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

Downward migration of per- and polyfluoroalkyl substances (PFAS) in lake sediments: Reconsideration of temporal trend analysis

Using sediment cores to reconstruct the contamination history of per- and polyfluoroalkyl substances (PFAS) is essential for chemical management but poses challenge. Herein, sediment cores, as well as surface water and sediments were taken from two Chinese lakes to investigate the vertical distribution and migration of PFAS. Wind wave, properties of sediment and water, and chemical characters of PFAS were examined to clarify the main factors influencing PFAS migration. Total PFAS concentrations in sediment cores ranged from 0.12 to 5.28 ng g-1 dry weight (dw) in Dianchi Lake and from 0.19 to 2.51 ng g-1 dw in Taihu Lake, respectively. Strong hydrodynamic disturbance (wind-wave erosion depth up to 30 cm) in Taihu Lake resulted in consistent PFAS levels and profiles throughout the sediment core, limiting its use for retrospective analysis. In Dianchi Lake, an increasing trend of total organic carbon-normalized PFAS indicated their persistent emission in China over the past decades. Perfluorooctane sulfonic acid increased markedly from early 2000s; temporal trend in composition for perfluorocarboxylates coincided with the global production transition. Finally, we proposed a three-step conceptual framework, including lake selection, key time point assessment, and contamination history reconstruction, to further improve the reliability of PFAS retrospective analysis in lake.

Perfluoroalkyl acids (PFAAs) and their precursors in sediments and adjacent riparian soils from the Three Gorges Reservoir, China: Contamination characteristics, source apportionment and ecological risks

Information on the occurrence and spatial distribution of perfluoroalkyl acids (PFAAs) and their precursors in sediments and adjacent riparian soils of Three Gorges Reservoir (TGR), which is one of the largest reservoirs in the world, is still limited. In this study, The total concentrations of these per- and polyfluoroalkyl substances (PFASs) ranged from 2220 to 19,300 pg/g in sediments and 298-9540 pg/g in soils. PFOA was the dominant PFAS in sediments and soils, accounting for 23.4% and 30.7% of the total median cocentrations of PFASs, respectively. PFAA precursors, such as 4:2 fluorotelomer sulfonate (4:2 FTS), 6:2 fluorotelomer sulfonate (6:2 FTS), and perfluorooctane sulfonamide (FOSA), were widely detected in sediments and soils. The distribution of PFASs exhibited distinct spatial variations and was more influenced by anthropogenic activities. Positive matrix factorization (PMF) identified fire-fighting foams (AFFF) and legacy fluoropolymer industry/textile treatment were the dominant sources in sediments (31.5%) and soils (30.8%), respectively. Finally, the ecological risk assessment showed that PFOS exhibited low to medium risks. Our findings indicate that the contamination of PFAA precursors must be considered when developing management measures to protect the TGR region.

Perfluoroalkyl substances (PFASs) in the major rivers of Korea: Distribution in the environment and bioaccumulation in crucian carp fish

The concentration of thirteen PFASs in water (n = 21), sediment (n = 21) and crucian carp fish muscle samples (n = 57) collected from three major rivers of Korea, including Namhan River, Yeongsan River and Nakdong River in June 2019 were determined to assess the potential risk of PFASs to aquatic life using bio-accumulation factor (BAF). The mean PFASs concentration in water (ng/L) were in order Nakdong River (69.63) > Yeongsan River (51.47) > Namhan River (13.30). The detection frequency rate of the long-chain PFASs, include PFHxA, PFOA and PFOS were high in river water samples. The PFASs in sediment samples were observed at low concentrations (<2 ng/g dw) in three rivers. The sediment/water partition coefficient (Kd) values of PFHpA were greatest in three rivers. The bioaccumulation factor (BAF) of PFHxA, PFUnDA and PFHpA were dominant in crucian carp fish samples. However, all the BAF levels for the carp samples were found to be <2000 (L/kg). Although the BAF values in crucian carp fish did not exceed the bioaccumulative level, several high long-chain PFASs concentrations were observed in water samples from surrounding hotspot sampling sites in Nakdong and Yeongsan River. Further study and monitoring of PFASs in various fish species and/or trophic level investigations are necessary to assess the impact of these pollutants on the river ecosystems.

Perfluoroalkane Sulfonamides and Derivatives, a Different Class of PFAS: Sorption and Microbial Biotransformation Insights

Perfluoroalkane sulfonamides and their derivatives (FASAs), an emerging subclass of per- and polyfluoroalkyl substances (PFAS), have attracted increasing attention due to their widespread applications, environmental persistence, and potential biological toxicity. Unlike perfluoroalkyl acids (PFAAs), FASAs can be transformed by microorganisms in the environment, producing fluorinated intermediates that eventually form stable PFAAs. A key difference of FASAs is that their pKas enable them to exist as neutral species or zwitterions, unlike all other PFAS subclasses, which are all anions. Sorption processes regulate the bioavailability of FASAs to microorganisms for transformation, driving the environmental transport and fate of FASAs. In this critical review, we provide a comprehensive overview of the classification, properties, and environmental fate of FASAs, with a focus on sorption and microbial transformation. We discuss recent advancements in understanding the sorption of FASAs onto soil, sediment, and microbial biomass, including key sorption descriptors and influencing factors. Additionally, we examine the microbial biotransformation of FASAs, detailing transformation pathways, key intermediates, transformation kinetics, and enzymes involved. Finally, we identify critical research gaps and propose future directions to advance the study of the sorption and biotransformation of FASAs in environmental systems. Mechanistic understanding of these processes is crucial for managing sites impacted with FASAs.

In situ occurrence and mobility of per and polyfluoroalkyl substances in soils amended with organic waste products

We evaluated the in situ occurrence and soil-water distribution of 75 anionic, zwitterionic, and cationic per- and polyfluoroalkyl substances (PFAS) in soils from five field experimental sites distributed in different climatic regions in France. Four sites received agronomical doses of organic waste products (OWPs, ∼5-10 t/ha per application) with repeated inputs between 1974 and 1996 (2 historical sites) and 1998-2018 (2 on-going sites), while one site received about two-fold larger amounts. Control soils without OWP application had detectable yet low PFAS levels, the Σ75PFAS remaining in most cases below 1 μg/kg. Soils amended with municipal sludge or urban composts exhibited the largest Σ75PFAS increase relative to controls (∼2-20 μg/kg), with soils receiving biowaste composts displaying the lowest Σ75PFAS (∼2 μg/kg). In most cases, Σ75PFAS increased significantly with time. While perfluorooctane sulfonate (PFOS) typically dominated the PFAS profiles in municipal sludge-amended soils, the other prevalent PFAS classes varied with sites and years: soils from older sites also had anionic and cationic electrochemical fluorination-derived precursors (e.g., EtFOSAA and PFOSAmS), while on-going sites had increased prevalence of short-chain perfluoroalkyl carboxylates (PFCAs) (3 sites) and perfluoroalkyl phosphinates (1 site). Interestingly, 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB), a major zwitterionic precursor found in French municipal sludge, was only detected at low levels in soils, indicating its transformation to degradation products. Leaching waters at a depth of 45 cm in the experimental plots had high levels of short-chain PFCAs (Mean C3-C5: 120-160 ng/L; Max C3-C5: 900-1600 ng/L), suggesting that land applied OWP containing PFCA precursors are important contributors to long-term groundwater contamination.

The response of PFAA mobility in highly contaminated sediment to sluice operation: Coupled effects of scour behavior and physicochemical properties

Despite their widespread occurrence and significant environmental implications, the influence of sluice operations on the mobility of perfluoroalkyl acid (PFAA) in riverine sediments remains largely unexplored. To address this gap, a series of flume experiments were conducted to simulate the sedimentary migration of PFAA under the turbulent conditions generated by opening a sluice. Our study provides novel insights into the mechanisms by which plunging turbulence modulates the transfer of sedimentary PFAAs across the sediment‒water interface. Significant transient release effects were observed in the dissolved and suspended particulate matter (SPM) phases of PFAA, with total concentrations maintaining relative stability over extended periods following disturbance. The fluviraption of plunging turbulence increased PFAA concentrations in the surface sedimentary and porewater phases but weakened the adsorption performance of resuspended particles for the chemicals in the lower reach of the sluice. The instantaneous release of PFAA from sediment, fueled by turbulence, was identified as the primary driver of total mass transfer across the interface, increasing exponentially with the Reynolds number (Rex, R2=0.99, p < 0.01). Notably, the peak PFAA release flux in the SPM phase lagged behind that in the dissolved phase, underscoring the dynamic interplay between phases. A structural equation model (SEM) revealed that plunging turbulence indirectly governs the cross-interface transfer of sedimentary PFAA by altering environmental physicochemical parameters and enhancing porewater diffusion. This finding underscores the complex, coupled effects of scour behavior and physicochemical properties on PFAA fate. Our study offers a unique perspective on the dynamic mechanisms underlying PFAA multimedia migration under sluice operation, contributing valuable insights for managing and regulating these emerging contaminants in aquatic environments.

