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EVIDENCE FOR MICROBIAL ENHANCED ELECTRICAL CONDUCTIVITY IN HYDROCARBON-CONTAMINATED SEDIMENTS
Citation:
Atekwana, E., E. A. Atekwana, S. Rossbach, D Werkema, J. W. Duris, L. Smart, J. Allen, D. P. Cassidy, AND W. Sauck. EVIDENCE FOR MICROBIAL ENHANCED ELECTRICAL CONDUCTIVITY IN HYDROCARBON-CONTAMINATED SEDIMENTS. GEOPHYSICAL RESEARCH LETTERS. American Geophysical Union, Washington, DC, 31:1-4, (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:
Electrical conductivity of sediments during microbial mineralization of diesel was investigated in a mesoscale column experiment consisting of biotic contaminated and uncontaminated columns. Microbial population numbers increased with a clear pattern of depth zonation within the contaminated column not observed in the uncontaminated column. Microbial community dynamics using rDNA intergenic spacer analysis showed fewer fragments with higher intensity in the contaminated column, suggesting a highly adapted microbial community. The contaminated column showed temporal increase in electrical conductivity, calcium, and dissolved inorganic carbon suggestiqg that the high conductivity is due to enhanced mineral weathering from microbial activity. The greatest change in electrical conductivity occurred in the unsaturated zone within the free diesel layer .Variations in electrical conductivity magnitude and microbial populations and their depth distribution in the contaminated column are similar to field observations. The results of this study suggest that geophysical methodologies may potentially be used to investigate microbial activity. INDEX TERMS: 0925 Magnetic and electrical methods, 0915 Downhole methods, 1831 Groundwater quality.