Impacts of divalent cations (Mg2+ and Ca2+) on PFAS bioaccumulation in freshwater macroinvertebrates representing different foraging modes

Effects of dissolved cations, dissolved organic carbon, and exposure concentrations on per- and polyfluoroalkyl substances bioaccumulation in freshwater algae

Per- and polyfluoroalkyl substances (PFAS) have attracted global attention because of their persistence, toxicity, bioaccumulation potential, and associated adverse effects. As important primary producers, freshwater algae constitute the base of the food web in freshwater aquatic ecosystems. However, the effects of key environmental factors on PFAS uptake and bioaccumulation in freshwater algae have not been thoroughly studied. In this study, three bioaccumulation experiments were conducted to evaluate the influence of dissolved cations, dissolved organic carbon, and exposure concentrations on PFAS bioaccumulation in algae. Among the 14 studied PFAS, seven long-chain PFAS tended to bioaccumulate in algae. Elevated divalent cations (Ca2+ and Mg2+) and dissolved organic carbon did not significantly change the algal bioconcentration factors (BCFs) of PFAS, suggesting complexity of the interactions among PFAS, environmental factors, and biotic activities. Additionally, increasing exposure concentrations (0.5, 1, 5, and 10 μg/L of each PFAS) increased PFAS concentrations in algae but decreased the BCF values. This indicated that attention should be paid to the application of BCFs in future studies, including ecological risk assessment. Moreover, fluorotelomer sulfonic acids (FTSs) were incompletely recovered, suggesting that biotransformation occurred. Further studies should be conducted to evaluate whether algae play a role in FTSs biotransformation and to determine the mechanisms. Studying the impacts of key environmental factors on PFAS bioaccumulation in algae is crucial for understanding the bioaccumulation processes that occur at the lowest trophic level and that eventually affect the dynamics of entire aquatic ecosystems.

The effects of perfluoroalkyl substance pollution on microbial community and key metabolic pathways in the Pearl River Estuary

The extensive use of perfluoroalkyl substances (PFASs) has raised significant concerns regarding their adverse environmental implications. However, the understanding of their behaviors and biological effects in natural estuarine ecosystems remain limited. This study employed a multidisciplinary approach integrating chemical analysis, biological sequencing, and statistical modeling to comprehensively investigate the distribution of PFASs, as well as their intrinsic relationship with microbial community in the Pearl River Estuary (PRE), a rapidly urbanized area. Our findings demonstrate that the total PFAS concentrations ranged from 52-127 ng L-1 in water, and 2-70 μg kg-1 dry weight in sediment, with notably distinct compositions across habitats. Aquatic microbial communities exhibited higher sensitivity to environmental variables, including PFAS concentrations, attributed to increased stochasticity and reduced spatial turnover. Conversely, sediments harbored microbial communities with higher phylogenetic diversity, rendering them less susceptible to PFAS-induced stress. Furthermore, PFAS concentrations significantly affected microbial carbon, nitrogen, and phosphorus cycling, predominantly through indirect alterations in characteristic genus composition. Importantly, noteworthy variations in impacts were observed between perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs), which might contingent upon C-F bond dissociation energies. The findings shed light on PFAS ecological roles and interaction patterns with microbial communities in human-impacted estuarine environments.

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

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

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

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

Fate, distribution, and transport dynamics of Per- and Polyfluoroalkyl Substances (PFASs) in the environment