Distribution patterns and influencing factors of PFAS in soils: A meta-analysis

Due to their high emission and persistence, per- and polyfluoroalkyl substances (PFAS) are ubiquitously distributed in the environment, with soil increasingly serving as a major medium for PFAS. Currently, research on the environmental distribution of PFAS primarily focuses on surface water and groundwater, while systematic global investigations into PFAS distribution in soil remain limited. In this study, we collected PFAS concentrations data from literatures published in 2006-2024 and Map of Forever Pollution in Europe. PFAS concentrations in global soil exhibited spatial heterogeneity (n.d. - 1838 ng/g), with relatively higher levels in Europe, the U.S., and Eastern China. For temporal trend, PFOA, PFHxS, and PFOS generally decreased in the time span of 2005-2019, but the declining trend was relatively sharper in the U.S. compared with China. The meta-analysis indicated that soil properties, including soil texture, organic carbon content, total nitrogen content, and pH, as well as socioeconomic levels such as GDP per capita, per capita consumption expenditure, population density, and industrial proportions, were key factors affecting the distribution of PFAS in soil. Emerging PFAS showed regional differences in detection frequencies, with HFPO-DA (63.84 %-100 %) and 6:2 Cl-PFESA (69.38 %-100 %) predominating in China, 6:2 FTAB (78 %) in the U.S, PreFOSs and PAPs (90 %-100 %) in Europe. This study provides information on the current status of PFAS pollution in soil and key factors affecting its regional distribution, which is beneficial for strengthening the investigation of PFAS soil pollution in areas with less research and developing control and management strategies for high pollution areas.

Analyzing the Release of Per- and Polyfluoroalkyl Substances from Spent Granular Activated Carbons by Standard Leaching Procedures

The recent national primary drinking water regulation for per- and polyfluoroalkyl substances (PFAS) is expected to drive a nationwide increase in granular activated carbon (GAC) usage in water treatment facilities across the United States. Proper management of PFAS-laden GAC waste streams is essential to prevent potential recontamination. This study systematically evaluates PFOA and PFOS leaching from four commercial GACs using three standard batch leaching procedures. Our findings indicate that PFOA leached 1-2 orders of magnitude more than PFOS across all GAC types and leaching procedures. In general, PFAS leaching was more notable for alkaline leaching conditions, especially for wood-based GAC. Additionally, real groundwater spiked with an 8 PFAS mixture was used to load GAC for leaching propensity demonstration, and similar conclusions were reached, where leaching was generally greater for shorter-chain and more hydrophilic PFAS. PFBA exhibited the highest leaching (10.4%), followed by GenX (0.91%) and PFBS (0.75%), while minimal desorption (<0.02%) was observed for long-chain PFOA, PFOS, PFOSA, and PFNA. The study concluded that a complex interplay of multiple interactions between the GAC surface, PFAS molecules, and constituents of leaching solutions controls leaching.

Per- and polyfluoroalkyl substances (PFAS) mass flux and mass balance at an aqueous film-forming foam release site in semiarid eastern New Mexico, USA

Passive flux meters (PFMs) directly measure groundwater chemistry mass flux and Darcy flux, providing insight into contaminant source-zone architecture and transport properties. This study uses PFMs to characterize PFAS flux in groundwater at a semiarid site with a thick (greater than 90-m) unsaturated zone where groundwater has been contaminated with per- and polyfluoroalkyl substances (PFAS) related to the use of aqueous film-forming foam (AFFF) for fire training and fire suppression. PFAS mass discharge (PFAS mass flux integrated over a control plane) in groundwater downgradient from several PFAS release areas is calculated using PFM results. In groundwater downgradient from fire-training areas, total PFAS mass discharge (summed across 14 compounds) was estimated to be between 6.0 and 31 g per day in 2020 and between 5.9 and 23 g per day in 2021. Site-specific documentation, generic information on AFFF properties, and literature values of PFAS concentration in AFFF are used to estimate site-specific PFAS-application rates at fire-training areas. These PFAS-application rates are compared to groundwater PFAS-discharge rates. Results suggest that transformation processes (exact pathways unknown) have led to increased discharge of measured PFAS in groundwater relative to initial AFFF formulations. The mass balance approach has broad applicability as a high-level approach that can provide insight into PFAS transport at AFFF sites.

PFAS removal via adsorption: A synergistic review on advances of experimental and computational approaches

Per- and polyfluoroalkyl substances (PFAS), commonly known as "forever chemicals", have become a major focus of current research due to their toxicity and persistence in the environment. These synthetic compounds are notoriously difficult to degrade, accumulating in water systems and posing long-term health and environmental risks. Adsorption is one of the most investigated technologies for PFAS removal. This review comprehensively reviewed the PFAS adsorption process, focusing not only on the adsorption itself, but also on the behavior of PFAS in the aquatic environment prior to adsorption because these behaviors directly affect PFAS adsorption. Significantly, this review summarized in detail the advances made in PFAS adsorption from the computational approach and emphasized the importance of integrated experimental and computational studies in gaining molecular-level understanding on the adsorption mechanisms of PFAS. Toward the end, the review identified several critical research gaps and suggested key interdisciplinary research needs for further advancing our understanding on PFAS adsorption.

Modeling PFAS Sorption in Soils Using Machine Learning

In this study, we introduce PFASorptionML, a novel machine learning (ML) tool developed to predict solid-liquid distribution coefficients (Kd) for per- and polyfluoroalkyl substances (PFAS) in soils. Leveraging a data set of 1,274 Kd entries for PFAS in soils and sediments, including compounds such as trifluoroacetate, cationic, and zwitterionic PFAS, and neutral fluorotelomer alcohols, the model incorporates PFAS-specific properties such as molecular weight, hydrophobicity, and pKa, alongside soil characteristics like pH, texture, organic carbon content, and cation exchange capacity. Sensitivity analysis reveals that molecular weight, hydrophobicity, and organic carbon content are the most significant factors influencing sorption behavior, while charge density and mineral soil fraction have comparatively minor effects. The model demonstrates high predictive performance, with RPD values exceeding 3.16 across validation data sets, outperforming existing tools in accuracy and scope. Notably, PFAS chain length and functional group variability significantly influence Kd, with longer chain lengths and higher hydrophobicity positively correlating with Kd. By integrating location-specific soil repository data, the model enables the generation of spatial Kd maps for selected PFAS species. These capabilities are implemented in the online platform PFASorptionML, providing researchers and practitioners with a valuable resource for conducting environmental risk assessments of PFAS contamination in soils.

Extractable Organofluorine Mass Balance Analysis of Aqueous Film-Forming Foam-Impacted Soils: Sample Pretreatment and a Combination of Target Analysis and Suspect Screening

The application of aqueous film-forming foams (AFFFs) has caused considerable per- and polyfluoroalkyl substances (PFAS) pollution in the environment. Soil serves as a long-term source of PFAS for the adjacent groundwater and surface water, but the lack of extractable organofluorine (EOF) mass balance data in the AFFF-impacted soils may lead to an underestimation of PFAS contamination. This study analyzed ten surface soil samples from three AFFF-impacted sites in Sweden, using alkaline extraction followed by acidic extraction. The alkaline and acidic fractions were subjected to further cleanup and analyzed separately for target, suspect screening, and EOF analysis to evaluate the extraction efficiencies of different PFAS in the soil samples and reveal PFAS remaining unknown in the AFFF-impacted soils. Total target PFAS concentrations ranged from 33.0 to 2.40 × 104 ng/g dry weight. Thirty-six PFAS were identified using suspect screening. Considerable amounts of zwitterionic and cationic PFAS (up to 58%) were identified in the acidic extraction fraction, while >95% of anionic PFAS were found in the alkaline extraction fraction. EOF mass balance analysis was conducted on AFFF-impacted soils for the first time. The high proportion of unexplained organofluorine (up to 65%) indicated the necessity for future investigation of the unknown PFAS in AFFF-impacted soils to comprehensively understand their fate and risk.

