Root uptake and translocation of perfluorinated alkyl acids by three hydroponically grown crops

Uptake, biotransformation and physiological response of TBBPA derivatives in Helianthus annus

Tetrabromobisphenol A (TBBPA) and its derivatives are widely used as brominated flame retardants. Because of their high production and wide environment distribution, TBBPA derivatives have increased considerable concern. Previous studies have primarily focused on TBBPA, with limited information available on its derivative. In this study, we investigated the uptake, biotransformation and physiological response of two derivatives, Tetrabromobisphenol A bis(allyl ether) (TBBPA BAE) and Tetrabromobisphenol A bis(2,3-dibromopropylether) (TBBPA BDBPE), in Helianthus annus (H. annus) through a short-term hydroponic assay. The results revealed that H. annus could absorb TBBPA BAE and TBBPA BDBPE from solution, with removal efficiencies of 98.33 ± 0.5% and 98.49 ± 1.56% after 10 days, respectively, which followed first-order kinetics. TBBPA BAE was absorbed, translocated and accumulated while TBBPA BDBPE couldn't be translocated upward due to its high hydrophobicity and low solubility. The concentrations of TBBPA derivatives in plants peaked within 72 h, and then decreased. We identified twelve metabolites resulting from ether bond breakage, debromination, and hydroxylation in H. annus. The high-level TBBPA BAE suppressed the growth and increased malondialdehyde (MDA) content of H. annus, while TBBPA BDBPE didn't pose a negative effect on H. annus. TBBPA BAE and TBBPA BDBPE increased the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with higher levels of these enzymes activity found in high concentration treatments. Contrastingly, TBBPA BAE exhibited higher toxicity than TBBPA BDBPE, as indicated by greater antioxidant enzyme activity. The findings of this study develop better understanding of biotransformation mechanisms of TBBPA derivatives in plants, contributing to the assessment of the environmental and human health impacts of these contaminants.

Uptake of perfluoroalkyl substances PFOS and PFOA by free-floating hydrophytes Pistia stratiotes L. and Eichhornia crassipes (Mart.) Solms

The phytoremediation potential of floating aquatic plants to accumulate and remove two common PFAS from contaminated water was investigated. Free-floating hydrophytes Eichhornia crassipes and Pistia stratiotes were grown in water spiked with 0.5, 1, or 2 ppm perfluorooctanoic acid (PFOA) or perfluorooctanesulfonic acid (PFOS) for seven days. Both species were able to accumulate PFOA and PFOS in this time frame, with translocation factors (TF) ranging from 0.13 to 0.57 for P. stratiotes and 0.18 to 0.45 for E. stratiotes, respectively. E. crassipes accumulated a greater amount of PFOA and PFOS than P. stratiotes, with 178.9 ug PFOA and 308.5 ug PFOS removed by E. crassipes and 98.9 ug PFOA and 137.8 ug PFOS removed by P. stratiotes at the highest concentrations. Root tissue contained a higher concentration of PFOA and PFOS than shoot tissue in both species, and the concentration of PFOS was generally significantly higher than PFOA in both E. crassipes and P. stratiotes, with concentrations of 15.39 and 27.32 ppb PFOA and 17.41 and 80.62 ppb PFOS in shoots and roots of P. stratiotes and 12.59 and 37.37 ppb PFOA and 39.92 and 83.40 ppb PFOS in shoots and roots of E. crassipes, respectively. Both species may be candidates for further phytoremediation studies in aquatic ecosystems.

Crop Contamination and Human Exposure to Per- and Polyfluoroalkyl Substances around a Fluorochemical Industrial Park in China

Due to their significant environmental impact, there has been a gradual restriction of the production and utilization of legacy per- and polyfluoroalkyl substances (PFAS), leading to continuous development and adoption of novel alternatives. To effectively identify the potential environmental risks from crop consumption, the levels of 25 PFAS, including fourteen perfluoroalkyl acids (PFAAs), two precursor substances and nine novel alternatives, in agricultural soils and edible parts of various crops around a fluoride industrial park (FIP) in Changshu city, China, were measured. The concentration of ΣPFAS in the edible parts of all crops ranged from 11.64 to 299.5 ng/g, with perfluorobutanoic acid (PFBA) being the dominant compound, accounting for an average of 71% of ΣPFAS. The precursor substance, N-methylperfluoro-octanesulfonamidoacetic acid (N-MeFOSAA), was detected in all crop samples. Different types of crops showed distinguishing accumulation profiles for the PFAS. Solanaceae and leafy vegetables showed higher levels of PFAS contamination, with the highest ΣPFAS concentrations reaching 190.91 and 175.29 ng/g, respectively. The highest ΣAlternative was detected in leafy vegetables at 15.21 ng/g. The levels of human exposure to PFAS through crop consumption for various aged groups were also evaluated. The maximum exposure to PFOA for urban toddlers reached 109.8% of the standard value set by the European Food Safety Authority (EFSA). In addition, short-chained PFAAs and novel alternatives may pose potential risks to human health via crop consumption.

Commercial compost amendments inhibit the bioavailability and plant uptake of per- and polyfluoroalkyl substances in soil-porewater-lettuce systems

Compost is widely used in agriculture as fertilizer while providing a practical option for solid municipal waste disposal. However, compost may also contain per- and polyfluoroalkyl substances (PFAS), potentially impacting soils and leading to PFAS entry into food chains and ultimately human exposure risks via dietary intake. This study examined how compost affects the bioavailability and uptake of eight PFAS (two ethers, three fluorotelomer sulfonates, and three perfluorosulfonates) by lettuce (Lactuca sativa) grown in commercial organic compost-amended, PFAS spiked soils. After 50 days of greenhouse experiment, PFAS uptake by lettuce decreased (by up to 90.5 %) with the increasing compost amendment ratios (0-20 %, w/w), consistent with their decreased porewater concentrations (by 30.7-86.3 %) in compost-amended soils. Decreased bioavailability of PFAS was evidenced by the increased in-situ soil-porewater distribution coefficients (Kd) (by factors of 1.5-7.0) with increasing compost additions. Significant negative (or positive) correlations (R2 ≥ 0.55) were observed between plant bioaccumulation (or Kd) and soil organic carbon content, suggesting that compost amendment inhibited plant uptake of PFAS mainly by increasing soil organic carbon and enhancing PFAS sorption. However, short-chain PFAS alternatives (e.g., perfluoro-2-methoxyacetic acid (PFMOAA)) were effectively translocated to shoots with translocation factors > 2.9, increasing their risks of contamination in leafy vegetables. Our findings underscore the necessity for comprehensive risk assessment of compost-borne PFAS when using commercial compost products in agricultural lands.

Perfluorooctanesulfonic Acid Alters the Plant's Phosphate Transport Gene Network and Exhibits Antagonistic Effects on the Phosphate Uptake

Per- and polyfluoroalkyl substances (PFASs), with significant health risks to humans and wildlife, bioaccumulate in plants. However, the mechanisms underlying plant uptake remain poorly understood. This study deployed transcriptomic analysis coupled with genetic and physiological studies using Arabidopsis to investigate how plants respond to perfluorooctanesulfonic acid (PFOS), a long-chain PFAS. We observed increased expressions of genes involved in plant uptake and transport of phosphorus, an essential plant nutrient, suggesting intertwined uptake and transport processes of phosphorus and PFOS. Furthermore, PFOS-altered response differed from the phosphorus deficiency response, disrupting phosphorus metabolism to increase phosphate transporter (PHT) transcript. Interestingly, pht1;2 and pht1;8 mutants showed reduced sensitivity to PFOS compared to that of the wild type, implying an important role of phosphate transporters in PFOS sensing. Furthermore, PFOS accumulated less in the shoots of the pht1;8 mutant, indicating the involvement of PHT1;8 protein in translocating PFOS from roots to shoots. Supplementing phosphate improved plant's tolerance to PFOS and reduced PFOS uptake, suggesting that manipulating the phosphate source in PFOS-contaminated soils may be a promising strategy for minimizing PFOS uptake by edible crops or promoting PFOS uptake during phytoremediation. This study highlighted the critical role of phosphate sensing and transport system in the uptake and translocation of PFOS in plants.

Imprinted covalent organic frameworks solid-phase microextraction fiber for in vivo monitoring of acidic per- and polyfluoroalkyl substances in live aloe

Per- and polyfluoroalkyl substances (PFASs) can lead to risks associated with animal and human health through the transfer along food chains. It is confirmed that PFASs can be transported to each part of plants after taken up by the roots. To better elucidate the underlying mechanisms for such exposure, it is highly valuable to develop analytical capabilities for in vivo monitoring of PFASs in live plants. In this work, a novel imprinted covalent organic frameworks (CMIP) solid-phase microextraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry was developed with low limits of detection for six acidic PFASs (0.1-0.3 ng g-1) and used for in vivo monitoring in live aloe. The CMIP coating shows good precision (RSD of intra and inter ≤9.6 % and 10.2 %, respectively) and possesses much higher extraction efficiency than the commercial coatings. After cultivating aloe in soil spiked PFASs, the in vivo assays gave a wealth of information, including steady-state concentrations, translocation factors, elimination rate constants, and half-life of PFASs. The in vivo tracing method for live plants can provide much needed and unique information to evaluate the risk of PFASs, which are very important for the safety of agriculture production.

