Investigating recycled water use as a diffuse source of per- and polyfluoroalkyl substances (PFASs) to groundwater in Melbourne, Australia

Occurrence and potential ecological risks of PFAS in Pampulha Lake, Brazil, a UNESCO world heritage site

Per- and polyfluoroalkyl substances (PFAS) comprise >4000 synthetic substances used in industrial applications and consumer products. PFAS used daily in households and manufacturing plants end up in domestic sewage, and industrial effluents can be discharged to surface water. Urban watersheds located in low and middle-income countries (LMIC), which lack sanitation infrastructure, are potential recipients of waste containing PFAS. Yet, only a few studies report PFAS occurrence in urban reservoirs and lakes, especially those located in the Global South due to resource limitations. This is the first study aimed to assess PFAS occurrence and ecological risks in Pampulha Lake, Brazil, a site which represents the reality of many other urban watersheds in LMIC as it is surrounded by densely populated areas and manufacturing plants. Surface water samples were collected monthly for 1 year from four sampling points at Pampulha Lake. Sample analysis was based on US Environmental Protection Agency Method 1633, which employs solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Species sensitivity distribution (SSD) curves were built to identify potentially susceptible species based on detected water concentrations. Bioaccumulation was estimated for fish tissue. Short-chain (perfluorobutanesulfonic acid, PFBS and perfluorohexanoic acid, PFHxA) and long-chain PFAS (perfluorodecanoic acid, PFDA; perfluorooctanoic acid, PFOA; perfluorododecanoic acid, PFDoA; and perfluorooctanesulfonic acid, PFOS) were detected at the μg L-1 range. Total PFAS concentrations in the wet season were generally higher than in the dry season, likely due to limited capacity of the treatment plant processing water from tributaries which receive raw sewage. More than 5 % of aquatic species are potentially susceptible to chronic effects of PFOS at detected concentrations (0.2-2.2 μg L-1). Predicted bioaccumulation of PFOS in fish was above advisory diet intake levels for humans. Results emphasize the need for studies related to PFAS occurrence in watersheds located in LMIC.

Emergency of per- and polyfluoroalkyl substances in drinking water: Status, regulation, and mitigation strategies in developing countries

The detection of per- and polyfluoroalkyl substances (PFAS) in water presents a significant challenge for developing countries, requiring urgent attention. This review focuses on understanding the emergence of PFAS in drinking water, health concerns, and removal strategies for PFAS in water systems in developing countries. This review indicates the need for more studies to be conducted in many developing nations due to limited information on the environmental status and fate of PFAS. The health consequences of PFAS in water are enormous and cannot be overemphasized. Efforts are ongoing to legislate a national standard for PFAS in drinking water. Currently, there are few known mitigation efforts from African countries, in contrast to several developing nations in Asia. Therefore, there is an urgent need to develop economically viable techniques that could be integrated into large-scale operations to remove PFAS from water systems in the region. However, despite the success achieved with removing long-chain PFAS from water, more studies are required on strategies for eliminating short-chain moieties in water.

Per- and poly-fluoroalkyl substances in agricultural contexts and mitigation of their impacts using biochar: A review

Growing concern over the presence of per- and polyfluoroalkyl substances (PFAS) in agricultural compartments (e.g., soil, water, plants, soil fauna) has led to an increased interest in scalable and economically feasible remediation technologies. Biochar is the product of pyrolyzing organic materials (crop waste, wood waste, manures, grasses) and has been used as a low-cost adsorbent to remove contaminants including PFAS. This review frames biochar as a strategy for mitigating the detrimental impacts of PFAS in agricultural systems and discusses the benefits of this strategy within the framework of the needs and challenges of contaminant remediation in agriculture. To gauge the optimal physicochemical characteristics of biochar in terms of PFAS adsorption, principal component analysis using >100 data points from the available literature was performed. The main biochar-based PFAS treatment strategies (water filtration, soil application, mixing with biosolids) were also reviewed to highlight the benefits and complications of each. Life cycle analyses on the use of biochar for contaminant removal were summarized, and data from selected studies were used to calculate (for the first time) the global warming potential and net energy demand of various agriculturally important biochar classes (crop wastes, wood wastes, manures) in relation to their PFAS adsorption performance. This review serves to identify key gaps in our knowledge of (i) PFAS adsorption by biochars in agricultural remediation applications and (ii) environmental costs/benefits of biochars in relation to their adsorptive properties toward PFAS. The concepts introduced in this review may assist in developing large-scale biochar-based PFAS remediation strategies to help protect the agricultural food production environment.

Biosolids, an important route for transporting poly- and perfluoroalkyl substances from wastewater treatment plants into the environment: A systematic review

The pervasive presence of poly- and perfluoroalkyl substances (PFAS) in diverse products has led to their introduction into wastewater systems, making wastewater treatment plants (WWTPs) significant PFAS contributors to the environment. Despite WWTPs' efforts to mitigate PFAS impact through physicochemical and biological means, concerns persist regarding PFAS retention in generated biosolids. While numerous review studies have explored the fate of these compounds within WWTPs, no study has critically reviewed their presence, transformation mechanisms, and partitioning within the sludge. Therefore, the current study has been specifically designed to investigate these aspects. Studies show variations in PFAS concentrations across WWTPs, highlighting the importance of aqueous-to-solid partitioning, with sludge from PFOS and PFOA-rich wastewater showing higher concentrations. Research suggests biological mechanisms such as cytochrome P450 monooxygenase, transamine metabolism, and beta-oxidation are involved in PFAS biotransformation, though the effects of precursor changes require further study. Carbon chain length significantly affects PFAS partitioning, with longer chains leading to greater adsorption in sludge. The wastewater's organic and inorganic content is crucial for PFAS adsorption; for instance, higher sludge protein content and divalent cations like calcium and magnesium promote adsorption, while monovalent cations like sodium impede it. In conclusion, these discoveries shed light on the complex interactions among factors affecting PFAS behavior in biosolids. They underscore the necessity for thorough considerations in managing PFAS presence and its impact on environmental systems.

The perils of poly- and perfluorinated chemicals on the reproductive health of humans, livestock, and wildlife

Poly- and perfluoroalkyl substances (PFAS) are a prominent class of persistent synthetic compound. The widespread use of these substances in various industrial applications has resulted in their pervasive contamination on a global scale. It is therefore concerning that PFAS have a propensity to accumulate in bodily tissues whereupon they have been linked with a range of adverse health outcomes. Despite this, the true extent of the risk posed by PFAS to humans, domestic animals, and wildlife remains unclear. Addressing these questions requires a multidisciplinary approach, combining the fields of chemistry, biology, and policy to enable meaningful investigation and develop innovative remediation strategies. This article combines the perspectives of chemists, soil scientists, reproductive biologists, and health policy researchers, to contextualise the issue of PFAS contamination and its specific impact on reproductive health. The purpose of this article is to describe the challenges associated with remediating PFAS-contaminated soils and waters and explore the consequences of PFAS contamination on health and reproduction. Furthermore, current actions to promote planetary health and protect ecosystems are presented to instigate positive social change among the scientific community.

Per- and polyfluoroalkyl substances (PFASs) in Chinese surface water: Temporal trends and geographical distribution

PFAS, recognized as persistent organic pollutants, present risks to both the ecological environment and human health. Studying PFASs in surface water yields insights into pollution dynamics. However, existing research on PFASs surface water pollution in China often focuses on specific regions, lacking comprehensive nationwide analyses. This study examined 48 research papers covering PFAS pollution in Chinese surface water, involving 49 regions and 1338 sampling sites. The results indicate widespread PFAS contamination, even in regions like Tibet. Predominant PFAS types include PFOA and PFOS, and pollution is associated with the relocation of industries from developed to developing countries post-2010. The shift from long-chain to short-chain PFASs aligns with recent environmental policy proposals. Geographic concentration of PFAS pollution correlates with industry distribution and economic development levels. Addressing point source pollution, especially from wastewater plant tailwater, is crucial for combating PFAS contamination. Greater emphasis should be placed on addressing short-chain PFASs.

