Transformation of novel polyfluoroalkyl substances (PFASs) as co-contaminants during biopile remediation of petroleum hydrocarbons

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

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

Multicomponent and Surface Charge Effects on PFOS Sorption and Transport in Goethite-Coated Porous Media under Variable Hydrochemical Conditions

Perfluorooctanesulfonate (PFOS), a toxic anionic perfluorinated surfactant, exhibits variable electrostatic adsorption mechanisms on charge-regulated minerals depending on solution hydrochemistry. This work explores the interplay of multicomponent interactions and surface charge effects on PFOS adsorption to goethite surfaces under flow-through conditions. We conducted a series of column experiments in saturated goethite-coated porous media subjected to dynamic hydrochemical conditions triggered by step changes in the electrolyte concentration of the injected solutions. Measurements of pH and PFOS breakthrough curves at the outlet allowed tracking the propagation of multicomponent reactive fronts. We performed process-based reactive transport simulations incorporating a mechanistic network of surface complexation reactions to quantitatively interpret the geochemical processes. The experimental and modeling outcomes reveal that the coupled spatio-temporal evolution of pH and electrolyte fronts, driven by the electrostatic properties of the mineral, exerts a key control on PFOS mobility by determining its adsorption and speciation reactions on goethite surfaces. These results illuminate the important influence of multicomponent transport processes and surface charge effects on PFOS mobility, emphasizing the need for mechanistic adsorption models in reactive transport simulations of ionizable PFAS compounds to determine their environmental fate and to perform accurate risk assessment.

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.

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

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

Using regular and transcriptomic analyses to investigate the biotransformation mechanism and phytotoxic effects of 6:2 fluorotelomer carboxylic acid (6:2 FTCA) in pumpkin (Cucurbita maxima L.)

Although 6:2 fluorotelomer carboxylic acid (6:2 FTCA), which is one of the most popular substitutes for perfluorooctanoic acid (PFOA), has been widely distributed in environments, little is known about its biotransformation mechanism and phytotoxic effects in plants. Here, we showed that 6:2 FTCA could be taken up by pumpkin (Cucurbita maxima L.) roots from exposure solution and acropetally translocated to shoots. Biotransformation of 6:2 FTCA to different carbon chain perfluorocarboxylic acid (PFCA) metabolites (C2-C7) via α-and β-oxidation in pumpkin was observed, and perfluorohexanoic acid (PFHxA) was the major transformation product. The results of enzyme assays, enzyme inhibition experiments and gene expression analysis indicated that cytochrome P450 (CYP450), glutathione-S-transferase (GST) and ATP-binding cassette (ABC) transporters were involved in the metabolism of 6:2 FTCA in pumpkin. Plant-associated rhizobacteria and endophyte also contributed to 6:2 FTCA degradation through β-oxidation. The chlorophyll (Chl) content and genes involved in photosynthesis were significantly improved by 6:2 FTCA. The reductions of antioxidant and metabolic enzyme activities reflected the antioxidant defense system and detoxification system of pumpkin were both damaged, which were further confirmed by the down-regulating associated genes encoding phenylpropanoid biosynthesis, endoplasmic reticulum-related proteins, ascorbate-glutathione cycle and ABC transporters. This study is helpful to understand the environmental behaviors and toxicological molecular mechanisms of 6:2 FTCA in plants.

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.

PFAS-CTAB Complexation and Its Role on the Removal of PFAS from a Lab-Prepared Water and a Reverse Osmosis Reject Water Using a Plasma Reactor

Electrical discharge plasma reactors with argon bubbling can effectively treat long-chain perfluoroalkyl acids (PFAAs) in contaminated water, and the addition of a cationic surfactant cetrimonium bromide (CTAB) is known to enhance the removal of short-chain PFAAs. However, the roles of PFAA chain length, functional group, and water matrix properties on PFAA-CTAB complexation are largely unknown. This work investigated the bulk liquid removal of different PFAAs by CTAB in the absence of plasma. Stepwise addition of CTAB was subsequently used to efficiently treat PFAAs in a lab-prepared water and a reverse osmosis (RO) reject water using an enhanced contact plasma reactor. The results show that CTAB inhibited the bulk liquid removal of long-chain PFAAs in the absence of plasma likely due to the formation of hydrophilic CTAB-PFAA mixed micelles and competition for interfacial access between long-chain PFAAs and CTAB. On the contrary, CTAB enhanced the removal of short- and ultrashort-chain PFAAs by forming hydrophobic complexes. After 6 h of treatment in the plasma reactor with CTAB, PFAAs were 86 to >99% removed from the lab-prepared water and 29 to >99% removed from the RO reject water. This study provides important insights for overcoming mass transfer limitations for PFAA treatment technologies.

Employing salt-tolerant bacteria Serratia marcescens subsp. SLS for biodegradation of oily kitchen waste

The high oil and salt content of kitchen waste (KW) inhibit bioconversion and humus production. To efficiently degrade oily kitchen waste (OKW), a halotolerant bacterial strain, Serratia marcescens subsp. SLS which could transform various animal fats and vegetable oils, was isolated from KW compost. Its identification, phylogenetic analysis, lipase activity assays, and oil degradation in liquid medium were assessed, and then it was employed to carry out a simulated OKW composting experiment. In liquid medium, the 24 h degradation rate of mixed oils (soybean oil: peanut oil: olive oil: lard = 1:1:1:1, v/v/v/v) was up to 87.37% at 30 °C, pH 7.0, 280 rpm, 2% oil concentration and 3% NaCl concentration. The ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS) method demonstrated that the mechanism of SLS strain metabolizing long-chain triglycerides (TAGs) (C53-C60), especially the biodegradation of TAG (C18:3/C18:3/C18:3) by the strain can reach more than 90%. Degradation of 5, 10, 15% concentrations of total mixed oil were also calculated to be 64.57, 71.25, 67.99% respectively after a simulated composting duration of 15 days. The results suggest that the isolated strain of S. marcescens subsp. SLS is suitable for OKW bioremediation in high NaCl concentration within a reasonably short period of time. The findings introduced a salt-tolerant and oil-degrading bacteria, providing insights into the mechanism of oil biodegradation and offering new avenues of study for OKW compost and oily wastewater treatment.

