Spectral Induced Polarization Signatures of PFAS-contaminated soils
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Concern continues to grow regarding the transport of aqueous film forming foam (AFFF) constituents from source zones leading to the contamination of soil and groundwater. Characterizing AFFF source zones is an important step in assessing spatial variations in concentrations of contaminants such as per- and polyfluoroalkyl substances (PFAS). Geophysics may facilitate non-invasive assessment of soil AFFF contamination across source zones. Spectral induced polarization (SIP) can be used to delineate subsurface physical and chemical properties in porous media, with proven sensitivity to sorption of constituents onto mineral surfaces. Laboratory and field SIP measurements were acquired on soil samples taken from two known AFFF source zones. SIP measurements were conducted both in situ and in a laboratory setting. Samples collected from the field were packed in bench columns with the same moisture content as they were collected from the field, and they were also packed under saturated conditions. Initial results support the sensitivity of the SIP method to AFFF constituents, including cationic and zwitterionic PFAS, sorbed to soils. The findings show evidence that AFFF constituents associated with the pore surface produced a measurable polarization response across AFFF impacted zones. Further studies are needed to examine the sensitivity limits through comparison of SIP responses to PFAS concentrations in soils.