Demonstrating removal credits for contaminants of emerging concern in recycled water through a reverse osmosis barrier-A predictive framework

The performance of individual reverse osmosis (RO) systems varies significantly with different contaminants of emerging concern (CECs). As such, log reduction values (LRVs) of the concentration of these chemicals cannot be arbitrarily credited in water treatment and water recycling. This study looks to present an approach to the management of chemical risks by providing a systematic validation of RO barrier performance with respect to LRV credits for various classes of CECs. In this work, a one-off sampling campaign across five treatment barriers (strainer filtration, ultrafiltration, RO, ion exchange, chlorination) of a full-scale water recycling plant was conducted, followed by a systematic sampling campaign for a period of six weeks across just the RO barrier. The CECs screening methodology used GC-MS for quantification of 948 trace organic chemicals along with specific 44 per- and polyfluoroalkyl substances (PFAS) screening using LC-MS/MS to demonstrate the removal credits of the RO barrier to a wide spectrum of CECs. The work was used to validate an LRV barrier credit framework so as to predict the performance of a polyamide RO membrane for removal of a range of chemical classes, under typical operational conditions. Conductivity was validated as an efficient surrogate for membrane integrity and RO performance, along with specified operational conditions associated with permeate flux and recovery rate. A bioassay method (photobacterium test) showed good potential to be used as a quick measure to indicate the general toxicity of a sample caused by chemical contamination, because of its high detection sensitivity and time and cost efficiency.

Target and Suspect Screening Integrated with Machine Learning to Discover Per- and Polyfluoroalkyl Substance Source Fingerprints

This study elucidates per- and polyfluoroalkyl substance (PFAS) fingerprints for specific PFAS source types. Ninety-two samples were collected from aqueous film-forming foam impacted groundwater (AFFF-GW), landfill leachate, biosolids leachate, municipal wastewater treatment plant effluent (WWTP), and wastewater effluent from the pulp and paper and power generation industries. High-resolution mass spectrometry operated with electrospray ionization in negative mode was used to quantify up to 50 target PFASs and screen and semi-quantify up to 2,266 suspect PFASs in each sample. Machine learning classifiers were used to identify PFASs that were diagnostic of each source type. Four C5-C7 perfluoroalkyl acids and one suspect PFAS (trihydrogen-substituted fluoroethernonanoic acid) were diagnostic of AFFF-GW. Two target PFASs (5:3 and 6:2 fluorotelomer carboxylic acids) and two suspect PFASs (4:2 fluorotelomer-thia-acetic acid and N-methylperfluoropropane sulfonamido acetic acid) were diagnostic of landfill leachate. Biosolids leachates were best classified along with landfill leachates and N-methyl and N-ethyl perfluorooctane sulfonamido acetic acid assisted in that classification. WWTP, pulp and paper, and power generation samples contained few target PFASs, but fipronil (a fluorinated insecticide) was diagnostic of WWTP samples. Our results provide PFAS fingerprints for known sources and identify target and suspect PFASs that can be used for source allocation.

Occurrence of per- and polyfluoroalkyl substances in aquatic environments and their removal by advanced oxidation processes

Per- and polyfluoroalkyl substances (PFAS), one of the main categories of emerging contaminants, are a family of fluorinated organic compounds of anthropogenic origin. PFAS can endanger the environment and human health because of their wide application in industries, long-term persistence, unique properties, and bioaccumulation potential. This study sought to explain the accumulation of different PFAS in water bodies. In aquatic environments, PFAS concentrations range extensively from <0.03 (groundwater; Melbourne, Australia) to 51,000 ng/L (Groundwater, Sweden). Additionally, bioaccumulation of PFAS in fish and water biota has been stated to range from 0.2 (Burbot, Lake Vättern, Sweden) to 13,900 ng/g (Bluegill samples, U.S.). Recently, studies have focused on PFAS removal from aqueous solutions; one promising technique is advanced oxidation processes (AOPs), including microwaves, ultrasound, ozonation, photocatalysis, UV, electrochemical oxidation, the Fenton process, and hydrogen peroxide-based and sulfate radical-based systems. The removal efficiency of PFAS ranges from 3% (for MW) to 100% for UV/sulfate radical as a hybrid reactor. Therefore, a hybrid reactor can be used to efficiently degrade and remove PFAS. Developing novel, efficient, cost-effective, and sustainable AOPs for PFAS degradation in water treatment systems is a critical area of research.

Perfluoroalkyl acid transformation and mitigation by nNiFe-activated carbon nanocomposites in steady-state flow column studies

The ongoing contamination of groundwater with per- and polyfluoroalkyl substances (PFAS) has resulted in a global and rapidly growing interest in PFAS groundwater remediation. Preferred technologies that lead to PFAS destruction are often limited by not addressing all PFAS, being energy-intensive or not being suited for in-situ application. We developed nNiFe-activated carbon (AC) nanocomposites and demonstrated varying degrees of PFAS reduction and fluoride generation with these nanocomposites in batch reactors for several PFAS. Here we explore nNiFe-AC's effectiveness to transform perfluoroalkyl acid acids (PFAAs) under steady-state flow (0.0044 to 0.15 mL/min) in nNiFe-AC:sand packed columns. Column experiments included, two perfluorooctane sulfonate (PFOS) in deionized water and two PFAA mixtures in deionized water or bicarbonate buffer containing five perfluoroalkyl carboxylates (PFCAs, C5-C9) and three perfluoroalkyl sulfonates (PFSAs, C4, C6 and C8) at temperatures of 50 or 60°C were evaluated. PFOS transformation was similar in PFOS-only and PFAA mixture column experiments. Overall, % PFAA transformation under flow conditions exceeded what we observed previously in batch reactors with up to 53% transformation of a PFAA mixture with ∼ 8% defluorination. Longer chain PFAS dominated the PFAAs transformed and a bicarbonate matrix appeared to reduce overall transformation. PFAA breakthrough was slower than predicted from only sorption due to transformation; some longer chain PFAS like PFOS did not breakthrough. Here, nNiFe-AC technology with both in-situ and ex-situ potential application was shown to be a plausible part of a treatment train needed to address the ongoing challenge for cleaning up PFAS-contaminated waters.

Residue Distribution and Daily Exposure of Per- and Polyfluoroalkyl Substances in Indica and Japonica Rice

Per- and polyfluoroalkyl substances (PFAS) have excellent chemical stability but have adverse environmental impacts of concern. Furthermore, bioaccumulation of PFAS in rice varieties─which is the essential staple food crop in Asia─has not been verified. Therefore, we cultivated Indica (Kasalath) and Japonica rice (Koshihikari) in the same Andosol (volcanic ash soil) paddy field and analyzed the air, rainwater, irrigated water, soil, and rice plants for 32 PFAS residues, throughout the cultivation to human consumption. During the rice cultivation period, the cultivation environment in atmospheric particulate matter (PM) constituted perfluoroalkyl carboxylic acids (PFCAs), with minimal perfluorinated sulfonic acids (PFSAs). Furthermore, perfluorooctanesulfonic acid (PFOS) migrates at a PM > 10 to drop in a cultivation field and was conducive to leakage and accumulation of PFCAs in air particles in the field environment. Moreover, precipitation was a sources of irrigation water contamination, and cultivated soil with a high carbon content could capture PFSAs and PFCAs (over C₁₀). There were no major differences in residual PFAS trends in the rice varieties, but the distribution of PFAS in the growing soil, air, and rainwater differed. The edible white rice part was mainly affected by irrigation water in both varieties. Monte Carlo simulations of daily exposure assessments of PFOS, PFOA, and perfluorononanic acid showed similar results for Indians consuming Indica rice and Japanese consuming Japonica rice. The results indicate that the ultratrace PFAS residue concentrations and their daily exposure were not cultivar-specific.

Distribution of legacy and novel per- and polyfluoroalkyl substances in surface and groundwater affected by irrigation in an arid region

Frequent exchange of surface water and groundwater occurs in arid/semi-arid areas due to high evaporation and intensive irrigation activities, affecting the migration and transformation of per- and polyfluoroalkyl substances (PFASs) and threatening drinking water safety. This study analyzed legacy PFASs and potential precursors in surface water, groundwater, soil, and aquifer solid samples collected from a typical arid area, the Hetao Irrigation District of Northern China, to explore PFASs distribution and transformation between surface and ground. Total PFASs (ΣPFASs) in surface water was 29-232 ng/L, higher than 2-77 ng/L in groundwater. ΣPFASs in soil were 0.29-0.59 ng/g, higher than 0.09-0.27 in the aquifer solids. Regarding horizontal distribution, the concentration of PFASs in groundwater increased in downtowns and the areas recharged with lake water. In terms of vertical distribution, ΣPFASs decreased with the increase of depth, and more PFASs adsorbed on clay particles in the aquifer. The total oxidable precursor analysis showed that 8:2 FT and 4:2 FT were the dominant precursors of PFASs, resulting in an increment of 0.1-4 ng/L PFASs. Hydrogen and oxygen stable isotope compositions suggest similar sources between surface water and groundwater in the study area, while principal component analysis and Bayesian inference also indicate that surface water is an important source of groundwater PFASs. The annual infiltration PFASs to groundwater from Ulansuhai was estimated by the water balance approach to be 9.39 kg. Results highlight the influence of agricultural irrigation activities and lake infiltration on groundwater PFASs in the arid region.