Hydroxyl Radical Transformations of Perfluoroalkyl Acid (PFAA) Precursors in Aqueous Film Forming Foams (AFFFs)

Historical releases of aqueous film forming foam (AFFF) are significant sources of poly- and perfluoroalkyl substances (PFASs), including perfluoroalkyl acids (PFAAs) and their precursors, to the environment. While several studies have focused on microbial biotransformation of polyfluorinated precursors to PFAAs, the role of abiotic transformations at AFFF-impacted sites is less clear. Herein, we use photochemically generated hydroxyl radical to demonstrate that environmentally relevant concentrations of hydroxyl radical (^•OH) can play a significant role in these transformations. High-resolution mass spectrometry (HRMS) was used to perform targeted analysis, suspect screening, and nontargeted analyses, which were used to identify the major products of AFFF-derived PFASs as perfluorocarboxylic acids, though several potentially semi-stable intermediates were also observed. Using competition kinetics in a UV/H₂O₂ system, hydroxyl radical rate constants (k_OH) for 24 AFFF-derived polyfluoroalkyl precursors were measured to be 0.28 to 3.4 × 10⁹ M^-1 s^-1. Differences in k_OH were observed for compounds with differing headgroups and perfluoroalkyl chain lengths. Also, differences in k_OH measured for the only relevant precursor standard available, n-[3-propyl]tridecafluorohexanesulphonamide (AmPr-FHxSA), as compared to AmPr-FHxSA present in AFFF suggest that intermolecular associations in the AFFF matrix may affect k_OH. Considering environmentally relevant [^•OH]_ss, polyfluoroalkyl precursors are expected to exhibit half-lives of ∼8 days in sunlit surface waters and possibly as short as ∼2 h during oxygenation of Fe(II)-rich subsurface systems.

Enhanced oil removal from oily sand by injecting micro-macrobubbles in swirl elution

Environmental contamination by petroleum hydrocarbons was exacerbated by oil pipeline breaks, marine oil spills and discharges from industrial production. To further improve the removal performance of petroleum hydrocarbons in solid particles, the deoiling experiments of swirl elution with micro-macrobubbles on oily sands were carried out in this paper. Experiment results indicated that when particles fell from the center of the bubble, the collision efficiency was 99.3%. The instantaneous contact angle (ICA) between the macrobubbles and the oil layer was improved in the presence of microbubbles. Furthermore, the maximum ICA of bubbles attaching to the oil layer was found to occur at pH 9 in the system of oily sand mixtures ranging from pH 5 to pH 14. This finding indicated that the slightly alkaline solution was more advantageous for bubbles to attach to the oil layer than the highly alkaline solution. The optimum condition for the elution of oily sand in the mixture of pH 7-14 was pH 12, and the oil removal efficiency was 85.4% for 10 min. The oil removal efficiency of swirl elution (SE) with bubbles on oily sand at pH 12 for 10 min was superior to either SE without bubbles or air flotation (AF). The results show that the swirl elution with bubbles can effectively enhance the oil removal efficiency of oily sands and provide guidance for controlling the environmental petroleum hydrocarbon contamination and reducing the usage of surfactants.

Behaviors of 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) in wheat seedlings: Bioaccumulation, biotransformation and ecotoxicity

As a new alternative to perfluorooctane sulfonate (PFOS), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) has been currently used in industrial and consumer applications, which has been frequently detected in environment media. However, the behaviors of 6:2 FTAB in plants are still unclear. This study investigated the bioaccumulation, biotransformation and ecotoxicity of 6:2 FTAB in wheat (Triticum aestivum L.) by hydroponic exposure. 6:2 FTAB was easily taken up by roots with the root concentration factor (RCF) as high as 94.8, but difficult to be acropetally translocated in the shoots with the translocation factor (TF) as low as 0.058. Two intermediates and six terminal perfluorocarboxylic acid (PFCA) metabolites were detected in roots and shoots. The detected metabolites included 6:2 fluorotelomer sulfonic acid (6:2 FTSA), 6:2 fluorotelomer carboxylic acid (6:2 FTCA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutyric acid (PFBA), pentafluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA), and 6:2 FTSA was the main metabolite. 6:2 FTAB significantly reduced the biomass of plant and prevented chlorophyll (Chl) accumulation, while caused no significant change in malondialdehyde (MDA) content. Significant reduction in glutathione (GSH) contents, excess production of reactive oxygen species (ROS), and obvious inhibition of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST) activities were observed, suggesting damage of antioxidant defense systems and failure to detoxication of 6:2 FTAB in wheat. These findings provide important knowledge for the fate of 6:2 FTAB in plants.

