Long-chain Perfluoroalkyl Carboxylic Acids Research Articles

Long-chain perfluoroalkyl carboxylic acids removal by biochar: Experimental study and uncertainty based data-driven predictive model

Long-chain perfluoroalkyl carboxylic acids removal by biochar: Experimental study and uncertainty based data-driven predictive model

A 20-year study reveal decrease in per- and polyfluoroalkyl substances (PFAS) in a pelagic seabird from the Western Mediterranean Sea

Despite the first ban on perfluorooctane sulfonic acid (PFOS) in 2009, it remains unclear whether Europe, a key regulator, has effectively reduced per- and polyfluoroalkyl substances (PFAS) in the environment over the past 20 years. This study investigates the levels and temporal trends of 19 PFAS compounds in the livers of 62 Scopoli's shearwaters (Calonectris diomedea) collected from the Mediterranean basin during 2003–2022. Over the past two decades, PFAS concentrations showed an overall significant decrease of 77%. PFOS was the most frequently and predominantly detected chemical in livers, closely followed by perfluorotridecanoic acid (PFTrDA) and perfluoroundecanoic acid (PFUnDA). However, the contribution of PFTrDA (32.4%) surpassed that of PFOS (30.3%) in 2009–2014, which can be attributed to its increased use as a substitute following the regulation on PFOS in 2009. Perfluoroalkyl carboxylic acids (PFCAs), along with PFOS, showed a general decline over the study periods, with the largest decrease occurring after 2015, corresponding to the regulations on PFCAs. An odd-numbered, long-chain PFCAs accumulation trend was observed in samples. Principal component analysis showed a shift from PFOS to PFCAs in Scopoli's shearwater PFAS patterns over 20 years. Our results offer valuable insights into the environmental behavior of PFAS, the complex interactions between regulations and compounds and their transfer to the marine ecosystems. Despite widespread declines, their persistent detection underscores the need for enhanced international cooperation efforts to comprehensively mitigate PFAS emissions, including those from developing regions and unregulated sources.

Occurrence characteristics, source analysis and ecological risk of PFASs in different cultivated soil at an urban scale in Yangtze River Basin

Per- and polyfluorinated substances (PFASs) contaminates the arable soil through multiple paths, and poses a threat to both farmland ecosystems and human health. In this study, the potential sources and distribution characteristics of 12 legacy PFASs in the soil and rivers for irrigation purposes were investigated in farmland systems, and the risks posed by PFASs to earthworm and aquatic organisms were also assessed. Based on field investigations in Yangtze River Basin, we found long-chain perfluoroalkyl carboxylic acids (PFCAs) were the major contaminants in arable soil and rivers for irrigation purposes, with PFOA (Perfluorooctanoic acid) being the most dominant monomer. Concentration levels of PFASs in arable soil were strongly related to land use types, the average concentration of PFASs (341.18 ± 600.19 ng/g) in the paddy fields was 100-fold higher than that of dry fields (3.79 ± 4.11 ng/g). Source apportionment revealed that PFASs detected in paddy fields were mainly associated with industrial effluents, domestic sewage, and irrigation water. In rivers for irrigation purposes, higher PFASs contamination were primarily distributed in industrial areas, such as plastic processing, paper, textile and electronics factories. The PFASs in the irrigation river water posed a low-medium risk to daphnia and fish, while the PFASs (PFOA and perfluorododecanoic acid (PFDoDA)) in soil posed a medium-high risk to earthworms. These results provided insights that sewage irrigation caused serious pollution of PFASs in the agricultural environment, should be paid more attention.