Manipulating Intrapore Energy Barriers in Graphene Oxide Nanochannels for Targeted Removal of Short-Chain PFAS

Removal of per- and polyfluoroalkyl substances (PFAS) from water has become a research topic of interest in recent times. However, it is very challenging to remove short-chain ( Collapse

Key Words

• asymmetrical nanochannels
• energy barriers
• graphene oxide membrane
• host−guest complexation
• nanofiltration
• short-chain PFAS
• β-cyclodextrin

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MESH Headings Collapse

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Affiliation(s)

Eubert Mahofa Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia
Sally El Meragawi Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia
Muhammed A Vilayatteri Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia
Swarit Dwivedi Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
Manas Ranjan Panda Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia
Petar Jovanović Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia
Adri C T van Duin Department of Mechanical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
Benny Freeman Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
Akshat Tanksale Department of Chemical and Biological Engineering, Monash University, Clayton, VIC 3800, Australia
Mainak Majumder Nanoscale Science and Engineering Laboratory (NSEL), Department of Mechanical and Aerospace Engineering, Monash University, 20 Research Way, Clayton, VIC 3800, Australia ARC Research Hub for Advanced Manufacturing of 2D Materials, Monash University, 20 Research Way, Clayton, VIC 3800, Australia

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Cumulative inhibitory effect of 6:2 chlorinated polyfluorooctane ether sulfonate in anaerobic digestion processes

Microbial anaerobic metabolism is crucial for biogeochemical cycles, impacting both natural and engineered ecosystems. However, the increasing emissions of 6:2 Cl-PFESA, an alternative to PFOS, pose significant risks. In this study, long-term high 6:2 Cl-PFESA concentration level of 10 µg/g TS exposure led to a substantial decrease in methane production from 204.8 ± 4.8 mL/g VS to 143.6 ± 3.5 mL/g VS, indicating a cumulative inhibitory effect on carbohydrate-related anaerobic digestion. Key processes such as polysaccharide release, hydrolysis, acetogenesis, and acetoclastic methanogenesis were contributed by 28.6 %, 9.3 %, 8.9 %, and 11.7 % of significant reduction, respectively, correlating with inhibition in relevant enzymatic activities and gene expressions. Hydrolytic bacteria such as Rectinema and Defluviitoga declined to 11.7 % from 14.3 % and 20.9 % from 23.9 %, reflecting decreased hydrolysis efficiency. Reduced transcription levels of acetogenesis- and acidogenesis-related genes further inhibited these processes. Conversely, methanogens Methanolinea and Methanothrix increased from 35.8 % to 55.7 % and 10.9-40.8 %, suggesting enzyme inhibition rather than methanogen abundance reduction. Additionally, 6:2 Cl-PFESA partially biotransformed into 6:2H-PFESA, facilitated by species like Dechloromonas, unclassified Xanthomonadales, and Betaproteobacteria. These findings confirm that the limited degradation and cumulative inhibitory effects of 6:2 Cl-PFESA during anaerobic digestion highlight its significant disruption to carbon cycling stability within ecosystems.

Sorption and mechanisms of legacy and emerging per- and polyfluoroalkyl substances (PFASs) on different particle size fractions of marine sediments

PFASs are ubiquitous in various environmental and biological media due to their extensive application and stability. However, the sorption of PFASs, especially emerging PFASs, on different particle size fractions of marine sediments remains unknown. Here, we investigated the sorption kinetics, isotherms, and mechanisms of six legacy and emerging PFASs on five different particle size fractions of marine sediments (F1 (69.4-190 μm), F2 (63.3-163 μm), F3 (5.25-72.6 μm), F4 (3.29-34.7 μm), and F5 (1.69-22.7 μm)). Our results indicated that the sorption kinetics and isotherms conformed well to the pseudo-second-order model and the Freundlich model, respectively, suggesting the nonlinear sorption of PFASs on marine sediments. The sorption capacities of PFASs decreased significantly with increasing sediment particle size from F5 to F1. Meanwhile, PFAS distribution coefficients (Kd) correlated positively with organic carbon content, specific surface area, and sediment pore volume. Kd values of PFOA and PFOS were 0.40-0.65 and 2.64-6.12 times higher than those of their substitutes, GenX and 6:2 FTSA. Hydrophobic interactions dominated PFAS sorption over electrostatic interactions. Overall, this study offers a comprehensive understanding of legacy and emerging PFAS distribution and mechanisms in marine sediments of varying particle sizes.

Implementation of Matrix-Matched Semiquantification of PFAS in AFFF-Contaminated Soil

This study presents a novel semiquantification approach for nontarget screening (NTS), combining matrix-matched calibration and ionization class-specific average calibration curves (ACCs) to address the lack of analytical reference standards for most per- and polyfluoroalkyl substances (PFAS). Ionization class-specific ACCs for carboxylic and sulfonic acids, sulfonamides, and cationic PFAS result in high accuracy, with median absolute accuracy quotients below 2.27×. The approach was applied to soil impacted by aqueous film-forming foam (AFFF) contamination. A total of 96 tentatively identified PFAS were semiquantified in addition to 28 quantified compounds based on available standards. Semiquantified concentrations exceeded those of target analytes, demonstrating the critical role of this method in capturing broader PFAS contamination. In this case, validation against extractable organofluorine (EOF) showed a 102% closed mass balance. The innovative approach not only enables comprehensive PFAS contamination assessment in complex matrices but also expands the scope of the NTS for environmental monitoring, remediation, and risk assessment of AFFF-contaminated sites.

Fate variations of Per- and polyfluoroalkyl substances in diverse aquatic environments: An overlooked influence of hydrodynamics

Per- and polyfluoroalkyl substances (PFASs) have become a significant global issue; nevertheless, information regarding the hydrodynamic effect on their catchment-scale fate remains lacking. Thus, this study investigated PFASs in water and paired sediment samples from diverse aquatic habitats within the Qinhuai River Basin (QRB), where high concentrations of PFASs are ubiquitous. Rarity score analysis reveals that PFASs were diffusely distributed across the QRB, yet specific sites were identified as emission hotspots. The sediment-water and suspended particulate matter-water partitioning coefficients of PFASs both exhibited significant correlations with chemical structures, ambient variables, land use, and flow velocity (p < 0.05). Flow velocity can promote the liberation of PFASs from particles into water, reducing their accumulation capacity; hence, the higher partitioning coefficients of PFASs were observed in relatively low-velocity aquatic systems, such as lakes, reservoirs, and ponds. A partial least-squares structural equation model was employed to further elucidate their effect pathways and magnitudes on partitioning coefficients. In addition, the primary sources of PFASs were identified, emphasizing their complexity. The ecological risks of PFASs were assessed, indicating priority PFAS species (long-chain PFCAs and HFPO-TA) for management and suggesting water as the preferable environmental medium for regulation. This is the first field investigation to quantify the significance of hydrodynamic influences on the catchment-scale fate of PFASs, improving our understanding of their distribution and behaviors from the perspective of environmental hydraulics.

Effect of coexisting Cd(Ⅱ) and As(V) on anionic PFASs sorption in soils: Models and mechanisms

An in-depth understanding of the sorption behaviors of per- and polyfluoroalkyl substances (PFASs) in soil is essential to assess their environmental risks accurately. Due to chemical industry production and waste treatment, co-contamination soil of heavy metals (HMs)-PFASs has become a public concern worldwide. This study investigated soil sorption behaviors of PFASs including perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and perfluorohexanesulfonic acid (PFHxS). A multiple linear regression (MLR) model was developed to predict the sorption of PFOS in soil. Validation results demonstrated that this model could effectively predict the distribution coefficients (Kd) of PFOS based on soil organic carbon (OC), silt, clay, and free Fe/Al-oxide contents, exhibiting a strong predictive ability (r2 = 0.942, p < 0.001). In six soils, HMs (Cd2+ and As5+) influence three anionic PFASs sorption primarily by altering the electrostatic and hydrophobic interactions between soil components and PFASs. The Kd values of PFOS tend to rise with increasing Cd2+ concentration but decline with increasing As5+ concentration. In contrast, HMs have a relatively minor influence on the sorption of PFOA and PFHxS. Moreover, a nonlinear model was constructed for the first time to quantify the impact of HMs on PFASs sorption. The model achieves exceptional prediction accuracy when applied to both experimental data from this study and literature data. A comprehensive understanding of PFASs sorption behavior in soil under conditions of coexisting HMs is of great significance for formulating targeted degradation and mitigation strategies for co-contaminated sites.

Mineralogical controls on PFAS and anthropogenic anions in subsurface soils and aquifers

Per- and polyfluoroalkyl substances (PFAS) migrate into the environment through various means, e.g., soil-amendment impurities and ambient atmospheric deposition, potentially resulting in vegetative uptake and migration to groundwater. Existing approaches for modeling sorption of PFAS commonly treat soil as an undifferentiated homogeneous medium, with distribution constants (e.g., Kd, Koc) generated empirically using surface soils. Considering the limited mineral variety expected in weathered geologic media, PFAS mobility can be better understood by accounting for predictable mineral assemblages that are ubiquitously distributed in US soils. Here we explore the role of minerals and electrostatic sorption in controlling PFAS mobility in subsurface settings at contaminated agricultural sites by measuring geochemical parameters and PFAS, and calculating pH-dependent mineral surface charges through full soil and aquifer columns. These data suggest subsurface mobility of short-chain PFAS largely is controlled by aluminum-oxide mineral(oid) electrostatic sorption, whereas long-chain PFAS mobility is controlled by organic matter and air-water interfacial area.