Occurrence, fate and risk assessment of per- and polyfluoroalkyl substances in wastewater treatment plants in Shaanxi, China

Wastewater treatment plants (WWTPs) are considered as major sinks for per- and polyfluoroalkyl substances (PFASs). However, conventional WWTPs with low efficiency are also a secondary point source of PFASs entering the environment. Herein, a large-scale investigation of PFASs was conducted in 44 WWTPs throughout Shaanxi Province in the transitional zone between North and South China. The composition profiles of target PFASs differed between wastewater and sludge samples. Perfluorobutanoic acid was dominant in wastewater influent and effluent samples, with maximum concentrations of 59.8 and 11.4 ng/L, respectively. Perfluorooctane sulfonic acid occurred predominantly in sludge samples, with a maximum concentration of 73.2 ng/g. Through wastewater treatment, short-chain PFASs with an even number of carbon atoms were mostly removed, whereas short-chain PFASs with an odd number of carbon atoms were primarily discharged into receiving water. Long-chain PFASs (perfluoroalkyl carboxylic acids: C ≥ 8; perfluoroalkane sulfonic acids: C ≥ 6) were not removed efficiently and secondary production might occur during treatment. Based on the risk quotient, PFASs residues in wastewater effluent posed minimal ecological risk, but the residues in sludge posed low to high potential risk. The mass loadings of PFASs discharged through wastewater and sludge were 15.5 and 3.74 kg/year, respectively, from all WWTPs in Shaanxi Province.

Global distributions, source-type dependencies, and concentration ranges of per- and polyfluoroalkyl substances in groundwater

A meta-analysis was conducted of published literature reporting concentrations of per- and polyfluoroalkyl substances (PFAS) in groundwater for sites distributed in 20 countries across the globe. Data for >35 PFAS were aggregated from 96 reports published from 1999 to 2021. The final data set comprises approximately 21,000 data points after removal of time-series and duplicate samples as well as non-detects. The reported concentrations range over many orders of magnitude, from ng/L to mg/L levels. Distinct differences in concentration ranges are observed between sites located within or near sources versus those that are not. Perfluorooctanoic acid (PFOA), ranging from <0.03 ng/L to ~7 mg/L, and perfluorooctanesulfonic acid (PFOS), ranging from 0.01 ng/L to ~5 mg/L, were the two most reported PFAS. The highest PFAS concentration in groundwater is ~15 mg/L reported for the replacement-PFAS 6:2 fluorotelomer sulfonate (6:2 FTS). Maximum reported groundwater concentrations for PFOA and PFOS were compared to concentrations reported for soils, surface waters, marine waters, and precipitation. Soil concentrations are generally significantly higher than those reported for the other media. This accrues to soil being the primary entry point for PFAS release into the environment for many sites, as well as the generally significantly greater retention capacity of soil compared to the other media. The presence of PFAS has been reported for all media in all regions tested, including areas that are far removed from specific PFAS sources. This gives rise to the existence of a "background" concentration of PFAS that must be accounted for in both regional and site-specific risk assessments. The presence of this background is a reflection of the large-scale use of PFAS, their general recalcitrance, and the action of long-range transport processes that distribute PFAS across regional and global scales. This ubiquitous distribution has the potential to significantly impact the quality and availability of water resources in many regions. In addition, the pervasive presence of PFAS in the environment engenders concerns for impacts to ecosystem and human health.

Assessing exposure of the Australian population to microplastics through bottled water consumption

The presence of microplastics in the environment is substantially documented; however, the pathways of dietary exposure to microplastics are not yet well understood. This is the first study to document the presence of microplastics in bottled water sold in Australia from commercial outlets. In total, 16 brands of bottled water (Australian Sourced: n = 11, Imported: n = 5) sold in the two largest supermarkets in Australia were analysed in triplicate (n = 48) for the presence of polyethylene, PE; polystyrene, PS; polypropylene, PP; polyvinyl chloride, PVC; polyethylene terephthalate, PET; polycarbonate, PC; polymethylmethacrylate, PMMA; and polyamide, PA. Microplastics were detected in 94% (n = 15) of the samples, with PP (n = 14, 88%), PET (n = 10, 63%), PA (n = 7, 44%), and PE (n = 6, 38%) the most frequently detected. On average, a litre of bottled water contained 13 ± 19 (St Dev) microplastics, ranging from 0 to 80 microplastics/L. The average size of the microplastics identified in this study was 77 ± 22 μm. It was found that bottled water sourced and packaged overseas contained four times as many microplastics compared to bottled water sourced in Australia. It was estimated that in 2017, 28.3% of the Australian population consumed on average 30.8 L of bottled water; therefore, using the result from this study it is estimated that Australians are exposed to 400 microplastics annually through the consumption of bottled water. To understand the total amount of microplastics that Australians could be exposed to through dietary routes, further work is required to observe the presence of microplastics in other beverages and food.

Application of soil amendments for reducing PFAS leachability and bioavailability

In this study, changes in PFAS leachability and bioavailability were determined following the application of RemBind®100 (R100) and RemBind®300 (R300; 1-10% w/w) to PFAS-contaminated soil (Ʃ₂₈ PFAS 3.093-32.78 mg kg^-1). Small differences were observed in PFAS immobilization efficacy when soil was amended with RemBind® products although adding 5% w/w of either product resulted in a >98% reduction in ASLP PFAS leachability. Variability in immobilization efficacy was attributed to differences in activated carbon composition which influenced physicochemical properties of RemBind® formulations and PFAS sorption. PFOS, PFHxS and PFOA relative bioavailability was also assessed in unamended and amended soil (5% w/w) using an in vivo mouse model. In unamended soil, PFAS relative bioavailability was >60% with differences attributed to physicochemical properties of soil which influenced electrostatic and hydrophobic interactions. However, when PFAS relative bioavailability was assessed in soil amended with 5% w/w R100, individual PFAS relative bioavailability was reduced to 16.1 ± 0.8% to 26.1 ± 0.9% with similar results observed when R300 (5% w/w) was utilised (14.4 ± 1.6% to 24.3 ± 0.8%). Results from this study highlight that soil amendments have the potential to reduce both PFAS leachability and relative bioavailability thereby decreasing mobility and potential exposure to soil-borne contaminants.

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) in groundwater: current understandings and challenges to overcome

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been frequently detected in groundwater globally. With the phase-out of perfluorooctane sulfonate (PFOS) and perfluorooctanate (PFOA) due to their risk to the ecosystem and human population, various novel PFASs have been used as replacements and detected in groundwater. In order to summarize the current understanding and knowledge gaps on PFASs in groundwater, we reviewed the studies about environmental occurrence, transport, and risk of legacy and novel PFASs in groundwater published from 1999 to 2021. Our review suggests that PFOS and PFOA could still be detected in groundwater due to the long residence time and the retention in the soil-groundwater system. Firefighting training sites, industrial parks, and landfills were commonly hotspots of PFASs in groundwater. More novel PFASs have been detected via nontarget analysis using high-resolution mass spectrometry. Some novel PFASs had concentrations comparable to that of PFOS and PFOA. Both legacy and novel PFASs can pose a risk to human population who rely on contaminated groundwater as drinking water. Transport of PFASs to groundwater is influenced by various factors, i.e., the compound structure, the hydrochemical condition, and terrain. The exchange of PFASs between groundwater and surface water needs to be better characterized. Field monitoring, isotope tracing, nontarget screening, and modeling are useful approaches and should be integrated to get a comprehensive understanding of PFASs sources and behaviors in groundwater.

