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LABORATORY AND FIELD RESULTS LINKING HIGH CONDUCTIVITIES TO THE MICROBIAL DEGRADATION OF PETROLEUM HYDROCARBONS
Citation:
Werkema, D, E. Atekwana, E. A. Atekwana, S. Rossbach, AND W. Sauck. LABORATORY AND FIELD RESULTS LINKING HIGH CONDUCTIVITIES TO THE MICROBIAL DEGRADATION OF PETROLEUM HYDROCARBONS. Presented at Symposium on the Application of Geophysics to Environmental and Engineering Problems, Colorado Springs, CO, February 22-26, 2004.
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:
The results of a l6-month field and l6-month meso-scale laboratory investigation of unconsolidated sandy environments contaminated by petroleum hydrocarbons that are undergoing natural biodegradation is presented. The purpose was to understand the processes responsible for causing the higher electrical conductivities observed at petroleum hydrocarbon contaminated sites. The results show that high conductivity, high microbial population numbers, shifts in microbial community dynamics, and elevated geochemical parameters all occur within the contaminated zone. Both investigations show that the highest conductivities occur within and slightly above the free-phase layer, not within the water saturated zone. Further analysis demonstrates highly elevated pore water conductivities within this conductive zone (~2-4 times background conductivity) as well as the maximum populations of oil degrading bacteria. The upper saturated zone reveals elevated concentrations of calcium and other ions suggesting enhanced mineral dissolution. These results suggest that the mechanism for the higher conductivity is directly or indirectly related to the microbial metabolism of the hydrocarbon and the resulting geochemical alterations within the contaminated zone. This study demonstrates the potential of geoelectrical investigations for assessing microbial degradation of hydrocarbon impacted sediments and the importance of meso-scale experiments for the interpretation of field data.