Understanding PFAS Behavior: Analysing Contamination Patterns in Surface Water and Sediment of the Apies River, South Africa

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants widely detected in water and sediment worldwide. Despite growing concerns about their ecological and health risks, their distribution in African aquatic environments remains understudied. This study addresses the knowledge gap in PFAS contamination by analysing the spatial and temporal distribution of 18 PFAS in Apies River water and sediment in Pretoria, South Africa. Surface water and sediment samples were collected upstream and downstream of the Apies River during dry seasons. The analysis of PFAS concentrations was conducted using liquid chromatography-tandem mass spectrometry. Statistical analysis, including paired t-tests, non-metric multidimensional scaling, and hierarchical cluster analysis, were applied to determine spatial and temporal trends. The study revealed significant spatial variations in PFAS contamination, with upstream locations consistently exhibiting higher concentrations than downstream. In surface water samples, L_PFBS, 4:2 FTS, 6:2 FTS, and L_PFHpS showed statistically significant differences (p < 0.05) between sites. Perfluorocarboxylic acids were the dominant PFAS class in surface water (50.47-57.15%), whereas perfluorosulfonic acids were more prevalent in sediments. Upstream sediment had higher L_PFHpS (43.00 ng/g), L_PFDS (38.89 ng/g), and L_PFHxS (23.91 ng/g) than downstream (31.96, 27.84, and 18.02 ng/g, respectively). The findings reveal contamination sources and partitioning between surface water and sediments, aiding in water quality management and pollution mitigation strategies.

Laboratory validation of a simplified model for estimating equilibrium PFAS mass leaching from unsaturated soils

Modelling per- and polyfluoroalkyl substance (PFAS) fate and transport in the vadose zone is inherently more complex than in the saturated zone due to the highly transient nature and the wetting phase saturation dependent hydraulic flux associated with the vadose zone. The chemical complexity of PFAS impart multiple partitioning processes which complicate the evaluation of PFAS transport in the vadose zone. To date, simplified screening models describing PFAS leaching have been developed to determine PFAS soil cleanup criteria in the vadose zone. Recent work has presented evidence that while PFAS transport in the vadose zone is governed by several non-equilibrium mechanisms, it is possible to predict PFAS mass flux using equilibrium modelling over month to year timescales. We hypothesized that by quantifying important equilibrium partitioning and hydraulic processes, we could simplify vadose zone leaching models for assessing mass flux from the vadose zone to the underlying groundwater. A mass flux, cell-based model which accounts for important partitioning processes (solid and air-water interfacial partitioning) and transience in hydraulic processes (water flux and water content) was developed and validated herein. Column studies were conducted under simulated rainfall conditions to provide transient hydraulic and PFAS leaching data. A HYDRUS 1-D with PFAS module model was calibrated to the hydraulic conditions of the simulated rainfall columns. Forward simulations were carried out using HYDRUS and the mass balance approximation models. The HYDRUS and mass balance approximations performed nearly identically for all PFAS, and both models predicted PFAS mass leaching within a half order of magnitude of most measured data. These results suggest that readily applicable empirical models and simplified numerical models can reasonably estimate month to year scale mass flux from the vadose zone for sites without major heterogeneity or transport non-ideality considerations.

Marine Transport Barrier for Traditional and Emerging Per- and Polyfluoroalkyl Substances in the Southeast Indian Ocean and Antarctic Marginal Seas

Traditional per- and polyfluoroalkyl substances (PFASs) have been observed in the remote Southern Ocean. In contrast, current knowledge about emerging PFASs, such as perfluoroether carboxylic acids (PFECAs), and their transport mechanisms remains ambiguous. In this study, the occurrence and transport of both traditional and emerging PFASs in the surface seawater of the Southeast Indian Ocean and Antarctic marginal seas are comprehensively discussed by integrating hydrological data. Long-chain PFASs were restricted to the north of the thermohaline front in the Southeast Indian Ocean, suggesting a transport barrier effect and the input of terrestrial contamination from low-latitude regions. Conversely, unexpectedly high levels of short-chain perfluorobutanoic acid (PFBA) were limited to the south of the Antarctic Circumpolar Current, preventing further northward transport. PFBA showed significant positive correlations with two emerging PFECAs, perfluoro-2-methoxyacetic acid (PFMOAA) and fluoro(heptafluoropropoxy)acetic acid (3:2 H-PFECA), which were also widely detected in Antarctic marginal seas for the first time. This suggests their similar sources and environmental behavior, as they were probably formerly accumulated in Antarctic snow through atmospheric deposition and released into seawater during the summertime melting process.

Using Suction Lysimeters for Determining the Potential of Per- and Polyfluoroalkyl Substances to Leach from Soil to Groundwater: A Review

In-situ porewater samples were proposed to best represent the fraction of perfluoroalkyl and polyfluoroalkyl substances (PFAS) with the potential to migrate to groundwater. While there are many techniques for collecting porewater samples, suction lysimeters are frequently being used for PFAS investigations. Suction lysimeters use vacuum to extract porewater from vadose zone soils, typically fine to medium sands, which retain and release enough porewater for analysis. Importantly, determining the rate of PFAS migration to groundwater requires an independent measure of water percolation. This review covers the installation and sampling methods for suction lysimeters and provides suggestions to improve the utility and reduce the variability of the results. Because the volume of soil represented by the porewater sample varies significantly depending on the soil-water content, which is spatially and temporally variable, many suction lysimeters may be required to accurately represent soil heterogeneity. A similar limitation applies to soil or leaching protocol samples. Suction lysimeters may not provide a representative sample for all PFAS due to interactions with lysimeter materials, air-water interfaces, and the use of vacuum. Consequently, lysimeter data are best applied in combination with soil-leaching protocols, groundwater transects, and soil analysis when making remedial decisions.

Unveiling the emerging concern of per- and polyfluoroalkyl substances (PFAS) and their potential impacts on estuarine ecosystems

Per- and polyfluoroalkyl substances (PFAS) have become ubiquitous chemicals that pose potentially serious threats to both human health and the integrity of the ecosystem. This review compiles current knowledge on PFAS contamination in estuaries, focusing on sources, abundance, distribution, fate, and toxic mechanisms. It also addresses the health risks associated with these compounds and identifies research gaps, offering recommendations for future studies. Estuaries are essential for maintaining biodiversity and serve as protective natural buffers against pollution flowing from land to sea. However, PFAS, known for their persistence and bioaccumulation potential, are detected in estuarine waters, sediments, and biota worldwide, with varying concentrations based on geographic locations and environmental matrices. Sources of PFAS in estuaries include routine items like nonstick kitchenware, industrial emissions, landfill sites, civilian and military airfields, and runoff from firefighting activities. The fate of PFAS in estuarine ecosystems is influenced by hydrology, biogeochemical interactions, and proximity to pollution sources.

Selective Quantification of Charged and Neutral Polyfluoroalkyl Substances Using the Total Oxidizable Precursor (TOP) Assay

Perfluoroalkyl acid (PFAA) precursors are a diverse subclass of per- and polyfluoroalkyl substances (PFASs) that can be transformed into PFAAs of public health concern. Unlike strongly acidic PFAAs, precursors can be anionic, cationic, neutral, or zwitterionic. Precursor charge affects the environmental fate, but existing quantification techniques struggle to ascertain the abundance of compounds within each charge group. To fill this gap, we developed and validated a solid-phase extraction procedure that separates precursors by charge and quantifies the sum of the precursors in each fraction with the total oxidizable precursor (TOP) assay. Method performance was demonstrated by spiking known concentrations of ten precursors into aqueous film-forming foam (AFFF)-impacted groundwater, municipal wastewater, and soil samples. Precursor fractionation and recovery were greater in groundwater and soil samples than in wastewater. Use of the method provided results that were consistent with expectations based on precursor transport properties. In surficial soils near an AFFF source zone, anionic precursors with five or fewer perfluorinated carbons accounted for about 95% of PFASs, but less than half of PFASs in the underlying groundwater. In municipal wastewater influent, the sum of precursors exceeded the sum of PFAAs and was approximately equally distributed among all charge fractions.

