Unstable Fingered Flow in Soil-Oil-Water-Air Systems: Theoretical Predictions and Experimental Verification

Abstract : Contamination of soils, sediments, and groundwater with non-aqueous phase liquids (NAPLs) is the widespread environmental problem. In situ remediation technologies are the only viable treatments. Cleanup procedures are often instituted and operated with limited knowledge of contaminant vapor and liquid mass transfer and transport. We have used this Air Force grant to improve and extend into three-phase systems two separate visualization techniques which can rapidly record fluid concentrations in our soil slabs: light transmission and attenuation of synchrotron radiation. The techniques are complementary, and both provide high temporal and spatial resolution of fluid concentrations. Using these improved techniques we have obtained data concerning the source and scope of oil and water flow important for in situ remediation. We found that preferential flow in two- and three-phase systems (also called fingering) can control the movement of water through oil-contaminated soils and, thus, affect many remediation techniques. From theoretical arguments and high-speed experiments, we have been able to determine properties such as the size and fluid content in the fingers. Early experiments suggest that surfactants break up the fingers, yielding a better water-oil mixture with positive effects for biological breakdown of oils.