PFAS resistance to degradation: DFT simulation of electron capture and defluorination

Defluorination of perfluorinated alkyl substances (PFASs) via the direct capture of excess electrons poses a promising path to environmental decontamination. Herein we show that quantum-chemical model optimization methods can be adapted to simulate the changes to molecular geometry that result from electron capture. These reaction pathways demonstrate that the introduction of an additional electron causes a loss of the helical arrangement along linear carbon tail chains. Regaining helicity is sufficiently favourable to enable fluoride release in C7-C10 PFAS chains; shorter chains are enthalpically hindered from degradation while the additional charge is stabilized on longer chains by the greater entropy their flexibility permits. These results suggest that reductive PFAS treatment processes could be made more effective under high pressure or confined conditions.

Association between Perfluoroalkyl Substances in Follicular Fluid and Polycystic Ovary Syndrome in Infertile Women

In recent years, perfluoroalkyl substances (PFASs), a family of fluorinated organic com pounds, have garnered much attention due to their reproductive and developmental toxicity in humans. Polycystic ovary syndrome (PCOS) is a prevalent endocrine disease that affects women of reproductive age and is a significant contributor to female infertility. A previous study suggested that PFASs play a possible role in PCOS. We conducted a clinical study investigating the relationship between PCOS and PFAS in follicular fluid. A total of 73 infertile patients with PCOS and 218 controls were recruited from the International Peace Maternity and Child Health Hospital, affiliated with the Shanghai Jiao Tong University School of Medicine. The concentrations of 12 PFASs in follicular fluid samples and sex hormones in serum were measured. Correlation analysis and multiple linear regression revealed a positive relationship between perfluorooctanoic acid (PFOA) and testosterone (T) concentrations. The adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for each PFAS were estimated using multivariable logistic regression and quantile-based g-computation (QGC). The PFOA concentrations in follicular fluid were correlated with increased odds of PCOS (second vs. first quartile: OR = 3.65, 95% CI: 1.47-9.05, p = 0.005; third vs. first quartile: OR = 2.91, 95% CI: 1.17-7.26, p = 0.022; fourth vs. first quartile: OR = 3.13, 95% CI: 1.21-8.09, p = 0.019; P for trend = 0.032). This association was confirmed with QGC. Mediation analysis suggested that the mediation effect of T in association with PFOA and PCOS was not statistically significant. Our study suggests that PFOA may be a risk factor for PCOS.

Direct fluoride monitoring using a fluorogenic RNA-based biosensor

Fluorinated compounds, whether naturally occurring or from anthropogenic origin, have been extensively exploited in the last century. Degradation of these compounds by physical or biochemical processes is expected to result in the release of fluoride. Several fluoride detection mechanisms have been previously described. However, most of these methods are not compatible with high- and ultrahigh-throughput screening technologies, lack the ability to real-time monitor the increase of fluoride concentration in solution, or rely on costly reagents (such as cell-free expression systems). Our group recently developed "FluorMango" as the first completely RNA-based and direct fluoride-specific fluorogenic biosensor. To do so, we merged and engineered the Mango-III light-up RNA aptamer and the fluoride-specific aptamer derived from a riboswitch, crcB. In this chapter, we explain how this RNA-based biosensor can be produced in large scale before providing examples of how it can be used to quantitatively detect (end-point measurement) or monitor in real-time fluoride release in complex biological systems by translating it into measurable fluorescent signal.

Interactions between biofilms and PFASs in aquatic ecosystems: Literature exploration

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been detected in most aquatic environments worldwide and are referred to as "forever chemicals" because of their extreme chemical and thermal stability. Biofilms, as basic aquatic bioresources, can colonize various substratum surfaces. Biofilms in the aquatic environment have to interact with the ubiquitous PFASs and have significant implications for both their behavior and destiny, which are still poorly understood. Here, we have a preliminary literature exploration of the interaction between PFASs and biofilms in the various aquatic environments and expect to provide some thoughts on further study. In this review, the biosorption properties of biofilms on PFASs and possible mechanisms are presented. The complex impact of PFASs on biofilm systems was further discussed in terms of the composition and electrical charges of extracellular polymeric substances, intracellular microbial communities, and overall contaminant purification functions. Correspondingly, the effects of biofilms on the redistribution of PFASs in the aqueous environment were analyzed. Finally, we propose that biofilm after adsorption of PFASs is a unique ecological niche that not only reflects the contamination level of PFASs in the aquatic environment but also offers a possible "microbial pool" for PFASs biodegradation. We outline existing knowledge gaps and potential future efforts for investigating how PFASs interact with biofilms in aquatic ecosystems.

Mechanisms and Opportunities for Rational In Silico Design of Enzymes to Degrade Per- and Polyfluoroalkyl Substances (PFAS)

Per and polyfluoroalkyl substances (PFAS) present a unique challenge to remediation techniques because their strong carbon-fluorine bonds make them difficult to degrade. This review explores the use of in silico enzymatic design as a potential PFAS degradation technique. The scope of the enzymes included is based on currently known PFAS degradation techniques, including chemical redox systems that have been studied for perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) defluorination, such as those that incorporate hydrated electrons, sulfate, peroxide, and metal catalysts. Bioremediation techniques are also discussed, namely the laccase and horseradish peroxidase systems. The redox potential of known reactants and enzymatic radicals/metal-complexes are then considered and compared to potential enzymes for degrading PFAS. The molecular structure and reaction cycle of prospective enzymes are explored. Current knowledge and techniques of enzyme design, particularly radical-generating enzymes, and application are also discussed. Finally, potential routes for bioengineering enzymes to enable or enhance PFAS remediation are considered as well as the future outlook for computational exploration of enzymatic in situ bioremediation routes for these highly persistent and globally distributed contaminants.

Biodegradation Potential of C7-C10 Perfluorocarboxylic Acids and Data from the Genome of a New Strain of Pseudomonas mosselii 5(3)

The use of bacteria of the genus Pseudomonas-destructors of persistent pollutants for biotechnologies of environmental purification-is an interesting area of research. The aim of this work was to study the potential of Pseudomonas mosselii strain 5(3) isolated from pesticide-contaminated soil as a degrader of C7-C10 perfluorocarboxylic acids (PFCAs) and analyze its complete genome. The genome of the strain has been fully sequenced. It consists of a chromosome with a length of 5,676,241 b.p. and containing a total of 5134 genes, in particular, haloalkane dehalogenase gene (dhaA), haloacetate dehalogenase H-1 gene (dehH1), fluoride ion transporter gene (crcB) and alkanesulfonate monooxygenase gene (ssuE), responsible for the degradation of fluorinated compounds. The strain P. mosselii 5(3) for was cultivated for 7 days in a liquid medium with various C7-C10 PFCAs as the sole source of carbon and energy, and completely disposed of them. The results of LC-MS analysis showed that the transformation takes place due to perfluorohexanoic acid with the release of various levels of stoichiometry (depending on PFCA) of fluorine ion mineralization indicators determined by ion chromatography. Thus, Pseudomonas mosselii strain 5(3) demonstrates a genetically confirmed high potential for the decomposition of C7-C10 PFCA.

Graphene Oxide and Its Derivatives as Adsorbents for PFOA Molecules

Effective, low-cost adsorbents are needed to remove perfluoroalkyl and polyfluoroalkyl substances (PFAS) from water sources. Carbon-based materials are promising PFAS adsorbents. Here, we explore the potential of graphite oxide (GO) and its derivatives as PFAS adsorbents by studying the adsorption of perfluorooctanoic acid (PFOA), a model PFAS molecule, on GO surfaces with O/C ratios up to 16.7% using molecular dynamics simulations. An adsorption free energy of approximately -30 kJ/mol (or -310 meV) is obtained for pristine graphene in pure water, and adsorbed PFOA molecules diffuse rapidly. As the O/C ratio increases, hydrophobic interactions' contribution to PFOA adsorption diminishes, but that by electrostatic interactions becomes important. Overall, adsorption is weakened, but favorable adsorption still occurs at an O/C ratio of 16.7%. The in-plane diffusion coefficient of adsorbed PFOA molecules decreases by more than 45 times as the O/C ratio increases to 8.3% but increases significantly when the O/C ratio increases further to 16.7%. Adding salt improves the adsorption owing to the salting-out and screening effects but slows the diffusion of adsorbed PFOA molecules, and these effects are more pronounced at low O/C ratios. These results show that GOs are effective PFOA adsorbents. Such effectiveness, along with GO's potentially low cost and the possibility of regenerating spent GO by removing adsorbed PFOA molecules through a mild electrical potential, makes GO a promising adsorbent for PFOA and similar molecules. The insights from the present study can help the rational design of GOs to realize their full potential.

Research Priorities for the Environmental Risk Assessment of Per- and Polyfluorinated Substances

Per- and polyfluorinated substances (PFAS) are a group of thousands of ubiquitously applied persistent industrial chemicals. The field of PFAS environmental research is developing rapidly, but suffers from substantial biases toward specific compounds, environmental compartments, and organisms. The aim of our study was therefore to highlight current developments and to identify knowledge gaps and subsequent research needs that would contribute to a comprehensive environmental risk assessment for PFAS. To this end, we consulted the open literature and databases and found that knowledge of the environmental fate of PFAS is based on the analysis of <1% of the compounds categorized as PFAS. Moreover, soils and suspended particulate matter remain largely understudied. The bioavailability, bioaccumulation, and food web transfer studies of PFAS also focus on a very limited number of compounds and are biased toward aquatic biota, predominantly fish, and less frequently aquatic invertebrates and macrophytes. The available ecotoxicity data revealed that only a few PFAS have been well studied for their environmental hazards, and that PFAS ecotoxicity data are also strongly biased toward aquatic organisms. Ecotoxicity studies in the terrestrial environment are needed, as well as chronic, multigenerational, and community ecotoxicity research, in light of the persistency and bioaccumulation of PFAS. Finally, we identified an urgent need to unravel the relationships among sorption, bioaccumulation, and ecotoxicity on the one hand and molecular descriptors of PFAS chemical structures and physicochemical properties on the other, to allow predictions of exposure, bioaccumulation, and toxicity. Environ Toxicol Chem 2023;42:2302-2316. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Formation of CoA Adducts of Short-Chain Fluorinated Carboxylates Catalyzed by Acyl-CoA Synthetase from Gordonia sp. Strain NB4-1Y

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) make up a group of anthropogenic chemicals with a myriad of applications. However, some PFAS have been shown to negatively impact human health and the environment, leading to increased regulation, with some countries making efforts to phase out their use. PFAS fate in the environment is driven by physical, chemical, and biological processes, with microbial communities in matrices such as soil and sewage sludge being known to generate a range of low-molecular-weight PFAS metabolites. Proposed metabolic intermediates for both mixed and pure microbial cultures include fluorinated carboxylates that may be activated by CoA prior to β-oxidation and defluorination, although thus far, no PFAS-CoA adducts have been reported. Herein, we expressed and purified acyl-CoA synthetase (ACS) from the soil bacterium Gordonia sp. strain NB4-1Y and performed an analysis of substrate scope and enzyme kinetics using fluorinated and nonfluorinated carboxylates. We determined that ACS was able to catalyze the formation of CoA adducts of 3,3,3-trifluoropropionic acid, 5,5,5-trifluoropentanoic acid, 4,5,5-trifluoropent-4-enoic acid, and 4,4,5,5,5-pentafluoropentanoic acid. Kinetic analysis revealed a 90-98% decrease in kcat between nonfluorinated carboxylates and their fluorinated analogues. This provides evidence to validate proposed enzymatic pathways for microbial PFAS metabolism that proceed via an activation step involving the formation of CoA adducts.

Impact of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) on secondary sludge microorganisms: removal, potential toxicity, and their implications on existing wastewater treatment regulations in Canada

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are two of the most commonly researched per- and polyfluoroalkyl substances (PFAS). Globally, many long-chain PFAS compounds including PFOS and PFOA are highly regulated and, in some countries, PFAS use in commercial products is strictly prohibited. Despite the legal regulation of these 'forever chemicals' under the Canadian Environmental Protection Act, PFOA and PFOS compounds are still found in high concentrations in discharges from wastewater treatment plants, both from liquid and sludge streams. Yet, their potential impact on wastewater treatment effectiveness remains poorly understood. The findings of this research show that: (1) PFOS and PFOA might be hindering the overall outcome treatment performance - calling into question the efficacy of Canada's existing wastewater treatment regulatory standard (Wastewater Systems Effluent Regulations, SOR/2012-139), and (2) specific microorganisms from the Thiobacillus and Pseudomonas genera seem capable of adsorbing PFOS and PFOA onto their cell wall and even degrading the chemicals, but it is unclear as to what extent degradation occurs. The results also raise questions whether existing wastewater regulations should be expanded to include the detection and monitoring of PFAS, as well as the establishment of a regulatory wastewater treatment plant discharge standard for PFAS that is protective of human and ecological health.

The Hidden Threat: Endocrine Disruptors and Their Impact on Insulin Resistance

The association between Insulin resistance, a global health issue, and endocrine disruptors (EDCs), chemicals interfering with the endocrine system, has sparked concern in the scientific community. This article provides a comprehensive review of the existing literature regarding the intricate relationship between EDCs and insulin resistance. Phthalates, commonly found in consumer products, are well-established EDCs with documented effects on insulin-signaling pathways and metabolic processes. Epidemiological studies have connected phthalate exposure to an increased risk of type 2 diabetes mellitus (T2DM). Perfluoroalkyl substances (PFAS), persistent synthetic compounds, have shown inconsistent associations with T2DM in epidemiological research. However, studies suggest that PFAS may influence insulin resistance and overall metabolic health, with varying effects depending on specific PFAS molecules and study populations. Bisphenol A (BPA), found in plastics and resins, has emerged as a concern for glucose regulation and insulin resistance. Research has linked BPA exposure to T2DM, altered insulin release, obesity, and changes in the mass and function of insulin-secreting β-cells. Triclosan, an antibacterial agent in personal care products, exhibits gender-specific associations with T2DM risk. It may impact gut microbiota, thyroid hormones, obesity, and inflammation, raising concerns about its effects on metabolic health. Furthermore, environmental EDCs like polycyclic aromatic hydrocarbons, pesticides, and heavy metals have demonstrated associations with T2DM, insulin resistance, hypertension, and obesity. Occupational exposure to specific pesticides and heavy metals has been linked to metabolic abnormalities.

Impact of per- and polyfluorinated alkyl substances (PFAS) on the marine environment: Raising awareness, challenges, legislation, and mitigation approaches under the One Health concept

Per- and polyfluorinated alkyl substances (PFAS) have long been known for their detrimental effects on the ecosystems and living organisms; however the long-term impact on the marine environment is still insufficiently recognized. Based on PFAS persistence and bioaccumulation in the complex marine food network, adverse effects will be exacerbated by global processes such as climate change and synergies with other pollutants, like microplastics. The range of fluorochemicals currently included in the PFAS umbrella has significantly expanded due to the updated OECD definition, raising new concerns about their poorly understood dynamics and negative effects on the ocean wildlife and human health. Mitigation challenges and approaches, including biodegradation and currently studied materials for PFAS environmental removal are proposed here, highlighting the importance of ongoing monitoring and bridging research gaps. The PFAS EU regulations, good practices and legal frameworks are discussed, with emphasis on recommendations for improving marine ecosystem management.

A proposed approach to defining per- and polyfluoroalkyl substances (PFAS) based on molecular structure and formula

Various groups and researchers, including the authors of this work, have proposed different definitions of what constitutes per- and polyfluoroalkyl substances (PFAS). The different definitions are all based on a structural definition. Although a structural definition is reasonable, such an approach is difficult to execute if the intent is to narrow or refine the definition. This approach can also lead to inexplicable demarcations of what are and what are not PFAS. Our objective was to create a narrow, simple PFAS definition that allows interested groups to communicate with a common understanding and will also serve as a starting point to focus on substances that are of real environmental concern. Our studies have demonstrated that numerous highly fluorinated complex structures exist that make a structure-based definition difficult. We suggest that a definition based on fractional fluorination expressed as the percentage of fluorine of a molecular formula using atom counting offers advantages. Using a combination of a structure-based definition and a definition based on the fractional percentage of the molecular formula that is fluorine can provide a more inclusive and succinct definition. Thus, we propose a new definition based on four substructures along with any structures where the molecular formula is 30% fluorine by atom count. Integr Environ Assess Manag 2023;19:1333-1347. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

The EU's Per- and Polyfluoroalkyl Substances (PFAS) Ban: A Case of Policy over Science

The proposal by the European Chemicals Agency (ECHA) to ban over 12,000 per- and polyfluoroalkyl substances (PFAS) has sparked a debate about potential consequences for the economy, industry, and the environment. Although some PFAS are known to be harmful, a blanket ban may lead to significant problems in attempting to replace PFAS-based materials for environmental transition, as well as in medical devices and everyday products. Alternative materials may potentially be less safe, as a rush to replace PFAS would reduce the time needed for toxicological analyses. Studies have shown that PFAS exhibit a diverse range of mechanisms of action, biopersistence, and bioaccumulation potential, and should thus not be treated as a single group. This is particularly true for the class of fluoropolymers. A targeted approach that considers the specific risks and benefits of each chemical may be more effective. Moreover, the proposed ban may also have unintended consequences for the environment as PFAS use is also associated with benefits such as reducing greenhouse-gas emissions and improving energy efficiency. Policymakers must carefully weigh up the potential consequences before making a final decision on the ban.

Enhanced removal of perfluorooctanoic acid with sequential photocatalysis and fungal treatment

In this paper, we report the degradation of perfluorooctanoic acid (PFOA), which is a persistent contaminant in the environment that can severely impact human health, by exposing it to a photocatalyst, bismuth oxyiodide (BiOI), containing both Bi4O5I2 and Bi5O7I phases and a fungal biocatalyst (Cunninghamella elegans). Individually, the photocatalyst (after 3 h) and biocatalyst (after 48 h) degraded 35-40% of 100 ppm PFOA with 20-30% defluorination. There was a marked improvement in the degree of degradation (90%) and defluorination (60%) when PFOA was first photocatalytically treated, then exposed to the fungus. GC- and LC-MS analysis identified the products formed by the different treatments. Photocatalytic degradation of PFOA yielded short-chain perfluorocarboxylic acids, whereas fungal degradation yielded mainly 5:3 fluorotelomer carboxylic acid, which is a known inhibitor of cytochrome P450-catalysed degradation of PFAS in C. elegans. The combined treatment likely resulted in greater degradation because photocatalysis reduced the PFOA concentration without generating the inhibitory 5:3 fluorotelomer carboxylic acid, enabling the fungus to remove most of the remaining substrate. In addition, new fluorometabolites were identified that shed light on the initial catabolic steps involved in PFOA biodegradation.

Anaerobic biotransformation of sulfonated anthraquinones by Pseudomonas nitroreducens WA and the fate of the sulfonic acid group in the presence of nitrate

The presence of the sulfonic acid group in sulfonated anthraquinones (SAs) resulted in the difficulty in the mineralization of anthraquinone ring. Little information is available on the removal pathway of the sulfonic acid group of SAs under aerobic/anaerobic conditions. Herein, sodium 1-aminoanthraquinone-2-sulfonate (ASA-2) was used as an important intermediate of SAs. A novel Pseudomonas nitroreducens WA capable of ASA-2 desulfonation was isolated from the Reactive Blue 19-degrading consortium WRB. Anaerobic desulfonation efficiency of 0.165 mM ASA-2 by strain WA reached 99% in 36 h at pH 7.5 and 35 ℃ using glucose as an electron donor. Further analysis showed that ASA-2 as an electron acceptor could be anaerobically transformed into 1-aminoanthraquinone and sulfite via the cleavage of C-S bond. Strain WA could also desulfonate sodium 1-amino-4-bromoanthraquinone-2-sulfonate and sodium anthraquinone-2-sulfonate. Under denitrification conditions, the formed sulfite could be oxidized to sulfate by nitrite via a chemical reaction, which was beneficial for nitrite removal. This phenomenon was observed in consortium WRB-amended system. Moreover, the consortium WRB could reduce the formed sulfite to sulfide due to the presence of Desulfovibrio. These results provide a theoretical basis for the anaerobic biodesulfonation of SAs along with nitrate removal and support for the development of sulfite-based biotechnology.

Microbial and thermal treatment techniques for degradation of PFAS in biosolids: A focus on degradation mechanisms and pathways

Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals detected in biosolids worldwide, which have become a significant concern for biosolids applications due to their increasing environmental risks. Hence, it is pivotal to understand the magnitude of PFAS contamination in biosolids and implement effective technologies to reduce their contamination and prevent hazardous aftermaths. Thermal techniques such as pyrolysis, incineration and gasification, and biodegradation have been regarded as impactful solutions to degrade PFAS and transform biosolids into value-added products like biochar. These techniques can mineralize PFAS compounds under specific operating parameters, which can lead to unique degradation mechanisms and pathways. Understanding PFAS degradation mechanisms can pave the way to design the technology and to optimize the process conditions. Therefore, in this review, we aim to review and compare PFAS degradation mechanisms in thermal treatment like pyrolysis, incineration, gasification, smouldering combustion, hydrothermal liquefaction (HTL), and biodegradation. For instance, in biodegradation of perfluorooctane sulfonic acid (PFOS), firstly C-S bond cleavage occurs which is followed by hydroxylation, decarboxylation and defluorination reactions to form perfluoroheptanoic acid. In HTL, PFOS degradation is carried through OH^-catalyzed series of nucleophilic substitution and decarboxylation reactions. In contrast, thermal PFOS degradation involves a three-step random-chain scission pathway. The first step includes C-S bond cleavage, followed by defluorination of perfluoroalkyl radical, and radical chain propagation reactions. Finally, the termination of chain propagation reactions produces very short-fluorinated units. We also highlighted important policies and strategies employed worldwide to curb PFAS contamination in biosolids.

Pyrene-Containing Polyamines as Fluorescent Receptors for Recognition of PFOA in Aqueous Media

The globally widespread perfluorooctanoic acid (PFOA) is a concerning environmental contaminant, with a possible toxic long-term effects on the environment and human health The development of sensible, rapid, and low-cost detection systems is a current change in modern environmental chemistry. In this context, two triamine-based chemosensors, L1 and L2, containing a fluorescent pyrene unit, and their Zn(II) complexes are proposed as fluorescent probes for the detection of PFOA in aqueous media. Binding studies carried out by means of fluorescence and NMR titrations highlight that protonated forms of the receptors can interact with the carboxylate group of PFOA, thanks to salt bridge formation with the ammonium groups of the aliphatic chain. This interaction induces a decrease in the fluorescence emission of pyrene at neutral and slightly acidic pH values. Similarly, emission quenching has also been observed upon coordination of PFOA by the Zn(II) complexes of the receptors. These results evidence that simple polyamine-based molecular receptors can be employed for the optical recognition of harmful pollutant molecules, such as PFOA, in aqueous media.

Confirming sulfluramid (EtFOSA) application as a precursor of perfluorooctanesulfonic acid (PFOS) in Brazilian agricultural soils

Perfluorooctanesulfonic acid (PFOS) is a manmade chemical with several industrial applications and also a potential byproduct of many other per- and polyfluorinated substances (PFAS) in the environment. Due to the gathered evidence on its environmental persistence, long-range transport, toxicity, and bioaccumulative and biomagnifying properties, PFOS, its salts and perfluorooctane sulfonyl fluoride (PFOSF), were listed for global restriction under the Stockholm Convention on Persistent Organic Pollutants in 2009. Nevertheless, Brazil has granted an acceptable purpose exemption for using PFOSF to produce sulfluramid (EtFOSA) and to apply it as insecticide to control leaf-cutting ants of the genus Atta and Acromyrmex. Previous studies have pointed out EtFOSA as a precursor of PFOS in the environment, including in soils. Therefore, we aimed to confirm the role of EtFOSA in PFOS formation in soils representing areas where sulfluramid-based ant baits are used. A biodegradation assay was carried out by applying technical EtFOSA in triplicate samples of ultisol (PV) and oxisol (LVd) and measuring the contents of EtFOSA, perfluorooctane sulfonamide acetic acid (FOSAA), perfluorooctane sulfonamide (FOSA), and PFOS at seven moments (0, 3, 7, 15, 30, 60, and 120 days). The monitored byproducts started being noticed on the 15th day. After 120 days, PFOS yields were 30% for both soils, whereas FOSA yields were 46% (PV soil) and 42% (LVd soil) and FOSAA yields were 6% (PV soil) and 3% (LVd soil). It can be expected that FOSAA and FOSA contents will eventually be converted into PFOS in the environment and that the presence of plants could boost PFOS formation. Therefore, the ongoing extensive and intensive use of sulfluramid-based ant baits pose a considerable source of PFOS to the environment.

Enhanced adsorption of short-chain perfluorobutanoic acid by functionalized periodic mesoporous organosilica: Performance and mechanisms

Removal of short-chain per- and polyfluoroalkyl substances (PFAS) represents a unique challenge in comparison to the long-chain homologs. In this study, a series of functionalized periodic mesoporous organosilica (PMO) materials with tunable molar ratio of fluoroalkyl to amine functional groups were developed and used as platform adsorbents to investigate the adsorption behavior of short-chain PFAS, with a focus on perfluorobutanoic acid (PFBA). Modification with fluoroalkyl group substantially enhanced the adsorption affinity of PFBA with the functionalized PMO materials. Adsorption free energy analysis suggested that although electrostatic interactions were more predominant in PFBA adsorption, modification of PMOs with increased fluoroalkyl group loadings increased the non-electrostatic interactions with PFBA, resulting in more favorable PFBA adsorption. The optimal functionalized PMO showed fast PFBA adsorption kinetics, excellent PFBA removal efficiency in various water chemistry conditions, and can be regenerated and reused for numerous cycles with methanol/water mixture containing 500-mM NH₃·H₂O as regenerant. Furthermore, the optimal functionalized PMO showed robust performance for the removal of PFAS mixtures under complex natural water matrix. Results of this study suggested the important role of non-electrostatic interactions in enhancing the removal of short-chain PFAS and can provide mechanistic insights into guiding the design of improved adsorbents for PFAS removal.

Association between perfluoroalkyl and polyfluoroalkyl internal exposure and serum α-Klotho levels in middle-old aged participants

Purpose

Exposure to perfluoroalkyl and polyfluoroalkyl substances causes oxidative stress, which is strongly associated with adverse health effects. Klotho protein plays an anti-aging role via antioxidation activity.

Methods

We investigated the levels of serum α-Klotho and PFAS exposure in adults who participated in the National Health and Nutrition Examination Survey from 2013 to 2016. A nationally representative subsample of 1,499 adults aged 40-79 years was analyzed for the associations of serum α-Klotho levels with serum PFAS exposures by correlation analysis and multiple general linear models. Of note, the potential confounding factors including age and gender were adjusted. Quantile-based g-computation models were used to assess the effects of mixed PFAS exposure on serum α-Klotho levels.

Results

The weighted geometric mean of serum α-Klotho was 791.38 pg/mL for the subjects during 2013-2016. After adjusting for potential confounders, serum Klotho levels showed a statistically significant downward trend with increasing quartiles of PFOA and PFNA. Multivariate adjusted general linear regression analysis showed that increased exposure to PFNA was substantially associated with lower serum levels of α-Klotho, and each 1-unit increase in PFNA concentration was accompanied by a 20.23 pg/mL decrease in α-Klotho level; while no significant association was observed between other PFAS exposures and serum α-Klotho levels. It was negatively correlated between α-Klotho and Q4 for PFNA relative to the lowest quartile (Q1) of exposure (P = 0.025). It was found that the strongest negative correlation between PFNA exposure and serum α-Klotho levels was in the middle-aged (40-59 years) female participants. Furthermore, the mixture of the four PFAS substances showed an overall inverse association with serum α-Klotho concentrations, with PFNA being the major contributor.

Conclusions

Taken together, in a representative sample of the U.S. middle-aged and elderly populations, serum concentrations of PFAS, especially PFNA, have been negatively associated with serum levels of α-Klotho, which is strongly associated with cognition and aging. It was important to note that the majority of associations were limited to middle-aged women. It will be meaningful to clarify the causal relationship and the pathogenic mechanisms of PFAS exposure and α-Klotho levels, which is helpful to aging and aging-related diseases.

Degradation of per- and polyfluoroalkyl substances in landfill leachate by a thin-water-film nonthermal plasma reactor

Per- and polyfluoroalkyl substances (PFAS) are present in landfill leachate, posing potential challenges to leachate disposal and treatment. This work represents the first study of a thin-water-film nonthermal plasma reactor for PFAS degradation in landfill leachate. Of the 30 PFAS measured in three raw leachates, 21 were above the detection limits. The removal percentage depended on the category of PFAS. For example, perfluorooctanoic acid PFOA (C8) had the highest removal percentage (77% as an average of the three leachates) of the perfluoroalkyl carboxylic acids (PFCAs) category. The removal percentage decreased when the carbon number increased from 8 to 11 and decreased from 8 to 4. The effects of various landfill leachate components, including sodium chloride, acetate, humic acids, pH, and surfactants, had no or minor impacts (<30%) on PFOA mineralization in synthetic samples. This might be explained by the plasma-generation and PFAS-degradation mainly occurring at the gas/liquid interface. Shorter-chain PFCAs were produced as intermediates of PFOA degradation, and shorter-chain PFCAs and perfluorosulfonic acids (PFSAs) were produced as intermediates of perfluorooctanesulfonic acid (PFOS). The concentrations of the intermediates decreased with decreasing carbon number, suggesting a stepwise removal of difluoromethylene (CF₂) in the degradation pathway. Potential PFAS species in the raw and treated leachates were identified at the molecular level through non-targeted Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The intermediates did not show accurate toxicity per Microtox bioassay.

Modeling the kinetics of perfluorooctanoic and perfluorooctane sulfonic acid biodegradation by Acidimicrobium sp. Strain A6 during the feammox process

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants of concern due to their health effects and persistence in the environment. Although perfluoroalkyl acids (PFAAs), such as perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are very difficult to biodegrade because they are completely saturated with fluorine, it has recently been shown that Acidimicrobium sp. A6 (A6), which oxidizes ammonium under iron reducing conditions (Feammox process), can defluorinate PFAAs. A kinetic model was developed and tested in this study using results from previously published laboratory experiments, augmented with results from additional incubations, to couple the Feammox process to PFAS defluorination. The experimental results show higher Feammox activity and PFAS degradation in the A6 enrichment cultures than in the highly enriched A6 cultures. The coupled experimental and modeling results show that the PFAS defluorination rate is proportional to the rate of ammonium oxidation. The ammonium oxidation rate and the defluorination rate increase monotonically, but not linearly, with increasing A6 biomass. Given that different experiments had different level of Feammox activity, the parameters required to simulate the Feammox varied between A6 cultures. Nonetheless, the kinetic model was able to simulate an anaerobic incubation system and show that PFAS defluorination is proportional to the Feammox activity.

Behavior of Per- and polyfluoroalkyl substances (PFAS) in Pilot-Scale vertical flow constructed wetlands treating landfill leachate

This study investigated the behavior of per- and polyfluoroalkyl substances (PFAS) in multiple pilot-scale vertical flow constructed wetlands (VFCW) treating landfill leachate. Eight pilot-scale VFCW columns planted with Typha latifolia or Scirpus Californicus were fed untreated municipal solid waste (MSW) landfill leachate that was diluted with potable water at a 1:10 ratio (1 part leachate to 10 parts total) at a fixed daily hydraulic loading rate of 0.525 m d^-1. Ninety-two PFAS were examined and 18 PFAS were detected at quantifiable concentrations (7 precursor species and 11 terminal species). The average concentration of Σ₉₂ PFAS in the influent was 3,100 ng L^-1, which corresponded with minimal reduction in the effluents from the four VFCW (decreases ranged from 1% to 12% on average for Σ₁₈ PFAS); however, precursors 6:3 FTCA, 7:3 FTCA, N-MeFOSAA, and N-EtFOSAA concentrations decreased significantly in the VFCW effluents, and significant decreases in the concentrations of these PFAA-precursors were concurrent with a significant increase in concentrations of five PFAAs (PFBA, PFNA, PFBS, PFOS, and PFOSI). This trend indicates that from a regulatory perspective, standalone VFCWs are likely to produce an apparent PFAS increase, which may also be true for many other leachate treatment processes incorporating aerobic biological treatment. Additional treatment to address PFAS should be integrated prior to the use of any system, including VFCWs, for the treatment of constituents of concern in MSW landfill leachate.

Enhancement of perfluorooctanoic acid and perfluorooctane sulphonic acid removal in constructed wetland using iron mineral: Performance and mechanisms

Polyfluoroalkyl substance (PFAS) pose a threat to the aquatic environment due to their environmental persistence. The removal of PFAS using constructed wetlands (CWs) has received interest, but the adsorption saturation and limited removal capacity of the substrate is frequently challenging. To enhance the microbial degradation and performance of the substrate, different configurations of iron minerals were used as substrate to remove perfluorooctane sulphonic acid (PFOS) and perfluorooctanoic acid (PFOA) from CWs. The addition of iron minerals resulted in elimination of 57.2% and 63.9% of PFOS and PFOA in the effluent, respectively, which were 35.0% and 36.8% higher than that of control. Moreover, up to 85.4%, 86%, and 85.1% of NH₄⁺, NO₃^-, and phosphorus, respectively, was removed using iron minerals. The enhanced electron transfer in iron mineral-based CWs was confirmed by a 61.2% increase in cytochrome C reductase content and an increased Fe(III)/Fe(II) ratio. Microbial analysis showed that the proportions of microbes with PFAS removal capacity (e.g. Burkholderiae and Pseudomonas), and the key pathways of the TCA cycle and glycolysis were increased in iron mineral-based CW. Based on these findings, we conclude that supplementation with iron mineral could enhance PFOA and PFOS removal in CWs.

Impact of biological activated carbon filtration and backwashing on the behaviour of PFASs in drinking water treatment plants

PFASs are present in surface water, tap water and even commercial drinking water and pose a risk to human health. In this study, the treatment efficiency of 14 PFASs was studied in a large drinking water treatment plant (DWTP) using Taihu Lake as the source, and it was found that the ozone/biological activated carbon (O₃-BAC) process was the most effective process for the removal of PFASs in DWTPs. For the O₃-BAC process, there were differences in the removal of PFASs by BACs (1,4,7,13 years) of different ages. The sterilization experiments revealed that for GAC, its physical adsorption capacity reached saturation after one year, while for BAC with mature biofilms, biosorption was the main mechanism for the removal of PFASs. The abundance of Alphaproteobacteria and Gammaproteobacteria in biofilms was positively correlated with the age of the BAC. The microbial community with higher abundance is beneficial to the biodegradation of organic matter and thus provides more active sites for the adsorption of PFASs. PFASs can leak in the early stage of filtration after backwashing, so it is necessary to pay close attention to the influent and effluent concentrations of PFASs during biofilm maturation after backwashing.

A review on superior advanced oxidation and photocatalytic degradation techniques for perfluorooctanoic acid (PFOA) elimination from wastewater

Perfluorooctanoic acid (PFOA) has been identified as the most toxic specie of the family of perfluorinated carboxylic acids (PFCAs). It has been widely distributed and frequently detected in environmental wastewater. The compound's unique features such as inherent stability, rigidity, and resistance to harsh chemical and thermal conditions, due to its multiple and strong C-F bonds have resulted in its resistance to conventional wastewater remediations. Photolysis and bioremediation methods have been proven to be inefficient in their elimination, hence this article presents intensive literature studies and summarized findings reported on the application of advanced oxidation processes (AOPs) and photocatalytic degradation techniques as the best alternatives for the PFOA elimination from wastewater. Techniques of persulfate, photo-Fenton, electrochemical, photoelectrochemical and photocatalytic degradation have been explored and their mechanisms for the degradation and defluorination of the PFOA have been demonstrated. The major advantage of AOPs techniques has been centralized on the generation of active radicals such as sulfate (SO₄^•-) hydroxyl (•OH). While for the photocatalytic process, photogenerated species (electron (e) and holes (h ⁺ _vb)) initiated the process. These active radicals and photogenerated species possessed potentiality to attack the PFOA molecule and caused the cleavage of the C-C and C-F bonds, resulting in its efficient degradation. Shorter-chain PFCAs have been identified as the major intermediates detected and the final stage entails its complete mineralization to carbon dioxide (CO₂) and fluoride ion (F^-). The prospects and challenges associated with the outlined techniques have been highlighted for better understanding of the subject matter for the PFOA elimination from real wastewaters.

Identification and characterization of diverse isomers of per- and polyfluoroalkyl substances in Chinese municipal wastewater

Linear and branched isomers of per- and polyfluoroalkyl substances (PFASs) are simultaneously present in the environment. However, isomer profiles of PFASs in municipal wastewater treatment plants (WWTPs) are still unknown because of the limitations of standards. Here, influent and effluent samples from 148 municipal WWTPs in China were collected. Ion mobility spectrometry was introduced into high-resolution mass spectrometry-based suspect screening methods to identify the target and suspect PFAS isomers. A total of 38 branched isomers of 14 typical PFASs were identified in wastewater samples. Linear PFASs had higher detection rates (22.3%-100%) than branched isomers (2.0%-98%). Compared to the influents, proportions of branched isomers of most PFASs (except for perfluoropentanoic acid and perfluorohexanoic acid) increased in the effluents. The conventional biological treatment processes (such as anaerobic-anoxic-aerobic and oxidation ditch treatments) had poor removal efficiency for linear PFASs (<21.4%) and branched isomers (<13.4%). No difference on removal efficiency among treatment processes was found. Furthermore, isomer composition in the WWTPs showed obvious differences between East China region and other regions, and the usage of short-chain PFASs (perfluorobutanesulfonic acid and perfluorohexanesulfonic acid) may be a key factor for driving this difference. This study sheds lights on the identification and characterization of PFAS isomers in WWTPs, which would be useful for development of monitoring and control strategies of PFASs.

Preliminary Study on the Protective Effects and Molecular Mechanism of Procyanidins against PFOS-Induced Glucose-Stimulated Insulin Secretion Impairment in INS-1 Cells

This study aimed to investigate the effects of perfluorooctanesulfonic acid (PFOS) exposure on glucose-stimulated insulin secretion (GSIS) of rat insulinoma (INS-1) cells and the potential protective effects of procyanidins (PC). The effects of PFOS and/or PC on GSIS of INS-1 cells were investigated after 48 h of exposure (protein level: insulin; gene level: glucose transporter 2 (Glut2), glucokinase (Gck), and insulin). Subsequently, the effects of exposure on the intracellular reactive oxygen species (ROS) activity were measured. Compared to the control group, PFOS exposure (12.5, 25, and 50 μM) for 48 h had no significant effect on the viability of INS-1 cells. PFOS exposure (50 μM) could reduce the level of insulin secretion and reduce the relative mRNA expression levels of Glut2, Gck, and insulin. It is worth noting that PC could partially reverse the damaging effect caused by PFOS. Significantly, there was an increase in ROS after exposure to PFOS and a decline after PC intervention. PFOS could affect the normal physiological function of GSIS in INS-1 cells. PC, a plant natural product, could effectively alleviate the damage caused by PFOS by inhibiting ROS activity.