Exposure to per- and polyfluoroalkyl substances, neonicotinoid insecticides, benzotriazoles and benzothiazoles: Associations with human non-alcoholic fatty liver disease

Evidence of the joint association between exposure to multiple environmental chemicals and non-alcoholic fatty liver disease (NAFLD) is scarce. In this study, 281 participants from Zhuhai, China (138 patients with NAFLD vs. 143 healthy participants) were recruited to explore the associations of 40 per- and polyfluoroalkyl substances (PFAS), 11 neonicotinoid insecticides (NEOs), and 8 benzotriazoles (BTRs) and benzothiazoles (BTHs) with the risk of NAFLD. Perfluorooctane sulfonate (PFOS) and its emerging alternatives (6:2 chlorinated polyfluorinated ether sulfonate [6:2 Cl-PFESA] and 8:2 fluorotelomer sulfonic acid [8:2 FTSA]), NEO metabolites (m-NEOs), BTR, and BTH were the predominant PFAS, NEOs, BTRs and BTHs, respectively. The total median concentrations of PFAS (20.4 ng/mL vs. 7.16 ng/mL) and NEOs (7.24 ng/mL vs. 6.23 ng/mL) in NAFLD group were significantly higher than those in healthy group. Sex differences in PFAS exposure have been observed among patients with NAFLD. 8:2 FTSA and short-chain PFAS were more predominant in female patients with NAFLD, whereas other emerging (i.e., 6:2 and 8:2 Cl-PFESA) and legacy PFAS (i.e., PFOS and long-chain perfluoroalkyl carboxylic acids) easily accumulated in male patients with NAFLD. The results of the multiple linear regression analysis indicated a significant positive association between PFOS and alanine transaminase (ALT) in serum samples from patients with NAFLD (β = 23.2, 95% confidence intervals (CI): 7.82, 38.5). Conversely, negative correlations were observed between 5-hydroxy-imidacloprid (5-OH-IMI) and γ-glutamyl transpeptidase (GGT) (β = −2.73, 95% CI: −5.29, −0.18), as well as between tolyltriazole (TTR) and total bilirubin (TBIL) (β = −0.70, 95% CI: −1.33, −0.08) and direct bilirubin (DBIL) (β = −0.59, 95% CI: −0.98, −0.20). The Bayesian kernel machine regression model revealed a positive joint effect of exposure to PFAS and NEO on elevated NAFLD outcomes, suggesting that exposure to PFAS and NEO might exacerbate the severity of NAFLD. This study fills the knowledge gap between multi-pollutant exposure and NAFLD risk.

Long-term removal of perfluoroalkyl substances via activated carbon process for general advanced treatment purposes

Granular or powdered activated carbon (GAC/PAC) processes are installed in full-scale drinking water treatment plants (DWTPs) to reduce disinfection byproduct precursors, odor, ammonia, and pesticides. This study investigated the ability of GAC/PAC processes in 23 DWTPs to remove per- and polyfluoroalkyl substances (PFASs). In the GAC process, filter breakthrough of perfluoroalkyl carboxylic acids (PFCAs) occurred faster as the PFCA chain length is decreased. During periods of high water temperatures (20−29 °C), the effluent concentration of two short-chain PFCAs (C4 and C5) surpassed that of the influent after the throughput reached 5,000−7,500 bed volumes (equivalent to 2−3 months) due to desorption. However, such desorption was not observed during periods of low water temperatures (5−19 °C). Meanwhile, long-chain PFCAs were consistently removed, as the GAC was replaced before breakthrough became noticeable. PFAS removal deteriorated at a remarkably fast rate after a partial breakthrough of several tens of percent. Biological activated carbon was proved ineffective in removing PFASs due to its diminished adsorption capacity after long-term use. The PAC process, however, exhibited a slight decrease in PFCA residual (10%) at higher water temperatures (15−30 °C). The PAC dose required for a certain residual ratio was lower with an increase in the hydrophobicity of PFAS; C8-PFCA only required 20 mg/L of PAC for 50% removal, while C4-PFCA required a significantly higher dose of 100−700 mg/L. Consequently, the activated carbon process, which removes organic contaminants in surface water, was inadequate in removing PFASs, particularly those with short chains. Thus, it is recommended that GAC filters be replaced more frequently (within two months) for short-chain PFAS removal. Further, the adsorption performance of PAC must be enhanced.