Occurrence and fate of poly- and perfluoroalkyl substances (PFAS) in urban waters of New Zealand

Information on the occurrence of PFAS in aquatic matrices of countries with no PFAS manufacturing, e.g., New Zealand, is limited. Also, the fingerprint of PFAS along an urban water cycle, following water path from wastewater treatment plant (WWTP) effluent to treated drinking water has not been widely assessed. Hence, 38 long-, short-, ultrashort-chain PFAS and fluorinated alternatives (including precursors) were monitored in this study by collecting composite samples from two urban WWTPs of New Zealand and grab samples from the water bodies receiving the WWTPs' effluents and a drinking water treatment plant, whose source water received the effluent of one of the studied WWTPs. ∑PFAS at concentrations 0.1 - 13 ng/L were detected in all wastewater samples, including influents and different treatment stages of the two WWTPs (WW1 and WW2). The fate of most PFAS was similar in the two WWTPs, despite large differences in WWTPs' PFAS loads in the influents, serving populations (1.6 vs 0.16 million), total capacities (300 vs 54 million liters per day), and designs (aerobic and anoxic secondary treatment vs aerobic only). The fate of PFAS in WWTPs appeared to be driven by a range of processes. For instance, a simultaneous increase (41.6%) in short-chain perfluorohexanoic acid (PFHxA) concentrations and decrease (49.7%) in precursor 6:2 fluorotelomer sulfonate (6:2 FTS) concentrations after secondary biological treatment suggested possible transformation of 6:2 FTS into PFHxA during the treatment. In contrast, the reason behind an average decrease of 35% in ultrashort-chain perfluoropropionic acid (PFPrA) concentrations after treatment was unclear, and further studies are recommended. The concentrations of a linear isomer of long-chain perfluorosulfonic acid (PFOS-L) decreased (48%) in the effluent, possibly due to its partitioning to sludge. Although the concentrations of PFAS in coastal waters suggested that the WW1 effluent is a potential source of PFAS, earlier dispersion model and no detection of PFAS in the receiving waters of WW2 implied that other sources, such as septic systems, peripheral industries, and the airport, could also be contributing to PFAS in coastal waters. The source of ultrashort-chain PFPrA (5.5 ng/L) detected in the treated drinking water produced from that river was unclear. The monitoring results confirm incomplete removal of PFAS in WWTPs, indicate a possible transformation of unknown precursors present in wastewater into short-chain perfluoroalkylcarboxylic acids (PFCAs) during biological treatment, and reveal a possible accumulation of perfluoroalkylsulfonic acids (PFSAs) in the sludge, overall suggesting the circulation of PFAS in urban water systems.

PFAS Molecules: A Major Concern for the Human Health and the Environment

Per- and polyfluoroalkyl substances (PFAS) are a group of over 4700 heterogeneous compounds with amphipathic properties and exceptional stability to chemical and thermal degradation. The unique properties of PFAS compounds has been exploited for almost 60 years and has largely contributed to their wide applicability over a vast range of industrial, professional and non-professional uses. However, increasing evidence indicate that these compounds represent also a serious concern for both wildlife and human health as a result of their ubiquitous distribution, their extreme persistence and their bioaccumulative potential. In light of the adverse effects that have been already documented in biota and human populations or that might occur in absence of prompt interventions, the competent authorities in matter of health and environment protection, the industries as well as scientists are cooperating to identify the most appropriate regulatory measures, substitution plans and remediation technologies to mitigate PFAS impacts. In this review, starting from PFAS chemistry, uses and environmental fate, we summarize the current knowledge on PFAS occurrence in different environmental media and their effects on living organisms, with a particular emphasis on humans. Also, we describe present and provisional legislative measures in the European Union framework strategy to regulate PFAS manufacture, import and use as well as some of the most promising treatment technologies designed to remediate PFAS contamination in different environmental compartments.

Microplastic contamination of an unconfined groundwater aquifer in Victoria, Australia

This is the first study to show microplastics contamination in an alluvial sedimentary aquifer that has been capped from the atmosphere. Microplastics are often reported in biotic and abiotic environments, but little is known about their occurrence in groundwater systems. In this study, eight of the most commonly found microplastics in the environment (polyethylene, PE; polystyrene, PS; polypropylene, PP; polyvinyl chloride, PVC; polyethylene terephthalate, PET; polycarbonate, PC; polymethylmethacrylate, PMMA; and polyamide, PA) were analysed in triplicate groundwater samples (n = 21) from five sampling sites across seven capped groundwater monitoring bores from Bacchus Marsh (Victoria, Australia) using Agilent's novel Laser Direct Infra-Red (LDIR) imaging system. Microplastics were detected in all samples, with PE, PP, PS and PVC detected in all seven bores. The average size of the microplastics identified was 89 ± 55 μm (St.Dev.), ranging from 18 to 491 μm. The average number of microplastics detected across all sites was 38 ± 8 microplastics/L, ranging from 16 to 97 particles/L. PE and PVC in total contributed to 59% of the total sum of microplastics detected. PE was consistently detected in all seven bores (average: 11 particles/L), while PVC was more pronounced in a bore adjacent to a meat processor (52 particles/L) compared to that of its overall average of 12 particles/L. A statistically significant positive correlation was observed between PVC and PS (R = 0.934, p ≤0.001). As this study collected samples from capped groundwater bores, the most probable avenue for microplastics was permeation through soil. Therefore, to further understand the fate and transport of microplastics within a groundwater system, it is necessary to analyse a greater range of groundwater bores not only from Australia but throughout the world.

Transport and environmental risks of perfluoroalkyl acids in a large irrigation and drainage system for agricultural production

The quality of irrigation water and drainage water is essential for local ecosystem and human health in agricultural regions. In this study, the transport analysis, source identification, and environmental risk assessment of perfluoroalkyl acids (PFAAs) were conducted in the largest irrigation area in northern China. The concentrations of the total PFAAs (ΣPFAA) ranged from 41.5 to 263 ng/L in surface water, and the short-chain perfluoroalkyl carboxylic acids (PFCAs) and perfluorooctanoic acid (PFOA), were dominant with a total contribution of 94%. Generally, the ΣPFAA levels increased from irrigation waters to drainage and receiving lake waters. PFOA showed the highest increase, with potential emission sources located in the catchment of the sub main drainage ditch D5. More PFOA (36.8 kg/y) was outflowed from Ulansuhai Lake to the Yellow River than that inflowed from the Yellow River to the irrigation district (6.15 kg/y). The results of a risk assessment indicated that avian wildlife living in Ulansuhai Lake were threatened by the PFOA and perfluorobutane sulfonate (PFBS) pollution. The estimated daily intakes (EDIs) of the sum of the PFOA, perfluorononanoic acid (PFNA), perfluorohexane sulfonic acid (PFHxS), and perfluorooctane sulfonic acid (PFOS) through aquatic food consumption for people with the different aquatic food preferences accounted for 6-42% (urban) and 4-27% (rural) of the strictest tolerant daily intake (TDI) value. The results of this study highlight the impact of local emissions of PFAS on massive irrigation and drainage systems, and ultimately, the ecosystem and human health.

Detection and removal of poly and perfluoroalkyl polluting substances for sustainable environment

PFAs (poly and perfluoroalkyl compounds) are hazardous and bioaccumulative chemicals that do not readily biodegrade or neutralize under normal environmental conditions. They have various industrial, commercial, domestic and defence applications. According to the Organization for Economic Co-operation and Development, there are around 4700 PFAs registered to date. They are present in every stream of life, and they are often emerging and are even difficult to be detected by the standard chemical methods. This review aims to focus on the sources of various PFAs and the toxicities they impose on the environment and especially on humankind. Drinking water, food packaging, industrial areas and commercial household products are the primary PFAs sources. Some of the well-known treatment methods for remediation of PFAs presented in the literature are activated carbon, filtration, reverse osmosis, nano filtration, oxidation processes etc. The crucial stage of handling the PFAs occurs in determining and analysing the type of PFA and its remedy. This paper provides a state-of-the-art review of determination & tools, and techniques for remediation of PFAs in the environment. Improving new treatment methodologies that are economical and sustainable are essential for excluding the PFAs from the environment.

