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INVESTIGATING THE GEOELECTRICAL RESPONSE OF HYDROCARBON CONTAMINATION UNDERGOING BIODEGRADATION
Citation:
Werkema, D, E. Atekwana, A. Endres, W. Sauck, AND D. P. Cassidy. INVESTIGATING THE GEOELECTRICAL RESPONSE OF HYDROCARBON CONTAMINATION UNDERGOING BIODEGRADATION. GEOPHYSICAL RESEARCH LETTERS 30(12):49-1-49-4, (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 newly proposed geoelectrical model for hydrocarbon contaminated sites predicts high
conductivities coincident with t he Contaminated zone a s opposed t o t he traditionally accepted low conductivity. The model attributes the high conductivities to mineral weathering resulting from byproducts of microbial redox processes. To evaluate this conductive model, in situ vertical conductivity measurements were acquired from a light non-aqueous phase liquid (LNAPL) contaminated site. The results showed high conductivities coincident with the zone of contamination and within the smear zone influenced by seasonal water table fluctuations. We infer this zone as an active zone of biodegradation and suggest significant microbial degradation under partially water saturated conditions. A simple Archie's Law analysis shows large p ore water conductivities necessary to reproduce the bulk conductivity measured at the contaminated location. This study supports the conductive layer model and demonstrates the potential of geoelectrical investigations for assessing microbial degradation of LNAPL impacted soils. INDEX TERMS: 0925 Magnetic and electrical methods, 5109 Magnetic electrical properties, 0915 Downhole methods, 1831 Groundwater quality.