Per- and polyfluoroalkyl substances (PFAS) from aqueous film-forming foam (AFFF) can persist for decades in soils above the water table (vadose zone) and slowly leach into groundwater. Because these soils act as long-term contaminant reservoirs, there is a critical need for improved methods to locate and monitor PFAS contamination at AFFF source zones.

This study evaluates spectral induced polarization (SIP), a non-invasive geophysical method, as a potential tool to detect PFAS in soils. SIP measures how electrical charges are stored and transported at the boundary between soil particles and water. These properties can change when contaminants, such as PFAS, attach to soil particles.

Laboratory column experiments were conducted using soils collected from an AFFF site. Columns were tested at high (100%) and low (30–35%) water saturation levels and spiked with three PFAS types: (1) AFFF, a PFAS mixture; (2) the zwitterionic compound TAmPr-FBSA; and (3) the anionic compound PFOA.

Results show that SIP is sensitive to PFAS type, soil properties, and water saturation. These findings suggest SIP could be developed into a screening-level tool to help identify and monitor PFAS-contaminated soils in the field, guiding cleanup strategies.