Environmental Science and Engineering Seminar
PFAS are emerging contaminants that have been widespread in the environment. A growing body of site investigations suggests that PFAS have accumulated significantly in soils at contamination sites, threatening to contaminate the groundwater underneath. Quantifying PFAS leaching in soils and mass discharge to groundwater is therefore critical for characterizing, managing, and mitigating long-term contamination risks. Many PFAS are surfactants that adsorb at air–water and solid–water interfaces, which leads to complex retention of PFAS in soils. Concomitantly, PFAS present in pore water can modify surface tension and in turn impact variably saturated flow, which further complicates the fate and transport of PFAS in soils. In this talk, I will give an overview of our recent work that aims to understand and quantify the primary processes that control the long-term leaching of PFAS. I will start by presenting a mathematical model that represents a set of PFAS-specific transport processes including concentration-dependent capillary pressure, and rate-limited and nonlinear adsorption at the air–water and solid–water interfaces. I will also discuss the incorporation of additional complexities to test hypotheses formulated from field observations. Insights from these analyses allow us to develop simplified models with a focus on the primary processes that dominantly control PFAS leaching. The simplified models provide efficient and accurate screening-type tools for quantifying long-term PFAS leaching from soils to groundwater.