Microbial biotransformation of aqueous film-forming foam derived polyfluoroalkyl substances

Per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foam (AFFF) comprise some perfluoroalkyl substances but a larger variety of polyfluoroalkyl substances. Despite their abundance in AFFF, information is lacking on the potential transformation of these polyfluoroalkyl substances. Due to the biological and chemical stability of the repeating perfluoroalkyl -(CF₂)_n- moiety common to all known AFFF-derived PFASs, it is not immediately evident whether the microbial biotransformation mechanisms observed for other organic contaminants also govern the microbial biotransformation of polyfluoroalkyl substances. Herein, we aim to: 1) review the literature on the aerobic or anaerobic microbial biotransformation of AFFF-derived polyfluoroalkyl substances in environmental media; 2) compile and summarize proposed microbial biotransformation pathways for major classes of polyfluoroalkyl substances; 3) identify the dominant biotransformation intermediates and terminal biotransformation products; and 4) discuss these findings in the context of environmental monitoring and source allocation. This analysis revealed that much more is currently known about aerobic microbial biotransformation of polyfluoroalkyl substances, as compared to anaerobic biotransformation. Further, there are some similarities in microbial biotransformations of fluorotelomer and electrochemical fluorination-derived polyfluoroalkyl substances, but differences may be largely due to head group composition. Dealkylation, oxidation, and hydrolytic reactions appear to be particularly important for microbial biotransformation of AFFF-derived polyfluoroalkyl substances, and these biotransformations may lead to formation of some semi-stable intermediates. Finally, this review discusses key knowledge gaps and opportunities for further research.

Aerobic BTEX biodegradation increases yield of perfluoroalkyl carboxylic acids from biotransformation of a polyfluoroalkyl surfactant, 6:2 FtTAoS

Aqueous film-forming foams (AFFFs) are important sources of per- and polyfluoroalkyl substances (PFASs) in soil, groundwater, and surface water. Soil microorganisms can convert polyfluorinated substances into persistent perfluoroalkyl acids, but the understanding of co-contaminant stimulation or inhibition of PFASs biotransformation is limited. In this study, we investigate how aerobic biotransformation of polyfluorinated substances was affected by common AFFF co-contaminants, such as gasoline aromatics: benzene, toluene, ethylbenzene, and o-xylene (BTEX). We performed aerobic microcosm studies by inoculating AFFF-impacted soil with medium containing 6:2 fluorotelomer thioether amido sulfonate (FtTAoS) and either diethyl glycol monobutyl ether (DGBE), a common AFFF ingredient, or BTEX compounds as the main carbon and energy source. BTEX-amended microcosms produced 4.3-5.3 fold more perfluoroalkyl carboxylates (PFCAs) than DGBE-amended ones, even though both organic carbon sources induced similar 6:2 FtTAoS biotransformation rates. In enrichments of AFFF-impacted solids selecting for BTEX biodegradation, we detected the presence of genes encoding toluene dioxygenase as well as larger abundances of transformation products from thioether oxidation that complement larger quantities of terminal transformation products. Our findings indicate that enrichment of BTEX-degrading microorganisms in the AFFF-impacted soil enhanced the conversion of 6:2 FtTAoS to PFCAs. These results provide insights into the high ratio of PFAAs to precursors at AFFF-impacted sites with history of BTEX bioremediation.

Simulating Impacts of Biosparging on Release and Transformation of Poly- and Perfluorinated Alkyl Substances from Aqueous Film-Forming Foam-Impacted Soil

Poly- and perfluorinated alkyl substances (PFASs) frequently co-occur with fuel-derived contaminants because of the use of aqueous film-forming foam (AFFF). Biosparging is a common remediation technology that injects oxygen into the saturated zone to encourage aerobic biodegradation, thereby altering aquifer redox conditions and potentially facilitating the biotransformation of polyfluorinated substances. Between 136 and 280 pore volumes of nitrogen-sparged or oxygen-sparged artificial groundwater amended with toluene were pumped through four saturated, AFFF-impacted soil columns to assess impacts on PFAS release and transformation. Column effluents and soils were analyzed for PFASs by high-resolution mass spectrometry. Significantly higher concentrations of five PFASs eluted from O₂-sparged columns compared to N₂-sparged columns shortly after sparging was initiated. The mass fractions eluted of many zwitterionic, sulfonamide-based PFASs were higher in both sets of columns than unaltered, non-biostimulated columns. Mass balance calculations suggested the transformation of sulfonamide-based precursors to perfluorinated sulfonamides (i.e., perfluorohexanesulfonamide) in oxygen- and nitrogen-sparged columns: recoveries of perfluorinated sulfonamides were 158-235% for C3-C6 homologs but recoveries of several prominent sulfonamide-based zwitterions were low. For example, the recovery of n-carboxyethyldimethyl-ammoniopropyl perfluorohexanesulfonamide was 9-13%. These results suggest biosparging can enhance the transformation and release of PFASs in saturated soils, which has important implications for site characterization and remediation.

Systematic Study on the Removal of Per- and Polyfluoroalkyl Substances from Contaminated Groundwater Using Metal-Organic Frameworks

Harmful per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in aquatic environments, but their remediation remains challenging. Metal-organic frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFAS, but little is known about the fundamentals of the PFAS@MOF adsorption process. To address this knowledge gap, we evaluated the performance of 3 different MOFs for the removal of 8 PFAS classes from aqueous film-forming foam-impacted groundwater samples obtained from 11 U.S. Air Force installations. Due to their different pore sizes/shapes and the identity of metal node, MOFs NU-1000, UiO-66, and ZIF-8 were selected to investigate the role of MOF structures, PFAS properties, and water matrix on the PFAS@MOF adsorption process. We observed that PFAS@MOF adsorption is (i) dominated by electrostatic and acid-base interactions for anionic and non-ionic PFAS, respectively, (ii) preferred for long- over short-chain PFAS, (iii) strongly dependent on the nature of PFAS head group functionality, and (iv) compromised in the presence of ionic and neutral co-contaminants by competing for ion-exchange sites and PFAS binding. With this study, we elucidate the PFAS@MOF adsorption mechanism from complex water sources to guide the design of more efficient MOFs for the treatment of PFAS-contaminated water bodies.

