Per- and polyfluoroalkyl substances (PFAS) bioaccumulation in freshwater aquatic ecosystems and associated ecological risks

Per- and polyfluoroalkyl substances (PFAS) have attracted global concern due to their persistence, toxicity, bioaccumulation potential, and associated adverse effects. Previous studies reported PFAS bioaccumulation in freshwater aquatic ecosystems. However, knowledge gaps exist for key environmental factors and exposure source impact on PFAS bioaccumulation for different trophic level organisms, and the extent of exposure risks related to PFAS impacted ecosystems. Therefore, this study employed multiple approaches involving various scales and complexities to study PFAS bioaccumulation in different trophic level organisms. In addition, measured field data from four PFAS impacted stream ecosystems were evaluated to assess potential ecological risks of aquatic life and aquatic-dependent wildlife in each stream community. The results suggested that PFAS bioaccumulation in aquatic organisms is species dependent. Among trophic levels, the 14PFAS concentrations generally followed an order of primary producer < primary consumer < secondary consumer. Within each trophic level, species exhibited the varied bioaccumulation capacity. The species dependent PFAS bioaccumulation is likely related to differences in exposure pathways and metabolic capacities of the species. PFAS characteristics were found as one of the critical factors influence PFAS bioaccumulation. In general, PFAS bioaccumulation increased with increasing perfluoroalkyl chain length for all tested species involving three trophic levels. For compounds with the same perfluoroalkyl chain length, the bioaccumulation metrics typically followed the trend of PFCAs < PFSAs < FTSs. Moreover, differences were observed across trophic levels in terms of PFAS functional groups. This may be attributed to the differences in specific uptake, elimination rates, and biotransformation capacity among trophic levels. Some of the key environmental factors showed observable effects on PFAS bioaccumulation in aquatic organisms. Increasing sediment organic carbon content decreased the bioaccumulation of PFAS to benthic macroinvertebrates. Elevated divalent cations and increased dissolved organic carbon did not significantly affect the algal BCFs of PFAS, but it was revealed that PFAS bioaccumulation in algae is concentration dependent, with increasing PFAS exposure concentrations resulting in decreased BCF values. For different exposure sources, water column organisms accumulated more PFAS with water column exposure source, while benthic organisms accumulated more PFAS with sediment exposure source. For ecological risk assessment, PFOA, PFHxS, and PFOS might cause ecological risk to aquatic life in four studied streams based on surface water-based and biota-based PFAS regulatory thresholds and screening values. Dietary intake modeling suggested that PFOS in Streams 3 and 4 presented the potential adverse effects to aquatic-dependent wildlife, such as piscivorous American mink and Great blue heron. Overall, this study improved the understanding of PFAS bioaccumulation in aquatic organisms, and key environmental factors influence on PFAS bioaccumulation. Sediment organic carbon content, PFAS exposure concentrations, and exposure source were identified to impact PFAS bioaccumulation in aquatic organisms. Collectively, the results of this study expanded current knowledges on PFAS bioaccumulation in freshwater aquatic ecosystems and associated ecological risks, which will benefit to develop bioaccumulation models and regulatory thresholds.