Natural and engineered clays and clay minerals for the removal of poly- and perfluoroalkyl substances from water: State-of-the-art and future perspectives

Poly- and perfluoroalkyl substances (PFAS) present globally in drinking-, waste-, and groundwater sources are contaminants of emerging concern due to their long-term environmental persistence and toxicity to organisms, including humans. Here we review PFAS occurrence, behavior, and toxicity in various water sources, and critically discuss their removal via mineral adsorbents, including natural aluminosilicate clay minerals, oxidic clays (Al, Fe, and Si oxides), organoclay minerals, and clay-polymer and clay‑carbon (biochar and graphene oxide) composite materials. Among the many remediation technologies, such as reverse osmosis, adsorption, advanced oxidation and biologically active processes, adsorption is the most suitable for PFAS removal in aquatic systems. Treatment strategies using clay minerals and oxidic clays are inexpensive, eco-friendly, and efficient for bulk PFAS removal due to their high surface areas, porosity, and high loading capacity. A comparison of partition coefficient values calculated from extracted data in published literature indicate that organically-modified clay minerals are the best-performing adsorbent for PFAS removal. In this review, we scrutinize the corresponding plausible mechanisms, factors, and challenges affecting the PFAS removal processes, demonstrating that modified clay minerals (e.g., surfactant, amine), including some commercially available products (e.g., FLUORO-SORB®, RemBind®, matCARE™), show good efficacy in PFAS remediation in contaminated media under field conditions. Finally, we propose future research to focus on the challenges of using clay-based adsorbents for PFAS removal from contaminated water due to the regeneration and safe-disposal of spent clay adsorbents is still a major issue, whilst enhancing the PFAS removal efficiency should be an ongoing scientific effort.

A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants

Poly- and perfluoroalkyl substances (PFAS) comprise more than 4,000 anthropogenically manufactured compounds with widescale consumer and industrial applications. This critical review compiles the latest information on the worldwide distribution of PFAS and evaluates their fate in wastewater treatment plants (WWTPs). A large proportion (>30%) of monitoring studies in WWTPs were conducted in China, followed by Europe (30%) and North America (16%), whereas information is generally lacking for other parts of the world, including most of the developing countries. Short and long-chain perfluoroalkyl acids (PFAAs) were widely detected in both the influents (up to 1,000 ng/L) and effluents (15 to >1,500 ng/L) of WWTPs. To date, limited data is available regarding levels of PFAS precursors and ultra-short chain PFAS in WWTPs. Most WWTPs exhibited low removal efficiencies for PFAS, and many studies reported an increase in the levels of PFAAs after wastewater treatment. The analysis of the fate of various classes of PFAS at different wastewater treatment stages (aerobic and/aerobic biodegradation, photodegradation, and chemical degradation) revealed biodegradation as the primary mechanism responsible for the transformation of PFAS precursors to PFAAs in WWTPs. Remediation studies at full scale and laboratory scale suggest advanced processes such as adsorption using ion exchange resins, electrochemical degradation, and nanofiltration are more effective in removing PFAS (~95-100%) than conventional processes. However, the applicability of such treatments for real-world WWTPs faces significant challenges due to the scaling-up requirements, mass-transfer limitations, and management of treatment by-products and wastes. Combining more than one technique for effective removal of PFAS, while addressing limitations of the individual treatments, could be beneficial. Considering environmental concentrations of PFAS, cost-effectiveness, and ease of operation, nanofiltration followed by adsorption using wood-derived biochar and/or activated carbons could be a viable option if introduced to conventional treatment systems. However, the large-scale applicability of the same needs to be further verified.

Occurrence of perfluorinated carboxylic acids in Mexico City's wastewater: A monitoring study in the sewerage and a mega wastewater treatment plant

An analytical method based on liquid chromatography coupled to mass spectrometry was validated to quantify five perfluorinated carboxylic acids (PFCA) namely, perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), and perfluoroundecanoic acid (PFUnA), in wastewater produced in a megacity. Sampling was performed on a monthly basis, obtaining samples from the undergrounded sewerage system and the main open-air canal transporting wastewater out the city. Steady levels of the sum of the target PFCA (ƩPFCA) were determined on both sites through the study: 419.4 ± 24.3 ng L^-1 in undergrounded sewage and 591.1 ± 39 ng L^-1 in the open-air canal. Short-chain PFCA (PFBA, PFHxA, and PFHpA) were abundant, while concentrations of PFOA and PFUnA remained lower in both sampling sites. The open-air canal was transected in four sampling points, which were sampled throughout the monitoring campaign, finding that furtive discharges of municipal and industrial wastewater increased the levels of short-chain PFCA, while those of PFOA and PFUnA were depleted. Relevant concentrations of PFBA (176.9 ± 3.3 ng L^-1), PFHxA (133.4 ± 2.5 ng L^-1), PFHpA (116.6 ± 3.9 ng L^-1), PFOA (133.1 ± 3.5 ng L^-1), and PFUnA (23.5 ± 6.5 ng L^-1) were found 60 km downstream, where the wastewater transported by the open-air canal is used in irrigation. A fraction of sewage is treated in a conventional wastewater treatment plant. The concentration of short-chain PFCA increased in effluent, adding extra loads of PFBA, PFHxA, and PFHpA to the environment.

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

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

Per- and Polyfluoroalkyl Substance (PFAS) Transport from Groundwater to Streams near a PFAS Manufacturing Facility in North Carolina, USA

We quantified per- and polyfluoroalkyl substance (PFAS) transport from groundwater to five tributaries of the Cape Fear River near a PFAS manufacturing facility in North Carolina (USA). Hydrologic and PFAS data were coupled to quantify PFAS fluxes from groundwater to the tributaries. Up to 29 PFAS were analyzed, including perfluoroalkyl acids and recently identified fluoroethers. Total quantified PFAS (ΣPFAS) in groundwater was 20-4773 ng/L (mean = 1863 ng/L); the range for stream water was 426-3617 ng/L (mean = 1717 ng/L). Eight PFAS constituted 98% of ΣPFAS; perfluoro-2-(perfluoromethoxy)propanoic acid (PMPA) and hexafluoropropylene oxide dimer acid (GenX) accounted for 61%. For PFAS discharge from groundwater to one tributary, values estimated from stream water measurements (18 ± 4 kg/yr) were similar to those from groundwater measurements in streambeds (22-25 ± 5 kg/yr). At baseflow, 32 ± 7 kg/yr of PFAS discharged from groundwater to the five tributaries, eventually reaching the Cape Fear River. Given the PFAS emission timeline at the site, groundwater data suggest the abundant fluoroethers moved through the subsurface to streams in ≪50 yr. Discharge of contaminated groundwater may lead to long-term contamination of surface water and impacts on downstream drinking water supplies. This work addresses a gap in the PFAS literature: quantifying PFAS mass transfer between groundwater and surface water using field data.

Legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Australian biosolids

Biosolids samples were collected from 19 Australian WWTPs during 2018 that cover a range of catchment types (urban, rural, industrial waste discharges) and treatment technologies. Samples were analysed for 44 PFAS using isotope dilution and alkaline extraction coupled with quantification with LC-MS/MS. The Σ₄₄PFAS mean concentration was 260 ng/g dry weight (dw) and ranged between 4.2 and 910 ng/g dw. The dominant compound class detected were the di-substituted phosphate esters (Σ₃PAPs mean 140 ng/g dw; range ND - 730 ng/g dw) which contributed 45% of the total mean Σ₄₄PFAS mass, followed by perfluoroalkyl carboxylic acids (Σ₁₁PFCAs mean 39 ng/g dw; range 2.3-120 ng/g dw) contributing 17%, and the perfluoroalkyl sulfonates (Σ₈PFSAs mean 28 ng/g dw; range 0.9-220 ng/g) which contributed 16%. Using the population data supplied by the participating WWTPs, the mean annual estimated biosolids-associated PFAS contribution is 6 mg per person per year and ranged between 0.6 mg and 15 mg. A similar population normalised concentration regardless of WWTP, region or capacity suggests that the domestic environment provides the baseline PFAS loading. Statistically significant higher Σ₄₄PFAS and PFOS concentrations were observed at urban locations. A weak correlation was observed between annual mass of PFAS associated with each individual WWTP and their percentage industrial waste contribution. This may be important for elevated PFAS concentrations observed in WWTPs with higher industrial waste inputs and requires further research.

Perfluoroalkyl Chemicals and Male Reproductive Health: Do PFOA and PFOS Increase Risk for Male Infertility?

Poly- and perfluoroalkyl substances (PFAS) are manmade synthetic chemicals which have been in existence for over 70 years. Though they are currently being phased out, their persistence in the environment is widespread. There is increasing evidence linking PFAS exposure to health effects, an issue of concern since PFAS such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) bioaccumulate in humans, with a half-life of years. Many epidemiological studies suggest that, worldwide, semen quality has decreased over the past several decades. One of the most worrying effects of PFOS and PFOA is their associations with lower testosterone levels, similar to clinical observations in infertile men. This review thus focuses on PFOS/PFOA-associated effects on male reproductive health. The sources of PFAS in drinking water are listed. The current epidemiological studies linking increased exposure to PFAS with lowered testosterone and semen quality, and evidence from rodent studies supporting their function as endocrine disruptors on the reproductive system, exhibiting non-monotonic dose responses, are noted. Finally, their mechanisms of action and possible toxic effects on the Leydig, Sertoli, and germ cells are discussed. Future research efforts must consider utilizing better human model systems for exposure, using more accurate PFAS exposure susceptibility windows, and improvements in statistical modeling of data to account for the endocrine disruptor properties of PFAS.

