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

Effects of temperature, relative humidity and soil organic carbon content on soil-air partitioning coefficients of volatile PFAS

Soil-air partitioning coefficient (KSA) values are often used to assess the environmental fate of organic contaminants in soil. Till now, sufficient KSA values have not yet been measured for many compounds of interest, including some emerging pollutants such as volatile PFAS. Moreover, the effects of environmental factors such as temperature, relative humidity and soil organic carbon content on KSA of volatile PFAS are also unclear. In this study, the KSA values of target volatile PFAS were measured under various temperature (20-40 °C), relative humidity (30-100 %) and soil organic carbon content (2.1 %-8.0 %) using a modified solid-phase fugacity meter. The results showed that higher temperatures, higher relative humidity and lower organic carbon content in soil may accelerate the diffusion of target volatile PFAS. Furthermore, the KSA measurements were used to derive a multiple linear regression model to depict the relationship between logKSA and temperature, relative humidity, soil organic carbon content and PFAS-specific logKOA. When compared with the predictions obtained from semi-empirical model, we argued that the multiple linear regression model is more robust and easier to implement for target volatile PFAS or other emerging volatile PFAS than the semi-empirical approach to help depict the diffusion process at target volatile PFAS contaminated sites.

Tissue distribution, biomagnification, human health risk, and risk mitigation of perfluoroalkyl acids (PFAAs) in the aquatic food web of an urban fringe lake: Insights from urban-rural and seasonal scales

Perfluoroalkyl acids (PFAAs), renowned for their exceptional physical and chemical properties, are ubiquitous in urban and rural environments. Despite their widespread usage, more knowledge is needed concerning their accumulation and transfer mechanisms within the aquatic food webs of urban fringe lakes, especially across rural-urban and seasonal scales. This study investigated the tissue distribution, bioaccumulation, biomagnification, associated human health risks, and potential risk mitigation strategies of 15 PFAAs within the food web of Luoma Lake, a prototypical urban fringe lake. All targeted PFAAs were detected in samples, with ∑PFAA concentrations ranging from 116.97 to 564.26 ng/g dw in muscles and 26.96-1850.95 ng/g dw in viscera. Spatial variations revealed significantly higher ∑PFAA concentrations in the muscles from the urban subregion (∑PFAA: 359.66 ± 76.48 ng/g dw) compared to the rural subregion (∑PFAA: 328.86 ± 87.51 ng/g dw). Seasonal fluctuations impacted PFAA concentrations in fish and crustacean muscles but exhibited negligible effects on bivalve muscles. Spatial variations only influenced PFAA concentrations in specific viscera (gill, liver, kidney), while seasonal changes had minimal effects on viscera. The organisms demonstrated varying bioaccumulation capacities, with crustaceans displaying the highest bioaccumulation potential, followed by crustaceans and fish. Both spatial and seasonal variations modulated the bioaccumulation patterns of PFAA in muscles, whereas bioaccumulation in viscera was only influenced by seasonal factors. Notably, PFAA biomagnification along the food web was exclusively governed by spatial distribution, remaining unaffected by seasonal changes. The human health risk assessment underscored the potential adverse health impacts of PFOS and PFOA, particularly on young children (aged 2 to <6 years). This study further proposed comprehensive recommendations for mitigating PFAA-induced health risks, encompassing source control, selective consumption, pre-cooking treatments, and strategic cooking method selection. This research provides crucial insights into the ecological behaviors and health implications of PFAA in urban fringe lakes.

The soil-air interfacial migration process of volatile PFAS at the contaminated sites: Evidence from stable carbon isotopes with CSIA

Volatile per- and polyfluoroalkyl substances (PFAS) are prone to transport among various environmental media, with the soil-air interfacial migration process being an important pathway that significantly influences their environmental fate. To assess the migration and transformations of target volatile PFAS at contaminated site using compound-specific stable isotope analysis (CSIA), it is necessary to understand the isotopic fractionation that occurs during their transfer from soil to air. We have established methods for pre-treatment and GC/CSIA analysis methods of target volatile PFAS in soil and air samples and ensured the accuracy of carbon isotope analysis. GC/IRMS δ13C measurements showed optimal precision at instrumental response above 1.35-2.75 Vs, with recommended minimum on-column C levels of 1.67-5.00 nmol for target volatile PFAS. Stable carbon isotope fractionation factors related to the soil-air interfacial migration process for target volatile PFAS were determined by performing laboratory simulations. The observed εsoil-air values are all negative, suggesting that the soil-air interfacial migration process for target volatile PFAS is kinetic fractionation, the removal of molecules containing lighter isotopes. By comparing the simulated and experimentally observed δ13C (‰) values of target volatile PFAS, we found consistent trends in the soil and inverse trends in the air. These δ13C (‰) values and the related isotope fractionation model provide valuable insights into the isotopic behavior of target volatile PFAS during soil-air interfacial migration process, aiding in the assessment of their environmental fate.

