Characterizing the long-term occurrence and anthropogenic drivers of per- and polyfluoroalkyl substances in surface water of the Rhine River

Uncovering the effects of the North Pacific Subtropical Gyre on per- and polyfluoroalkyl substances distribution in the Tropical Western Pacific

The accumulation of per- and polyfluoroalkyl substances (PFAS) in subtropical gyres, commonly referred to as "garbage patches", remains insufficiently characterized. In this study, we collected surface seawater samples from 40 sites across the Tropical Western Pacific (TWP) and identified 19 different PFAS. Of them, perfluoro-n-butanoic acid (PFBA) exhibits the highest concentration (median 329.2 pg/L). The concentration of ΣPFAS in nearshore region (median 910.5 pg/L) is higher than those in two other oceanic regions (with medians of 773.8 pg/L in Philippine Sea and 863.1 pg/L in Equatorial Current, respectively). However, in North Pacific Subtropical Gyre (NPSG), the ΣPFAS concentration (median 1056.5 pg/L) is higher than that in the nearshore region and significantly higher than in North Equatorial Current (NEC) (p < 0.05) and the composition and concentrations of PFAS in this region significantly differ from those in other oceanic regions (p < 0.05). Additionally, PFBA, an alternative perfluoroalkyl carboxylic acid (PFCA), is significantly enriched in the NPSG (p < 0.05). These suggest that alternative PFAS have now become the main PFAS pollutants in the surface waters of TWP, with PFOA and its alternatives making up the majority. Enrichment of PFCA is observed in the surface seawater of NPSG, with enrichment factors influenced by chain length and human activities. This study provides the first comprehensive analysis of the distribution and migration characteristics of PFAS in TWP, emphasizing the influence of subtropical gyre on PFAS accumulation.

Unveiling PFAS hazard in European surface waters using an interpretable machine-learning model

Per- and polyfluoroalkyl substances (PFAS), commonly known as "forever chemicals", are ubiquitous in surface waters and potentially threaten human health and ecosystems. Despite extensive monitoring efforts, PFAS risk in European surface waters remain poorly understood, as performing PFAS analyses in all surface waters is remarkably challenging. This study developed two machine-learning models to generate the first maps depicting the concentration levels and ecological risks of PFAS in continuous surface waters across 44 European countries, at a 2-km spatial resolution. We estimated that nearly eight thousand individuals were affected by surface waters with PFAS concentrations exceeding the European Drinking Water guideline of 100 ng/L. The prediction maps identified surface waters with high ecological risk and PFAS concentration (>100 ng/L), primarily in Germany, the Netherlands, Portugal, Spain, and Finland. Furthermore, we quantified the distance to the nearest PFAS point sources as the most critical factor (14%-19%) influencing the concentrations and ecological risks of PFAS. Importantly, we determined a threshold distance (4.1-4.9 km) from PFAS point sources, below which PFAS hazards in surface waters could be elevated. Our findings advance the understanding of spatial PFAS pollution in European surface waters and provide a guideline threshold to inform targeted regulatory measures aimed at mitigating PFAS hazards.

PFAS removal from reverse osmosis and nanofiltration brine by granular activated carbon: Thermodynamic insights into salinity effects

We explored an underexplored area in water treatment by examining the removal of per- and polyfluoroalkyl substances (PFAS) from reverse osmosis/nanofiltration (RO/NF) brine. We first compared multiple RO/NF membranes, revealing that DK and NF270 showed sub-optimal removal (<90 %) of C4-C8 PFAS, SW30 had low flux (<15 L/m2/h at 8 bar), and NFX exhibited significant adsorption of perfluorosulfonic acids (e.g., 8 µmol/m2). To address the PFAS-enriched brine generated from membrane treatment, we further evaluated activated carbon (GAC) and anion-exchange (AIX) resin, both of which efficiently removed moderate- and long-chain PFAS from brine. Although AIX outperformed GAC, the ion exchange contribution was small for short-chain PFAS like perfluorobutanoic acid (PFBA, C4) but increased with chain length, driven by the hydrophobic effect facilitating the migration to near-surface regions of resins. Equilibrium batch experiments and thermodynamic modeling revealed a disproportionate salinity impact on PFAS adsorption by GAC, with short-chain PFAS (e.g., PFBA) experiencing more pronounced adsorption reduction than longer-chained homologs as NaCl concentrations increased. This reduction was driven by a significant change in a free energy component unrelated to the hydrophobic or electrostatic interactions, likely due to the competitive adsorption of Cl- ions and short-chain PFAS anions or the formation of hydration shells around Na+ and Cl- ions, obstructing the pathways for weakly hydrophobic PFAS (e.g., PFBA) within the GAC pore network. The salting-out effect was found to be unimportant. This study provides new insights into salinity-dependent sorptive removal of PFAS from high-ionic-strength water such as RO/NF brine.