Uptake and distribution of perfluoroalkyl substances by grafted tomato plants cultivated in a contaminated site in northern Italy

Poly- and perfluoroalkyl substances (PFAS) are highly persistent and mobile pollutants raising alarming concerns due to their capability to accumulate in living organisms and exert toxic effects on human health. We studied the accumulation of different PFAS in the leaves and fruits of tomato plants grown on a PFAS-polluted soil in North-East Italy. Tomato plants were grafted with different rootstocks characterized by different vigor, and irrigated with PFAS-polluted groundwater. Leaves and fruits of the first and sixth truss were analyzed at full plant maturity. All tomato varieties accumulated PFAS in leaves and fruits, with the highest concentrations detected in the most vigorous rootstock and reflecting the PFAS concentration profile of the irrigation water. PFAS with a chain length from 4 to 8 C atoms and with carboxylic and sulfonic functional groups were detected in plant leaves, whereas only carboxylic C4, C5, and C6 PFAS were detected in tomato fruits. A general trend of decreasing PFAS concentrations in fruits upon increasing height of the plant trusses was observed. Calculation of the target hazard quotient (THQ) showed increasing values depending on the plant vigor. The hazard index (HI) values showed values slightly higher than 1 for the most vigorous plants, indicating potential risks to human health associated with the consumption of contaminated tomato fruits.

Tissue-specific distribution and bioaccumulation of perfluoroalkyl acids, isomers, alternatives, and precursors in citrus trees of contaminated fields: Implication for risk assessment

The ingestion of fruits containing perfluoroalkyl acids (PFAAs) presents potential hazards to human health. This study aimed to fill knowledge gaps concerning the tissue-specific distribution patterns and bioaccumulation behavior of PFAAs and their isomers, alternatives, and precursors (collectively as per-/polyfluoroalkyl substances, PFASs) within citrus trees growing in contaminated fields. It also assessed the potential contribution of precursor degradation to human exposure risk of PFASs. High concentrations of total target PFASs (∑PFASstarget, 92.45-7496.16 ng/g dw) and precursors measured through the total oxidizable precursor (TOP) assay (130.80-13979.21 ng/g dw) were found in citrus tree tissues, and short-chain PFASs constituted the primary components. The total PFASs concentrations followed the order of leaves > fruits > branches, bark > wood, and peel > pulp > seeds. The average contamination burden of peel (∑PFASstarget: 57.75%; precursors: 71.15%) was highest among fruit tissues. Bioaccumulation factors (BAFs) and translocation potentials of short-chain, branched, or carboxylate-based PFASs exceeded those of their relatively hydrophobic counterparts, while ether-based PFASs showed lower BAFs than similar PFAAs in above-ground tissues of citrus trees. In the risk assessment of residents consuming contaminated citruses, precursor degradation contributed approximately 36.07% to total PFASs exposure, and therefore should not be ignored.

Bioaccumulation Characteristics of Typical Perfluoroalkyl Compounds in Alfalfa Under Salt Stress

Medicago sativa, commonly known as alfalfa, is widely distributed worldwide, known for its strong stress resistance and well-developed root system, making it an important plant in ecological restoration research. To investigate the absorption and transport characteristics of alfalfa for typical perfluoroalkyl substances (PFAS) under salt stress, a 30-day indoor greenhouse experiment was conducted. The results showed that alfalfa exhibited varying degrees of absorption and transport for the selected PFAS. The highest BCF (Bioconcentration Factor) for shoot tissue reached 725.4 (for PFBA), and the highest TF (Translocation Factor) reached 53.8 (for PFPeA). Different PFAS compounds exhibited distinct bioaccumulation behaviors, with short-chain PFAS more readily entering the plant's root system and being transported upwards, while long-chain PFAS tended to adsorb to the surface of the root system. Furthermore, salt stress did not significantly affect the uptake of PFAS by alfalfa. This suggests that alfalfa is salt-tolerant and holds great potential for ecological restoration in short-chain PFAS-contaminated sites.

Bioaccumulation of PFASs in cabbage collected near a landfill site in China: Laboratory and field investigations

Previous studies found that the bioaccumulation of PFASs in vegetables poses potential risks to the health of residents in local areas near landfills in China. Therefore, our study investigated the uptake of perfluoroalkyl and polyfluoroalkyl substances (PFASs) and their accumulation and distribution in cabbage roots, stems, and leaves under both field and laboratory hydroponic conditions. It was found that the sum of concentration of 15 PFASs (designated as Σ15PFASs) in roots, stems, and leaves ranged from 24.8 to 365 ng/g, 49.2 to 204 ng/g, 11.9 to 115 ng/g, respectively, in the order of roots > stems > leaves, which were generally higher than the range in soil samples (6.07-63.91 ng/g). The dominant compounds in cabbage were PFBA and PFDA in field and hydroponic samples, respectively. The hydroponic experimental results revealed that the sum concentration of 10 PFASs (designated as Σ10PFASs) was the highest in roots, and PFDA was the dominant compound in different cabbage fractions. Bioconcentration factors of short-chain PFBA, PFPeA, and PFBS in hydroponics followed the trend of leaves > stems > roots, indicating that they were readily transported from roots to stems, and then to leaves, with the majority stored in leaves at abundance levels of 53 %, 71 %, and 60 %, respectively. Additionally, the much higher concentration factor for 6:2 FTS in leaves suggested a higher potential health risk than PFOS in terms of dietary consumption of cabbage leaves.

Per- and polyfluoroalkyl substances (PFAS) in grocery store foods: method optimization, occurrence, and exposure assessment

Dietary exposure to per- and polyfluoroalkyl substances (PFAS) is poorly understood. Evaluating PFAS in food is complicated by the need to evaluate varied matrices and a lack of a standard, matrix-specific sample extraction methods. Prior food studies implemented universal rather than matrix-specific extraction approaches, which may yield false negatives and an underestimation of PFAS dietary exposure if methods are not suitable to all matrices. Here the objectives were to screen and optimize PFAS extraction methods for plants, tissues, and dairy; apply optimized extraction methods to a grocery store food survey; and compare estimated exposure to published reference doses (RfDs). Optimized, matrix-specific extractions generally yielded internal standard recoveries of 50-150% and matrix spike recoveries of 70-130%. The frequency of PFAS detection in grocery store foods (16 of 22 products) was higher than in previous work. PFAS were detected at concentrations of 10 ng kgdw-1 (perfluorobutane sulfonate; washed green beans and perfluorohexanoic acid; unwashed tomato) to 2680 ng kgdw-1 (perfluorohexane sulfonate; radish). Concentrations of perfluorooctanoic acid (PFOA) in carrots, lettuce, radish, and canned green beans yielded median exposure intake (EI) values of 0.016-0.240 ng per kgbw-day, which exceeded the EPA RfD (0.0015 ng per kgbw-day). Washing reduced radish PFOA concentrations below detection, but EIs at the reporting limit still exceeded the RfD. The combination of improved data quality and greater frequency of PFAS detection vs. prior studies plus EI > RfD for some PFAS suggests a need for matrix-specific extractions and analysis of PFAS in additional grocery store foods from broader geographic regions.

Biotechnology to reduce logistics burden and promote environmental stewardship for Air Force civil engineering requirements

This review provides discussion of advances in biotechnology with specific application to civil engineering requirements for airfield and airbase operations. The broad objectives are soil stabilization, waste management, and environmental protection. The biotechnology focal areas address (1) treatment of soil and sand by biomineralization and biopolymer addition, (2) reduction of solid organic waste by anaerobic digestion, (3) application of microbes and higher plants for biological processing of contaminated wastewater, and (4) use of indigenous materials for airbase construction and repair. The consideration of these methods in military operating scenarios, including austere environments, involves comparison with conventional techniques. All four focal areas potentially reduce logistics burden, increase environmental sustainability, and may provide energy source, or energy-neutral practices that benefit military operations.

