Long-term laboratory-based evaluation of PFAS mobility after granular activated carbon (GAC) treatment: Influence of vegetation and soil properties

Per- and polyfluoroalkyl substances (PFAS) associated with contamination from aqueous film forming foams are persistent, mobile contaminants that pose risks to groundwater and ecosystems. This study evaluated the effectiveness of granular activated carbon (GAC) application (1% w/w), with and without vegetation cover (perennial ryegrass), in reducing PFAS mobility under controlled laboratory-based rainfall simulation conditions using trays with (L50 ×W20 ×H5cm) dimensions. Two soils with contrasting textures but similar PFAS contamination levels were used in the experiment. Leaching behaviour was evaluated over one year with simulated rainfall events using the laboratory rainfall simulator, capturing both infiltration and surface runoff, as well as particulates in the runoff. PFAS mobility was influenced by soil texture, groundcover and wetting and drying cycles. Soil A (sandy clay loam) generated more runoff, while Soil B (sandy loam) allowed greater initial infiltration. Perfluorooctane sulfonic acid (PFOS) concentration was increased in the runoff of untreated soil after a prolonged drying cycle due to the upward flux of PFOS during the drying period. GAC reduced PFAS concentrations by up to 97% in runoff and 99% in infiltration across both soil types, even over a year with multiple wetting and drying cycles. Groundcover initially increased PFAS concentrations in runoff, likely due to upward transport and evapotranspiration, but this effect diminished as vegetation was established. Combined GAC and vegetation treatments achieved > 99% PFAS reduction in most cases, with plant effects more evident after 60 days. These findings support in-situ GAC application, with or without vegetation, as a viable approach for managing PFAS-contaminated soils. Plants may cause a temporary increase in PFAS mobility during the initial period following plant application, with or without GAC, and management practices should account for this risk.