Developing turn-key remediation techniques for dense non-aqueous liquids (DNAPLs) has been a challenge due to insufficient remediation monitoring techniques. Advancement has been made in developing ways to alter, mobilize, and breakdown chlorinated solvents (e.g. Surfactant Enhanced Aquifer Remediation (SEAR)), yet with mobilization come problems. Once solvents are mobilized, reliable and working monitoring programs are needed to measure subsurface plume movement and concentrations. Unknown variables (i.e. complex site geology/hydrogeology) provide challenges. Regulatory agencies are reluctant to approve remedial designs that lack sufficient monitoring plans. Research at the United States Environmental Protection Agency (EPA) suggests a potential solution: use geoelectrical methods to monitor subsurface surfactant floods.
In 2006, EPA initiated SEAR-based research which focused on measuring changes in aqueous properties and density in the pore fluid. Results generated a conductivity response model showing the most relevant geophysical measurements in its ability to predict pore water conductivity. Pore water conductivity was shown to be directly proportional to Direct Current (DC) resistivity measurements, induced polarization, and complex resistivity measurements. Subsequent research used silica sand and the spectral induced polarization (SIP) responses were measured. This yielded a real and imaginary conduction response. Surfactant addition to saturated sands resulted in an electrolytic conductive response proportional to the free ions available in the surfactant.
The present work proposes to change the medium to various sand/clay mixtures, hypothesizing that the addition of surfactants to sand/clay mediums will result in an increased geoelectrical measured response. Experimental design will include spiking the medium with three surfactants and four known perchloroethylene (PCE) concentrations. Pore fluid and grain surface electrolytic conduction will be measured.
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