Spectral induced polarization (SIP) measurements across a PFAS-contaminated source zone

There is a need to develop field-scale, in situ screening technologies for assessing variations in aqueous film-forming foam (AFFF) concentrations in soils at former fire training and storage sites. Field-scale Spectral Induced Polarization (SIP) geophysical measurements were acquired on a transect crossing an AFFF source zone. Soil samples were acquired to determine variations in poly- and per-fluoroalkyl substances (PFAS) concentrations in soils, characterize soil texture, and create triplicate soil columns for laboratory SIP measurements. Field and laboratory observations show that SIP measurements are sensitive to the concentration of AFFF constituents associated with soil pore surface area. The specific polarizability and the phase of the SIP measurements for the laboratory samples were linearly correlated with total soil-sorbed PFAS concentration. The phase from the field SIP measurements was highest over the location of maximum PFAS concentration measured on the laboratory samples. However, a significant correlation between field-measured phase and laboratory-measured total PFAS concentration still needs to be established. These observations, along with the demonstrated sensitivity of the SIP response to the removal of soil PFAS using a methanol wash procedure, support the case for SIP characterization of AFFF source zones.