Quantification of PFAS in soils treated with biosolids in ten northeastern US farms

This study, one of the few conducted to date on working farms in the US, examined per- and polyfluoroalkyl substances (PFAS) contamination in 10 farms treated with biosolids using a paired control-treatment approach. Biosolids are nutrient-rich and inexpensive soil amendments, however, if the biosolids contain PFAS which are known to be toxic, mobile and to bioaccumulate, they can leave lasting negative impacts on farming soil and water. Our study showed significantly higher concentrations of PFAS in biosolids-treated (treatment) soils compared to (untreated) controls. Soil depth, soil physicochemical properties (e.g., organic matter and pH), and biosolids sources affected concentrations and types of PFAS in treated soils. While PFAS precursors were present in biosolids, they were absent in treated soils, likely due to biotransformation to terminal perfluoroalkyl products. The detection of shorter-chain PFAS in surface water highlights their greater mobility, raising concerns beyond the boundaries of the biosolids-treated farms.

Zwitterionic, cationic, and anionic PFAS in freshwater sediments from AFFF-impacted and non-impacted sites of Eastern Canada

Zwitterionic, cationic, and anionic per- and polyfluoroalkyl substances (PFAS) were investigated in freshwater sediments of Canada, including sites impacted by aqueous film-forming foams (AFFFs). The first step of the project involved optimizing the extraction method with equilibrated sediment-water-AFFF samples. The analytical method had acceptable linearity, accuracy, and precision in the sediment matrix, and was further validated with NIST SRM 1936. In the second step of the project, the method was applied to determine over 70 target PFAS in field-collected sediments (n = 102). At federal contaminated sites of Ontario, Newfoundland, and Québec (ditches and creeks at international airports with fire training or fire equipment testing areas), summed PFAS averaged 30 ng/g (maximum of 160 ng/g) with molecular patterns dominated by perfluorooctane sulfonate (maximum PFOS: 84 ng/g). Based on maximum observed concentrations >10 ng/g, other key PFAS at these AFFF-impacted sites included negative ion mode perfluorohexane sulfonate, perfluorohexane sulfonamide, fluorotelomer sulfonates (6:2 FTS and 8:2 FTS) and 5:3 fluorotelomer acid, and positive ion mode N-dimethylammoniopropyl perfluorohexane sulfonamide and 5:1:2 fluorotelomer betaine. In contrast, environmental sediment samples collected at a larger spatial scale (province-wide survey) were characterized by low ΣPFAS (generally <1 ng/g), with PFOS/PFOA below chronic toxicity thresholds for aquatic life.

Release of poly- and perfluoroalkyl substances from AFFF-impacted soils: Effects of water saturation in vadose zone soils

Soil samples collected from an aqueous film-forming foam (AFFF)-impacted sandy soil formation at two depth intervals above the water table were used in bench-scale column experiments to evaluate the release of poly- and perfluoroalkyl substances (PFASs) under different degrees of water saturation. Artificial rainwater was applied to the soils under constant and variably saturated conditions. Results from constant saturation experiments suggest that retention of PFAS mass at air-water interfaces was evident in the deep soil (foc < 0.00068 g/g), particularly for longer chain and zwitterionic compounds, while PFAS mass release from the shallow soil (foc = 0.0034 g/g) was consistent with kinetically controlled desorption from the soil. The release profiles for the perfluoroalkyl sulfonamides (FASAs) differed from other PFASs examined, with more FASAs generally being eluted under fully saturated conditions from both the shallow and deep soils. Importantly, variably saturated conditions resulted in more PFAS eluting from the soils: the average release rate of PFHxS from both soils was 10-fold higher under variably saturated conditions than under constant conditions. Both soils retained significant fractions of the total PFAS mass even after extensive flushing (51-83.8 % for PFOS). These results suggest that PFAS transport in vadose zone soils is influenced by air-water interfaces, but solid-phase desorption also plays a role. Overall, these results are consistent with observations in the field and serve to confirm key mechanisms that control PFAS leaching.

Advances in waste-derived functional materials for PFAS remediation

Per- and polyfluoroalkyl substances (PFAS) are synthetic organofluoride compounds, widely used in industries since the 1950s for their hydrophobic properties. PFAS contamination of soil and water poses significant environmental and public health risks due to their persistence, chemical stability, and resistance to degradation. The Chemical Abstracts Service catalogs approximately 4300 PFAS globally. Research in various regions such as North America, Asia, Europe, and remote polar zones has revealed the accumulation of perfluorooctane sulfonate (PFOS) in the tissues of various animal species, with concentrations reaching up to 1900 ng/g in aquatic species like dolphins and whales. Researchers have employed various remediation techniques such as solvent extraction, ion exchange, precipitation, adsorption, and membrane filtration, each of which has its drawbacks. Adsorption, particularly using waste-derived functional materials like biochar, is emerging as a promising method for PFAS remediation due to its cost-effectiveness and sustainability. For example, waste timber-derived biochar exhibits adsorption efficiency comparable to commercial activated carbon. This review highlights advancements in using agricultural, industrial, and biological waste-derived materials for sustainable PFAS remediation. We discuss innovative modification techniques like hydrothermal synthesis, pyrolysis, calcination, co-precipitation, the sol-gel method, and ball milling. The study also examines adsorption mechanisms, factors affecting adsorption efficiency, and the technological challenges in scaling up waste-derived material use. It aims to explore developments, challenges, and future directions for using these materials for efficient PFAS remediation and contributing to sustainable environmental cleanup solutions.

Toxicity of Per- and Polyfluoroalkyl Substances and Their Substitutes to Terrestrial and Aquatic Invertebrates-A Review

Per- and polyfluoroalkyl substances (PFASs) have been widely used in daily life but they cause certain impacts on the environment due to their unique carbon-fluorine chemical bonds that are difficult to degrade in the environment. Toxicological studies on PFASs and their alternatives have mainly focused on vertebrates, while terrestrial and aquatic invertebrates have been studied to a lesser extent. As invertebrates at the bottom of the food chain play a crucial role in the whole ecological chain, it is necessary to investigate the toxicity of PFASs to invertebrates. In this paper, the progress of toxicological studies on PFASs and their alternatives in terrestrial and aquatic invertebrates is reviewed, and the accumulation of PFASs, their toxicity in invertebrates, as well as the neurotoxicity and toxicity to reproduction and development are summarized. This provides a reference to in-depth studies on the comprehensive assessment of the toxicity of PFASs and their alternatives, promotes further research on PFASs in invertebrates, and provides valuable recommendations for the use and regulation of alternatives to PFASs.

Mobilization of poly- and perfluoroalkyl substances (PFAS) from heterogeneous soils: Desorption by ethanol/xanthan gum mixture

Remediating soils contaminated by per- and polyfluoroalkyl substances (PFAS) is a challenging task due to the unique properties of these compounds, such as variable solubility and resistance to degradation. In-situ soil flushing with solvents has been considered as a remediation technique for PFAS-contaminated soils. The use of non-Newtonian fluids, displaying variable viscosity depending on the applied shear rate, can offer certain advantages in improving the efficiency of the process, particularly in heterogeneous porous media. In this work, the efficacy of ethanol/xanthan mixture (XE) in the recovery of a mixture of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorobutane sulfonate (PFBS) from soil has been tested at lab-scale. XE's non-Newtonian behavior was examined through rheological measurements, confirming that ethanol did not affect xanthan gum's (XG) shear-thinning behavior. The recovery of PFAS in batch-desorption exceeded 95 % in ethanol, and 99 % in XE, except for PFBS which reached 94 %. 1D-column experiments revealed overshoots in PFAS breakthrough curves during ethanol and XE injection, due to over-solubilization. XE, (XG 0.05 % w/w) could recover 99 % PFOA, 98 % PFBS, 97 % PFHxS, and 92 % PFOS. Numerical modeling successfully reproduces breakthrough curves for PFOA, PFHxS, and PFBS with the convection-dispersion-sorption equation and Langmuir sorption isotherm.

PFAS fate using lysimeters during degraded soil reclamation using biosolids

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

Spatial and seasonal distribution, sources, and health risks of PM2.5 loaded per- and polyfluoroalkyl substances (PFASs) in a typical megacity

Per- and polyfluoroalkyl substances (PFASs), a class of ubiquitous and emerging environmental pollutants, have garnered considerable attention due to the scarcity of knowledge regarding their atmospheric sources and the associated human health risks from aerosol exposure. This study investigated the spatial-temporal distribution and potential sources of PFASs in Nanjing city of eastern China by collecting 66 PM2.5 samples from industrial, urban, and rural areas between July 2022 and August 2023. Employing ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), 21 distinct PFASs were detected with concentrations ranging from 9.62 to 136 pg·m-3, predominantly higher in urban areas. Airborne PFASs concentrations exhibited seasonal fluctuations, with the highest levels observed in autumn, followed by spring, summer and winter. Diagnostic ratio and positive matrix factorization (PMF) for source analyses revealed the significant influence of long-range transport, the textile and paper packaging industry, and the decomposition of fluorochemical precursors were identified as the main contributors, accounting for 18.2 %, 15.8 %, and 16.1 % respectively. Population exposure was evaluated through deposition and dermal penetration modeling, with inhalation intake estimated at 2.05 pg·kg-1·d-1 and dermal contact intake at 1.01 pg·kg-1·d-1. Among the 21 assessed PFASs, perfluoro-n-hexanoic acid (PFHxA) was identified posing the most significant risk regarding respiratory effects, skin sensitization, and carcinogenic potential. This research provides critical insights into the spatial and seasonal distribution of atmospheric PFASs and the assessment of combined human exposure risks in rapidly developing areas.

