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 filmforming
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.