Exposure of Lemna minor (Common Duckweed) to Mixtures of Uranium and Perfluorooctanoic Acid (PFOA)

A variety of processes, both natural and anthropogenic, can have a negative impact on surface waters, which in turn can be detrimental to human and environmental health. Few studies have considered the ecotoxicological impacts of concurrently occurring contaminants, and that is particularly true for mixtures that include contaminants of emerging concern (CEC). Motivated by this knowledge gap, the present study considers the potential ecotoxicity of environmentally relevant contaminants in the representative aquatic plant Lemna minor (common duckweed), a model organism. More specifically, biological effects associated with exposure of L. minor to a ubiquitous radionuclide (uranium [U]) and a fluorinated organic compound (perfluorooctanoic acid [PFOA], considered a CEC), alone and in combination, were monitored under controlled laboratory conditions. Lemna minor was grown for 5 days in small, aerated containers. Each treatment consisted of four replicates with seven plants each. Treatments were 0, 0.3, and 3 ppb PFOA; 0, 0.5, and 5 ppb U; and combinations of these. Plants were observed daily for frond number and signs of chlorosis and necrosis. Other biological endpoints examined at the conclusion of the experiment were chlorophyll content and antioxidant capacity. In single-exposure experiments, a slight stimulatory effect was observed on frond number at 0.3 ppb PFOA, whereas both concentrations of U had a detrimental effect on frond number. In the dual-exposure experiment, the combinations with 5 ppb U also had a detrimental effect on frond number. Results for chlorophyll content and antioxidant capacity were less meaningful, suggesting that environmentally relevant concentrations of PFOA and U have only subtle effects on L. minor growth and health status. Environ Toxicol Chem 2023;42:2412-2421. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

The concentration of pesticides in tomato: a global systematic review, meta-analysis, and health risk assessment

To improve farming productivity, a large number of pesticides have been used worldwide in recent decades, leading to the pollution of soil, agri-products, and water, directly/indirectly affecting human health. In this regard, many studies were conducted in different countries on residual pesticides in the environment. In the current study, residual pesticides including chlorpyrifos, cypermethrin, diazinon, malathion, and metalaxyl in tomatoes were meta-analyzed and health risk of consumers was estimated. For this purpose, based on a systematic review, data from 47 studies were extracted and meta-analyzed, and the health impact of pooled concentrations was assessed via a health risk method. According to the results, metalaxyl had the most concentration followed by malathion, cypermethrin, diazinon, and chlorpyrifos, respectively. The non-carcinogenic risk (n-CR) was calculated from crop consumption also showed that exposure to malathion has the most risk. Among the investigated communities, Iranian consumers were in considerable health risk (THQ > 1). Considering that the potential for the use of pesticides will increase with the need for food in the future, hence, governments must manage the usage by governments via alternative methods such as cultural, biological, physical, and genetic modifications.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) and the influence of supplements on the performance of short-rotation crops

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic compounds threatening water quality and food safety worldwide. Phytoremediation is a nature-based, cost-effective, and scalable solution with high potential for treating PFAS-contaminated sites. However, there is a large knowledge gap regarding choice of plant species and methods to enhance performance. This study assessed the PFAS phytoextraction potential of sunflower (Helianthus annuus), mustard (Brassica juncea), and industrial hemp (Cannabis sativa) in a greenhouse experiment, using inorganic fertilizer and a microbial mixture as supplements. PFAS concentrations were measured using UPLC-MS/MS, and bioconcentration factors for different plant tissues and removal efficiency were determined. Perfluoroalkyl carboxylic acid (PFCA) accumulation was 0.4-360 times higher than that of perfluoroalkyl sulfonic acid (PFSA) homologues of similar perfluorocarbon chain length. Inorganic fertilizer significantly (p < 0.001) reduced PFAS concentration in all plant tissues, whereas the microbial mixture tested did not affect PFAS concentration. PFAS uptake ranged from 0.2 to 33% per crop cycle. Overall, the potential number of crop cycles required for removal of 90% of individual PFAS ranged from six (PFPeA) to 232 (PFOA) using sunflower, 15 (PFPeA) to 466 (PFOS) using mustard and nine (PFPeA) to 420 (PFOS) using Hemp. In this study, the percentage of PFAS removal by plants was determined, and an estimation of the time required for PFAS phytoextraction was determined for the first time. This information is important for practical phytoremediation applications.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) by weeds: Effect of PFAS physicochemical properties and plant physiological traits

Phytoextraction is a promising technology that uses plants to remediate contaminated soil. However, its feasibility for per- and polyfluoroalkyl substances (PFAS) and the impact of PFAS properties and plant traits on phytoextraction efficacy remains unknown. In this study, we conducted greenhouse experiment and evaluated the potential of weeds for phytoextraction of PFAS from soil and assessed the effects of PFAS properties and plant traits on PFAS uptake via systematic correlation analyses and electron probe microanalyzer with energy dispersive spectroscopy (FE-EPMA-EDS) imaging. The results showed that 1) phytoextraction can remove 0.04%- 41.4%wt of PFAS from soil, with extracted PFAS primarily stored in plant shoots; 2) Weeds preferentially extracted short-chain PFAS over long-chain homologues from soil. 3) PFAS molecular size and hydrophilicity determined plant uptake behavior, while plant morphological traits, particularly root protein and lipid content, influenced PFAS accumulation and translocation. Although plants with thin roots and small leaf areas exhibited greater PFAS uptake and storage ability, the impact of PFAS physicochemical properties was more significant. 4) Finally, short-chain PFAS were transported quickly upwards in the plant, while uptake of long-chain PFOS was restricted.

Linking drivers of plant per- and polyfluoroalkyl substance (PFAS) uptake to agricultural land management decisions

Widespread contamination of the per- and polyfluoroalkyl substance (PFAS) in agricultural areas is largely attributed to the application of sewage sludge in which the PFAS can be concentrated. This creates a pathway for these contaminants to enter the food chain and, by extension, causes human health and economic concerns. One barrier to managing land with PFAS contamination is the variation in reported plant uptake levels across studies. A review of the literature suggests that the variation in plant uptake is influenced by a host of factors including the composition of PFAS chemicals, soil conditions, and plant physiology. Factors include (1) the chemical components of the PFAS such as the end group and chain length; (2) drivers of soil sorption such as the presence of soil organic matter (SOM), multivalent cation concentration, pH, soil type, and micropore volume; and (3) crop physiological features such as fine root area, percentage of mature roots, and leaf blade area. The wide range of driving factors highlights a need for research to elucidate these mechanisms through additional experiments as well as collect more data to support refined models capable of predicting PFAS uptake in a range of cropping systems. A conceptual framework presented here links drivers of plant PFAS uptake found in the literature to phytomanagement approaches such as modified agriculture or phytoremediation to provide decision support to land managers.

Enhancement of perfluorooctanoic acid and perfluorooctane sulphonic acid removal in constructed wetland using iron mineral: Performance and mechanisms

Polyfluoroalkyl substance (PFAS) pose a threat to the aquatic environment due to their environmental persistence. The removal of PFAS using constructed wetlands (CWs) has received interest, but the adsorption saturation and limited removal capacity of the substrate is frequently challenging. To enhance the microbial degradation and performance of the substrate, different configurations of iron minerals were used as substrate to remove perfluorooctane sulphonic acid (PFOS) and perfluorooctanoic acid (PFOA) from CWs. The addition of iron minerals resulted in elimination of 57.2% and 63.9% of PFOS and PFOA in the effluent, respectively, which were 35.0% and 36.8% higher than that of control. Moreover, up to 85.4%, 86%, and 85.1% of NH₄⁺, NO₃^-, and phosphorus, respectively, was removed using iron minerals. The enhanced electron transfer in iron mineral-based CWs was confirmed by a 61.2% increase in cytochrome C reductase content and an increased Fe(III)/Fe(II) ratio. Microbial analysis showed that the proportions of microbes with PFAS removal capacity (e.g. Burkholderiae and Pseudomonas), and the key pathways of the TCA cycle and glycolysis were increased in iron mineral-based CW. Based on these findings, we conclude that supplementation with iron mineral could enhance PFOA and PFOS removal in CWs.

Bioaccumulation of Per- and Polyfluoroalkyl Substances (PFAS) in Ferns: Effect of PFAS Molecular Structure and Plant Root Characteristics

The present study assessed the bioaccumulation potential of per- and polyfluoroalkyl substances (PFAS) in ferns and linked root uptake behaviors to root characteristics and PFAS molecular structure. Tissue and subcellular-level behavioral differences between alternative and legacy PFAS were compared via an electron probe microanalyzer with energy dispersive spectroscopy (EPMA-EDS) and differential centrifugation. Our results show that ferns can accumulate PFAS from water, immobilize them in roots, and store them in harvestable tissue. The PFAS loading in roots was dominated by PFOS; however, a substantial amount of associated PFOS could be rinsed off by methanol. Correlation analyses indicated that root length, surface and project area, surface area per unit length of the root system, and molecular size and hydrophobicity of PFAS were the most significant factors affecting the magnitude of root uptake and upward translocation. EPMA-EDS images together with exposure experiments suggested that long-chain hydrophobic compounds tend to be adsorbed and retained on the root epidermis, while short-chain compounds are absorbed and quickly translocated upward. Our findings demonstrated the feasibility of using ferns in phytostabilization and phytoextraction initiatives of PFAS in the future.