Combination of suspect and nontarget screening with exposure assessment for per- and polyfluoroalkyl substance prioritization in Chinese municipal wastewater

Municipal wastewater treatment plants (WWTPs) are significant sources of per- and polyfluoroalkyl substances (PFASs) in aquatic environments, making their identification and priority rank crucial for risk control. Wastewater samples were collected from 148 municipal WWTPs in China to determine the occurrence and risk prioritization of PFASs. A total of 61 PFASs were identified, including 14 legacy and 47 emerging PFASs, using machine learning prediction-enhanced suspect and nontarget screening techniques. PFASs were detected in all wastewater samples, with perfluorocarboxylic acid (PFCA), perfluorosulfonic acid (PFSA), fluoromeric sulfonic acid (FTSA), and perfluoroalkyl sulfonamide-like (PFSM) substances being the predominant classes. The exposure loads of legacy and emerging PFASs to the Chinese population were 71.8 and 52.9 μg·day-1·people-1, respectively, and textile and clothing products might be the primary PFAS exposure pathways. Through a risk prioritization method integrating toxicity and exposure data, ten legacy and five emerging PFASs were flagged as high-priority substances requiring additional attention. As the PFAS risk removal efficiency by conventional biological treatment processes was only 0.7 %, the PFAS risk priority patterns in influent and effluent were similar (r = 0.86, p < 0.01). In addition, there were significant regional differences in the PFAS risk distribution, and the PFAS risk in eastern China was higher than that in other regions. This study offers novel insights for the identification and priority control assessment of PFASs and other emerging environmental contaminants.

Occurrence, risk assessment and source apportionment of perfluoroalkyl acids in the river of a hill-plain intersection region: The impacts of land use and river network structure

Studying the impacts of land use and river network structure on perfluoroalkyl acids (PFAAs) footprint in rivers is crucial for predicting the fate of PFAAs in aquatic environments. This study investigated the distribution, ecological risks, sources and influence factors of 17 PFAAs in water and sediments of rivers from hills to plain areas. The results showed that the detection frequencies were higher for short-chain PFAAs than long-chain PFAAs in water, whereas an opposite pattern was found in sediments. The concentration of ∑PFAAs ranged from 59.2 to 414 ng/L in water and from 1.4 to 60.1 ng/g in sediments. Perfluorohexanoic acid and perfluorooctanoic acid were identified as the main pollutants in the river. The average concentrations of PFAAs were higher in the aquaculture areas (water: 309.8 ng/L; sediments: 43.27 ng/g) than in residential areas (water: 206.03 ng/L; sediments: 11.7 ng/g) and farmland areas (water: 123.12 ng/L; sediments: 9.4 ng/g). Environmental risk assessment showed that PFAAs were mainly low risk or no risk in water, but were moderate risk and even high risk in sediments, especially for perfluorooctane sulfonate. Source apportionment found that PFAA sources were mostly from industry, wastewater discharge, and surface runoff. Dissolved oxygen, chemical oxygen demand, water system circularity, network connectivity and organic matter were significantly correlated to PFAA concentration, indicating that the physicochemical properties and river network might directly influence the environmental behavior of PFAAs. The built-up area was positively correlated with PFAAs. These findings indicated that a comprehensive understanding of the influences of land use and river network structure on PFAAs in rivers is essential for managers to formulate effective PFAA control strategies.

Effect of physicochemical parameters on the occurrence of per- and polyfluoroalkyl substances (PFAS) in aquatic environment

Perfluoroalkyl substances (PFAS) and their distribution in aquatic environments have been studied extensively, but more information is needed to link these occurrences to their physicochemical characteristics. Understanding how these parameters influence PFAS can help predict their fate, mobility, and occurrences in water. This study reviewed the influence of physicochemical parameters on the occurrences of PFAS in aquatic environment using the relevant keywords to retrieve articles from databases spanning mostly between 2017 and 2024. The result suggests that high pH, turbidity, and dissolved oxygen, give high concentration of PFAS, while high electrical conductivity, temperature and salinity give low PFAS concentration in the water. Therefore, monitoring and safeguarding the aquatic bodies for human and environmental safety is imperative. Future studies should include the effects of the physicochemical properties on PFAS occurrences in the natural environment and focus on an organism's distinctive characteristics to comprehend the bioaccumulation and biomagnification of PFAS in them and environmental matrices.