Out of sight, into the spotlight: Beyond the current state of science on per- and poly-fluoroalkyl substances in groundwater

Per- and poly-fluoroalkyl substances (PFAS) have emerged as a silent menace, infiltrating groundwater systems worldwide. Many countries, preoccupied with tackling legacy pollutants, have inadvertently neglected the emerging threat of PFAS. This review provides an exhaustive analysis beyond the current state of knowledge and sustainable pathways vis-a-vis addressing PFAS in groundwater systems globally. Despite the positive progression in PFAS research, significant knowledge gaps and paucity of data persist globally. Sampling trains, smart contaminant detectors, filters, and sensors offer promising pathways for the complete extraction and detection of novel and transformed PFAS species. Major hotspots are firefighting locations, landfills, and superfund sites. While studies have documented the global occurrence of PFAS in groundwater, with concentrations increasing over time and varying across regions, the factors influencing these trends, transport, fate, toxicity, and interactions with co-contaminants, remain largely unexplored. Advanced models accounting for environmental complexities and interactions are crucial for understanding PFAS migration in groundwater, however, their development is hindered by a scarcity of studies on the complexities and PFAS interactions. Emerging technologies, including nanotechnology, enzyme, genetic engineering, flexible treatment train, and machine learning algorithms present exciting opportunities for PFAS treatment, however, their cost-effectiveness, scalability, and long-term stability must be thoroughly investigated. Sustainable management requires addressing nomenclature inconsistencies and developing region-specific mitigative measures. These serve as a clarion call for the scientific community, policymakers, and stakeholders to unite in confronting the formidable challenges posed by PFAS contamination, as the fate of our groundwater resources and the well-being of countless lives hang in the balance.

Toxic layering and compound extremes: Per- and polyfluoroalkyl substances (PFAS) exposure in rural, environmental justice copper mining communities

Per- and polyfluoroalkyl substances (PFAS) are pervasive environmental pollutants with significant impacts on ecosystems and public health. This study aimed to characterize PFAS concentrations in an environmental justice community impacted by active/legacy copper mining, compounded by wildfires and flash floods. Additionally, the study explored the (re)mobilization of PFAS and co-occurrence with metal(loid)s following these events. Twenty-eight PFAS compounds in 35 residential and 8 control surface soil samples were analyzed via liquid chromatography-tandem mass spectrometry (LCMS/MS). The maximum total PFAS concentration observed in the residential samples was 96.40 μg kg-1, compared to 1.69 μgkg-1 in the control samples. Perfluorobutanoic acid (PFBA) had a maximum concentration of 61 μg kg-1 in residential samples, while Perfluorohexane sulfonic acid (PFHxS) had the highest concentration in the control samples at 0.92 μg kg-1. Long-chain PFAS were most dominant in this study. Perfluorooctane sulfonic acid (PFOS) (58 % of the samples), Perfluorooctanoic acid (PFOA) (35 %), and Perfluorohexane sulfonic acid (PFHxS) (72 %) exceeded the U.S. EPA Soil-to-Groundwater Risk-Based Screening Levels, highlighting the potential risk of contaminants migrating from soil to groundwater, which could ultimately impact groundwater quality. Co-occurrence analysis showed that increases in PFAS concentrations were positively associated with Zn (β = 1.25, p = 0.0034) and Ba (β = 1.23, p = 0.0284) but negatively associated with Pb (β = -0.83, p = 0.0115) and Co (β = -1.38, p = 0.04671). In general, a spatial distribution map indicated that greater PFAS concentrations were observed near potential sources i.e., active mines. This evidence combined with select metal co-occurrence highlights the potential role of mining activities on PFAS concentration.

PFAS, PCBs, PCDD/Fs, PAHs and extractable organic fluorine in bio-based fertilizers, amended soils and plants: Exposure assessment and temporal trends

Bio-based fertilizers (BBFs) produced from organic waste contribute to closed-loop nutrient cycles and circular agriculture. However, persistent organic contaminants, such as per- and poly-fluoroalkyl substances (PFAS), polychlorobiphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), as well as polyaromatic hydrocarbons (PAHs) can be present in organic waste or be formed during valorization processes. Consequently, these hazardous substances may be introduced into agricultural soils and the food chain via BBFs. This study assessed the exposure of 84 target substances and extractable organic fluorine (EOF) in 19 BBFs produced from different types of waste, including agricultural and food industrial waste, sewage sludge, and biowaste, and through various types of valorization methods, including hygienization at low temperatures (<150 °C) as well as pyrolysis and incineration at elevated temperatures (150-900 °C). The concentrations in BBFs (ΣPFOS & PFOA: <30 μg kg-1, Σ6PCBs: <15 μg kg-1, Σ11PAHs: <3 mg kg-1, Σ17PCDD/Fs: <4 ng TEQ kg-1) were found to be below the strictest thresholds used in individual EU countries, with only one exception (pyrolyzed sewage sludge, Σ11PAHs: 5.9 mg kg-1). Five BBFs produced from sewage sludge or chicken manure contained high concentrations of EOF (>140 μg kg-1), so monitoring of more PFAS is recommended. The calculated expected concentrations in soils after one BBF application (e.g. PFOS: <0.05 μg kg-1) fell below background contamination levels (PFOS: 2.7 μg kg-1) elsewhere in the literature. This was confirmed by the analysis of BBF-amended soils from field experiments (Finland and Austria). Studies on target legacy contaminants in sewage sludge were reviewed, indicating a general decreasing trend in concentration with an apparent half-life ranging from 4 (PFOS) to 9 (PCDD/Fs) years. Modelled cumulative concentrations of the target contaminants in agricultural soils indicated low long-term risks. Concentrations estimated and analyzed in cereal grains were low, indicating that exposure by cereal consumption is well below tolerable daily intakes.

Influence of kinetic air-water interfacial partitioning on unsaturated transport of PFAS in sandy soils

This study investigates the impact of kinetic air-water partitioning on the transport of perfluoroalkyl substances (PFAS) within homogeneous and heterogeneous sandy vadose zones under transient unsaturated flow conditions. These experimental conditions are realistic for field behavior, where transient flow foments the continual growth and collapse of air-water interfaces (AWIs), and where layered heterogenous conditions enhance the perturbations of AWIs. Short-chain PFAS behave like conservative tracers with negligible air-water interface partitioning, whereas longer-chain PFAS demonstrate non-equilibrium retention behavior, especially in heterogeneous media. AWI partitioning kinetics were found to be important in controlling PFAS transport and mass flux, particularly during PFAS sorption to the air-water interface, which results because of the different nature and more rapid changes in AWI during drainage, wherein PFAS are moving toward the interface to achieve equilibrium, than during imbibition, where PFAS are leaving the interface to achieve equilibrium. Neglecting these kinetic AWI sorption processes can result in an underestimate of the PFAS transport velocities and mass flux reaching the water table. The presence of trapped air may also inhibit PFAS partitioning in a similar manner by causing longer diffusion paths from bulk water to a portion of the AWIs. The modified HYDRUS effectively captured the transport processes and provided an excellent match to the measured breakthrough curves. To assess relevance using realistic transient infiltration rates, simulations were conducted using precipitation data from an actual site. The results showed that accounting for kinetic AWI partitioning increases the cumulative PFOS mass flux to groundwater by a factor of 2.3 compared to equilibrium conditions, significantly impacting PFAS porewater concentrations. This difference was threefold under experimental conditions, suggesting that the importance of kinetic effects may vary significantly over the long term and under different climatic conditions or soil types, due to their strong dependence on water flux.