Phytoremediation of fluoroalkylethers (ether-PFASs): A review on bioaccumulation and ecotoxilogical effects

Fluoroalkylethers (ether-PFASs), as alternatives to phased-out per- and perfluoroalkyl substances (PFASs), have attracted mounting attention due to their ubiquitous detection in aquatic environment and their similarity to legacy PFASs in terms of persistence and toxicity. In this review, the sources and distribution of ether-PFASs in soil ecosystem as well as their toxic impacts on soil microbial community are summarized. The plant uptake and bioaccumulation potential of ether-PFASs are presented, and a wide range of the influencing factors for their uptake and translocation is discussed. In response to ether-PFASs, the corresponding phytotoxic effects, such as seed germination, plant growth, photosynthesis, oxidative damage, antioxidant enzymes activities, and genotoxicity, are systematically elucidated. Finally, the current knowledge gaps and future research prospective are highlighted. The findings of this review will advance our understanding for the environmental behavior and implications ether-PFASs in soil-plant systems and help explore the strategies for ether-PFASs remediation to minimize their adverse toxicity.

Effects of physicochemical properties and co-existing zinc agrochemicals on the uptake and phytotoxicity of PFOA and GenX in lettuce

Even though the potential toxicity and treatment methods for per- and polyfluoroalkyl substances (PFAS) have attracted extensive attention, the plant uptake and accumulation of PFAS in edible plant tissues as a potential pathway for human exposure received little attention. Our study in a hydroponic system demonstrated that perfluorooctanoic acid (PFOA) and its replacing compound, 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy) propanoic acid (GenX) displayed markedly different patterns of plant uptake and accumulation. For example, the root concentration factor (RCF) of PFOA in lettuce is almost five times of that of GenX while the translocation factor (TF) of GenX is about 66.7% higher than that for PFOA. The co-presence of zinc amendments affected the phyto-effect of these two compounds and their accumulation in plant tissues, and the net effect on their plant accumulation depended on both the properties of Zn amendments and PFAS. Zinc oxide nanoparticles (ZnONPs) at 100 mg/L did not affect the uptake of PFOA in either lettuce roots or shoots; however, Zn2+ at the same concentration significantly increased PFOA accumulation in both tissues. In contrast, both Zn amendments significantly lowered the accumulation of GenX in lettuce roots, but only ZnONPs significantly hindered the GenX accumulation in lettuce shoots. The co-exposure to ZnONPs and PFOA/GenX resulted in lower oxidative stress than the plants exposed to PFOA or GenX alone. However, both zinc agrochemicals with or without PFAS led to lower root dry biomass. The results shed light on the property-dependent plant uptake of PFAS and the potential impact of co-existing nanoagrochemicals and their dissolved ions on plant uptake of PFOA and GenX.

Uptake and translocation of both legacy and emerging per- and polyfluorinated alkyl substances in hydroponic vegetables

The extensive use of per- and polyfluorinated alkyl substances (PFASs) and their substitutes has resulted in their frequent detections in environmental matrices. However, limited information is known about their uptake into vegetables and health risk through diet, particularly for those emerging alternatives. In this study, a total of 17 PFASs (namely 12 legacy PFASs and 5 of their alternatives) were compared for their accumulation into four staple vegetables (lettuce, Chinese cabbage, chrysanthemum coronarium, and cucumber) in hydroponic system with single PFAS concentration being 10 μg/L, except for 8:2 chlorinated polyfluoroalkyl ether sulfonate (Cl-PFESA) as 0.5 μg/L. The sum concentrations of 17 PFASs in edible parts were in the order of Chinese cabbage leaf (13,456 ng/g) > lettuce leaf (5996 ng/g) > cucumber fruit (4115 ng/g) >chrysanthemum coronarium stem (3999 ng/g). For perfluorooctanoate acid (PFOA) and its alternatives, hexafluoropropylene oxide trimer acid (HFPO-TA) preferentially accumulated in roots than PFOA with root concentration factors being 35.7-99.9. Translocation to edible parts was more remarkable for hexafluoropropylene oxide dimer acid (HFPO-DA) compared with PFOA in lettuce and cucumber. For perfluorooctanesulfonate acid (PFOS) and its alternatives, roots of all the four vegetables were found to more readily accumulate 8:2 Cl-PFESA than PFOS, but 8:2 Cl-PFESA was hardly translocated to the aerial parts. Significantly (p < 0.05) higher edible concentrations of 8:2 and 6:2 fluorotelomer sulfonic acids (FTSA) than that of PFOS were observed for cucumber.

Cross-sectional associations of maternal PFAS exposure on SARS-CoV-2 IgG antibody levels during pregnancy

BACKGROUND

Perfluoroalkylated substances (PFAS) are man-made, persistent organic compounds with immune-modulating potentials. Given that pregnancy itself represents an altered state of immunity, PFAS exposure-related immunotoxicity is an important environmental factor to consider in SARS-CoV-2 infection during pregnancy as it may further affect humoral immune responses.

AIM

To investigate the relationship between maternal plasma PFAS concentrations and SARS-CoV-2 antibody levels in a NYC-based pregnancy cohort.

METHODS

Maternal plasma was collected from 72 SARS-CoV-2 IgG + participants of the Generation C Study, a birth cohort established at the beginning of the COVID-19 pandemic in New York City. Maternal SARS-CoV-2 anti-spike IgG antibody levels were measured using ELISA. A panel of 16 PFAS congeners were measured in maternal plasma using a targeted UHPLC-MS/MS-based assay. Spearman correlations and linear regressions were employed to explore associations between maternal IgG antibody levels and plasma PFAS concentrations. Weighted quantile sum (WQS) regression was also used to evaluate mixture effects of PFAS. Models were adjusted for maternal age, gestational age at which SARS-CoV-2 IgG titer was measured, COVID-19 vaccination status prior to IgG titer measurement, maternal race/ethnicity, parity, type of insurance and pre-pregnancy BMI.

RESULTS

Our study population is ethnically diverse with an average maternal age of 32 years. Of the 16 PFAS congeners measured, nine were detected in more than 60% samples. Importantly, all nine congeners were negatively correlated with SARS-CoV-2 anti-spike IgG antibody levels; n-PFOA and PFHxS, PFHpS, and PFHxA reached statistical significance (p < 0.05) in multivariable analyses. When we examined the mixture effects using WQS, a quartile increase in the PFAS mixture-index was significantly associated with lower maternal IgG antibody titers (beta [95% CI] = -0.35 [-0.52, -0.17]). PFHxA was the top contributor to the overall mixture effect.

CONCLUSIONS

Our study results support the notion that PFAS, including short-chain emerging PFAS, act as immunosuppressants during pregnancy. Whether such compromised immune activity leads to downstream health effects, such as the severity of COVID-19 symptoms, adverse obstetric outcomes or neonatal immune responses remains to be investigated.

Transport and transformation of perfluoroalkyl acids, isomer profiles, novel alternatives and unknown precursors from factories to dinner plates in China: New insights into crop bioaccumulation prediction and risk assessment

Perfluoroalkyl acids (PFAAs) are contaminants of global concern, and the inadvertent consumption of PFAA-contaminated crops may pose a threat to public health. Therefore, systematically studying their source tracing, bioaccumulation prediction and risk assessments in crops is an urgent priority. This study investigated the source apportionment and transport of PFAAs and novel fluorinated alternatives (collectively as per- and polyfluoroalkyl substances, PFASs) from factories to agricultural fields in a fluorochemical industrial region of China. Furthermore, bioaccumulation specificities and prediction of these chemicals in different vegetables were explored, followed by a comprehensive risk assessment from agricultural fields to dinner plates which considered precursor degradation. A positive matrix factorization model revealed that approximately 70 % of PFASs in agricultural soils were derived from fluorochemical manufacturing and metal processing. Alarming levels of ∑PFASs ranged 8.28-84.3 ng/g in soils and 163-7176 ng/g in vegetables. PFAS with short carbon chain or carboxylic acid group as well as branched isomers exhibited higher environmental transport potentials and bioaccumulation factors (BAFs) across a range of vegetables. The BAFs of different isomers of perfluorooctanoic acid (PFOA) decreased as the perfluoromethyl group moved further from the acid functional group. Hexafluoropropylene oxide dimer acid (GenX) showed relatively low BAFs, probably related to its ether bond with a high affinity to soil. Vegetables with fewer Casparian strips (e.g., carrot and radish), or more protein, possessed larger BAFs of PFASs. A bioaccumulation equation integrating critical parameters of PFASs, vegetables and soils, was built and corroborated with a good contamination prediction. After a total oxidizable precursors (TOP) assay, incremental perfluoroalkyl carboxylic acids (PFCAs) were massively found (325-5940 ng/g) in edible vegetable parts. Besides, precursor degradation and volatilization loss of PFASs was firstly confirmed during vegetable cooking. A risk assessment based on the TOP assay was developed to assist the protection of vegetable consumers.