Anthropogenic impacts on polycyclic aromatic hydrocarbons in surface water: Evidence from the COVID-19 lockdown

The lockdown restrictions against coronavirus disease 2019 (COVID-19) have led to unprecedented reductions in global anthropogenic activities. Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic combustion-induced pollutants, but the influence of anthropogenic responses to COVID-19 on PAH contamination remains largely unknown. Here we quantified the impacts of lockdown restrictions on 16PAH pollution based on the data in concentrations dissolved in the water phase and absorbed on the suspended particulate matter (SPM) in the Elbe River from 2015 to 2021 and determined the changes in source contributions classified by individual years and stations. Results show that the annual average PAH concentrations in water and SPM were determined as 0.055 μg·L-1 and 3.77 mg·kg-1 from 2015 to 2021, respectively. Pronounced declines in PAH on SPM (up to -18 %) were observed during the three lockdowns in Germany from 2020 to 2021. However, dramatic rebounds of anthropogenic activities during the removal of the lockdown led to increases (up to 29 %) in ∑16PAH concentrations compared to the same period in previous years. Through the source apportionment method, vehicle and coal emissions were the two most predominant sources of PAHs in the river. Vehicle contribution decreased during the lockdown, while coal emissions increased by 5 %. Health risks for three age groups were assessed as potential low risk and decreased by 18 % from 1.54 × 10-4 in 2015 to 1.27 × 10-4 in 2019, and rebounded to 1.40 × 10-4 in 2020-2021. The findings of this study highlight the strong consistency between PAH concentrations and anthropogenic intensity, implying that source control from improved cleaner production is an effective pathway for mitigating PAH contamination in the aquatic environment.

Unveiling the intricate connection between per- and polyfluoroalkyl substances and prostate hyperplasia

The presence of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in various everyday products has raised concerns about their potential impact on prostate health. This study aimed to investigate the effects of different types of PFAS on prostate health, including PFDeA, PFOA, PFOS, PFHxS, and PFNA. To assess the relationship between PFAS exposure and prostate injury, machine learning algorithms were employed to analyze prostate-specific antigen (PSA) metrics. The analysis revealed a linear and positive dose-dependent association between PFOS and the ratio of free PSA to total PSA (f/tPSA). Non-linear dose-response relationships were observed between the other four types of PFAS and the f/tPSA ratio. Additionally, the analysis showed a positive association between the mixture of PFAS and prostate hyperplasia, with PFNA having the highest impact followed by PFOS. These findings suggest that elevated serum levels of PFDeA, PFOA, PFOS, and PFNA are linked to prostate hyperplasia. Therefore, this study utilized advanced machine learning techniques to uncover potential hazardous effects of PFAS exposure on prostate health, specifically the positive association between PFAS and prostate hyperplasia.

Evaluation and prediction of anthropogenic impacts on long-term multimedia fate and health risks of PFOS and PFOA in the Elbe River Basin

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have aroused great concern owing to their widespread occurrence and toxic effects. However, their long-term trends and multimedia fate remain largely unknown. Here, we investigate the spatiotemporal characteristics and periodic oscillations of PFOS and PFOA in the Elbe River between 2010 and 2021. Anthropogenic emission inventories and multimedia fugacity model were developed to analyse their historical and future transport fates and quantify related human risks in each medium for the three age groups. The results show that average PFOS and PFOA concentrations in the Elbe River were 4.08 and 3.41 ng/L, declining at the annual rate of 7.36% and 4.98% during the study period, respectively. Periodic oscillations of their concentrations and mass fluxes were most pronounced at 40-60 and 20-40 months. The multimedia fugacity model revealed that higher concentrations occurred in fish (PFOS: 14.29, PFOA: 0.40 ng/g), while the soil was their dominant sink (PFOS: 179, PFOA: 95 tons). The exchange flux between water and sediment was the dominant pathway in multimedia transportation (397 kg/year). Although PFOS and PFOA concentrations are projected to decrease by 22.41% and 50.08%, respectively, from 2021 to 2050, the hazard quotient of PFOS in fish is a low hazard. This study provides information for the assessment of PFOS and PFOA pollution in global watersheds and the development of related mitigation policies, such as banning fish predation in polluted rivers, to mitigate their risks.

Occurrence, bioaccumulation, fate, and risk assessment of emerging pollutants in aquatic environments: A review

Significant concerns on a global scale have been raised in response to the potential adverse impacts of emerging pollutants (EPs) on aquatic creatures. We have carefully reviewed relevant research over the past 10 years. The study focuses on five typical EPs: pharmaceuticals and personal care products (PPCPs), per- and polyfluoroalkyl substances (PFASs), drinking water disinfection byproducts (DBPs), brominated flame retardants (BFRs), and microplastics (MPs). The presence of EPs in the global aquatic environment is source-dependent, with wastewater treatment plants being the main source of EPs. Multiple studies have consistently shown that the final destination of most EPs in the water environment is sludge and sediment. Simultaneously, a number of EPs, such as PFASs, MPs, and BFRs, have long-term environmental transport potential. Some EPs exhibit notable tendencies towards bioaccumulation and biomagnification, while others pose challenges in terms of their degradation within both biological and abiotic treatment processes. The results showed that, in most cases, the ecological risk of EPs in aquatic environments was low, possibly due to potential dilution and degradation. Future research topics should include adding EPs detection items for the aquatic environment, combining pollution, and updating prediction models.