A quantitative classification method of land uses and assessment of per-and poly-fluoroalkyl substances (PFAS) occurrence in freshwater environments

We developed a quantitative method for classifying land uses for PFAS-related investigations in freshwater environments and determined PFAS ambient concentrations associated with specific land-use classes. Furthermore, our study presents a comprehensive assessment of the ambient occurrence and risks of PFAS mixtures beyond the usually studied PFOS-PFOA mixtures. Eighty-five inland (freshwater only) sites were sampled for water, sediment, and riparian soil in Victoria, south-east Australia, and analyzed for 33 PFAS. PFAS were detected in 91% of water samples, 34% of sediment samples, and 28% of riparian soil samples. Four land-use classes were defined: remote, agricultural, mixed, and urban. In the remote land-use class, only PFOS was detected at a low ambient concentration (0.0002 μg/L) in one water sample. Short-chain PFCA were frequently detected in the agricultural and mixed water samples. PFBA had the highest median ambient concentration in both land uses (ca. 0.01 μg/L), contributing to both ΣPFAS (40%) and ΣPFCA (50%) concentrations. In the urban land-use class, several congeners (PFBA, PFPeA, PFHxA, PFOA, PFHxS, and PFOS) had median ambient concentrations at or close to 0.01 μg/L and contributed similarly to ΣPFAS (10-20%). Elevated risk to the aquatic environment was found only for PFOS in two mixed and eight urban sites. This pattern was consistent with the finding for PFAS mixtures, where the elevated risk was driven by PFOS at those same sites. Our study provides critical information about environmentally relevant ambient concentrations and PFAS mixtures. This information, together with the land-use classification approach presented herein, can be used as reference levels for several critical purposes, including identifying PFAS-contaminated sites, informing land use planning and development decisions, setting standards and guidelines, and tracking changes over time.

Leachability of per- and poly-fluoroalkyl substances from contaminated concrete

The historical use and storage of aqueous film-forming foams (AFFF) containing per- and poly-fluoroalkyl substances (PFAS) at a range of sites including airports, defence, and port facilities have resulted in a legacy of contaminated infrastructure such as concrete. Contaminated concrete constitutes an ongoing source of PFAS contamination requiring management to ensure the protection of human health and the environment. In this study, modified Leaching Environmental Assessment Framework (LEAF) and Australian Standard Leaching Procedure (ASLP) were used to examine the leachability of PFAS, specifically, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS) and perfluorohexanoic acid (PFHxA) from AFFF-contaminated concrete collected from an Australian Defence Fire Training Area (FTA). In general, PFAS readily leached from intact contaminated concrete monoliths with the cumulative proportion (%) decreasing in the order: PFHxA (>95%) > PFOS (26-84%) ≈ PFHxS (14-78%) > PFOA (<1-54%). Higher leachability for PFHxA from concrete is consistent with previous findings for solids, however, inconsistent for PFOA with higher retention (lower leachability) in concrete as compared to PFOS. Duration of exposure to water (0.5-48 h) and temperature (25 °C and 50 °C) had little influence on the proportion of PFAS leachability from powdered concrete. A higher proportion of PFAS leached from a <2 mm concrete powder size fraction as compared to 2-20 mm and 20 mm size fractions. This behavior reflects an increase in surface area with decreasing concrete particle size. Reducing the particle size could enhance PFAS removal from waste concrete.

Environmental Occurrence and Biotic Concentrations of Ultrashort-Chain Perfluoroalkyl Acids: Overlooked Global Organofluorine Contaminants

Per- and polyfluoroalkyl substances (PFASs) are a large group of anthropogenic fluorinated chemicals. Ultrashort-chain perfluoroalkyl acids (PFAAs) have recently gained attention due to their prevalence in the environment and increasing environmental concerns. In this review, we established a literature database from 1990 to 2024, encompassing environmental and biological concentrations (>3,500 concentration records) of five historically overlooked ultrashort-chain PFAAs (perfluoroalkyl carboxylic and sulfonic acids with less than 4 carbons): trifluoroacetic acid (TFA), perfluoropropanoic acid (PFPrA), trifluoromethanesulfonic acid (TFMS), perfluoroethanesulfonate (PFEtS), and perfluoropropanesulfonate (PFPrS). Our data mining and analysis reveal that (1) ultrashort-chain PFAAs are globally distributed in various environments including water bodies, solid matrices, and air, with concentrations usually higher than those of longer-chain compounds; (2) TFA, the most extensively studied ultrashort-chain PFAA, shows a consistent upward trend in concentrations in surface water, rainwater, and air over the past three decades; and (3) ultrashort-chain PFAAs are present in various organisms, including plants, wildlife, and human blood, serum, and urine, with concentrations sometimes similar to those of longer-chain compounds. The current state of knowledge regarding the sources and fate of TFA and other ultrashort-chain PFAAs is also reviewed. Amid the global urgency to regulate PFASs, particularly as countries worldwide have intensified such efforts, this critical review will inform scientific research and regulatory policies.

Sorption of per- and polyfluoroalkyl substances by lignin in pulp and paper wastewater

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic chemicals commonly found in the environment. PFAS pose multifaceted challenges including identifying sources and exposure pathways, detecting and quantifying their presence, characterizing their fate and transport, and assessing their risks. PFAS and fluorotelomer polymers can be found in the pulp and paper (P&P) wastewater systems, but their behavior remains poorly understood. The constituents of P&P waste include lignin hydrolysis products, hence PFAS interactions with lignin likely affect PFAS removal efforts. This study employed quantitative ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-MS/MS) to investigate the sorption-desorption capacity and mechanisms of PFAS interaction with lignin. PFAS with sulfonate functional groups displayed higher affinity for lignin (solid phase) based on their partitioning coefficient (Kd), while PFAS with carboxylate head groups persisted in the P&P wastewater (aqueous phase). Sorption to lignin exhibited an increase with chain length (CF2)n among compounds with the same functional group. Long-chain (C ≥ 6) PFAS demonstrated higher sorption compared to short-chain (C ≤ 5) homologs. The sorption-desorption capacities, partitioning coefficients, and kinetics of PFAS reported in this study can facilitate predictive models for PFAS and assist in the development of efficient P&P waste treatment and management.

Remediation of per- and polyfluoroalkyl substances (PFAS) contaminated soil via soil washing with various water-organic solvents

The feasibility of soil washing for remediating PFAS-contaminated clay soil using various water-organic solvents was systematically investigated based on the combination of batch and column tests. Batch tests using 22 types of solvents highlighted that 0 % (water) and 5 % solvents could effectively extract PFCAs (≤ C9), while long-chain PFCAs (≥ C10) and PFSAs required 80 % solvents for optimal extraction, with efficiency in the order of EtOH ≤ MeOH < Acetonitrile (ACN), suggesting a strong correlation with carbon chain lengths and functional head groups. Column tests with six selected washing solutions indicated rapid desorption of PFOA and PFOS initially, peaking at liquid-to-solid (L/S) ratios of 3-4 for 0 % and 5 % solutions, and at an L/S ratio of 1 for 80 % solutions. To remediate 1 kg-dry soil to meet the legislatively permissible levels for groundwater in Japan (PFOA + PFOS < 50 ng/L), 11 L of 0 % solution (water) or 5 L of 80 % ACN are required for washing out PFOA, while 62 L of 0 % solution (water) or 53 L of 80 % ACN for PFOS. Future research should address the treatment of PFAS-rich wastewater generated from washing PFAS-contaminated soils and the impacts of washing solutions on soil.

Residential Garden Produce Harvested Near a Fluorochemical Manufacturer in North Carolina Can Be An Important Fluoroether Exposure Pathway

Dietary intake can be an important exposure route to per- and polyfluoroalkyl substances (PFASs). Little is known about the bioaccumulation of emerging per- and polyfluoroalkyl ether acids (PFEAs) in garden produce from PFAS-impacted communities and the associated dietary exposure risk. In this study, 53 produce samples were collected from five residential gardens near a fluorochemical manufacturer. Summed PFAS concentrations ranged from 0.0026 to 38 ng/g wet weight of produce, and water-rich produce exhibited the highest PFAS levels. The PFAS signature was dominated by PFEAs, and hexafluoropropylene oxide-dimer acid (commonly known as GenX) was detected in 72% of samples. Based on average measured GenX concentrations, chronic-exposure daily limits were as low as 289 g produce/day for children (3-6 yr). This analysis does not consider other PFEAs that were present at higher concentrations, but for which reference doses were not available. This study revealed that consuming residential garden produce grown in PFAS-impacted communities can be an important exposure pathway.

Unraveling drivers of per- and polyfluoroalkyl substances (PFASs) occurrence and removal in leachate: Insights from disposal methods, geo-climate, and biodegradation

Leachate is a substantial reservoir of per- and polyfluoroalkyl substances (PFASs) within the environment. However, comprehensive information on the occurrence and fate of PFASs in leachate, particularly in semi-arid and moderate-elevation regions where PFASs may aggregate, is lacking. Here, 13 legacy PFASs were investigated in leachate from landfills and an incineration plant in such area. PFASs concentrations ranged from 6063 to 43,161 ng·L-1 in raw leachate, influenced by leachate origin, climate, wastewater disposal, and especially bacterial communities. Bacteroidetes and Firmicutes were enriched in raw leachate, while Proteobacteria dominated during leachate treatment processes, possibly due to PFASs selection pressure. In addition, top 20 biomarkers indicated the potential of these bacterial indicators for PFASs detection. Tracing analysis also suggested that PFASs in groundwater may have originated from leachate and effluent from wastewater treatment plants. PFASs levels in groundwater showed a significant correlation with the presence of Brevundimonas, Leptothrix, Malikia, and Sphaerotilus. The pathogenic bacterium Brevundimonas suggested potential human health risks, while Leptothrix, Malikia, and Sphaerotilus may serve as indicators of groundwater contamination. This study is believed to provide insights into how to prevent and control PFASs-related environmental pollution.