PFAS accumulation in several terrestrial plant and invertebrate species reveals species-specific differences

Despite the known persistence and bioaccumulation potential of perfluoroalkyl substances (PFAS), much uncertainty exists regarding their bioavailability in the terrestrial environment. Therefore, this study investigated the influence of soil characteristics and PFAS concentrations on the adsorption of PFAS to soil and their influence on the PFAS bioavailability to terrestrial plants and invertebrates. PFAS concentrations and profile were compared among different invertebrate and plant species and differences between leaves and fruits/nuts of the plant species were assessed. Soil concentrations were primarily affected by organic carbon content. The PFAS accumulation in biota was, except for PFOA concentrations in nettles, unrelated to the soil concentrations, as well as to the soil characteristics. The PFAS profiles in soil and invertebrates were mainly dominated by PFOA and PFOS, whereas short-chained PFAS were more abundant in plant tissues. Our results show that different invertebrate taxa accumulate different PFAS, likely due to dietary differences. Both long-chained and, to lesser extent, short-chained PFAS were observed in herbivorous invertebrate taxa, whereas the carnivorous invertebrates only accumulated long-chained PFAS. Correlations were observed between PFOA concentrations in herbivorous invertebrates and in the leaves of some plant species, whereas such relationships were absent for the carnivorous spiders. It is essential to continuously monitor PFAS exposure in terrestrial organisms, taking into account differences in bioaccumulation, and subsequent potential toxicity, among taxa, in order to protect the terrestrial ecosystem.

Critical review on phytoremediation of polyfluoroalkyl substances from environmental matrices: Need for global concern

Poly- and perfluoroalkyl substances (PFAS) are a class of emerging organic contaminants that are impervious to standard physicochemical treatments. The widespread use of PFAS poses serious environmental issues. PFAS pollution of soils and water has become a significant issue due to the harmful effects of these chemicals both on the environment and public health. Owing to their complex chemical structures and interaction with soil and water, PFAS are difficult to remove from the environment. Traditional soil remediation procedures have not been successful in reducing or removing them from the environment. Therefore, this review focuses on new phytoremediation techniques for PFAS contamination of soils and water. The bioaccumulation and dispersion of PFAS inside plant compartments has shown great potential for phytoremediation, which is a promising and unique technology that is realistic, cost-effective, and may be employed as a wide scale in situ remediation strategy.

Perfluorooctanoic acid uptake in the mustard species Brassica juncea

Perfluorooctanoic acid (PFOA), a surfactant, is a member of the perfluoroalkyl acids (PFAAs) family and is a contaminant of emerging concern for human and environmental health. Perfluorooctanoic acid is a persistent organic pollutant, but currently little is known about (a) the potential ecological and toxicological effects of PFOA and (b) how PFOA moves in the environment. This study uses a radiotracer (¹⁴ C-PFOA) to study the uptake and translocation of PFOA in hydroponically grown brown mustard [Brassica juncea (L.) Czern.], a representative crop species. Plants were exposed in quadruplicate over the course of 7 d (with plants sampled on Days 4 and 7) to PFOA concentrations of 0, 1, 5, 10, and 15 mg L^-1 . Uptake was quantified via liquid scintillation counting of samples from the nutrient solution, roots, stems, and leaves. Transfer factors (roots to shoots) ranged from 0.15 to 4.73 kg kg^-1 . Bioconcentration factors (solution to plant) ranged from 0.36 to 62.29 L kg^-1 . Factors were influenced by plant compartment, day sampled, and treatment level.

Chemicals/materials of emerging concern in farmlands: sources, crop uptake and potential human health risks

Certain chemicals/materials that are contaminants of emerging concern (CECs) have been widely detected in water bodies and terrestrial systems worldwide while other CECs occur at undetectable concentrations. The primary sources of CECs in farmlands are agricultural inputs, such as wastewater, biosolids, sewage sludge, and agricultural mulching films. The percent increase in cropland area during 1950-2016 was 30 and the rise in land use for food crops during 1960-2018 was 100-500%, implying that there could be a significant CEC burden in farmlands in the future. In fact, the alarming concentrations (μg kg^-1) of certain CECs such as PBDEs, PAEs, and PFOS that occur in farmlands are 383, 35 400 and 483, respectively. Also, metal nanoparticles are reported even at the mg kg^-1 level. Chronic root accumulation followed by translocation of CECs into plants results in their detectable concentrations in the final plant produce. Thus, there is a continuous flow of CECs from farmlands to agricultural produce, causing a serious threat to the terrestrial food chain. Consequently, CECs find their way to the human body directly through CEC-laden plant produce or indirectly via the meat of grazing animals. Thus, human health could be at the most critical risk since several CECs have been shown to cause cancers, disruption of endocrine and cognitive systems, maternal-foetal transfer, neurotoxicity, and genotoxicity. Overall, this comprehensive review provides updated information on contamination of chemicals/materials of concern in farmlands globally, sources for their entry, uptake by crop plants, and their likely impact on the terrestrial food chain and human health.

Insight into the uptake and translocation of per- and polyfluoroalkyl substances in hydroponically grown lettuce

The prevalence of per- and polyfluoroalkyl substances (PFASs) in agricultural soils has raised concerns regarding the health risks associated with the consumption of PFAS-contaminated agricultural products. The present study investigated the uptake and translocation of nine PFASs in lettuce using a hydroponic setting. During the uptake experiments, long-chain PFASs (≥ C8) exhibited greater accumulations in lettuce roots, while short-chain PFASs (≤ C7) manifested preferential transport to the shoots. The average root concentration factors of PFASs were positively correlated with their log Kow values. A significantly negative relationship was found between the average translocation factors of PFASs and their molecular volume. Sorption of long-chain PFASs by lettuce roots was enhanced after heating the roots to increase the cell membrane permeability. The accumulation of perfluorododecanoic acid increased significantly in shoots of lettuce plants without roots as compared to whole lettuce plants. Results of the present study indicate that sorption to root surface tissues and efficiency in passing through the root Casparian strip are two important factors that affect the uptake and distribution of PFASs within plants.

Perfluorinated alkyl substances affect the growth, physiology and root proteome of hydroponically grown maize plants

Poly- and perfluorinated alkyl substances (PFAS) are a group of persistent organic pollutants causing serious global concern. Plants can accumulate PFAS but their effect on plant physiology, especially at the molecular level is not very well understood. Hence, we used hydroponically-grown maize plants treated with a combination of eleven different PFAS (each at 100 μg L^-1) to investigate their bioaccumulation and effects on the growth, physiology and their impact on the root proteome. A dose-dependent decrease in root growth parameters was evidenced with a significant reduction in the relative growth rate, fresh weight of leaves and roots and altered photosynthetic parameters in PFAS-treated plants. Higher concentration of shorter PFAS (C < 8) was detected in the leaves, while long-chain PFAS (C ≥ 8) were more retained in roots. From the root proteome analysis, we identified 75 differentially abundant proteins, mostly involved in cellular metabolic and biosynthetic processes, translation and cytoskeletal reorganization. Validating the altered protein abundance using quantitative real-time PCR, the results were further substantiated using amino acid and fatty acid profiling, thus, providing first insight into the altered metabolic state of plants exposed to PFAS from a proteomics perspective.

Phytoremediation prospects of per- and polyfluoroalkyl substances: A review

Extensive use of per- and polyfluoroalkyl substances (PFASs) in various industrial activities and daily-life products has made them ubiquitous contaminants in soil and water. PFAS-contaminated soil acts as a long-term source of pollution to the adjacent surface water bodies, groundwater, soil microorganisms, and soil invertebrates. While several remediation strategies exist to eliminate PFASs from the soil, strong ionic interactions between charged groups on PFAS with soil constituents rendered these PFAS remediation technologies ineffective. Pilot and field-scale data from recent studies have shown a great potential of PFAS to bio-accumulate and distribute within plant compartments suggesting that phytoremediation could be a potential remediation technology to clean up PFAS contaminated soils. Even though several studies have been performed on the uptake and translocation of PFAS by different plant species, most of these studies are limited to agricultural crops and fruit species. In this review, the role of both aquatic and terrestrial plants in the phytoremediation of PFAS was discussed highlighting different mechanisms underlying the uptake of PFASs in the soil-plant and water-plant systems. This review further summarized a wide range of factors that influence the bioaccumulation and translocation of PFASs within plant compartments including both structural properties of PFASs and physiological properties of plant species. Even though phytoremediation appears to be a promising remediation technique, some limitations that reduced the feasibility of phytoremediation in the practical application have been emphasized in previous studies. Additional research directions are suggested, including advanced genetic engineering techniques and endophyte-assisted phytoremediation to upgrade the phytoremediation potential of plants for the successful removal of PFASs.