Identification of key features relating to the coexistence mechanisms of trace elements and per- and polyfluoroalkyl substances (PFASs) in marine mammals

Organic and inorganic substances coexist in the livers of marine mammals and may correlate with one another; however, their coexistence mechanisms and relevant key features remain largely unknown. In this study, temporal variations (2011–2021) in the concentrations of nine trace elements and 19 per- and polyfluoroalkyl substances (PFASs) in the livers of Indo-Pacific humpback dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) were investigated. Interannual Cd in dolphins increased significantly whereas Pb concentrations decreased over the past decade (p < 0.05). Interannual levels of seven and four PFASs in dolphins and porpoises decreased significantly with time (p < 0.05). By further extending the timescale to 1993–2021, the sensitivity of trace elements to annual change further increased, whereas the sensitivity of PFASs remained relatively stable. Cu levels, similar to the majority of PFASs, were negatively correlated with the body length of the studied cetaceans, which led to positive correlations of Cu with six long-chain perfluoroalkyl carboxylic acids, perfluorodecane sulfonic acid, and perfluoroethylcyclohexane sulfonic acid. The concentrations of trace elements in the cetacean liver were closely correlated with cetacean sex, species, and body length, whereas PFAS concentration was responsive to time-related features such as stranded season and year. By further employing a machine learning method, we demonstrated that body length and a time-related factor (year) played a crucial role in predicting the concentrations of certain trace elements and PFASs, respectively, particularly Cu and perfluoroheptanoic acid.

Evidence of large-scale deposition of airborne emissions of per- and polyfluoroalkyl substances (PFASs) near a fluoropolymer production plant in an urban area

Airborne emissions of per- and polyfluoroalkyl substances (PFASs) from fluoropolymer manufacturing facilities—especially those producing polyvinylidene (PVDF)—have rarely been investigated. Once PFASs are released into the air from the facility stacks, they settle in the surrounding environment, contaminating all surfaces. Human beings living in close proximity to these facilities can be exposed through air inhalation and ingestion of contaminated vegetables, drinking water or dust. In this study, we collected nine surface soil and five outdoor settled dust samples within 200 m of the fence line of a PVDF and fluoroelastomer production site near Lyon (France). Samples were collected in an urban area including a sports field. High concentrations of long-chain perfluoroalkyl carboxylic acids (PFCAs) (C ≥ 9) were found at sampling points downwind of the facility. Perfluoroundecanoic acid (PFUnDA) was the predominant PFAS in surface soil (12–245 ng/g dw), whereas perfluorotridecanoic acid (PFTrDA) was in outdoor dust (<0.5–59 ng/g dw). The PFAS profiles observed in soil and dust samples very likely originate from the processing aids used for PVDF and fluoroelastomer production. To our knowledge, long-chain PFCA concentrations as high as reported herein have never been found outside the perimeter fencing of a fluoropolymer plant. PFAS concentrations in other environmental compartments (such as air, vegetables or groundwater) should be monitored to assess all potential pathways to exposure of nearby residents before carrying out human biomonitoring.

Occurrence and Bioaccumulation Patterns of Per- and Polyfluoroalkyl Substances (PFAS) in the Marine Environment.

Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic compounds used in commercial applications, household products, and industrial processes. The concern around the environmental persistence, bioaccumulation and toxicity of this vast contaminant class continues to rise. We conducted a review of the scientific literature to compare patterns of PFAS bioaccumulation in marine organisms and identify compounds of potential concern. PFAS occurrence data in seawater, sediments, and several marine taxa was analyzed from studies published between the years 2000 and 2020. Taxonomic and tissue-specific differences indicated elevated levels in protein-rich tissues and in air-breathing organisms compared to those that respire in water. Long-chain perfluoroalkyl carboxylic acids, particularly perfluoroundecanoic acid, were detected at high concentrations across several taxa and across temporal studies indicating their persistence and bioaccumulative potential. Perfluorooctanesulfonic acid was elevated in various tissue types across taxa. Precursors and replacement PFAS were detected in several marine organisms. Identification of these trends across habitats and taxa can be applied towards biomonitoring efforts, determination of high-risk taxa, and criteria development. This review also highlights challenges related to PFAS biomonitoring including (i) effects of environmental and biological variables, (ii) evaluation of protein binding sites and affinities, and (iii) biotransformation of precursors.