The occurrence of per- and polyfluoroalkyl substances (PFASs) in fluoropolymer raw materials and products made in China

Perfluorooctanoic acid (PFOA), its salts, and related compounds were listed as new persistent organic pollutants by the Stockholm Convention in 2019. In this study, the occurrence of residues of PFOA and other per- and polyfluoroalkyl substances (PFASs) in raw materials and fluoropolymer products from the Chinese fluoropolymer industries are reported for the first time. The PFOA concentrations in raw materials and fluoropolymer products were in the range of 6.7 to 1.1 × 10⁶ ng/g, and <MDL (method detection limit) to 5.3 × 10³ ng/g, respectively. Generally, the levels of PFOA in raw materials were higher than in products, implying that PFOA in the emulsion/dispersion resin could be partly removed during the polymerization or post-processing steps. By tracking a company's polytetrafluoroethylene (PTFE) production line, it was found that over a 5 year period, the residual levels of PFOA in emulsion samples declined from 1.1 × 10⁶ to 28.4 ng/g, indicating that the contamination of PFOA in fluoropolymer products from production source gradually decreased after its use had been discontinued. High concentrations of HFPO-TrA (2.7 × 10⁵ to 8.2 × 10⁵ ng/g) were detected in some emulsion samples indicating this alternative has been widely applied in fluoropolymer manufacturing in China.

Electrochemical adsorption of perfluorooctanoic acid on a novel reduced graphene oxide aerogel loaded with Cu nanoparticles and fluorine

Perfluorooctanoic acid (PFOA) is widely concerned because its serious toxicity to the environment and ecosystems. In order to effectively and conveniently remove PFOA from aqueous solutions, reduced graphene oxide aerogel modified by Cu nanoparticles and fluorine (Cu/F-rGA) was prepared by the microbubble template method as an electrode in electrosorption. The removal capacity of Cu/F-rGA electrode to PFOA was 489% and 45.9% higher at + 0.8 V than that of open circuit and unmodified electrode, respectively. These significant improvements can be attributed to the advantages of Cu/F-rGA in ligand exchange reaction and electrostatic attraction under voltage assistance. The regeneration of Cu/F-rGA electrode maintained 75.51% capacity after 10 times electrosorption-desorption by applying reverse voltage. These properties provided potential for the reuse and application of Cu/F-rGA electrode. The electrosorption isotherm and model results showed that PFOA tended to be parallel to the adsorption site at low temperature and perpendicular at high temperature. The number of PFOA molecules connected to each adsorption site was 0.72-1.76, and the number of adsorption layers of PFOA on the electrode was between 1.46 and 2.87. Findings from this study provide a green and effective strategy to remove PFOA from aqueous solutions with low energy consumption.

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Dagang Oilfield: Multimedia distribution and contributions of unknown precursors

A systematic survey was conducted on twenty-six per- and polyfluoroalkyl substances (PFASs) in fifty-one paired samples of surface water, sediment, and soil from Dagang Oilfield, Tianjin, China. Perfluorooctanoic acid, perfluorooctane sulfonic acid, p-perfluorous nonenoxybenzenesulfonate (OBS), and 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) were ubiquitous in the oilfield with field log K_d of 1.3-2.2, indicating a high partition potential from surface water to sediment. Total petroleum hydrocarbons (TPH) are a predictor for PFAS contamination at oilfield. The concentrations of OBS and 6:2 FTAB were higher in surface water and sediment with elevated TPH level. With total oxidizable precursor assay, unknown precursors for C2-C3 perfluoroalkyl carboxylic acids (PFCAs) (57-99 mol%) contributed more than those for C4-C12 PFCAs in the three mediums. The unknown C4-, C6-, and C8-based precursors tended to be precursors for perfluoroalkyl sulfonates at the oilfield, and C8 fluorotelomer-based precursors particularly occurred in the surface water. The concentrations of C4- and C8-based precursors were found positively correlated with TPH levels (r = 0.67-0.72, p < 0.05), while C6 precursors may also come from other sources. Further studies are necessary to clarify the mass balance and risk assessment for unknown PFASs.

Fate and transport of per- and polyfluoroalkyl substances (PFASs) in the vadose zone

Per- and polyfluoroalkyl substances (PFASs) are a heterogeneous group of persistent organic pollutants that have been detected in various environmental compartments around the globe. Emerging research has revealed the preferential accumulation of PFASs in shallow soil horizons, particularly at sites impacted by firefighting activities, agricultural applications, and atmospheric deposition. Once in the vadose zone, PFASs can sorb to soil, accumulate at interfaces, become volatilized, be taken up in biota, or leach to the underlying aquifer. At the same time, polyfluorinated precursor species may transform into highly recalcitrant perfluoroalkyl acids, changing their chemical identity and thus transport behavior along the way. In this review, we critically discuss the current state of the knowledge and aim to interconnect the complex processes that control the fate and transport of PFASs in the vadose zone. Furthermore, we identify key challenges and future research needs. Consequently, this review may serve as an interdisciplinary guide for the risk assessment and management of PFAS-contaminated sites.