Perfluorobutanoic Acid (PFBA) Induces a Non-Enzymatic Oxidative Stress Response in Soybean (Glycine max L. Merr.)

Short-chain perfluoroalkyl substances (PFAS) are generally considered to be of less environmental concern than long-chain analogues due to their comparatively shorter half-lives in biological systems. Perfluorobutanoic acid (PFBA) is a short-chain PFAS with the most root–shoot transfer factor of all PFAS. We investigated the impact of extended exposure of soybean plants to irrigation water containing environmentally relevant (100 pg–100 ng/L) to high (100 µg–1 mg/L) concentrations of PFBA using phenotypical observation, biochemical characterization, and transcriptomic analysis. The results showed a non-monotonous developmental response from the plants, with maximum stimulation and inhibition at 100 ng/L and 1 mg/L, respectively. Higher reactive oxygen species and low levels of superoxide dismutase (SOD) and catalase (CAT) activity were observed in all treatment groups. However transcriptomic analysis did not demonstrate differential expression of SOD and CAT coding genes, whereas non-enzymatic response genes and pathways were enriched in both groups (100 ng/L and 1 mg/L) with glycine betaine dehydrogenase showing the highest expression. About 18% of similarly downregulated genes in both groups are involved in the ethylene signaling pathway. The circadian rhythm pathway was the only differentially regulated pathway between both groups. We conclude that, similar to long chain PFAS, PFBA induced stress in soybean plants and that the observed hormetic stimulation at 100 ng/L represents an overcompensation response, via the circadian rhythm pathway, to the induced stress.

The development of diffusive equilibrium, high-resolution passive samplers to measure perfluoroalkyl substances (PFAS) in groundwater

Per- and poly-fluoroalkyl substances (PFAS) are a group of anthropogenic, highly recalcitrant organic compounds consisting of thousands of individual species that are of increasing importance as groundwater contaminants. In-situ measurements of PFAS would be useful to better understand vertical profiles and mobility, contamination in partially saturated media, and to reduce sampling artifacts associated with groundwater collection and analysis. Diffusive equilibrium, high-resolution passive samplers (HRPPs) can be directly driven (>10 m) in sediments or groundwater. The samplers equilibrate with porewater through diffusion across the sampler membrane, providing high spatial resolution (sample every 20 cm) porewater concentrations of dissolved species. The objective of this study was to develop an HRPP to measure PFAS in contaminated groundwater and saturated media. To achieve this objective, a screening study was conducted to demonstrate quantitative measurement of selected PFAS as well as the kinetics of uptake into a sampler using both nylon and stainless steel membranes. Utilizing the results of the screening study, a prototype sampler was demonstrated in a laboratory flow box. Over a deployment period of 28 days, concentrations of several perfluoroalkyl carboxylic acids (PFCAs), a perfluoroalkyl sulfonate (PFSA), and a precursor PFAS reached equilibrium with porewater (sampler concentration >90 percent of porewater concentration). Application of these samplers could provide improved understanding of the behavior of PFAS in saturated or partially saturated groundwater systems and allow better assessment of fate and transport in the subsurface. Reliable subsurface site characterization will yield robust site assessments, conceptual models, and improve remediation designs as well as increase confidence in post remedial assessments at PFAS-impacted locations.

Foliar uptake overweighs root uptake for 8:2 fluorotelomer alcohol in ryegrass (Lolium perenne L.): A closed exposure chamber study

Fluorotelomer alcohols (FTOHs) are a kind of volatile monomers that can be released from FTOH-based products and their ubiquitous occurrence raises concerns for their plant uptake. To study plant uptake pathway, translocation, and transformation characteristics of 8:2 FTOH, ryegrass (Lolium perenne L.) was selected as a model plant for 8:2 FTOH exposure via air and/or soil uptake for 4 weeks in custom-built closed exposure chambers. The bio-degradation of spiked 8:2 FTOH in the soil led to the production of C6-C8 perfluoroalkyl carboxylic acids (PFCAs) and other intermediates, and perfluorooctanoic acid (PFOA) was the main product (54.9%-88.9%). In the ryegrass, foliar uptake of 8:2 FTOH contributed 78.1% ± 3.4% to the total shoot accumulation while PFOA in shoot was mainly from root uptake of PFOA and the further biotransformation of other unmonitored intermediates biodegraded from 8:2 FTOH in the soil (83.7% ± 7.3%). The results in this study provides the first laboratory evidences that foliar uptake of airborne 8:2 FTOH can be a major pathway over root uptake and its subsequent biotransformation contribute to the burden of PFCA accumulation in plants.

Non-target and suspect-screening analyses of hydroponic soybeans and passive samplers exposed to different watershed irrigation sources

Water scarcity increases the likelihood of irrigating food crops with municipal wastewater that may pose potential dietary risks of regulated and non-regulated organic chemical uptake to edible plant tissues. Only a few studies have used high resolution mass spectrometry (HRMS) to assess the uptake of chemicals of concern into food crops. This study used non-target and suspect-screening analyses to compare total chemical features, tentatively identified chemicals (TICs), and EPA ToxCast chemicals in soybean plants and passive samplers exposed to five different irrigation sources that were collected from an agricultural watershed during mild drought conditions. Secondary-treated municipal wastewater effluent, two surface waters, two ground waters, and deionized municipal tap water were used for two hydroponic experiments: soybean roots and shoots and Composite Integrative Passive Samplers (CIPS) harvested after fourteen days of exposure and soybeans after fifty-six days. CIPS were sealed in separate glass amber jars to evaluate their efficacy to mimic chemical features, TICs, and ToxCast chemical uptake in plant roots, shoots, and beans. Total soybean biomass and water use were greatest for tap water, municipal wastewater, and surface water downstream of the municipal wastewater facility relative to groundwater samples and surface water collected upstream of the wastewater facility. ToxCast chemicals were ubiquitous across watershed irrigation sources in abundance, chemical use category, and number. Wastewater-exposed soybeans had the fewest extractable TICs in plant tissues of all irrigation sources. More ToxCast chemicals were identified in CIPS than extracted from irrigation sources by solid phase extraction. ToxCast chemicals in beans and CIPS were similar in number, chemical use category, and log Kow range. CIPS appear to serve as a useful surrogate for ToxCast chemical uptake in beans, the edible food product.

The Phytomanagement of PFAS-Contaminated Land

Globally, several hundred thousand hectares of both agricultural and urban land have become contaminated with per- and polyfluoroalkyl substances (PFAS). PFAS compounds are resistant to degradation and are mobile in soil compared to other common contaminants. Many compounds have KD values (matrix/solution concentration quotients) of <10. PFAS compounds endanger the health of humans and ecosystems by leaching into groundwater, exposure via dust, and, to a lesser extent, through plant uptake. This review aims to determine the feasibility of phytomanagement, the use of plants, and the use of soil conditioners to minimize environmental risk whilst also providing an economic return in the management of PFAS-contaminated land. For most sites, PFAS combinations render phytoextraction, the use of plants to remove PFAS from soil, inviable. In contrast, low Bioaccumulation Coefficients (BAC; plant and soil concentration quotients) timber species or native vegetation may be usefully employed for phytomanagement to limit human/food chain exposure to PFAS. Even with a low BAC, PFAS uptake by crop plants may still exceed food safety standards, and therefore, edible crop plants should be avoided. Despite this limitation, phytomanagement may be the only economically viable option to manage most of this land. Plant species and soil amendments should be chosen with the goal of reducing water flux through the soil, as well as increasing the hydrophobic components in soil that may bind the C-F-dominated tails of PFAS compounds. Soil conditioners such as biochar, with significant hydrophobic components, may mitigate the leaching of PFAS into receiving waters. Future work should focus on the interactions of PFAS with soil microbiota; secondary metabolites such as glomalin may immobilize PFAS in soil.

Exposure pathways and bioaccumulation of per- and polyfluoroalkyl substances in freshwater aquatic ecosystems: Key considerations

Due to the bioaccumulative behavior, toxicity, and recalcitrance to degradation, per- and polyfluoroalkyl substances (PFAS) are a focus for many researchers investigating freshwater aquatic ecosystems. PFAS are a diverse set of chemicals that accumulate and transport quite differently in the environment depending on the length of their fluoroalkyl chains and their functional groups. This diversity in PFAS chemical characteristics combined with varying environmental factors also impact the bioaccumulation of these compounds in different organisms. In this review, we evaluate environmental factors (such as organic carbon, proteins, lipids, and dissolved cations) as well as PFAS characteristics (head group, chain-length, and concentration) that contribute to the significant variation seen in the literature of bioaccumulation metrics reported for organisms in aquatic ecosystems. Of the factors evaluated, it was found that PFAS concentration, dissolved organic matter, sediment organic matter, and biotransformation of precursor PFAS tended to significantly impact reported bioaccumulation metrics the most. Based on this review, it is highly suggested that future studies provide sufficient details of important environmental factors, specific organism traits/ behavior, and PFAS concentrations/compounds when reporting on bioaccumulation metrics to further fill data gaps and improve our understanding of PFAS in aquatic ecosystems.