PFAS levels in fish species in the Po River (Italy): New generation PFAS, fish ecological traits and parasitism in the foreground

Per- and polyfluoroalkyl substances (PFAS) are resistant to breakdown and are now considered ubiquitous and concerning contaminants. Although scientific and legislative interest in these compounds has greatly increased in recent decades, our knowledge about their environmental fate and their effects on organisms is still incomplete, especially those of the new generation PFAS. In this study, we analysed the level of PFAS contamination in the fish fauna of the Po River, the most important waterway in Italy, to evaluate the influence of different factors (such as fish ecological traits and parasitism) on the accumulation of 17 PFAS. After solvent extraction and purification, hepatic or intestinal tissues from forty specimens of bleak, channel catfish, and barbel were analysed by liquid chromatography coupled with mass spectrometry (LOQ = 2.5 ng/g w.w.). The prevalent PFAS were perfluorooctane sulfonate (PFOS), present in all samples at the highest concentration (reaching a maximum of 126.4 ng/g and 114.4 ng/g in bleak and channel catfish, respectively), and long-chain perfluoroalkyl carboxylic acids (PFDA and PFUnDA). Perfluorooctanoic acid and new generation PFAS (Gen X and C6O4) were not detected. Comparison of the hepatic contamination between the benthic channel catfish and the pelagic bleak showed similar concentrations of PFOS (p > 0.05) but significantly higher concentrations of other individual PFAS and of the sum of all measured PFAS (p < 0.05) in bleak. No correlation was found between the hepatic level of PFAS and fish size in channel catfish.For the first time, PFAS partitioning in a parasite-fish system was studied: intestinal acanthocephalans accumulated PFOS at lower levels than the intestinal tissue of their host (barbel), in contrast to what has been reported for other pollutants (e.g., metals). The infection state did not significantly alter the level of PFAS accumulation in fish, and acanthocephalans do not appear to be a good bioindicator of PFAS pollution.

Phytoscreening for Per- and Polyfluoroalkyl Substances at a Contaminated Site in Germany.

The aim of this study was to perform a phytoscreening of per- and polyfluoroalkyl substances (PFAS) at a contaminated site in Germany, to investigate the applicability of this technique for PFAS contaminations. Foliage of three species, namely, white willow (Salix alba L.), black poplar (Populus nigra L.), and black alder (Alnus glutinosa L.), were sampled to evaluate seasonal and annual variations in PFAS concentrations. The results of the phytoscreening clearly indicated species and specific differences, with the highest PFAS sum concentrations ∑23 observed in October for white willow (0-1800 μg kg-1), followed by black poplar (6.7-32 μg kg-1) and black alder (0-13 μg kg-1). The bulk substances in leaves were highly mobile short-chain perfluoroalkyl carboxylic acids (PFCAs). In contrast, the PFAS composition in soil was dominated by long-chain PFCAs, perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA), as a result of the lower mobility with ∑23PFAS ranging between 0.18 and 26 μg L-1 (eluate) and between 66 and 420 μg kg-1 (solid). However, the PFAS composition in groundwater was comparable to the spectrum observed in leaves. Spatial interpolations of PFAS in groundwater and foliage correspond well and demonstrate the successful application of phytoscreening to detect and delineate the impact of the studied PFAS on groundwater.

Vital Environmental Sources for Multitudinous Fluorinated Chemicals: New Evidence from Industrial Byproducts in Multienvironmental Matrices in a Fluorochemical Manufactory.