Per- and Polyfluoroalkyl Substances in Ducks and the Relationship with Concentrations in Water, Sediment, and Soil

The present study examined the occurrence and concentration of per- and polyfluoroalkyl substances (PFAS) measured in game ducks (13 compounds), water, sediment, and soils (33 compounds) in waterways in Victoria, Australia. The study aimed to identify potential ecological and human health risks from measured PFAS concentrations. Four species of duck and samples of water, sediment, and soil were collected from 19 wetlands, which were chosen based on their popularity as hunting locations. The risks posed by 3 PFAS (perfluorooctanoic acid, perfluorohexane sulfonic acid [PFHxS], and perfluorooctane sulfonic acid [PFOS]) to the environment and human health were assessed using available national ecological and human health guidelines. A diverse range of short- and long-chain carboxylic and sulfonic acids were found in the environment and in ducks. Concentrations were generally low and varied between wetlands, duck species, tissue analyzed (breast or liver), and environmental compartment (water, sediment, soil). Higher PFOS concentrations in water and sediments were observed at wetlands near sources of contamination (i.e., a defense base or urban environment). Elevated PFOS and PFOS + PFHxS concentrations in ducks were observed near local point sources but also at wetlands with no known point sources of contamination. There were clear differences in PFAS concentrations detected in duck tissues versus the environment, highlighting complexities of bioaccumulation, movement of animals, and spatiotemporal variation and raising questions about the relevance of using abiotic criteria to assess risk to biota. Human health risk assessment showed that only ducks inhabiting wetlands near local sources of PFAS were likely to pose a risk to consumers. Further studies are required to improve our knowledge of PFAS toxicokinetics and chronic impacts in biota to guide management decisions. Environ Toxicol Chem 2021;40:846-858. © 2020 SETAC.

The occurrence and distributions of per- and polyfluoroalkyl substances (PFAS) in groundwater after a PFAS leakage incident in 2018

Per- and polyfluoroalkyl substances (PFAS) concentrations of groundwater in three cities of the Nakdong River Basin in South Korea were quantified to investigate PFAS contamination and the effect of PFAS leakage incident that occurred in the study area in 2018. Groundwater PFASs concentration ranged from non-detectable (N.D.) to 36.9 ng/L (mean 14.1 ng/L), in which, perfluorooctanoic acid (PFOA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorohexane sulfonate (PFHxS) were commonly observed. Compared to long-chain (C ≥ 8) PFAS, short-chain (<C8) PFAS are more commonly detected in groundwater. Statistical differences were found between the groundwater obtained from different land use. PFAS detected in groundwater from industrial land use were significant different (p<0.01) than other land usages. Spatial difference of PFAS concentrations and distributions in groundwater were also found. PFAS concentrations in groundwater at the furthest downstream area (mean 26.4 ng/L) were the highest followed by the middle reaches (mean 16.2 ng/L), and the upstream area (mean 4.3 ng/L). PFHxS, which was detected dominantly in the middle reach areas, contributed 51% of the total PFAS concentration, but was not detected in the upstream area. There was no health risk by drinking groundwater but found the effect of PFHxS leakage incident on groundwater.

Disposal of products and materials containing per- and polyfluoroalkyl substances (PFAS): A cyclical problem

Per- and polyfluoroalkyl substances (PFAS), highly stable and persistent chemicals used in numerous industrial applications and consumer goods, pose an exceptionally difficult challenge for disposal. Three approaches are currently available for PFAS wastes: landfilling, wastewater treatment and incineration. Each disposal approach can return either the original PFAS or their degradation products back to the environment, illustrating that the PFAS problem is cyclical. Landfilling and wastewater treatment do not destroy PFAS and simply move PFAS loads between sites. Consumer products and various materials discarded in landfills leach PFAS over time, and landfill leachate is commonly sent to wastewater treatment plants. From wastewater treatment plants, PFAS are carried over to sludge and effluent. Sewage sludge can be landfilled, incinerated, or applied on agricultural fields, and PFAS from treated sludge (biosolids) can contaminate soil, water, and crops. Incineration of PFAS-containing wastes can emit harmful air pollutants, such as fluorinated greenhouse gases and products of incomplete combustion, and some PFAS may remain in the incinerator ash. Volatile PFAS are emitted into the air from landfills and wastewater treatment plants, and research is urgently needed on the potential presence of PFAS compounds in air emissions from commercially run incinerators. Monitoring of waste streams for PFAS, stopping PFAS discharges into water, soil and air and protecting the health of fence-line communities close to the waste disposal sites are essential to mitigate the impacts of PFAS pollution on human health.

Importance of surface roughness on perfluorooctanoic acid (PFOA) transport in unsaturated porous media

Understanding the subsurface transport of perfluorooctanoic acid (PFOA) is of considerable interest for evaluating its potential risks to humans and ecosystems. In this study, packed-column experiments were conducted to examine the influence of surface roughness on PFOA transport in unsaturated glass beads, quartz sand and limestone porous media. Results showed decreasing moisture content significantly increased the air-water interfacial adsorption of PFOA and led to greater retardation in all three types of porous media. Particularly, rougher surface (limestone > quartz sand > glass beads) and smaller grain size (i.e. a larger solid specific surface area, SSSA) significantly enhanced PFOA retardation under unsaturated conditions. These results were further supported by bubble column experiments and SSSA analysis of porous media, which demonstrate that except for the factors affecting PFOA transport in solid-water interface (e.g. surface charge and chemical heterogeneity), the greater retardation of PFOA during transport is attributed to the larger air-water interfacial areas associated with rougher surface and smaller grain size and hence greater interfacial adsorption of PFOA. Our results indicated the importance of surface roughness on the retention and transport of PFOA in the unsaturated zone.

Groundwater quality

Groundwater is a vital component of water supply for residential, industrial, and agricultural purposes. However, many groundwater basins are being used unsustainably and groundwater contamination is a growing water quality problem. Although anthropogenic activities and natural processes have been increasing the contamination in this valuable water resource, several remediation techniques have been developed in the last few decades to reduce these contamination levels. This review paper focuses on the recent studies developed on groundwater pollutions, remediation practices, and groundwater quality management. PRACTITIONER POINTS: Groundwater pollution is mainly due to anthropogenic activities and it is considered as a growing water quality problem. Groundwater bioremediation is one of the sustainable long-term solutions that uses the microorganisms to degrade the complex environmental pollutants. Groundwater quality management techniques play a significant role to restore or maintain water quality, which is critical for the sustainable development.

Challenges of aqueous per- and polyfluoroalkyl substances (PFASs) and their foreseeable removal strategies

Per- and polyfluoroalkyl substances (PFASs) are artificial refractory organic pollutants which are widely presented in aqueous environment. Due to the unquiet strength of the highly polarized carbon-fluorine bond (C-F) and their hydrophobic/lipophobic feature as well as biological persistence properties, the remediation and treatment of PFASs is a big challenge. Preliminary studies indicate that a few kinds of technical approaches could remove or transfer PFASs, but the effectiveness is not high as expected or limited while most of the techniques are only tested at laboratory scale. A review of existing treatment technologies was thus conducted for the purpose to outlook these technologies, and more importantly, to propose the foreseeable technique. As such, a constructed wetland-microbial fuel cell (CW-MFC) technology was recommended, which is a newly emerged technology by integrating physical, chemical and enhanced biological processes plus the wetland plants function with strong eco-friendly feature for a comprehensive removal of PFASs. It is expected that the review can strengthen our understanding on PFASs' research and thus can help selecting reasonable technical means of aqueous PFASs control.

