Cross-media transport of legacy and novel per- and polyfluoroalkyl substances (PFAS) in soil profiles, groundwater and surface water: Implications for environmental modelling and risk assessment across terrestrial-aquatic Interface

Legacy and novel per - and polyfluoroalkyl substances (PFAS) are emerging contaminants of global concern, and understanding the cross-media transport of PFAS in soil profiles, groundwater and surface water is critical for their environmental modelling and risk assessment across terrestrial-aquatic interface. This study investigated such transport by quantifying vertical-transport potential throughout 0–6 m soil profiles and the retentive effects of critical soil components, while characterizing spatiotemporal variations under hydrological dynamics in an area of ∼65 km 2 adjacent to the Yangtze River in central China. Source apportionment identified industrial emissions as primary input of PFAS in topsoil, and short-chain or fluorotelomer-based PFAS exhibited a greater downward transport potential. Organic carbon was the key soil component controlling PFAS vertical attenuation (contributing 32.7%–48.2%), with solid organic carbon (SldOC) strongly retaining longer-chain PFAS and dissolved organic carbon (DOC) preferentially immobilizing shorter-chain PFAS. Iron oxide, particularly amorphous iron fraction, was another crucial soil component governing PFAS vertical attenuation (contributing 37.7%–57.3%). Clay exhibited greater retention of PFAS than sand or silt. A quantitative structure-property relationship (QSPR) for anionic PFAS, based on molecular hydrophobicity and electronegativity, was developed for predicting soil-groundwater partitioning. Spatial heterogeneity and PFAS hotspots in groundwater and surface water were found to be more pronounced during flood period relative to normal and dry periods, which may be attributed to intense soil leaching/runoff and active hydraulic exchanges. High concentrations of PFAS in soil, groundwater and surface water are posing potential risks to human health and ecosystems, and these risks became especially pronounced when cross-media transport of PFAS from soil to adjacent water bodies through leaching and runoff was considered. The findings advanced the understanding of contamination mechanisms and driving factors of PFAS across the terrestrial-aquatic interface, informing environmental modelling and risk management.