Geoelectrical response of surfactant solutions in a quartzitic sand analog aquifer

In this project, the resistivity and phase shift of ten surfactant aqueous solutions in a sand matrix were measured using spectral induced polarization (SIP). In addition, specific conductivity, pH, dissolved oxygen, and dielectric constant measurements of the solutions were also evaluated. The frequency range assessed was 0.091-12000Hz. The surfactants, which are typically used in the remediation of tetrachloroethylene, were Aerosol MA 80-I, Dowfax 8390, and Steol CS-330. The surfactants were mixed into solutions of both deionized and tap water at varying concentrations and injected into a closed system of silica sand. The surfactant treatments altered resistivity, specific conductivity, and pH to varying degrees. Increased real and specific conductivities associated with surfactant presence support the work of Werkema (2008), and the correlation between real and specific conductivities indicates that the primary electrical conduction mechanism in quartz sand-water environment. A decrease in the pH response associated with high concentration surfactant solutions could impact subsurface organisms, potentially affecting bioremediation. Phase, dissolved oxygen, and dielectric constant response to surfactant showed little change from the control. The positive results suggest that geoelectrical changes may be an applicable property to map and monitor surfactant floods in the subsurface. In order to better understand how the geoelectrical response of surfactant solutions would respond in a field situation, it will be necessary to increase the complexity of the experimental set-up. Increasing the heterogeneity of both the solid materials and pore fluid through the addition of clays and chlorinated solvents are potential avenues to follow.