Comparing PFAS analysis in batch leaching and column leaching tests

Laboratory leaching tests are tools to assess the mobility of environmental contaminants released from granular materials. Comparative leaching tests were performed using four PFAS-contaminated soils whose concentration patterns of 10 selected perfluoroalkyl and polyfluoroalkyl substances (PFAS) differed due to the two types of contamination sources. This study aimed to evaluate the equivalence of two usual laboratory-scale leaching test procedures, batch and column percolation tests, at liquid-to-solid ratios (L/S) of 2 l/kg, which is the current practice within the German assessment framework, and 10 l/kg (relevant for some EU regulations such as the landfill directive). The differences between the replicates of leaching tests investigating PFAS were smaller for column percolation tests than for batch tests, probably mainly due to the greater sample size and the better representativeness of the sample portion analyzed. It was observed that batch tests overestimate the release of shorter-chain PFAS, whereby the effect was greater with carboxylic than with sulfonic acids. Currently, the limits of detection of analyses given by the DIN standard with regard to PFCA and PFSA in soils are partly not sufficient to detect very low contents, whereas the detection of selected PFCA and PFSA in eluates is more sensitive, in accordance with the available standards. This results in limitations when calculating mass balances.

Distinctive adsorption and transport behaviors of short-chain versus long-chain perfluoroalkyl acids in a river sediment

Perfluoroalkyl acids (PFAAs) embrace perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and other concerning chemicals of different chain length and terminal moieties. PFAAs can leach from municipal wastewater facilities as point sources discharging into rivers and receiving streams. In this study, we investigated the adsorption and transport behaviors of six select PFAAs in a Hudson River (USA) sediment in both batch and mesocosm studies. The adsorption capacities single and dual solute systems followed the order: PFBA < PFHxA ≈ PFBS < PFHxS < PFOA << PFOS. Mesocosm experiment that receives a continuous point source discharge of a mixture of these six PFAAs reached equilibrium after 4 weeks of operation. Total adsorbed PFAAs in the sediment was extracted and analyzed, following PFHxS (0.85 mg, 20.4%) ≈ PFBS (0.92 mg, 21.7%) < PFOA (1.02 mg, 27.3%) ≈ PFHxA (1.04 mg, 29.8%) < PFBA (1.12 mg, 30.1%) << PFOS (1.55 mg, 39.2%). PFOS showed highest adsorption, concentrating on the surface layer. Noticeably, two short-chain PFAAs, PFBA and PFHxA, were found with high vertical mobility, partitioning into deeper sediment. Two hotspots for PFAA sediment contamination were formed near the sediment surface downstream from the point source, providing new prospects to guide PFAA sediment cleanup and monitoring. Graphical abstract.

Speciation and biogeochemical behavior of perfluoroalkyl acids in soils and their environmental implications: A review

Perfluoroalkyl acids (PFAAs) are emerging organic pollutants that have attracted significant attention in the fields of environmental chemistry and toxicology. Although PFAAs are pervasive in soils and sediments, there is a paucity of research regarding their environmental forms and driving mechanisms. This review provides an overview of the classification and biotoxicity of per- and polyfluoroalkyl substances (PFAS), organic pollutant forms, PFAS extraction and analytical methods, the prediction of PFAS distribution in soils, and current PFAS remediation strategies. Four predominant PFAA forms have been proposed in soils: (i) aqueous-extracted PFAAs, (ii) organic-solvent extracted PFAAs, (iii) embedded or sequestered PFAAs, and (iv) covalently bound PFAAs. Furthermore, it suggests suitable extraction methods and predictive models for different PFAA forms, which are instrumental in the research on PFAA speciation and prediction in soils. Simultaneously, it was proposed that elemental cycling and microbial activity may affect the speciation of PFAS. Additionally, the categorization of PFAA forms facilitated the analysis of pollution remediation. Understanding the interplay between PFAA speciation, element cycling, and bacterial activity during soil remediation is essential for understanding remediation mechanisms and assessing the long-term stability of remediation methods. Future studies should expand the investigation of varying PFAA forms in different media, consider the potential binding forms of PFAAs to minerals, organic matter, and microbes, and evaluate the possible mechanisms of PFAA speciation variation.

Elucidating per- and polyfluoroalkyl substances (PFASs) soil-water partitioning behavior through explainable machine learning models

In this study, an optimized random forest (RF) model was employed to better understand the soil-water partitioning behavior of per- and polyfluoroalkyl substances (PFASs). The model demonstrated strong predictive performance, achieving an R2 of 0.93 and an RMSE of 0.86. Moreover, it required only 11 easily obtainable features, with molecular weight and soil pH being the predominant factors. Using three-dimensional interaction analyses identified specific conditions associated with varying soil-water partitioning coefficients (Kd). Results showed that soils with high organic carbon (OC) content, cation exchange capacity (CEC), and lower soil pH, especially when combined with PFASs of higher molecular weight, were linked to higher Kd values, indicating stronger adsorption. Conversely, low Kd values (< 2.8 L/kg) typically observed in soils with higher pH (8.0), but lower CEC (8 cmol+/kg), lesser OC content (1 %), and lighter molecular weight (380 g/mol), suggested weaker adsorption capacities and a heightened potential for environmental migration. Furthermore, the model was used to predict Kd values for 142 novel PFASs in diverse soil conditions. Our research provides essential insights into the factors governing PFASs partitioning in soil and highlights the significant role of machine learning models in enhancing the understanding of environmental distribution and migration of PFASs.

Innovative techniques for combating a common enemy forever chemicals: A comprehensive approach to mitigating per- and polyfluoroalkyl substances (PFAS) contamination

The pervasive presence of per and polyfluoroalkyl substances (PFAS), commonly referred to as "forever chemicals," in water systems poses a significant threat to both the environment and public health. PFAS are persistent organic pollutants that are incredibly resistant to degradation and have a tendency to accumulate in the environment, resulting in long-term contamination issues. This comprehensive review delves into the primary impacts of PFAS on both the environment and human health while also delving into advanced techniques aimed at addressing these concerns. The focus is on exploring the efficacy, practicality, and sustainability of these methods. The review outlines several key methods, such as advanced oxidation processes, novel materials adsorption, bioremediation, membrane filtration, and in-situ chemical oxidation, and evaluates their effectiveness in addressing PFAS contamination. By conducting a comparative analysis of these techniques, the study aims to provide a thorough understanding of current PFAS remediation technologies, as well as offer insights into integrated approaches for managing these persistent pollutants effectively. While acknowledging the high efficiency of adsorption and membrane filtration in reducing persistent organic pollutants due to their relatively low cost, versatility, and wide applicability, the review suggests that the integration of these methods could result in an overall enhancement of removal performance. Additionally, the study emphasizes the need for researcher attention in key areas and underscores the necessity of collaboration between researchers, industry, and regulatory authorities to address this complex challenge.

Legacy and Novel Per- and Polyfluoroalkyl Substances in Surface Soils across China: Source Tracking and Main Drivers for the Spatial Variation

China aims to actively control the contamination of globally concerning per- and polyfluoroalkyl substances (PFASs). Evaluation of the current situation can provide a critical reference point for tracking the effectiveness of ongoing progress. Herein, we present the first comprehensive assessment of the spatial variations of 20 legacy and 54 novel PFASs in Chinese background soils in 2021. Novel PFASs were extensively detected in 98.4% of the samples, with 21 species being first reported, which greatly facilitated the appointment of diverse emission sources that aligned with local industrial structures. However, legacy PFASs still dominated the ∑74PFAS profile (median 0.51 ng/g, 0.050-8.33 ng/g). The spatial heterogeneity of soil PFASs was positively driven by economic development and atmospheric deposition, enabling the establishment of predictive models to project the national distribution and temporal trends. Elevated PFAS levels were predominantly distributed in the more industrialized eastern and southern regions, as well as other coastal areas with greater precipitation. ∑74PFAS in surface soils was estimated to increase by 12.9 pg/(g year) over 2002-2021, which would continue alongside economic growth, albeit with greater contributions from novel alternatives. Our work provides comprehensive baseline and predictive data to inform policies toward PFAS control in China.