Per- and Polyfluoroalkyl Substances (PFASs) are persistent organic pollutants with significant environmental and health impacts due to their widespread occurrence, bioaccumulation potential, and resistance to degradation. This paper comprehensively reviews current knowledge of PFAS fate and transport mechanisms by correlating PFAS leaching, retention, and movement to their physicochemical properties and environmental factors based on observing PFAS fate and transport in unsaturated zones, surface water, sediments, plants, and atmosphere. The complex and unique physiochemical properties of PFASs, such as their carbon-fluorine bonds and amphiphilic nature, determine their environmental behavior and persistence. Recent studies emphasize that concentration-dependent affinity coefficients predict the transport of diverse PFAS mixtures by considering the impact of the Air-Water Interface (AWI). These studies highlight the complex interactions that influence PFAS behavior in environmental systems and the need for refined modeling techniques to account for transport dynamics. Competitive adsorption at the AWI, influenced by PFAS physicochemical properties and environmental factors, is crucial. PFAS chain length profoundly affects PFAS volatility and mobility, i.e., longer chains show higher solid matrix adsorption, while shorter chains exhibit greater atmospheric deposition potential. Solution chemistry, encompassing pH and ionic strength, variably alters PFAS sorption behaviors. Mathematical models, such as the Leverett Thermodynamic Model (LTM) and Surface Roughness Multipliers (SRM), effectively predict PFAS retention, offering enhanced accuracy for surface-active solutes through empirical adjustments. Co-contaminants' presence influences the transport behavior of PFASs in the environment. Microbial activity alters PFAS retention, while microplastics, especially polyamide, contribute to their adsorption. These complex interactions govern PFAS fate and transport in the environment. The paper identifies critical gaps in current understanding, including the fate of PFASs, analytical challenges, ecological risk assessment methods, and the influence of episodic events on PFAS transport dynamics. This paper also investigates the research gap in refining current models and experimental approaches to predict PFAS transport accurately and enhance risk mitigation efforts. Addressing these gaps is crucial for advancing remediation strategies and regulatory frameworks to mitigate PFAS contamination effectively.

Biological effects of perfluoroalkyl substances on running water ecosystems: A case study in Beiluo River, China

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that pose a threat to the biodiversity of the Beiluo River, a polluted watercourse on the Loess Plateau impacted by diverse human activities. However, the occurrence, spatial distribution, and substitution characteristics of PFASs in this region remain unclear. This study aimed to unravel PFAS distribution patterns and their impact on the aquatic ecosystems of the Beiluo River Basin. The total PFAS concentration in the area ranged from 16.64-35.70 ng/L, with predominantly perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs), collectively contributing 94%. The Mantel test revealed threats to aquatic communities from both legacy long-chain (perfluorooctanoic acid and sodium perfluorooctane sulfonic acid) and emerging (6:2 fluorotelomer sulfonic acid, 2-Perfluorohexyl ethanoic acid, and hexafluoropropylene oxide dimer acid (Gen-X)) PFSAs. The canonical correspondence analysis ordination indicated that trace quantities of emerging PFASs, specifically 2-Perfluorohexyl ethanoic acid and hexafluoropropylene oxide dimer acid (Gen-X), significantly influenced geographical variations in aquatic communities. In conclusion, this study underscores the importance of comprehensively exploring the ecological implications and potential risks associated with PFASs in the Beiluo River Basin.

A modified QuEChERS sample processing method for the determination of per- and polyfluoroalkyl substances (PFAS) in environmental biological matrices

QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample processing methods have previously been applied to a range of compounds and matrices. This study presents a modified QuEChERS sample processing method that was validated and employed for 24 per- and polyfluoroalkyl substances (PFAS) for various biological matrices. PFAS are a group of synthetic chemicals that have attracted substantial attention as some compounds are acknowledged to be persistent, toxic, and bioaccumulative. It is crucial to determine PFAS in diverse environmental matrices. Currently, limited sample processing methods for PFAS in biological matrices are available and the majority only focus on a few compounds such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). Thus, there is a demand to develop a sample processing method which is effective for many commonly tested PFAS compounds in environmental biological samples. In this study, the detailed sample processing procedures and method performance are described. The highlights of this method are: •The extraction solvent and salts were adjusted for PFAS extraction from environmental biological matrices.•The modified QuEChERS method is effective for extraction and cleanup from a variety of matrices including algae, plants, invertebrates, amphibians, and fish.