Multiscale risk assessment of PFASs in concentrated stormwater infiltration systems: Coupling molecular mechanisms, microbial succession, and long-term hydrological simulations.

Résumé

Concentrated stormwater infiltration systems are widely used in Sponge City construction to control runoff and promote groundwater recharge. However, long-term accumulation of per- and polyfluoroalkyl substances (PFASs) within infiltration media may pose environmental risks. Based on field investigation and screening, perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) were selected as representative PFASs for subsequent investigation. Soil column experiments, plant bioassays, microbial community analysis, and numerical simulations were combined to investigate PFASs retention, biological responses, and long-term migration risks in concentrated infiltration systems. The results showed that PFNA generally exhibited higher retention than PFOA, while increasing hydraulic loading reduced PFASs removal efficiencies. Bioretention soil media amended with water treatment residuals (BSM+WTR) enhanced PFASs retention and reduced downward migration compared with conventional media. Plant physiological and transcriptomic analyses indicated that PFASs accumulation affected antioxidant regulation, photosynthesis-related pathways, and plant growth. Microbial community analysis further revealed changes in diversity and community composition following prolonged PFASs exposure. Although modified media enhanced PFASs retention, biological responses were still observed in PFASs-accumulated media, indicating that retention performance alone may not fully reflect the ecological consequences of long-term accumulation. Long-term simulations showed that PFOA exhibited greater migration potential than PFNA. A VIKOR-based assessment identified the BSM + WTR configuration as the optimal media option. By integrating contaminant retention, molecular responses, microbial community succession, and long-term hydrological simulations within a unified risk assessment framework, this study provides a multiscale approach for evaluating PFASs risks in concentrated infiltration systems.