Emerging eco-friendly technologies for remediation of Per- and poly-fluoroalkyl substances (PFAS) in water and wastewater: A pathway to environmental sustainability

Per- and polyfluoroalkyl substances (PFAS) are rampant, toxic contaminants from anthropogenic sources, called forever chemicals for their recalcitrance. Although banned in several parts of the world for public health implications, including liver, kidney, and testicular diseases, PFAS are abundant in water sources due to easy dispersion. With chemical properties resulting from strong hydrophobic bonds, they defile many physicochemical removal methods. Though adsorption processes such as granular activated carbon (GAC) are widely used, they are marred by several limitations, including cost and secondary contamination. Thus, eco-friendly methods involving a synergy of the removal principles have been preferred for ease of use, cost-effectiveness, and near-zero effect on the environment. We present novel eco-friendly methods as the solution to PFAS remediation towards environmental sustainability. Current eco-friendly methods of PFAS removal from water sources, including electrocoagulation, membrane/filtration, adsorption, and phytoremediation methods, were highlighted, although with limitations. Novel eco-friendly methods such as microbial fuel cells, photoelectrical cells, and plasma treatment offer solutions to PFAS remediation and are quite efficient in terms of cost, result, and environmental sustainability. Overall, the successful integration of eco-friendly techniques in a seamless manner ensures the desired result. We also present a balanced position on the ecosystem impact of these ecofriendly methods, noting the successes towards environmental sustainability while exposing the gaps for further research.

Removal of perfluoroalkyl acids (PFAAs) from aqueous solution by water hyacinth (Eichhornia crassipes): Uptake, accumulation, and translocation

Although Eichhornia crassipes, commonly known as water hyacinth, has been widely used in wastewater treatment, further investigations are still needed to explore the removal efficiency of perfluoroalkyl acids (PFAAs) from the aqueous environment using this floating aquatic plant. In this study, a hydroponic experiment was conducted to assess accumulation, bioconcentration factors (BCFs), translocation factors (TFs), and removal rates of eight PFAAs by water hyacinth. The obtained results indicated that all PFAAs, including five perfluoroalkyl carboxylic acids (PFCAs) with chain lengths C4-C8 and three perfluoroalkyl sulfonic acids (PFSAs) with C4, C6, and C8, were readily accumulated in water hyacinth. Throughout the duration of the experiment, there was a noticeable increase in PFAA concentrations and BCF values for different plant parts. For the root, PFAAs with more carbon numbers showed a higher uptake than the shorter homologues, with PFSAs being more readily accumulated compared to PFCAs with the same carbon number in the molecules. In contrast, the levels of long-chain PFAAs were comparatively lower than those of short-chain substances in the stem and leaf. Notably, PFAAs with less carbon numbers, like PFPeA, PFBA, and PFBS, showed a remarkable translocation from the root to the stem and leaf with TFs >1. For the whole plant, no significant correlation was found between BCFs and organic carbon-water partition coefficients (Koc), octanol-water partition coefficients (Kow), membrane-water distribution coefficients (Dmw), or protein-water distribution coefficients (Dpw). The removal rates of PFAAs ranged from 40.3 to 63.5 % throughout the three weeks of the experiment while the removal efficiencies varied from 48.9 % for PFHxS to 82.6 % for PFPeA in the last week.

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.

Perfluoroalkyl acid precursors in agricultural soil-plant systems: Occurrence, uptake, and biotransformation

Perfluoroalkyl acid (PFAA) precursors have been used in various consumer and industrial products due to their hydrophobic and oleophobic properties. In recent years, PFAA precursors in agricultural soil-plant systems have received increasing attention as they are susceptible to biotransformation into metabolites with high biotoxicity risks to human health. In this review, we systematically assessed the occurrence of PFAA precursors in agricultural soils, taking into account their sources and biodegradation pathways. In addition, we summarized the findings of the relevant literature on the uptake and biotransformation of PFAA precursors by agricultural plants. The applications of biosolids/composts and pesticides are the main sources of PFAA precursors in agricultural soils. The physicochemical properties of PFAA precursors, soil organic carbon (SOC) contents, and plant species are the key factors influencing plant root uptakes of PFAA precursors from soils. This review revealed, through toxicity assessment, the potential of PFAA precursors to generate metabolites with higher toxicity than the parent precursors. The results of this paper provide a reference for future research on PFAA precursors and their metabolites in soil-plant systems.

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.