Translocation, bioaccumulation, and distribution of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in plants

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are persistent in the environment and have been detected in a variety of plants such as vegetables, cereals, and fruits. Increasing evidence shows that plants are at a risk of being adversely affected by PFASs. This review concludes that PFASs are predominantly absorbed by roots from sources in the soil; besides, the review also discusses several factors such as soil properties and the species of PFASs and plants. In addition, following uptake by root, long-chain PFASs (C ≥ 7 for PFCA and C ≥ 6 for PFSA) were preferentially retained within the root, whereas the short-chain PFASs were distributed across tissues above the ground — according to the studies. The bioaccumulation potential of PFASs within various plant structures are further expressed by calculating bioaccumulation factor (BAF) across various plant species. The results show that PFASs have a wide range of BAF values within root tissue, followed by straw, and then grain. Furthermore, owing to its high water solubility than other PFASs, PFOA is the predominant compound accumulated in both the soil itself and within the plant tissues. Among different plant groups, the potential BAF values rank from highest to lowest as follows: leaf vegetables > root vegetables > flower vegetables > shoot vegetables. Several PFAS groups such as PFOA, PFBA, and PFOS, may have an increased public health risk based on the daily intake rate (ID). Finally, future research is suggested on the possible PFASs degradation occurring in plant tissues and the explanations at genetic-level for the metabolite changes that occur under PFASs stress.

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Long-chain PFASs are preferentially retained in the roots

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BAF values were ranked as root > straw > grain in one plant

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PFOA is the main compound in soil and within plant tissues

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PFOA, PFBA, and PFOS have a potential risk to humans through dietary exposure

Distribution, sources, and dietetic-related health risk assessment of perfluoroalkyl acids (PFAAs) in the agricultural environment of an industrial-agricultural interaction region (IAIR), Changshu, East China

The exploration of the distribution and dietetic-related health risks of perfluoroalkyl acids (PFAAs) in industrial-agricultural interaction regions (IAIRs) is of significant importance, due to the transfer of many PFAA-related factories to developing countries with intensive agricultural activities. In the present study, based on the local diet, edible parts of rice, vegetables, fish, and their corresponding soils and irrigation/aquaculture water were investigated in a typical Chinese city (Changshu). The concentrations of total perfluoroalkyl acids (ΣPFAAs) in the edible parts of rice /vegetables and fish tissues ranged from 26.69 to 37.09 ng/g dw, 12.93 to 40.77 ng/g dw, and 13.27 to 29.82 ng/g ww, with perfluorohexanoic acid (PFPeA) and perfluorooctane sulfonic acid (PFOS) as the most dominant compounds. The PFAA concentrations in the corresponding rice soils, vegetable soils, irrigation water, and aquaculture water ranged from 11.99 to 26.33 ng/g dw, 14.06 to 36.19 ng/g dw, 141.36 to 297.00 ng/L, and 179.23 to 235.82 ng/L, respectively. Biota-sediment accumulation factor (BSAF) values for the plant-soil system were far greater than those for bioaccumulation factor (BAF) values for the plant-irrigation water system. PFAAs were more inclined to accumulate in the gills of fish as determined by their highest BAF values. Correlation analysis showed that PFAAs in root vegetables had a stronger correlation with those in soil compared with those in irrigation water. Source analysis showed that emissions from fluoride industries, textiles, and food industries may be the dominant sources of PFAAs in agricultural environments. The estimated dietary intake (EDI) for the selected diet was lower than that for rice/vegetables but was higher than that found in fish. Toddlers (2-5 years) had the highest exposure risk, and rural residents were more exposed to PFAAs than urban residents under the selected diet.

Source apportionment and crop bioaccumulation of perfluoroalkyl acids and novel alternatives in an industrial-intensive region with fluorochemical production, China: Health implications for human exposure

Due to their great environmental hazards, the widely used legacy perfluoroalkyl acids (PFAAs) are gradually restricted, and novel alternatives are being developed and applied. For efficient control of emerging environmental risks in agricultural production, we systematically studied the source apportionment in field soils and bioaccumulation characteristics in multiple crops of 12 PFAAs and five novel alternatives in an industrial-intensive region of China, followed by human exposure estimation and health risk assessment. Compared with perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), shorter-chained PFAAs and novel alternatives have become the dominant components in local soils and crops, indicating their wide application. A positive matrix factorization (PMF) model coupled with multivariate analysis identified fluoropolymer manufacturing and textile treatment as the principal sources. The bioaccumulation factors (BAFs) of individual PFAAs and alternatives in crops decreased with increasing carbon chain lengths. As a novel alternative of PFOA, hexafluoropropylene oxide dimer acid (GenX) exhibited much higher BAFs; for the alternative of PFOS, 6:2 chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) showed lower BAFs. The bioaccumulation capacities of PFAAs and alternatives were also associated with soil organic matter and crop species. Through crop consumption, short-chained PFAAs and novel alternatives might pose emerging human health threats.

Maize plant (Zea mays) uptake of organophosphorus and novel brominated flame retardants from hydroponic cultures

The root uptake and root-shoot translocation of seven organophosphorus flame retardants (OPFRs) and four novel brominated flame retardants (NBFRs) were assessed in this investigation using hydroponic grown maize plants (Zea mays). Three initial liquid concentrations for each considered compound were examined (i.e., 0.3 μg L^-1, 3 μg L^-1, 30 μg L^-1). The results indicated that the 30 μg L^-1 treatments were phytotoxic, as they resulted in a significant decrease in shoot dry weight. Plant-driven removal of the tested FRs decreased with the increasing initial spiking level and were reportedly higher for the NBFRs (range 42%-10%) than OPFRs (range 19%-7%). All the considered FRs were measured in the roots (range 0.020-6.123 μg g^-1 dry weight -DW-) and shoots (range 0.012-1.364 μg g^-1 DW) of the tested plants, confirming that there was uptake. Linear relationships were identified between the chemical concentrations in the plant parts and the tested hydroponic concentrations. Root concentration factors were positively correlated with the specific lipophilicity (i.e., logK_ow) of the tested FRs and were determined to be higher for the NBFRs than the OPFRs. The NBFRs had a higher root uptake rate than the OPFRs, and this trend was more significant with the increasing treatment concentrations. Shoot/root concentration factors were found to be lower than the unity value for 10 of the 11 tested compounds. These results can be related to the specific molecular configurations and the occurrence of different functional groups in the tested compounds. The results will help to improve risk assessment procedures and fine tune our understanding of human receptor responses to the ingestion of maize crops grown on agricultural sites irrigated with water contaminated by FRs.

Removal of per- and poly-fluoroalkyl substances (PFASs) by wetlands: Prospects on plants, microbes and the interplay

Per- and polyfluoroalkyl substances (PFASs) represent a large family of synthetic organofluorine aliphatic compounds. They have been extensively produced since 1940s due to enormous applications as a surface-active agent, and water and oil repellent characteristics. PFASs are made to be non-biodegradable, therefore, many of them have been found in the environment albeit strict regulations have been in place since 2002. PFASs are extremely toxic compounds that can impart harm in both fauna and flora. Recent investigations have shown that wetlands might be useful for their removal from the environment as a passive and nature-based solution. To this end, understanding the role of plants, microbes, and their combined plant-microbe interplay is crucial because it could help design a sophisticated passive treatment wetland system. This review focuses on how these components (plants, microbe, substrate) can influence PFASs removal in wetlands under natural and controlled conditions. The information on underlying removal mechanisms is mostly retrieved from laboratory-based studies; however, pilot- and field-scale data are also presented to provide insights on their real-time performance. Briefly, a traditional wetland system works on the principles of phytouptake, bioaccumulation, and sorption, which are mainly due to the fact that PFASs are synthetic compounds that have very low reactivity in the environment. Nevertheless, recent investigations have also shown that Feammox process in wetlands can mineralize the PFASs; thus, opens new opportunities for PFASs degradation in terms of effective plant-microbe interplay in the wetlands. The choice of plants and bacterial species is however crucial, and the system efficiency relies on species-specific, sediment-specific and pollutant-specific principles. More research is encouraged to identify genetic elements and molecular mechanisms that can help us harness effective plant-microbe interplay in wetlands for the successful removal of PFASs from the environment.