Stability of Nitrogen-Containing Polyfluoroalkyl Substances in Aerobic Soils

Zwitterionic per- and polyfluoroalkyl substances (PFASs) used in aqueous film-forming foams (AFFFs) could face diverse environmental fates once released at military bases, airports, fire-training areas, and accidental release sites. Here, we studied for the first time the transformation potential of four electrochemical fluorination (ECF)-based PFAS zwitterions (two carboxyl betaines and two tertiary amines) in aerobic soils. The two perfluoroalkyl sulfonamide derivatives were precursors to perfluorooctanesulfonate (PFOS), while the amide derivatives were precursors to perfluorooctane carboxylate (PFOA). These zwitterions and four other previously reported zwitterions or cations were compared for their transformation pathways and kinetics. Structural differences, especially the nitrogen head groups, largely influenced the persistence of these compounds in aerobic soils. The perfluoroalkyl sulfonamide-based compounds showed higher microbial stability than the corresponding perfluoroalkyl amide-based ones. Their stability in aerobic soils is ranked based on the magnitude of DT₅₀ (time for 50% of substance to disappear): quaternary ammonium ≈ carboxyl betaine ≫ tertiary amine > amine oxide. The PFASs containing quaternary ammonium or betaine groups showed high stability in soils, with the longest DT₅₀ likely to be years or decades, while those with tertiary amine or amine oxide groups showed DT₅₀ of weeks or months. These eight ECF-based precursors provide insights into the degradation pathways and persistence in surface soils of other perfluoroalkyl cations and zwitterions present in AFFFs.

Sequestration and potential release of PFAS from spent engineered sorbents

Per- and poly-fluoroalkyl substances (PFAS) have contaminated land and water at numerous sites worldwide that now require remediation. The most common approach for treating contaminated water currently relies on removal of PFAS by sorption. The spent sorbents loaded with PFAS can potentially be disposed of at landfills, provided the sorbed contaminants remain sequestered and certain risk criteria are met. Hence, it is essential that remediation sorbents (i) rapidly adsorb a large variety of PFAS under varying water chemistry conditions, and (ii) do not release the adsorbed PFAS in due course. This review aims at establishing the current state of knowledge about the potential release of PFAS that may occur during and after treatment. The scientific literature currently provides data for a very restricted range of long-chain PFAS. Our knowledge of the dynamics of PFAS adsorption processes on engineered sorbents is limited, and even less is known about their desorption processes. The sorption of PFAS can be strongly affected by changes in the solution pH, ionic strength and dissolved organic matter content, and the process is also subject to complex competition mechanisms in the presence of other PFAS as well as organic contaminants and inorganic salts. Several studies suggest that changes in one or several of these factors may trigger the release of PFAS from engineered sorbents. This phenomenon is more likely to occur for PFAS with shorter carbon chain lengths (<C8), at high pH and in the presence of other PFAS or other anionic sorbates. The release of PFAS from spent sorbent materials, stored or deposited under conditions that vary over time, is highly undesirable, as they can potentially become a secondary source of PFAS in the environment. Our analysis identifies a number of knowledge-gaps that should be urgently addressed in order to design sustainable remediation solutions, including an improved management of spent sorbent materials.

Copper Nanoparticle Loading and F Doping of Graphene Aerogel Enhance Its Adsorption of Aqueous Perfluorooctanoic Acid

Perfluorooctanoic acid (PFOA) persists in the environment for a long time due to its stable physical and chemical properties, and it is harmful to the environment and biological system. In order to effectively remove PFOA from aqueous solution, Cu nanoparticles and fluorine-modified graphene aerogel (Cu/F-rGA) were fabricated by the microbubble template method. Compared with unmodified aerogels (rGA), the adsorption rate of PFOA on Cu/F-rGA was enhanced 2.68-fold. These significant improvements were assumed to benefit from the ligand exchange reaction and hydrophobic and F-F interactions. The regeneration of Cu/F-rGA maintained 73.26% with ethanol as the desorption solvent after 10 times adsorption-desorption. The fitting results of the statistical physics model showed that PFOA tended to be parallel to the adsorption site at low temperature and perpendicular at high temperature. The number of PFOA molecules connected to each adsorption site was 0.53 to 1.41, and the number of adsorption layers of PFOA on the Cu/F-rGA was between 1.63 and 2.51. Compared with the response surface methodology and artificial neural network, an adaptive neuro-fuzzy inference system had more accurate analysis and prediction results. These results provide an effective and alternative strategy to remove PFOA from aqueous solution with environment-friendly consumption.

Exposure to per- and polyfluoroalkyl substances and premature skin aging

Per- and polyfluoroalkyl substances (PFASs) are a ubiquitous group of persistent chemicals distributed globally in the environment. Skin aging is a notorious process that is prematurely induced by the interaction between endogenous and exogenous factors, including exposure to environmental chemicals. The existing evidence suggests that skin absorption of PFASs through dermal contact may be an important route of exposure to these chemicals in humans. On the other hand, PFASs intake by other routes may lead to PFASs bioaccumulation in the skin via tissue bio-distribution. Additionally, the presence of PFASs in consumer and cosmetic products combined with their daily close contact with the skin could render humans readily susceptible to dermal absorption. Therefore, chronic low-dose dermal exposure to PFASs can occur in the human population, representing another important route of exposure to these chemicals. Studies indicate that PFASs can threaten skin health and contribute to premature skin aging. Initiation of inflammatory-oxidative cascades, induction of DNA damage such as telomere shortening, dysregulation of genes engaged in dermal barrier integrity and its functions, signaling of the mitogen activated protein kinase (MAPK) pathway, and last but not least the down-regulation of extracellular matrix (ECM) components are among the most likely mechanisms by which PFASs can contribute to premature skin aging.

