Determining site-specific soil screening levels for PFAS at an airport source area
Marcy Nadel1, Mark Brusseau1, Bo Guo1, Min Ma1, Joseph Quinnan2, Dina Drennan3
1 University of Arizona, Tucson, AZ
2 Arcadis U.S., Inc., Novi, MI
3 BEM Systems, Inc., Lakewood, CO
Soils impacted by aqueous film-forming foam (AFFF) use at military and civilian airports are a major, ongoing source of per- and polyfluoroalkyl substances (PFAS) in the environment. This study determines site-specific soil screening levels (SSLs) for three PFAS using field and laboratory data from an AFFF source area at U.S. Air Force installation. We apply multiple PFAS-specific approaches: a one-dimensional analytical solution transport model, modified U.S. Environmental Protection Agency (EPA) dilution-attenuation factor (DAF) equation, and field-measured soil and porewater concentrations. The modeling effort is supported by high-resolution soil characterization, including measurements of physical, hydraulic, and geochemical properties. Such SSLs are used to quantify the risk of PFAS leaching to groundwater, which often results in human and environmental exposures. Our PFAS-specific approaches reflect the complexity of PFAS partitioning and vadose zone transport, an area of active research. Differences among the SSLs generated for each PFAS by the different approaches highlight the dominant processes controlling soil retention and mass discharge at this site.