Combining Field Datasets and Mathematical Modeling to Quantify PFAS Leaching and Mass Discharge at an AFFF-Impacted Site

Abstract

The widespread use of per- and polyfluoroalkyl substances (PFAS) in a variety of manufactured products since the 1940s has led to their ubiquitous presence in the environment. In particular, vadose zones at PFAS-contaminated sites have been demonstrated to be significant reservoirs of PFAS. Thus, quantifying PFAS mass discharge from the vadose zone to groundwater has been a major focal point of recent research. The interfacial partitioning of PFAS to the solid-water and air-water interfaces in the dynamic variably saturated soil media complicates PFAS leaching in the vadose zone. Field observations of PFAS concentrations in soil and porewater are becoming available at a growing number of PFAS-contaminated sites. However, few studies have utilized these real-site datasets to validate and improve mathematical modeling for quantifying PFAS leaching and mass discharge to groundwater. This thesis applies mathematical models that account for PFAS-specific retention and transport processes to simulate PFAS leaching and mass discharge at an AFFF-impacted site. The mathematical models are constrained by a series of datasets collected at the field site under both ambient and artificial rainfall conditions. Model simulations and analyses illustrate how field measurements can be combined with mathematical modeling to quantify PFAS source strength and mass discharge rates in the vadose zone. The results have also identified field parameters and datasets that should be prioritized to improve site characterization and remedial actions.