A critical review of modeling Poly- and Perfluoroalkyl Substances (PFAS) in the soil-water environment

Due to their health effects and the recalcitrant nature of their CF bonds, Poly- and Perfluoroalkyl Substances (PFAS) are widely investigated for their distribution, remediation, and toxicology in ecosystems. However, very few studies have focused on modeling PFAS in the soil-water environment. In this review, we summarized the recent development in PFAS modeling for various chemical, physical, and biological processes, including sorption, volatilization, degradation, bioaccumulation, and transport. PFAS sorption is kinetic in nature with sorption equilibrium commonly quantified by either a linear, the Freundlich, or the Langmuir isotherms. Volatilization of PFAS depends on carbon chain length and ionization status and has been simulated by a two-layer diffusion process across the air water interface. First-order kinetics is commonly used for physical, chemical, and biological degradation processes. Uptake by plants and other biota can be passive and/or active. As surfactants, PFAS have a tendency to be sorbed or concentrated on air-water or non-aqueous phase liquid (NAPL)-water interfaces, where the same three isotherms for soil sorption are adopted. PFAS transport in the soil-water environment is simulated by solving the convection-dispersion equation (CDE) that is coupled to PFAS sorption, phase transfer, as well as physical, chemical, and biological transformations. As the physicochemical properties and concentration vary greatly among the potentially thousands of PFAS species in the environment, systematic efforts are needed to identify models and model parameters to simulate their fate, transport, and response to remediation techniques. Since many process formulations are empirical in nature, mechanistic approaches are needed to further the understanding of PFAS-soil-water-plant interactions so that the model parameters are less site dependent and more predictive in simulating PFAS remediation efficiency.

Structure Database and In Silico Spectral Library for Comprehensive Suspect Screening of Per- and Polyfluoroalkyl Substances (PFASs) in Environmental Media by High-resolution Mass Spectrometry

Per and polyfluoroalkyl substances (PFASs) are an important class of organic pollutants. Many diverse PFASs are used in commerce and most are not amenable to conventional targeted chemical analysis due to lack of reference standards. Therefore, methods for elucidating the chemical structure of previously unreported or unexpected PFASs in the environment rely extensively on high-resolution mass spectrometry (HRMS). High-throughput structure identification by HRMS is hindered by a lack of PFAS molecular databases and tandem mass spectral libraries. Here, we report a new approach for generating an environmentally relevant PFAS molecular database constructed from curated structure lists and biotic/abiotic in silico predicted transformation products. Further, we have generated a predicted tandem mass spectral library using computational mass spectrometry tools. Results demonstrate the utility of the generated database and approach for identifying PFASs in HRMS-enabled suspect- and nontarget screening studies.

Resolving unknown isomers of emerging per- and polyfluoroalkyl substances (PFASs) in environmental samples using COSMO-RS-derived retention factor and mass fragmentation patterns

Chromatographic retention factors (k) and mass spectral fragmentation patterns of per- and polyfluoroalkyl substances (PFASs) were determined using the optimized parameters in liquid chromatography with tandem high-resolution mass spectrometry (LC-HRMS) analysis. Characteristic fragment ions obtained at various collision energies (MS² fragmentation) were used to determine the structures of newly discovered (emerging) PFASs detected from industrial effluent and surface water samples. Moreover, COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) derived octanol-water partition coefficients (K_ow), along with mean isotropic polarizabilities calculated from Density Functional Theory (DFT), of known PFASs were plotted against their experimental k values (k_exp) to obtain a multivariable regression model that can be used to predict k values of unknown PFASs. The k values of different structural isomers of unknown PFASs were calculated and compared to k_exp. The predicted k value for the isomer that matches the MS² fragmentation observed was found to be within 4.2 % of k_exp. This study demonstrates the applicability of an approach that combines the observed MS² fragmentation patterns and k values, together with computationally-derived log K_ow and polarizabilities, in assigning the structures of unknown PFASs at environmentally relevant conditions when no reference standards are available.

Spatial Trends of Anionic, Zwitterionic, and Cationic PFASs at an AFFF-Impacted Site

Soil and groundwater from an aqueous film-forming foam (AFFF)-impacted site were sampled at high resolution (n = 105 for soil, n = 58 for groundwater) and analyzed for an extensive list of anionic, zwitterionic, and cationic poly- and perfluoroalkyl substances (PFASs). Spatial trends for perfluoroalkyl acids and many precursors enabled a better understanding of PFAS composition, transport, and transformation. All PFASs without analytical standards were semi-quantified. Summed PFAS and individual PFAS concentrations were often higher at depth than near the surface in soil and groundwater. Zwitterionic and cationic compounds composed a majority of the total PFAS mass (up to 97%) in firefighter training area (FTA) soil. Composition of PFAS class, chain length, and structural isomers changed with depth and distance from the FTA, suggesting in situ transformation and differential transport. The percentage of branched perfluorooctane sulfonate increased with depth, consistent with differential isomeric transport. However, linear perfluorooctanoic acid (PFOA) was enriched, suggesting fluorotelomer precursor transformation to linear PFOA. Perfluorohexane sulfonamide, a potential transformation product of sulfonamide-based PFASs, was present at high concentrations (maximum 448 ng/g in soil, 3.4 mg/L in groundwater). Precursor compounds may create long-term sources of perfluoroalkyl acids, although many pathways remain unknown; precursor analysis is critical for PFAS fate and transport understanding.