Per- and polyfluoroalkyl substances (PFASs) in the soil-plant system: Sorption, root uptake, and translocation

Per- and polyfluoroalkyl substances (PFASs) are ubiquitous in the environment but pose potential risks to ecosystems and human health. The soil-plant system plays an important role in the bioaccumulation of PFASs. Because most PFASs in the natural environment are anionic and amphiphilic (both lipophilic and hydrophilic), their sorption and accumulation behaviors differ from those of neutral organic and common ionic compounds. In this review, we discuss processes affecting the availability of PFASs in soil after analyzing the potential mechanisms underlying the sorption and uptake of PFASs in the soil-plant system. We also summarize the current knowledge on root uptake and translocation of PFASs in plants. We found that the root concentration factor of PFASs for plants grown in soil was not significantly correlated with hydrophobicity, whereas the translocation factor was significantly and negatively correlated with PFAS hydrophobicity regardless of whether plants were grown hydroponically or in soil. Further research on the cationic, neutral, and zwitterionic forms of diverse PFASs is urgently needed to comprehensively understand the environmental fates of PFASs in the soil-plant system. Additional research directions are suggested, including the development of more accurate models and techniques to evaluate the bioavailability of PFASs, the effects of root exudates and rhizosphere microbiota on the bioavailability and plant uptake of PFASs, and the roles of different plant organelles, lipids, and proteins in the accumulation of PFASs by plants.

Comparison of 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) and perfluorooctane sulfonate (PFOS) accumulation and toxicity in mung bean

With the regulation of perfluorooctanesulfonate (PFOS), 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) has been used as a potential PFOS alternative in electroplating. In this study, the uptake, translocation and phytotoxicity of PFOS and 6:2 Cl-PFESA in mung bean (Vigna radiata (Linn.) Wilczek.) were investigated. The uptake kinetics of PFOS and 6:2 Cl-PFESA fit the Michaelis-Menten equation well, suggesting that the uptake is a carrier-mediated process. The root concentration factor (RCF) of 6:2 Cl-PFESA (34.55 mL g^-1 dw) was 1.27 times that of PFOS (27.11 mL g^-1 dw), and the translocation factor (TF) of 6:2 Cl-PFESA (0.177) was 1.07 times that of PFOS (0.165). Exposure to 6:2 Cl-PFESA and PFOS both resulted in the inhibition of mung bean seedling development. Treatment with 6:2 Cl-PFESA and PFOS led to the concentration-dependent elevation of malondialdehyde (MDA), carbonyl groups, and phosphorylated histone H2AX (γ-H2AX) levels in mung bean roots. The MDA and carbonyl group contents induced by 6:2 Cl-PFESA were 1.10-1.35 and 1.03-1.14 times, respectively, those of PFOS. The hydroxyl free radical (·OH) levels in mung bean roots after exposure to PFOS and 6:2 Cl-PFESA were elevated significantly, and the ·OH levels induced by 6:2 Cl-PFESA were higher than those induced by PFOS. Hydroxyl free radical levels were positively correlated with the MDA and carbonyl group contents in mung bean roots (p < 0.05). The dynamic changes in some antioxidative enzyme activities in mung bean seedlings were determined, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). The results demonstrated the phytotoxicities of 6:2 Cl-PFESA and PFOS to mung bean in the early developmental stage. 6:2 Cl-PFESA is more harmful to mung beans than PFOS. The production of hydroxyl radical is the mechanism that causes the toxicity of PFOS and 6:2 Cl-PFESA toward plants.

Phytoremediation of poly- and perfluoroalkyl substances: A review on aquatic plants, influencing factors, and phytotoxicity

Poly- and perfluoroalkyl substances (PFASs) are a group of emerging organic contaminants which are persistent to normal physicochemical treatments. The widespread use of PFASs has caused significant environmental issues. The bioaccumulation and distribution of PFASs within plant compartments have revealed great potentials for phytoremediation. In this review, the roles of aquatic plants in the process of PFASs remediation were highlighted. Moreover, there were different underlying mechanisms of PFASs uptake between terrestrial and aquatic plants. On the other hand, a wide range of influencing factors for bioaccumulation and translocation of PFASs within plant compartments are also presented and discussed. In response to exposure of PFASs, corresponding phytotoxic effects has affected the growth and metabolism of plants, which could provide beneficial guides of the phytotoxic tolerance for plant species selection in applications of phytoremediation. Finally, the discussion about whether phytoremediation is a viable option for PFASs removal and further research priorities are suggested.

Uptake of perfluorinated alkyl acids by crops: results from a field study

Four crops with different edible plant parts (radish, lettuce, pea and maize) were grown in outdoor lysimeters on soil spiked with 13 perfluorinated alkyl acids (PFAAs) at 4 different levels. PFAA concentrations were measured in soil, soil pore water, and different plant parts at harvest. Edible part/soil concentration factors ranged over seven orders of magnitude and decreased strongly with increasing PFAA chain length, by a factor of 10 for each additional fluorinated carbon (nCF) for pea. Three processes were responsible for most of the variability. The first was sorption to soil; calculating whole plant concentration factors on the basis of concentration in pore water instead of soil reduced the variability from five orders of magnitude to two. Second, the journey of the PFAAs with the transpiration stream to the leaves was hindered by retention in the roots driven by sorption; root retention factors increased by a factor 1.7 for each nCF. Third, transfer of PFAAs from the leaves to the fruit via the phloem flow was also hindered - presumably by sorption; fruit/leaf concentration factors decreased by a factor 2.5 for each nCF. A simple mathematical model based on the above principles described the measured concentrations in roots, leaves, fruits and radish bulbs within a factor 4 in most cases. This indicates that the great diversity in PFAA transfer from soil to crops can be largely described with simple concepts for four markedly different species.

Variety-Selective Rhizospheric Activation, Uptake, and Subcellular Distribution of Perfluorooctanesulfonate (PFOS) in Lettuce (Lactuca sativa L.)

Perfluorooctanesulfonate (PFOS) as an accumulative emerging persistent organic pollutant in crops poses severe threats to human health. Lettuce varieties that accumulate a lower amount of PFOS (low-accumulating crop variety, LACV) have been identified, but the regarding mechanisms remain unsolved. Here, rhizospheric activation, uptake, translocation, and compartmentalization of PFOS in LACV were investigated in comparison with those of high-accumulating crop variety (HACV) in terms of rhizospheric forms, transporters, and subcellular distributions of PFOS. The enhanced PFOS desorption from the rhizosphere soils by dissolved organic matter from root exudates was observed with weaker effect in LACV than in HACV. PFOS root uptake was controlled by a transporter-mediated passive process in which low activities of aquaporins and rapid-type anion channels were corrected with low expression levels of PIPs (PIP1-1 and PIP2-2) and ALMTs (ALMT10 and ALMT13) genes in LACV roots. Higher PFOS proportions in root cell walls and trophoplasts caused lower root-to-shoot transport in LACV. The ability to cope with PFOS toxicity to shoot cells was poorer in LACV relative to HACV since PFOS proportions were higher in chloroplasts but lower in vacuoles. Our findings provide novel insights into PFOS accumulation in lettuce and further understanding of multiprocess mechanisms of LACV.

Biological and behavioral responses of European honey bee (Apis mellifera) colonies to perfluorooctane sulfonate exposure

Bees provide pollination services to managed and wild ecosystems but are threatened globally due to multiple stressors, including exposure to contaminants. Perfluorooctane sulfonate (PFOS) is a widely detected and persistent contaminant that accumulates and biomagnifies in food chains. In this exposure effect study, small whole colonies of Apis mellifera (1000 bees) were exposed to PFOS using a purpose-built cage system over a 4-week period. The PFOS exposure concentrations were provided to bees in sugar syrup at concentrations detected in the environment, ranging from 0 to 1.6 mg L^-1 . A range of biological and behavioral responses were monitored. Bee tissue, honey, and fecal matter were analyzed using isotope dilution combined with liquid chromatography-tandem mass spectrometry adapted for bee and honey matrix analysis. Bee mortality increased significantly with PFOS exposure at 0.8 mg L^-1  or greater, and brood development ceased entirely at 0.02 mg L^-1  or greater. Colony activity, temperament, hive maintenance, and defense were adversely affected in all PFOS exposure treatments compared with the control, even at the lowest PFOS exposure of 0.02 mg L^-1 . Perfluorooctane sulfonate was detected in bee tissue with a mean bioaccumulation factor of 0.3, and it was also identified in honey and in feces collected from the hive cages. These findings provide the first evidence that PFOS exposure adversely affects honey bee colonies and may transfer to honey. With PFOS contaminating thousands of sites worldwide, our study has implications for exposed bee populations under natural conditions, pollination services, the honey industry, and human health. Integr Environ Assess Manag 2021;17:673-683. © 2021 SETAC.