Direct emissions from fluorochemical manufactory are an important source of per- and polyfluoroalkyl substances (PFASs) to the environment. In this study, a wide range of PFASs, including 8 legacy PFASs, 8 long-chain perfluoroalkyl carboxylic acids (PFCAs), and 40 emerging PFASs, were investigated through a target screening in multienvironmental matrices from a fluorochemical manufactory in China. Indoor dust was the most polluted matrix, wherein 52 PFASs were detected, and the median concentration of long-chain PFCA was 276 ng/g. A high level of short-chain PFAS in total suspended particles (median concentration = 416 ng/m3) and the effluent in the manufactory (Σ48PFAS = 212 μg/L) will undoubtedly increase the burden on the surrounding environment. Twenty-four industrial byproducts were ascertained to be generated during the electrochemical fluorination (ECF) process, and eight fluorinated alternatives were considered to be produced during product development. Twelve PFASs were quantified for the first time in the working environments. Perfluoropropane sulfonic acid, perfluoro (2-ethoxyethane) sulfonic acid (PFEESA), and 2-perfluorohexyl ethanoic acid are abundant fluorinated alternatives, with median levels of 1187-17204 ng/g in the dust. Significant positive correlations between ECF-related PFAS products and byproducts indicate that the detected values are strongly connected with the industrial source. Hierarchical cluster analysis further manifests their affiliation. Our findings raise the need for further investigations of emerging PFAS (including the first report of PFAS, such as PFEESA, in the environment) which may be released during the production process in the fluorochemical manufactories.

Effect of solution chemistry on the transport of short-chain and long-chain perfluoroalkyl carboxylic acids (PFCAs) in saturated porous media.

Perfluorocarboxylic acids (PFCAs) are one of the most widely detected classes of PFAS in the global environment after decades of intensive use. This study investigated the impact of perfluorinated carbon chain length on the transport behavior of PFCAs by testing and modeling two short-chain (PFPeA and PFHxA) and two long-chain PFCAs (PFOA and PFDA) in laboratory water-saturated columns. Moreover, their transport behavior was examined under different solution chemistry conditions, including pH, ionic strength, and cationic type. The experimental and simulation results indicated that the chain length had a limited impact on transport behaviors of PFPeA, PFHxA, and PFOA under various pH and ionic strengths, evidenced by their tracer-like breakthrough curves. In contrast, the mobility of PFDA was significantly affected by pH and ionic strengths. Additionally, the transport of all four PFCAs was inhabited in the presence of the divalent cation Ca2+. This study could help predict migration behavior and assess the potential risk of PFCAs in the subsurface system.

Pilot study comparison of regenerable and emerging single-use anion exchange resins for treatment of groundwater contaminated by per- and polyfluoroalkyl substances (PFASs)

This study reports the results of an 8-month pilot study comparing both regenerable and emerging single-use anion exchange resins (AERs) for treatment of per- and polyfluoroalkyl substances (PFASs) at a source zone impacted by historical use of aqueous film-forming foam (AFFF). Two regenerable (Purolite A860 and A520E) and three single-use (Purolite PFA694E, Calgon CalRes 2301, and Dowex PSR2+) AERs were tested in parallel, collecting effluent samples after treatment for 30-sec and 2-min total empty bed contact time (EBCT). Results demonstrate that single-use AERs significantly outperform regenerable resins, particularly for treatment of long-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs). No detectable concentrations of ≥C7 PFCAs or PFSAs were observed within 150,000 bed volumes (BVs) after treatment with the single-use resins (2-min EBCT). Analysis of effluent samples following 30-sec EBCT treatment shows that even the shortest-chain PFSAs do not reach 50% breakthrough within the first 350,000 BVs, though differences in removal of short-chain PFCAs was less dramatic. The regenerable polyacrylic A860 resin performed very poorly compared to all polystyrene resins, with >90% breakthrough of all PFASs occurring within 10,000 BVs. The greater affinity of polystyrene resins is attributed to increased hydrophobic interactions in addition to electrostatic ion exchange. Analysis of breakthrough profiles reveals empirical correlation with ion exchange affinity coefficients (logKex) measured in batch experiments. Postmortem analysis of PFASs extracted from spent resins revealed chromatographic elution behavior and competition among PFASs for adsorption to the resins. PFSAs and long-chain PFCAs were preferentially adsorbed to earlier sections in the AER columns, whereas short-chain PFCAs were competitively displaced towards the later sections of the columns and into the effluent, consistent with effluent concentrations of the latter structures exceeding influent values. These results provide insights into the mechanisms that govern PFAS adsorption to AERs in real multisolute groundwater matrices and support findings from other diverse sites regarding PFAS affinity, elution behavior, and competition for exchange sites.

