Resistivity and Self-Potential Tomography Applied to Groundwater Remediation and Contaminant Plumes: Sandbox and Field Experiments

Abstract

Geophysical methods can be used to remotely characterize contaminated sites and monitor in situ enhanced remediation processes. We have conducted one sandbox experiment and one contaminated field investigation to show the robustness of electrical resistivity tomography and self-potential (SP) tomography for these applications. In the sandbox experiment, we injected permanganate in a trichloroethylene (TCE)-contaminated environment under a constant hydraulic gradient. Inverted resistivity tomograms are able to track the evolution of the permanganate plume in agreement with visual observations made on the side of the tank. Self-potential measurements were also performed at the surface of the sandbox using non-polarizing Ag-AgCl electrodes. These data were inverted to obtain the source density distribution with and without the resistivity information. A compact horizontal dipole source located at the front of the plume was obtained from the inversion of these self-potential data. This current dipole may be related to the redox reaction occurring between TCE and permanganate and the strong concentration gradient at the front of the plume. We demonstrate that time-lapse self-potential signals can be used to track the kinetics of an advecting oxidizer plume with acceptable accuracy and, if needed, in real time, but are unable to completely resolve the shape of the plume. In the field investigation, a 3D resistivity tomography is used to characterize an organic contaminant plume (resistive domain) and an overlying zone of solid waste materials (conductive domain). After removing the influence of the streaming potential, the identified source current density had a magnitude of 0.5 A m-2. The strong source current density may be attributed to charge movement between the neighboring zones that encourage abiotic and microbially enhanced reduction and oxidation reactions. In both cases, the self-potential source current density is located in the area of strong resistivity gradient.

Department(s)

Geosciences and Geological and Petroleum Engineering

Sponsor(s)

United States. Department of Energy. Office of Biological and Environmental Research
Chevron Energy Technology Company

Comments

Chevron grant #CW852844

Keywords and Phrases

Conductive Materials; Contamination; Current Density; Electric Conductivity; Geophysics; Groundwater; Pollution; Redox Reactions; Remediation; Tomography; Concentration Gradients; Contaminant Plume; Contaminated Environment; Electrical Resistivity Tomography; Ground Water Remediation; Hydrogeophysics; Self Potential; Self-potential Signals; Groundwater Pollution; Chemical Reaction; Electrical Resistivity; Experimental Study; Geophysical Method; Organic Pollutant; Plume; Remediation; Remote Sensing; Site Investigation; Tomography; Trichloroethylene

International Standard Serial Number (ISSN)

0022-1694

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2015 Elsevier, All rights reserved.

Publication Date

01 Nov 2015

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