Dominance of Mass Transfer over Water Chemistry in Rapid PFAS Mobilization from a PFAS-Spiked Landfill-Impacted Soil: Drinking-Water Implications

Abstract Per- and poly-fluoroalkyl substances (PFAS) released from contaminated soils can migrate into surface water and groundwater, posing risks to drinking water resources. However, the combined effects of water chemistry and hydrodynamic conditions on PFAS mobilization remain poorly understood. In this study, we investigated the release of six U.S. EPA-regulated PFAS compounds from a PFAS-spiked, landfill-impacted soil under varying water chemistry parameters (pH, ionic strength, calcium, phosphate and humic acid) in both stirring and static water conditions. Under stirring conditions, the PFAS release was rapid, with most PFAS released within 5 min. Variations in water chemistry had minimal influence on PFAS release, indicating that intense mixing dominated mass transfer processes over water chemistry effect. Under static conditions, water chemistry can affect the PFAS release. Departing from conventional understanding, decreasing pH or increasing Ca2+ concentration enhanced PFAS release into the aqueous phase and the corelease of PFAS and metals was observed, indicating that metal precipitation and desorption may play important roles in PFAS release. The presence of phosphate and humic acid facilitated PFAS release, whereas variations in ionic strength exhibited no influence. Overall, these findings highlight rapid PFAS release from soils into surface waters and its potential risks to drinking water supplies.