Endocrine disruption by PFAS: A major concern associated with legacy and replacement substances

Perand poly-fluorinated alkyl substances (PFAS) have been used for decades in a great variety of processes and products by virtue of their exceptional properties, versatility and chemical stability. Nevertheless, it is increasingly recognized that these substances can represent a serious hazard to human health and living organisms due to their persistence, long-range transport potential and tendency to accumulate in biota. For this reason, some efforts have been made across the EU to identify alternative molecules, with a shorter carbon chain and theoretically safer profile, that might replace the previous generation of legacy PFAS. Unfortunately, this strategy has not been entirely successful and serious concerns are still posed by PFAS in different human populations. Among others, an emerging aspect is represented by the adverse effects that both legacy and alternative PFAS can exert on the human endocrine system, with respect to vulnerable target subpopulations. In this review we will briefly summarize PFAS properties, uses and environmental fate, focusing on their effects on human reproductive capacity and fertility, body weight control and obesity as well as thyroid function.

Influences of Chemical Properties, Soil Properties, and Solution pH on Soil-Water Partitioning Coefficients of Per- and Polyfluoroalkyl Substances (PFASs)

The aim of this study was to assess the soil-water partitioning behavior of a wider range of per- and polyfluoroalkyl substances (PFASs) onto soils covering diverse soil properties. The PFASs studied include perfluoroalkyl carboxylates (PFCAs), perfluoroalkane sulfonates (PFSAs), fluorotelomer sulfonates (FTSs), nonionic perfluoroalkane sulfonamides (FASAs), cyclic PFAS (PFEtCHxS), per- and polyfluoroalkyl ether acids (GenX, ADONA, 9Cl-PF3ONS), and three aqueous film-forming foam (AFFF)-related zwitterionic PFASs (AmPr-FHxSA, TAmPr-FHxSA, 6:2 FTSA-PrB). Soil-water partitioning coefficients (log K_d values) of the PFASs ranged from less than zero to approximately three, were chain-length-dependent, and were significantly linearly related to molecular weight (MW) for PFASs with MW > 350 g/mol (R² = 0.94, p < 0.0001). Across all soils, the K_d values of all short-chain PFASs (≤5 -CF2- moieties) were similar and varied less (<0.5 log units) compared to long-chain PFASs (>0.5 to 1.5  log units) and zwitterions AmPr- and TAmPr-FHxSA (∼1.5 to 2 log units). Multiple soil properties described sorption of PFASs better than any single property. The effects of soil properties on sorption were different for anionic, nonionic, and zwitterionic PFASs. Solution pH could change both PFAS speciation and soil chemistry affecting surface complexation and electrostatic processes. The K_d values of all PFASs increased when solution pH decreased from approximately eight to three. Short-chain PFASs were less sensitive to solution pH than long-chain PFASs. The results indicate the complex interactions of PFASs with soil surfaces and the need to consider both PFAS type and soil properties to describe mobility in the environment.

Enhancement of auxiliary agent for washing efficiency of diesel contaminated soil with surfactants

We used five types of surfactants assisted with sodium salts, including sodium tartrate (ST), sodium chloride (SC), and humic acid sodium (HAS) as auxiliary agents for soil washing to remove diesel from contaminated soil. Decontamination enhancement of diesel polluted soil washing with biosurfactant and H₂O₂ was examined, which showed higher effectiveness for newly contaminated soil. An increase in temperature and sodium salt addition exhibited a profound enhancement in diesel removal from aged contaminated soils. Compared to ST and SC, HAS exhibited a higher removal efficiency with saponin washing for aged diesel contaminated soil by lowering surface tension, shifting zeta potential, and increasing the number of micelles. Phytotoxicity experiments showed no significant inhibition of germination of lettuce, arugula, and cucumber with 0.2 g L^-1 saponin incubation. Conversely, there was a promotion on the root extension of lettuce and cucumber except for arugula. Similarly, the addition of 2% HAS (wight of saponin) improved on root growth of lettuce, arugula, and cucumber, increasing by 25%, 5%, and 22% at the period of 14 d, respectively. Because of excellent removal efficiency and non-toxicity, enhanced wash with saponin and HAS might be considered in the future design of full-scale remediation processes of diesel contaminated soil.

Accumulation of six PFAS compounds by woody and herbaceous plants: potential for phytoextraction

Per and polyfluoroalkyl substances (PFAS) consist of a large group of compounds used to make products more resistant to stains, grease, and water and for fire suppression. They have been widely detected in the environment and exposure has been linked to adverse human health effects. Phytoremediation could be used to remediate PFAS-impacted sites, but there is little information on herbaceous and woody plant species uptake of PFAS compounds from soil. A greenhouse study evaluated the potential for eight herbaceous and seven woody plant species to absorb PFAS compounds. Six PFAS compounds: PFPeA, PFHxA, PFOA, PFBS, PFHxS, and PFOS were added weekly to irrigation water, and the plants grown for up to 14 weeks after an initial establishment period. Significant accumulation of all PFAS compounds occurred in at least one plant species. Mass recovery in above-ground tissue by the best performing plant ranged from a low of 3.8% for PFOS by Festuca rubra to a high of 42% for PFPeA by Schedonorus arundinaceus. Hyperaccumulation, defined as tissue/soil concentrations >10/1, was observed for all six PFAS compounds in at least one plant species. These results demonstrate the potential use of phytoremediation as a tool for remediating PFAS-contaminated sites.