A sensitive method for simultaneous determination of 12 classes of per- and polyfluoroalkyl substances (PFASs) in groundwater by ultrahigh performance liquid chromatography coupled with quadrupole orbitrap high resolution mass spectrometry

Per- and polyfluoroalkyl substances (PFASs) comprise a large group of chemicals with diverse physicochemical properties, which make their simultaneous determination a challenging task. A trace analytical method based on ultrahigh performance liquid chromatography-quadrupole Orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was developed for simultaneous determination of 54 PFASs belonging to 12 classes in groundwater, including 24 perfluorocarbons and 30 precursors. This method provided good linearity of calibration standards (R² > 0.99), excellent method limits of quantification (MLOQs) (0.5-250 pg/L), satisfactory matrix spiking recoveries (63%-148%), high precision (intra-day relative standard deviations (RSDs) 1.4-11.4%, inter-day RSDs 1.6-12.9%, and inter-week RSDs 2.1-12.7%), and short runtime (13 min), suitable for high throughput studies. The newly established method was successfully applied to detect PFASs in the groundwater samples collected from Hebei Province, China. Twenty PFASs were detected with the total concentration of 0.3-32.9 ng/L, indicating the contamination level similar to that in drinking water. The dominant PFASs were perfluorobutanesulfonate (PFBS), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA) and perfluorooctanoic acid (PFOA). In addition, 6:2 fluorotelomer phosphate diester (6:2 diPAP) and 6:2 fluorotelomer sulfonate (6:2 FTS) were found as the major precursors. The total PFAS concentrations were lower than the cumulative permissible limit of 70 ng/L for PFOS and PFOA recommended by the United States Environmental Protection Agency (USEPA) for drinking water in 2016. In a nutshell, this study provided a fast and sensitive method based on HRMS for the simultaneous analysis of a wide range of PFASs, present at trace levels in groundwater samples.

Importance of Al/Fe oxyhydroxide coating and ionic strength in perfluorooctanoic acid (PFOA) transport in saturated porous media

Understanding subsurface transport of per- and polyfluoroalkyl substances (PFASs) is of critical importance for the benign use and risk management of PFASs. As one of the most commonly found PFASs, perfluorooctanoic acid (PFOA) is used as a representative PFAS and water-saturated column experiments were conducted to investigate the effect of Al/Fe oxyhydroxide coating and ionic strength on its transport at an environmentally relevant PFOA concentration (6.8 μg L^-1). Our results showed a clear increase in PFOA retardation in Al/Fe oxyhydroxide coated sand (retardation factor: Al: 1.87-5.58, Fe: 1.28-4.05) than those in uncoated sand (1.00-1.05), due to the stronger electrostatic attraction between anionic PFOA and Al/Fe oxyhydroxide coated sand surface. Notably, Al oxyhydroxide have a more profound effect on PFOA retention and retardation than Fe oxyhydroxide. Besides, higher ionic strength significantly inhabited PFOA retention and retardation in positively charged sand, and the considerable retention of PFOA (∼90%) in deionized water than those in 1.5 mM and 30.0 mM NaCl (<10%) clearly proves the role of competitive adsorption of Cl^- on PFOA transport in positively charged sand. In contrast, higher ionic strength (0 mM-30 mM NaCl) slightly increased PFOA retardation in negatively charged sand, illustrating the dominance of electrostatic interaction. Our findings advance current knowledge to understand PFOA transport in natural media with different surface charge property under environmental PFOA concentrations.

Contamination profiles and health risks of PFASs in groundwater of the Maozhou River basin

Per-and polyfluoroalkyl substances (PFASs) are a group of chemicals with a wide range of industrial and commercial applications, but little is known about the contamination of PFASs in groundwater and their linkage to surface water. Here we investigated the occurrence of PFASs in groundwater and surface water at the Maozhou River basin in order to understand their contamination profiles and potential health risks. The results showed that total PFASs concentrations ranged from 9.9 to 592.2 ng/L, 50.2-339.9 ng/L and 3.7-74.3 ng/g in groundwater, river water and sediment, respectively. The detection frequencies of C4-C8 chains (C₄-C₈) PFASs were higher than C9-C14 chains PFASs in the river and groundwater. Statistical analysis showed an obvious correlation between the major contaminants in the river and those in the groundwater, indicating the potential linkage of PFASs in the groundwater to the surface water. The wastewater indicator found in groundwater suggested domestic wastewater was only one of the source for the PFASs in the river and groundwater of Maozhou River basin. Moreover, human health risk assessment showed low risks from the PFASs to the residents by drinking groundwater.

Capture of Perfluorooctanoic Acid Using Oil-Filled Graphene Oxide-Silica Hybrid Capsules

Fluorinated hydrocarbon (FHC) contamination has attracted global attention recently because of persistence within the environment and ecosystems of many types of FHC. The surfactant perfluorooctanoic acid (PFOA) is particularly commonly found in contaminated sites, and thus, urgent action is needed for its removal from the environment. In this study, water dispersible hybrid capsules were successfully prepared from an oil-in-water emulsion stabilized by graphene oxide and including a silicate precursor to grow a strong, mesoporous capsule shell surrounding the droplets. These capsules were decorated with amine groups to present a positively charged outer corona that attracts negative PFOA molecules. The aminated capsules were effectively applied as a novel technology to adsorb and sequester PFOA contamination in water. It was confirmed that PFOA removal by the capsules was pH and PFOA concentration dependent, with adsorption efficiencies of >60 mg g^-1 under ideal conditions. PFOA removal kinetics followed using high-performance liquid chromatography and liquid chromatography-mass spectrometry showed that capture of PFOA by the capsules reached a maximum of >99.9% in 2-3 days.

Removal of poly- and perfluoroalkyl substances (PFAS) from water by adsorption: Role of PFAS chain length, effect of organic matter and challenges in adsorbent regeneration

Poly- and perfluoroalkyl substances (PFAS) are a wide group of environmentally persistent organic compounds of industrial origin, which are of great concern due to their harmful impact on human health and ecosystems. Amongst long-chain PFAS, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are the most detected in the aquatic environment, even though their use has been limited by recent regulations. Recently, more attention has been posed on the short-chain compounds, due to their use as an alternative to long-chain ones, and to their high mobility in the water bodies. Therefore, short-chain PFAS have been increasingly detected in the environmental compartments. The main process investigated and implemented for PFAS removal is adsorption. However, to date, most adsorption studies have focused on synthetic water. The main objective of this article is to provide a critical review of the recent peer-reviewed studies on the removal of long- and short-chain PFAS by adsorption. Specific objectives are to review 1) the performance of different adsorbents for both long- and short-chain PFAS, 2) the effect of organic matter, and 3) the adsorbent regeneration techniques. Strong anion-exchange resins seem to better remove both long- and short-chain PFAS. However, the adsorption capacity of short-chain PFAS is lower than that observed for long-chain PFAS. Therefore, short-chain PFAS removal is more challenging. Furthermore, the effect of organic matter on PFAS adsorption in water or wastewater under real environmental conditions is overlooked. In most studies high PFAS levels have been often investigated without organic matter presence. The rapid breakthrough of PFAS is also a limiting factor and the regeneration of PFAS exhausted adsorbents is very challenging and needs more research.

Contamination profiles and risk assessment of per- and polyfluoroalkyl substances in groundwater in China

Per- and polyfluoroalkyl substances (PFASs) have attracted attention due to the potential risk they pose to ecosystems and human health. A total of 169 groundwater samples were collected from four representative regions in order to analyze PFASs concentrations in China. The total concentration of PFASs (∑PFASs) in groundwater ranged from 0.05 to 198.80 ng L^-1, with an average of 3.97 ng L^-1. All targeted PFASs were detected in the studied areas. The detection frequency and average concentration of perfluorooctanoic acid (PFOA) were the highest (79.29% and 1.61 ng L^-1, respectively). The contamination profiles of PFASs in each study area varied due to natural geographical conditions and human activities. According to the results of the potential source identification, the point sources of perfluorooctane sulfonate (PFOS) were mainly concentrated in Lanzhou, and the distribution of PFASs was slightly affected by atmospheric deposition in all the studied areas. The obtained concentrations of PFOA and PFOS may pose no threat to the residents due to water consumption.

