HR: 15:45h
AN: NS44A-02    [Abstracts]
TI: 3D Self-Potential Inversion for Monitoring DNAPL Contaminant Distributions
AU: * Minsley, B J
EM: minsley@mit.edu
AF: Earth Resources Laboratory, Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Sogade, J
EM: sogade@erl.mit.edu
AF: Earth Resources Laboratory, Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Vichabian, Y
EM: yerv@erl.mit.edu
AF: Earth Resources Laboratory, Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AU: Morgan, F D
EM: morgan@erl.mit.edu
AF: Earth Resources Laboratory, Department of Earth, Atmospheric, and Planetary Sciences Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 United States
AB: Self-potential (SP) data are collected over an area known to be contaminated with Dense Non-Aqueous Phase Liquids (DNAPLs) at the Savannah River Site in South Carolina. The field experiment consists of approximately 100 SP measurements on a surface grid and in four boreholes, and is repeated after one year. DNAPLs are known to undergo redox reactions during their degradation in the environment, which is often biologically mediated. Self-potential geophysics is employed in this study because of its sensitivity to the in-situ biochemical processes that degrade the contaminants. These reactions provide an electrochemical source that is manifested as an SP signature at the measurement locations remote from the contaminated areas. 3D inversion of the SP data is therefore needed to spatially locate the distribution of sources, which is related to contaminant presence. The inversion incorporates the 3D resistivity structure collected at the same site, and is better constrained in depth by using borehole data and regularization. Ground truth information taken after the first field experiment provides concentration data with depth for several DNAPL species in five boreholes. There is a good correlation between the ground truth data and SP source inversion, though this comparison is limited by several factors: the difference in resolution of the ground truth and inverted data, and the dependence of the redox processes on other constituents that were not measured during the ground truthing, such as oxygen content or microbial presence. Inversion of the second year's dataset provides information on the changes in the contaminant distribution, either due to natural degradation or ongoing remediation.
DE: 0400 Biogeosciences
DE: 0614 Biological effects
DE: 0903 Computational methods, potential fields
DE: 0925 Magnetic and electrical methods
DE: 1899 General or miscellaneous
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly