Electrochemical oxidation offers a promising approach for degrading perfluorocarboxylic acids (PFCAs); however, the coexistence and competition of degradation pathways remain poorly understood. Herein, a range of complementary methodologies was employed to investigate perfluorooctanoic acid (PFOA) degradation using a Pt anode under controlled oxidative conditions. Two representative degradation channels were systematically confirmed, namely Channel 1, involving the formation of short-chain PFCAs, and Channel 2, featuring stepwise defluorination via CnF2n+1• and COF2. A quantitative framework based on fluorine mass balance revealed that Channel 2 accounts for the majority of fluorine release (78.3-82.1%), fundamentally clarifying the dominant mineralization mechanism of PFOA. Trifluoroacetic acid, selected as a structurally simplified model compound, was used to probe the transformation behavior of COF2 for the first time. The observed defluorination efficiency significantly exceeds the theoretical limit in the absence of COF2 hydrolysis, providing indirect but compelling evidence for its transformation under electrochemical conditions. The study further reveals that degradation channel selectivity is dynamically regulated by interfacial conditions, with elevated temperatures enhancing the formation of short-chain PFCAs, whereas higher reaction rates accelerate their subsequent degradation. Overall, these findings provide insightful mechanistic understanding of PFCAs degradation and offer theoretical guidance for limiting the formation of persistent short-chain byproducts.

Electrochemical oxidation on boron-doped diamond (BDD) anodes is effective for per- and polyfluoroalkyl substances (PFAS) removal, and the degradation process is highly sensitive to anion-dependent interfacial conditions. Although anion effects in electrochemical systems are often discussed in terms of solution-phase reactivity, their role in regulating PFAS transformation at the anodic interface remains unclear, particularly for short-chain PFAS. Here, perfluorobutanoic acid (PFBA) was used as a representative short-chain PFAS to probe electrochemical degradation in BDD systems with different supporting electrolytes. Among five common electrolytes, Na2SO4 exhibited the highest PFBA removal and defluorination efficiencies, with an apparent rate constant that was 1.6 and 2.6 times those of the Na2S2O8 and NaNO3 systems, respectively. Evidence shows that this enhancement is not primarily governed by sulfate-radical or persulfate-mediated pathways, but instead arises from interfacial processes at the BDD anode. Specifically, sulfate regulates the electrode-solution interface, suppresses oxygen evolution, and facilitates anodic direct electron transfer to initiate PFBA oxidation, while sustaining effective •OH participation in the subsequent chain defluorination process. Non-target screening, targeted quantification, and in situ analysis support a decarboxylation-initiated pathway followed by CF2O formation and stepwise defluorination. These findings provide mechanistic insight for electrolyte selection and interfacial design in electrochemical PFAS treatment systems.

Electrochemical advanced oxidation processes are promising for perfluorooctanoic acid (PFOA) degradation; however, strategies for enhancing degradation performance through rational regulation of the reaction medium remain insufficiently understood. In this study, systematic screening of nitrogen-containing compounds showed that discrete inorganic nitrogen species (e.g., ammonium and nitrate) failed to induce any measurable degradation or defluorination of PFOA. In contrast, nitrogen-containing compounds with lone-pair electrons (e.g., glycine and nitrilotriacetic acid) acted as effective promoters, enabling a maximum PFOA removal efficiency of 88.4% within 300 min. Using glycine as a representative additive, mechanistic investigations demonstrated that cooperative coordination among glycine, PFOA, and the Pt electrode surface promotes anodic direct electron transfer. In parallel, glycine-assisted electrochemical processes generate reactive oxidizing species, particularly reactive nitrogen species (e.g., •NO3) and hydroxyl radicals (•OH), which contribute to indirect oxidation pathways. These two processes act synergistically to govern the PFOA degradation. Fluorine mass balance analysis further revealed that stepwise defluorination via CnF2n+1• and COF2 formation dominated mineralization, accounting for 85.4-97.9% of fluorine release, whereas short-chain intermediates constituted only a minor route. Overall, this study elucidates the coupled roles of interfacial coordination regulation and reactive nitrogen chemistry in electrochemical PFAS degradation, providing mechanistic guidance for effective electrochemical treatment systems.

Firefighting training sites are point sources of per- and polyfluoroalkyl substances (PFAS) originating from aqueous film-forming foams (AFFF) released into the surrounding environment. In this study, multimedia samples, including air, wastewater/river water, soil/sediments, herbaceous plants, and tree bark/leaves, were collected from a typical firefighting site in China. By developing an integrated screening method specifically tailored for AFFF-related PFAS, we efficiently identified PFAS across multiple media, comprehensively characterizing their contamination profiles in both atmospheric and terrestrial compartments. In total, 122 PFAS in 62 classes were detected. Notably, 18 AFFF-related PFAS were reported for the first time in environmental media, 10 of which were exclusively detectable through the diagnostic fragment-based screening strategy, underscoring the critical role of this strategy in uncovering structurally unknown PFAS. The highest PFAS diversity (113 compounds) was observed in herbaceous plant systems. Air samples contained 51 PFAS, dominated by anionic fluorotelomer-based PFAS and sulfonamide derivatives. A total of 37 and 38 PFAS were identified in tree bark and leaves, respectively, showing a 76 % overlap with airborne PFAS profiles. These findings establish firefighting-derived PFAS as an important source of atmospheric contamination, highlighting a critical knowledge gap that warrants further investigation.

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

Microplastics (MPs) negatively impact various terrestrial animals, but their comprehensive effects on Gallus gallus domesticus, key agricultural and ecological species connecting people and the environment, are not well-documented. This study investigates the effects of polyethylene (PE) MPs and phthalate esters (PAEs) on chicken growth, liver metabolism, and gut microbiota using multi-omics and 16S rRNA sequencing technology. Results show that PE MPs, particularly those containing PAEs, significantly reduced body weight gain and hepatic triglyceride levels by up to 71.2 % and 50.1 %, respectively (p < 0.05). The clean MPs affected energy metabolism, while PAE-spiked MPs disrupted fatty acid metabolism and triggered immune and inflammatory responses in the liver. Key genes related to fatty acid metabolism such as FAN, SCD and ELOVL5 were significantly downregulated, leading to imbalances in lipid metabolism. These disruptions in PAE-spiked MPs exposure were associated with the altered gut microbiota balance, including increased Firmicutes/Bacteroidetes ratios and changes in Actinobacteriota and Proteobacteria abundance. Totally, the study highlights a "Trojan Horse" effect, where MPs act as carriers for PAEs, intensifying toxicity through gut-liver axis interactions. The findings emphasize the role of gut microbiota in mediating liver dysfunction and impaired growth.

Per- and polyfluoroalkyl substances (PFAS) have attracted considerable attention due to their environmental persistence and the challenges of remediation. PFAS, typically composed of hydrophobic fluorocarbon chains linked to hydrophilic head groups, exhibit excellent surface activity, leading to their spontaneous accumulation/adsorption at the air-water interface (AWI). This review systematically summarizes the mechanisms of PFAS adsorption at the AWI, the methodologies for determining the AWI adsorption coefficient (Kaw), the factors influencing Kaw, the enrichment of PFAS across various environmental media, and the remediation technologies leveraging this adsorption mechanism. PFAS accumulation at the AWI occurs in various environmental compartments, including the surface microlayer (SML), natural foams, aerosols, and the vadose zone. The degree of PFAS enrichment generally follows the order: aerosols > natural foams > surface microlayer, which is closely associated with the differences in the specific surface area of these carriers. Sea spray aerosols (SSA) exhibit significant PFAS enrichment, serving as a key secondary emission source of PFAS in coastal areas. The vadose zone acts as a long-term reservoir, potentially releasing PFAS into groundwater for decades to centuries. Foam fractionation and aerosol separation are two promising technologies for remediation of PFAS-contaminated water. Future research should focus on elucidating the mechanistic impacts of diverse factors, developing unified fitting and predictive models, expanding investigations to emerging PFAS, and optimizing removal technologies to enhance remediation efficiency of short-chain PFAS.

Due to the lack of transparency in the production and applications of emerging per- and polyfluoroalkyl substances (PFAS), it is a huge challenge to grasp the real PFAS pollution profile in a specific region or industry by target analysis. This study collected extensive samples across China, including municipal wastewater from 9 major cities and wastewater from various manufacturing stages at 3 large semiconductor factories. Suspect and nontarget screening were conducted along with target analysis, and 82 PFAS in 25 classes were identified. Notably, this is the first study to investigate PFAS contamination in semiconductor wastewater on the Chinese mainland. Moreover, 13 classes of PFAS were reported for the first time worldwide in semiconductor wastewater, including multiple hydrosubstituted perfluoroalkyl carboxylic acid (mH-PFCA), ether-inserted PFCA (OPFCA), and perfluoroalkyl alcohol (PA) derivatives. The highest total concentrations of target, suspect, and nontarget PFAS in semiconductor wastewater (12 μg/L) were substantially higher than those measured in all municipal wastewater (25-950 ng/L). The composition of PFAS varied regionally in semiconductor wastewater. Total oxidizable precursor assay revealed the presence of unknown precursors (0.043-0.83 nmol/L), which cannot be directly monitored but may pose a greater PFAS contamination risk in semiconductor water treatment and discharge processes.

While the aerobic transformation of emerging per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foams (AFFF) has been extensively studied, their fate under anoxic/anaerobic conditions remains poorly characterized. This study investigated the stability and biotransformation of nine emerging polyfluoroalkyl compounds in a composite AFFF under nitrate-, sulfate-, and iron-reducing conditions. The biotransformation behavior of seven compounds under anoxic conditions is reported for the first time. After 300 days of incubation, 6:2 fluorotelomer sulfonate and three compounds containing betaine or quaternary ammonium groups exhibited high persistence across all three reducing conditions. In contrast, the other five compounds containing thioether or tertiary amine groups underwent significant biotransformation, which followed first-order kinetics. Their biotransformation rates followed a consistent hierarchy: nitrate-reducing > sulfate-reducing > iron-reducing conditions. No abiotic transformation was observed under anoxic conditions, in contrast to previous studies conducted under aerobic conditions. Based on the products identified by high-resolution mass spectrometry, comprehensive redox-dependent biotransformation pathways were proposed. Notably, no significant defluorination products were observed, particularly with the absence of short-chain perfluoroalkyl carboxylic acids. Redox-dependent shifts in microbial composition led to differential expression of functional enzymes, ultimately governing the varying biotransformation behavior of AFFF-derived PFAS. This study provides fundamental insights into the fate of emerging PFAS in anoxic subsurface environments.

Legacy and emerging PFAS in the air, wastewater, and sludge from two wastewater treatment plants (WWTPs) in Tianjin were investigated in this study. The semi-quantified nontarget PFAS accounted for up to 99 % of ƩPFAS in the gas phase, and aqueous film-forming foam (AFFF)-related PFAS were predominant in wastewater (up to 2250 ng/L, 79 % of ƩPFAS) and sludge (up to 4690 ng/g, 95 % of ƩPFAS). Furthermore, field-derived air particle-gas, air-wastewater, and wastewater particle-wastewater distribution coefficients of emerging PFAS are characterized, which have rarely been reported. The emerging substitute p-perfluorous nonenoxybenzenesulfonate (OBS) and AFFF-related cationic and zwitterionic PFAS show a stronger tendency to partition into particle phase in air and wastewater than perfluorooctane sulfonic acid (PFOS). The estimated total PFAS emissions from the effluent and sludge of WWTP A were 202 kg/y and 351 kg/y, respectively. While the target PFAS only accounted for 20-33 % of the total emissions, suggesting a significant underestimation of environmental releases of the nontarget PFAS and unknown perfluoroalkyl acid precursors through the wastewater and sludge disposal. Overall, this study highlights the importance of comprehensive monitoring and understanding the behavior of legacy and emerging PFAS in wastewater systems, and fills a critical gap in our understanding of PFAS exposure.

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

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

With long-term production and widespread application, per-and polyfluoroalkyl substances(PFAS) have been detected in various media worldwide, including the atmosphere. Since the gradual restriction and phase-out of C8perfluoroalkyl acids(PFAAs), environmental contamination by emerging PFAS substitutes such as short-chain PFAA homologues, perfluoroether carboxylic, and sulfonic acids has been reported. Although there has been extensive monitoring of emerging PFAS substitutes in the aquatic environment, few studies have conducted target analysis and nontarget screening(NTS) of emerging unknown PFAS in the atmosphere over the past decade. To fill the gap, this review focused on emerging PFAS in the atmosphere in addition to legacy PFAS. The reported sampling, pretreatment, and instrumental analysis methods for target analysis and NTS of both neutral and ionic PFAS in the atmosphere are summarized, along with the advantages and current limitations of different sampling and NTS methods for PFAS in the atmosphere. The global levels, composition, and spatiotemporal distribution characteristics of legacy and emerging PFAS in the atmosphere are summarized and their transport, transformation, and dry/wet deposition are elucidated. The review highlights the importance of developing and applying the all-in-one strategy integrating target, suspect screening, and NTS to gain insights into emerging PFAS in the atmosphere and provide a reference for future research.

Occupational exposure to per- and polyfluoroalkyl substances (PFASs) is of serious concern because their adverse health effects. Nevertheless, knowledge regarding contamination in e-waste dismantling regions is rather scarce. We therefore analysed seven neutral PFASs (n-PFASs) and forty ionized PFASs (i-PFASs) in dust and hand wipes collected from an e-waste dismantling plant and homes. Both dust (1370 ng/g) and workers' hand wipe (1100 ng/m2) in e-waste dismantling workshops contained significantly higher median levels of ∑PFASs than those from homes (684 ng/g and 444 ng/m2) (p < 0.01). ∑PFAS concentrations in dust and on workers' hand wipes from workshops were significantly higher than those from storage area. 8:2 fluorotelomer alcohol was the dominant n-PFAS in workshop dust (70.7%) and on worker's hand wipes (46.6%). Perfluoroalkyl carboxylic acids (C2 -C3) were the significant components (based on concentration) of i-PFASs in dust (57.9%) and on hand wipes (89.6%). A significant positive correlation (p < 0.001) of ∑PFAS concentrations between workshop dust and workers' hand wipes was observed, indicating that they come from common sources. Compared to dust ingestion, hand-to-mouth contact was highlighted as a vital exposure route, accounting for 68.8% for workers and 72.2% for residential population, respectively, of the sum of two exposure doses.

Electrochemical oxidation (EO) has been shown to have the unique ability to degrade perfluorooctanoic acid (PFOA), although the radical chemistry involved in this degradation is unclear, particularly in the presence of chloride ions (Cl-). In this study, reaction kinetics, free radical quenching, electron spin resonance, and radical probes were used to examine the roles of ·OH and reactive chlorine species (RCS, including Cl·, Cl2•-, and ClO·) in the EO of PFOA. Using EO in the presence of NaCl, PFOA degradation rates of 89.4%-94.9% and defluorination rates of 38.7%-44.1% were achieved after 480 min with PFOA concentrations ranging from 2.4 to 240 μM. The degradation occurred via the synergistic effect of ·OH and Cl· rather than through direct anodic oxidation. The degradation products and density functional theory (DFT) calculations revealed that Cl· triggered the first step of the reaction, thus the initial direct electron transfer was not the rate-limiting step of PFOA degradation. The change in Gibbs free energy of the reaction caused by Cl· was 65.57 kJ mol-1, which was more than two times lower than that triggered by ·OH. However, ·OH was involved in the subsequent degradation of PFOA. The synergistic effect of Cl· and ·OH in PFOA degradation is demonstrated for the first time in this study, which is promising for the development of electrochemical technology to remove perfluorinated alkyl substances from the environment.

Wastewater treatment plants (WWTPs) are typical point sources of per- and polyfluoroalkyl substances (PFAS) released into the environment. The suspect and nontarget screening based on gas chromatography or liquid chromatography-high resolution mass spectrometry were performed on atmosphere, wastewater, and sludge samples collected from two WWTPs in Tianjin to discover emerging PFAS and their fate in this study. A total of 40 PFAS (14 neutral and 26 ionic) and 64 PFAS were identified in the atmosphere and wastewater/sludge, respectively, among which 5 short-chain perfluoroalkyl sulfonamide derivatives, 4 ionic PFAS, and 15 aqueous film-forming foam-related cationic or zwitterionic PFAS have rarely or never been reported in WWTPs in China. Active air sampling is more conducive to the enrichment of emerging PFAS, while passive sampling is inclined to leave out some ultrashort-chain PFAS or unstable transformation intermediates. Moreover, most precursors and intermediates could be enriched in the atmosphere at night, while the PFAS associated with aerosols with high water content or particles enter the atmosphere easily during the day. Although most emerging PFAS could not be eliminated efficiently in conventional treatment units, deep bed filtration and advanced oxidation processes could partly remove some emerging precursors.

Per- and polyfluoroalkyl substances (PFASs) have attracted extensive attention because of their persistence, long-distance migration ability, bioaccumulation, and biological toxicity. Currently, regulatory strategies concerning PFASs in the environment primarily focus on perfluoroalkyl acids (PFAAs). However, most polyfluoroalkyl compounds can be degraded to PFAAs by environmental microorganisms, also known as precursors. Exploring the microbial transformation behavior of precursors is fundamental to comprehensively evaluate the environmental risk of PFASs and formulate control and remediation schemes of PFAS-contaminated sites. Furthermore, anaerobic microbial reductive defluorination of PFAAs is a potential and challenging remediation technology. This review summarizes degradation rules and transformation pathways of precursors (fluorotelomer compounds and perfluorooctane sulfonamide derivatives), PFAAs, and novel PFASs by microorganisms and discusses factors affecting the microbial degradation. Finally, the future research directions are put forward.

The objectives of this study were to identify both legacy and emerging per- and polyfluoroalkyl substances (PFAS) from three typical fluoridated industrial parks (FIPs) in China, and to assess their environmental occurrence and fate. Complementary suspect target and nontarget screening were implemented, and a total of 111 emerging PFAS were identified. Based on the multi-mass scale analysis, 25 emerging PFAS were identified for the first time, including 24 per- and polyfluoroalkyl ether carboxylic acids (PFECAs) and 1 ultra-short chlorinated perfluoroalkyl carboxylic acids (Cl-PFCAs, C2), with a maximum percentage of 48.2 % in nontarget PFAS (exclude target PFAS). The composition of PFAS identified in different media was influenced by functional groups, carbon chain length, substituents and ether bond insertion, with poly-hydrogen substituted being preferably in water and a more diverse pattern of PFECAs in sediments. The patterns of PFAS homologs revealed distinct differences among the three typical FIPs in the shift of PFAS production patterns. The C4-PFAS and short-chain carboxylic acids (≤C6) were the main PFAS in the Fuxin and Changshu, respectively. In contrast, perfluorooctanoic acid (PFOA, C8) remained dominant in Zibo, and the highest point concentrations in water and sediment were up to 706 µg/L and 553 µg/g, respectively.

In the present study, the uptake and translocation mechanisms of phthalate esters (PAEs) and their primary mono esters metabolites (mPAEs), and the mechanisms of PAEs metabolism in plants were elucidated. The objectives of this study were to: (i) elucidate the fractionation of PAEs and mPAEs in Chinese cabbage (Brassica rapa var. chinensis) by hydroponic experiment, (ii) investigate the PAEs and mPAEs uptake mechanisms in root by inhibitor experiments, (iii) explain the molecular mechanisms of PAE interactions with the plant macromolecules by proteomics analysis and molecular docking, and (iv) reveal the involvement of carboxylesterase in the plant metabolism of PAEs. The results demonstrated that both the apoplastic and symplastic pathways contributed to the uptake of di-n-butyl phthalate (DnBP), di-(2-ethylhexyl) phthalate (DEHP), mono-n-butyl phthalate (MnBP), and mono-(2-ethylhexyl) phthalate (MEHP) by vacuum-infiltration-centrifugation method. The energy-dependent active process was involved for the uptake of DnBP, DEHP, MnBP, and MEHP. The passive uptake pathways of anion mPAEs and neutral PAEs differ. Aquaporins contributed to the uptake of anion MnBP and MEHP, and slow-type anion channel was also responsible for the uptake of anion MEHP. Molecular interactions of PAEs and macromolecules were further characterized by proteomic analysis and molecular docking. PAEs were transferred via non-specific lipid transfer protein by binding hydroponic amino acid residues. The carboxylesterase enzyme was attributed to the metabolism of PAEs to form mPAEs by using crude enzyme extract and commercial pure enzyme. This study provides both experimental and theoretical evidence for uptake, accumulation, and metabolism of PAEs in plants.