Emerging and legacy contaminants across land-use gradients and the risk to aquatic ecosystems

Information on potentially harmful emerging and legacy chemicals is essential to understand the risks to the environment and inform regulatory actions. The objective of this study was to assess the occurrence, concentration, and distribution of emerging and legacy contaminants across a gradient of land-use intensity and determine the risk posed to aquatic ecosystems. The land-use intensity gradient considered was: background/undeveloped < low-intensity agriculture < high-intensity agriculture < urban residential < urban industrial. Twenty-five sites were sampled for surface water, sediment, and soil. A total of 218 chemicals were analyzed: pesticides, per- and poly-fluoroalkyl substances (PFAS), polybrominated biphenyls and polybrominated diphenyl ethers (PBDEs), phthalates, and short-chain chlorinated paraffins (SCCPs). The risk posed by the analyzed chemicals to the aquatic environment was measured using hazard quotients (HQs), which were calculated by dividing the maximum measured environmental concentration by a predicted no-effect concentration for each chemical. A HQ > 1 was considered to indicate a high risk of adverse effects from the given chemical. A total of 68 chemicals were detected: 19 pesticides, 18 PFAS, 28 PBDEs, two phthalates, and SCCPs (as total SCCPs). There were no significant differences in the overall chemical composition between land uses. However, the insecticide bifenthrin, PFAS, PBDEs, and phthalates were more frequently found in samples from residential and/or industrial sites, suggesting urban land uses are hotspots and potential large-scale sources of these chemicals. Nineteen chemicals had a HQ > 1; most had a restricted spatial distribution limited to high-intensity agriculture and industrial sites in Melbourne. Bifenthrin and the perfluorooctanesulfonic acid (PFOS) had the highest HQs in residential and industrial sites, suggesting an increased risk to aquatic ecosystems in urban settings. The results of this study will enhance future research, predictive methods, and effective targeting of monitoring, and will help guide regulatory management actions and mitigation solutions.

Effect of Sample Storage on the Quantitative Determination of 29 PFAS: Observation of Analyte Interconversions during Storage

In this study, we measured the effects of sample type and storage temperature on the stability of 29 per- and polyfluorinated alkyl substances (PFAS) in water. Spiked bottled water, surface water, and two types of effluent samples were stored in HDPE containers at +20, 4, and -20 °C over a period of up to 180 days. The analytes studied included C₄ through C₁₄ perfluorinated carboxylates (PFCAs); C₄ through C₁₀ and C₁₂ perfluorinated sulfonates (PFSAs); 4:2, 6:2, and 8:2 fluorotelomer sulfonates (FTS); three perfluorooctane sulfonamides (PFOSA, N-MeFOSA, and N-EtFOSA); two perfluorooctane sulfonamide ethanols (N-MeFOSE and N-EtFOSE); and two perfluorooctane sulfonamide acetic acids (N-MeFOSAA and EtFOSAA). Overall, 10 analytes, PFOA, PFNA, 8:2 FTS, PFOSA, N-MeFOSA, NEtFOSA, N-MeFOSAA, N-EtFOSAA, N-MeFOSE, and N-EtFOSE, showed increasing or decreasing concentration trends under at least one of the experimental conditions investigated. Increases in concentrations of N-MeFOSAA and N-EtFOSAA in surface water and effluent samples at +20 and 4 °C correlated with the decreases in the concentrations of N-MeFOSE and N-EtFOSE, respectively, suggesting analyte interconversion during sample storage. This is the first time such analyte conversion is reported in samples under storage, and this work demonstrates the importance of assessing stability of PFAS in environmentally relevant matrices. The significance of this study extends beyond sample storage for analysis, as toxicological and exposure studies conducted at room temperature also need to consider the significance of analyte degradation through the exposure process.

Occurrence and distribution of organic and inorganic pollutants in groundwater

Depletion of groundwater resources and continued decline in overall groundwater quality is a cause of concern because large human population around the world uses groundwater as a source of drinking water. This paper presents a comprehensive review of studies published in the year 2018 that documented issues of groundwater pollution, sources, and distribution reported from across the world due to anthropogenic, hydroclimatogical, and natural processes. Groundwater pollution due to organic contaminants focuses particularly on pesticides, herbicides, and contaminants of emerging concern. Pollution due to inorganic pollutants such as arsenic and other heavy metals is also reviewed with particular emphasis on regions that have reported a significantly higher incidence of these pollutants in groundwater. A compilation of various studies is also included in the review paper that showed increased incidences of waterborne illnesses due to fecal and microbial contamination due to poor sanitary practices. Reviews of groundwater contaminants such as fluoride and nitrate are included to provide readers a holistic understanding of groundwater pollution problem around the world. PRACTITIONER POINTS: Groundwater pollution issues during 2018 are reviewed and documented. Occurrence of organic and inorganic pollutants in groundwater is reported. Groundwater pollution vulnerability remains a critical issue.

Regulation of Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS) in Drinking Water: A Comprehensive Review

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are receiving global attention due to their persistence in the environment through wastewater effluent discharges and past improper industrial waste disposal. They are resistant to biological degradation and if present in wastewater are discharged into the environment. The US Environmental Protection Agency (USEPA) issued drinking water Health Advisories for PFOA and PFOS at 70 ng/L each and for the sum of the two. The need for an enforceable primary drinking water regulation under the Safe Drinking Water Act (SDWA) is currently being assessed. The USEPA faces stringent legal constraints and technical barriers to develop a primary drinking water regulation for PFOA and PFOS. This review synthesizes current knowledge providing a publicly available, comprehensive point of reference for researchers, water utilities, industry, and regulatory agencies to better understand and address cross-cutting issues associated with regulation of PFOA and PFOS contamination of drinking water.

An investigation into per- and polyfluoroalkyl substances (PFAS) in nineteen Australian wastewater treatment plants (WWTPs)

Quantifying the emissions of per- and polyfluoroalkyl substances (PFAS) from Australian wastewater treatment plants (WWTP) is of high importance due to potential impacts on receiving aquatic ecosystems. The new Australian PFAS National Environmental Management Plan recommends 0.23 ng L^-1 of PFOS as the guideline value for 99% species protection for aquatic systems. In this study, 21 PFAS from four classes were measured in WWTP solid and aqueous samples from 19 Australian WWTPs. The mean ∑₂₁PFAS was 110 ng L^-1 (median: 80 ng L^-1; range: 9.3-520 ng L^-1) in aqueous samples and 34 ng g^-1 dw (median: 12 ng g^-1 dw; range: 2.0-130 ng g^-1 dw) in WWTP solids. Similar to WWTPs worldwide, perfluorocarboxylic acids were generally higher in effluent, compared to influent. Partitioning to solids within WWTPs increased with increasing fluoroalkyl chain length from 0.05 to 1.22 log units. Many PFAS were highly correlated, and PCA analysis showed strong associations between two groups: odd chained PFCAs, PFHxA and PFSAs; and 6:2 FTS with daily inflow volume and the proportion of trade waste accepted by WWTPs (as % of typical dry inflow). The compounds PFPeA, PFHxA, PFHpA, PFOA, PFNA, and PFDA increased significantly between influent and final effluent. The compounds 6:2 FTS and 8:2 FTS were quantified and F-53B detected and reported in Australian WWTP matrices. The compound 6:2 FTS was an important contributor to PFAS emissions in the studied Australian WWTPs, supporting the need for future research on its sources (including precursor degradation), environmental fate and impact in Australian aquatic environments receiving WWTP effluent.

A single analytical method for the determination of 53 legacy and emerging per- and polyfluoroalkyl substances (PFAS) in aqueous matrices

A quantitative method for the determination of per- and polyfluoroalkyl substances (PFAS) using liquid chromatography (LC) tandem mass spectrometry (MS/MS) was developed and applied to aqueous wastewater, surface water, and drinking water samples. Fifty-three PFAS from 14 compound classes (including many contaminants of emerging concern) were measured using a single analytical method. After solid-phase extraction using weak anion exchange cartridges, method detection limits in water ranged from 0.28 to 18 ng/L and method quantitation limits ranged from 0.35 to 26 ng/L. Method accuracy ranged from 70 to 127% for 49 of the 53 extracted PFAS, with the remaining four between 66 and 138%. Method precision ranged from 2 to 28% RSD, with 49 out of the 53 PFAS being below < 20%. In addition to quantifying > 50 PFAS, many of which are currently unregulated in the environment and not included in typical analytical lists, this method has efficiency advantages over other similar methods as it utilizes a single chromatographic separation with a shorter runtime (14 min), while maintaining method accuracy and stability and the separation of branched and linear PFAS isomers. The method was applied to wastewater influent and effluent; surface water from a river, wetland, and lake; and drinking water samples to survey PFAS contamination in Australian aqueous matrices. The compound classes FTCAs, FOSAAs, PFPAs, and diPAPs were detected for the first time in Australian WWTPs and the method was used to quantify PFAS concentrations from 0.60 to 193 ng/L. The range of compound classes detected and different PFAS signatures between sample locations demonstrate the need for expanded quantitation lists when investigating PFAS, especially newer classes in aqueous environmental samples. Graphical abstract.