Degradation and Plant Transfer Rates of Seven Fluorotelomer Precursors to Perfluoroalkyl Acids and F-53B in a Soil-Plant System with Maize (Zea mays L.).

Fluorotelomer precursors in soil constitute a reservoir for perfluoroalkyl acids (PFAAs) in the environment. In the present study, precursor degradation and transfer rates of seven fluorotelomer precursors and F-53B (chlorinated polyfluoroalkyl ether sulfonates) were investigated in pot experiments with maize plants (Zea mays L.). The degradation of fluorotelomer precursors to perfluoroalkyl carboxylic acids (PFCAs) and their uptake spectra corresponded to those of fluorotelomer alcohol (FTOH) in terms of the number of perfluorinated carbon atoms. Short-chain PFCAs were translocated into the shoots (in descending order perfluoropentanoic, perfluorobutanoic, and perfluorohexanoic acid), whereas long-chain PFCAs mainly remained in the soil. In particular, fluorotelomer phosphate diesters (diPAPs) were retained in the soil and showed the highest degradation potential including evidence of α-oxidative processes. F-53B did not degrade to PFAAs and its constituents were mainly detected in the roots with minor uptake into the shoots. The results demonstrate the important role of precursors as an entry pathway for PFCAs into the food chain.

Background per- and polyfluoroalkyl substances (PFAS) in laboratory fish diet: Implications for zebrafish toxicological studies

Current attention is focused on determining the potential for per- and polyfluoroalkyl substances (PFAS) to adversely impact human health. Zebrafish are a popular biological model because they share early development pathways with humans. A dietary exposure paradigm is growing in popularity in the zebrafish model because the outcomes often translate to humans. To create a diet of known composition, it is crucial to understand background PFAS levels present in zebrafish diet. Background PFAS, if present, potentially confounds interpretation of toxicological data. To date, no studies document the PFAS background levels in laboratory fish diet and there is only limited information on some pet foods. The objective of this study was to develop and validate an analytical method for up to 50 target PFAS in high lipid and protein content laboratory fish diets and pet foods. Long-chain perfluoroalkyl carboxylic acids (C9-C13) and perfluorooctane sulfonate (PFOS) were quantified in 11 out of 16 laboratory fish diets and in three out of five pet fish foods. Foods for pet birds, lizards, and dogs were below the limit of detection for all PFAS. In two of the laboratory fish diets, PFOS concentrations were >1.3 ng/g and the total PFAS for the three laboratory fish diets exceeded 1.0 ng/g. Hundreds of biomedical laboratories across the world utilize these commercial laboratory fish diets, and these results indicate that numerous zebrafish colonies may be inadvertently receiving significant dietary PFAS exposures. In light of this new information, it is critical to design PFAS studies with appropriate controls with measured background PFAS concentrations in the diet and to urge caution when interpreting the results.

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

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

Effect of Solution Chemistry on the Transport of Short-Chain and Long-Chain Perfluoroalkyl Carboxylic Acids (Pfcas) in Saturated Porous Media

Effect of Solution Chemistry on the Transport of Short-Chain and Long-Chain Perfluoroalkyl Carboxylic Acids (Pfcas) in Saturated Porous Media

Implication of cation-bridging interaction contribution to sorption of perfluoroalkyl carboxylic acids by soils

