Geochemical data from closely spaced vertical intervals in a hydrocarbon-impacted aquifer were used to assess the relationship between bulk conductivity and zones of enhanced microbial activity. The bulk conductivity was measured using in situ vertical resistivity probes. Microbial activity was verified using terminal electron acceptors (nitrate, sulfate, iron, and manganese), dissolved inorganic carbon (DIC), and major ion chemistry. Peaks in bulk conductivity in the aquifer overlapped with zones where nitrates and sulfates were depleted, total petroleum hydrocarbon, iron, manganese, dissolved ions, and DIC were elevated, suggesting a link between higher electrical conductivity and zones of enhanced microbial activity stimulated by the presence of hydrocarbon. Thus the subsurface expression of microbial activity is apparently recorded in the bulk conductivity measurements. Our results argue for combining geophysics with biogeochemistry studies to delineate subsurface zones of enhanced microbial activity.


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Downhole Methods; Groundwater Quality; Magnetic And Electrical Methods; Magnetic And Electrical Properties; Aquifers; Carbon; Data Acquisition; Electric Conductivity; Hydrocarbons; Microorganisms; Nitrates; Bulk Conductivity; Dissolved Organic Carbon (DIC); Microbial Activity; Terminal Electron Acceptors; Geophysics; Borehole Geophysics; Groundwater Pollution; Water Quality

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2004 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Dec 2004

Included in

Geology Commons