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GEOELECTRICAL STRATIGRAPHY AND ANALYSIS OF A HYDROCARBON IMPACTED AQUIFER
Citation:
Werkema, D, E. Atekwana, A. Endres, AND W. Sauck. GEOELECTRICAL STRATIGRAPHY AND ANALYSIS OF A HYDROCARBON IMPACTED AQUIFER. Presented at Joint Assembly of the European Geophysical Society, and the American Geophysical Union and European Union of Geosciences Spring 2003 meeting, Nice, France, April 4-13, 2003.
Impact/Purpose:
Research is being conducted to improve and evaluate the resolution of the CR, EM, seismic, and GPR methods over complex geological formations (such as fractured geologies) and to evaluate the capability of these geophysical methods to delineate subsurface organic contaminants.
Description:
A recently proposed geoelectrical model for hydrocarbon impacted sites predicts anomalously high conductivities coincident with aged contaminated zones. These high conductivities are attributed to an enhancement of mineral weathering resulting from byproducts of microbial redox processes. To evaluate this model, high resolution in situ vertical bulk conductivity measurements were acquired from a mature light non-aqueous phase liquid (LNAPL) contaminated site. The geoelectrical stratigraphy showed conductivity maxima coincident with the free phase LNAPL zone, and occurring within the water table fluctuation zone. This zone is inferred as an active zone of biodegradation suggesting significant microbial degradation under partially saturated conditions. A simple Archie's Law analysis reveals that large pore water saturation and/or large pore water conductivity enhancements are necessary to produce the bulk conductivity observed at the contaminated locations. These results support the conductive model and demonstrate the potential of geoelectrical investigations for assessing microbial degradation of mature LNAPL impacted soils.