Sorption of four perfluoroalkyl carboxylic acids (PFCAs) including perfluoropentanoic acid, perfluoroheptanoic acid, perfluorodecanoic acid, and perfluorododecanoic acid by three soils with cation exchange sites occupied by K+, Ca2+, or Fe3+ was measured using the batch equilibration method. We hypothesize that partitioning in soil organic matters (SOM) is the primarily operative mechanism for PFCA sorption by K+-soils, and sorption by Ca2+- or Fe3+-soils could be enhanced via cation-bridging interaction. The measured sorption isotherms for all four PFCAs by soils were linear within the aqueous concentration between 0 and 60 μg/L, and the distribution coefficients ranged between 14.8 and 173 L/kg. Long-chain PFCAs manifested greater sorption by the soils with higher SOM content. Compared to sorption by K+-soils, sorption of PFCAs by Ca2+- and Fe3+-soils increased by 19.9–90.2% and 38.5–219%, respectively. The relative contributions of cation-bridging interaction to the overall PFCA sorption were estimated to be 16.6–48.7% for Ca2+-soils and 27.8–67.7% for Fe3+-soils. These results demonstrate that multivalent exchangeable cations could play an important role, yet previously ignored, in controlling sorption and transport of PFCAs in soils.

External and internal human exposure to PFOA and HFPOs around a mega fluorochemical industrial park, China: Differences and implications.

Hexafluoropropylene oxide dimer and trimer acids (HFPO-DA and HFPO-TA) are used as alternatives to legacy perfluorooctanoic acid (PFOA); however, little is known about their human exposure risks. In this study, the concentrations of PFOA and HFPO were measured in major human exposure matrices and human bio-samples of local residents near a mega fluorochemical industrial park in Shandong, China, to characterize their external and internal exposures. Although HFPO-DA was detected in drinking water and indoor dust, it exhibited a considerably low bioaccumulation potential in animal-origin food and human samples (urine, hair, and serum), implying that it might be a benign alternative to PFOA. Although the estimated daily intake (EDI) of HFPO-TA was comparable to that of PFOA, its concentration in urine was higher than that of PFOA, implying that it might be eliminated faster than PFOA. A simple one-compartment pharmacokinetic model was applied to estimate the serum concentrations of the target compounds and subsequently compare them with the measured concentrations. The predicted concentration of PFOA in serum based on its concentration in urine and half-life was close to the measured value, confirming the distinct internal exposure of PFOA in the local residents. However, the measured concentrations of HFPO in serum were considerably lower than those predicted from the external EDI and urine concentrations, implying that they were eliminated faster than expected in humans. Various perfluoroalkyl substances were detected in human hair, and their compositions were similar to those in human serum, suggesting that hair is a good non-invasive indicator for long-term exposure to legacy long-chain perfluoroalkyl carboxylic acids and HFPOs. This study provided valuable information about the human exposure to legacy PFOA and HFPOs in highly impacted areas near point sources and necessitates studies on the toxicokinetics of HFPOs.

Perfluoroalkyl substances in precipitation from the Tibetan Plateau during monsoon season: Concentrations, source regions and mass fluxes

Atmospheric wet deposition is an important process for the occurrence of perfluoroalkyl substances (PFASs) in polar/remote mountain regions; however, there are limited data on PFASs in precipitation from the Tibetan Plateau (TP). Precipitation (rain from May to October 2017) was therefore collected across the TP to investigate the concentrations, composition profiles, sources, and fluxes of perfluoroalkyl acids (PFAAs). The average ∑PFAA concentrations ranged from 212.3 pg L−1 to 547.7 pg L−1, and perfluoroalkyl carboxylic acids (PFCAs) accounted for 87% of the measured PFAAs (mean value). Significant positive associations (p < 0.05) were found for most PFCAs in the southeast TP, indicating that they may come from similar sources. The monthly PFAA deposition flux ranged from 12.6 to 68.9 ng m−2 month−1, decreasing from east to west. As climate of the eastern TP is controlled mainly by the Indian monsoon, indicating that the Indian monsoon plays an important role in delivering PFAAs to the TP. PCA (principal component analysis) combined with back-trajectory analysis was used to estimate the atmospheric transport pathways, and the PSCF (potential source contribution function) model was applied to define the potential source regions of individual PFAAs. The results suggested that northeast India, Bangladesh, and southern Nepal are the potential sources of C4–C7 PFCAs; C8–C10 PFCAs are more influenced by emissions from southern Nepal and Bhutan; while the source regions of long-chain PFCAs (C11–C12) can be attributed to northern India and Pakistan. Specifically, PFOS (perfluorooctane sulfonic acid) has a local contribution from the central TP.