Distribution of perfluoroalkyl substances (PFASs) in aquatic plant-based systems: From soil adsorption and plant uptake to effects on microbial community

Abstract

This study systematically explored the distribution of perfluoroalkyl substances (PFASs) through soil adsorption and plant bioaccumulation in aquatic plant-based systems, derived from a surface flow constructed wetland (CW) planted with Typha angustifolia. The water-soil-plant systems were fortified with eight perfluoroalkyl subsntances (PFASs) at different concentrations. The potential for individual PFAS adsorption onto soil substrate and bioaccumulation in the plants increased with the increasing PFAS initial concentrations. Longer-chain PFASs exhibited higher affinity to soil substrate compared to shorter-chain PFASs. The highest concentration in the soil was observed for PFOS (51.3 ng g−1), followed by PFHxS (9.39 ng g−1), and PFOA (5.53 ng g−1) at low PFAS level. The perfluoroalkyl chain length dependent trend was also seen in the roots with the highest individual PFAS concentration for PFOS (68.9 ng g−1), followed by PFOA (18.5 ng g−1) and PFHxS (13.4 ng g−1). By contrast, shorter-chain PFASs were preferentially translocated from roots to shoots in Typha angustifolia. A significant (p < 0.05) positive correlation between bioaccumulation factor (BAFplant/water) (whole plant) and perfluoroalkyl chain length was observed. PFASs content in the plant compartments increased with increasing PFAS concentrations in the soil. Mass balance analysis indicates that approximately 40.7–99.6% of PFAS mass added to the system was adsorbed onto the soil and bioaccumulated in the plant tissues of T. angustifolia. Soil adsorption played a vital role in PFAS mass distribution. The results of Illumina high-throughput sequencing show that the bacterial diversity decreased upon PFAS exposure. The most predominant phyla retrieved were Proteobacteria (24.7–39.3%), followed by Actinobacteria (4.2–41.1%), Verrucomicrobia (7.9–25.1%), Bacteroidetes (10.2–20.4%), Cyanobacteria (0.4–16.5%), and Firmicutes (1.1–6.4%). The PFAS enrichment caused the changes (p > 0.05) in the structure and composition of bacterial community. This study helps to gain insight into a better understanding of the potential for PFASs distribution in an aquatic plant-based system and the impact on dynamic of microbial community exposed to PFASs.