Remediation of perfluorooctanoic acid (PFOA) polluted soil using pulsed corona discharge plasma

Perfluorooctanoic acid (PFOA) from contaminated soil accumulates in higher organisms, and causes health risks to humans. In this research, 71 % of the PFOA was degraded, of which 51 % was decomposed into short chain by-products, 19 % mineralized, and 1 % volatilized with 30 kV of voltage, 50 Hz of discharge frequency, 1 % of soil moisture, 300 ppm of PFOA concentration and 6.3 of soil pH using pulsed positive discharge plasma. From a series of experiments, electrons were identified as the dominant active means of PFOA degradation. The decomposition by-products were analyzed by LC-MS. The results indicated that PFOA was decomposed into small by-products including perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutyric acid (PFBA), pentafluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA). Moreover, in plasma treated soil, the concentration of ammonia nitrogen increased from less than 10 ppm-462 ppm, and the average dry weight of lettuce was 1.6 mg higher than that in natural soil. Additionally, Planctomycetes and Nitrospirae increased after treatment, indicating that plasma technology promotes the process of nitrogen cycle. Thus, PFOA polluted soil could be remediated using this pulse corona plasma technology, and simultaneously improve the fertility of soil without chemical injections.

Effect of competition between petroleum-degrading bacteria and indigenous compost microorganisms on the efficiency of petroleum sludge bioremediation: Field application of mineral-based culture in the composting process

The effect of competition between isolated petroleum-degrading bacteria (PDB) and indigenous compost microorganisms (ICM) on the efficiency of composting process in bioremediation of petroleum waste sludge (PWS) was investigated. After isolating two native PDB (Acinetobacter radioresistens strain KA5 and Enterobacter hormaechei strain KA6) from PWS, their ability for growth and crude oil degradation was examined in the mineral-based culture (MBC). Then, the PDB isolate were inoculated into the composting experiments and operated for 12 weeks. The results showed that the PDB degraded 21.65-68.73% of crude oil (1-5%) in the MBC after 7 days. The PDB removed 84.30% of total petroleum hydrocarbon (TPHs) in the composting bioreactor containing the initial TPH level of 20 g kg^-1. Removal of petroleum hydrocarbons (PHCs) in the composting experiments proceeded according to the first-order kinetics. The computed values of degradation rate constants and half-lives showed a better performance of the PDB than ICM for TPHs removal. This finding suggests that simultaneous application of the PDB and ICM in the composting reactors resulted in a decline in the effectiveness of the PDB which is due to competition between them. The study also verified that the capability of PDB in degrading PHCs can be successfully scaled-up from MBC to composting process.

Bioaccumulation of Zwitterionic Polyfluoroalkyl Substances in Earthworms Exposed to Aqueous Film-Forming Foam Impacted Soils

Critical knowledge gaps remain regarding the fate and effects of zwitterionic, cationic, and anionic perfluoroalkyl and polyfluoroalkyl substances (PFASs), including assessment of their bioaccumulation potential. Here, biota soil accumulation factors (BSAFs) were assessed in earthworms (Eisenia fetida) exposed to soil microcosms amended with zwitterionic fluorotelomers and anionic perfluoroalkyl acids. The 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) bioaccumulated in earthworms [BSAF ∼ 2.5-5.4 (g_dw,worm/g_dw,soil)^-1] but to a lesser extent than perfluorooctane sulfonate (PFOS: BSAF ∼ 21-29). The BSAF of perfluorocarboxylates increased from ∼2.0 for C₄-C₆ analogues to ∼92 for perfluorotridecanoate (C₁₃). In earthworms exposed to Ansulite and Arctic Foam aqueous film-forming foams (AFFFs), the BSAF was related to perfluorinated chain length for n:3 fluorotelomer betaines (FtBs), n:1:2 FtB, and n:2 FTAB. Earthworms were also collected in situ from a fire-equipment testing site at a major Canadian airport. Summed PFAS concentrations were between 65 000 and 830 000 ng g^-1 wet weight, possibly the highest burden recorded in terrestrial biota. Fluorotelomer sulfonates (6:2 FTS, 8:2 FTS, and 10:2 FTS) and FtB were particularly prevalent. Field worms also displayed elevated concentrations of n:3 acids (n = 3-11), but not those from laboratory microcosms exposed to fluorotelomer-based AFFFs. The findings provide an important confirmation to recent data suggesting that fluorotelomer compounds may accumulate in invertebrate species with limited metabolization.

Perfluoroalkyl substances in the riverine and coastal water of the Beibu Gulf, South China: Spatiotemporal distribution and source identification

Few studies have examined the perfluoroalkyl substances (PFASs) contamination in less-developed coastal regions. In the present study, we collected 19 riverine and 21 coastal surface water samples in the summer and winter of 2017 to investigate PFASs contamination in the Beibu Gulf, South China. The results show that eleven and twelve target PFASs were detected in the summer and winter, respectively. The total PFASs (ΣPFASs) concentrations in the water of the Beibu Gulf were in the range of 1609-4727 pg/L and 610-4920 pg/L in summer and winter, respectively. Perfluoropentanoic acid (PFPeA), perfluorobutanoic acid (PFBA) and perfluorobutane sulfonate (PFBS) were the predominantly detected PFASs in both seasons with maximum concentrations of 2968 pg/L, 1771 pg/L, and 1764 pg/L, respectively. Strong positive correlations between some PFASs were observed (e.g., PFBA and PFBS, PFOS and PFBS, p < 0.05), suggesting these correlated pollutants may share similar sources. PFASs contamination in the Beibu Gulf was strongly affected by ocean currents, and their concentrations were lower than most coastal waters around the world. Risk assessment indicates a low risk associated with target PFASs to aquatic organisms in the Beibu Gulf. The results of the present research provided a baseline and good overview of the spatial distribution of PFASs along the Beibu Gulf.