HR: 0830h
AN: NS51B-04    [Abstracts]
TI: Investigating the Impact of Microbial Metabolic Byproducts on Electrical Measurements
AU: * Davis, C A
EM: cadk9d@umr.edu
AF: University of Missouri-Rolla, Department of Geological Sciences and Engineering, 125 McNutt Hall , Rolla, MO 65409 United States
AU: Atekwana, E A
EM: atekwana@umr.edu
AF: University of Missouri-Rolla, Department of Geological Sciences and Engineering, 125 McNutt Hall , Rolla, MO 65409 United States
AU: Slater, L D
EM: lslater@andromeda.rutgers.edu
AF: Rutgers University, Department of Earth and Environmental Sciences, 101 Warren Street, Newark, NJ 07102 United States
AU: Atekwana, E A
EM: eliota@umr.edu
AF: University of Missouri-Rolla, Department of Geological Sciences and Engineering, 125 McNutt Hall , Rolla, MO 65409 United States
AU: Rossbach, S
EM: silvia.rossbach@wmich.edu
AF: Western Michigan University, Department of Biological Sciences, 1903 West Michigan Ave, Kalamazoo, MI 49008 United States
AU: Allen, J P
EM: jonathan.allen@wmich.edu
AF: Western Michigan University, Department of Biological Sciences, 1903 West Michigan Ave, Kalamazoo, MI 49008 United States
AB: The main goal of this research group is to test the hypothesis that microbial interaction with geologic media over short and long term can result in changes in physical properties which can be imaged using geophysical methodologies. Bacteria are able to alter mineral surface chemistry, affect water-rock interactions, and modify groundwater geochemistry with the potential to induce changes in in-situ physical properties of subsurface geologic media (e.g. porosity and permeability). Thus the challenge is decoupling these processes and quantifying their magnitudes and impact on the geophysical measurements. In order to better understand the relationship between biological processes and the electrical response of microbially-impacted geologic media, bench-scale laboratory column experiments were conducted to investigate the effect of microbial byproducts (i.e. organic acids) on electrical measurements. Organic acids are common intermediates of microbial mineralization of organic carbon in natural environments, and have the potential to impact electrical measurements (1) by directly contributing to the ionic strength of an aqueous solution, (2) indirectly through the dissolution of minerals which may increase the pore water conductivity of the solution, and (3) through the dissolution of minerals leading to secondary or enhanced porosity. Electrical measurements were collected for three organic acids (acetic, formic, propionic) at three different concentrations (10, 100, 1000 uM) and compared to electrical measurements on salts (sodium chloride, calcium chloride, aluminum chloride) of the same concentration. With the exception of formic acid, no significant difference was observed between the conductivity magnitude of the organic acids and salts at the same concentrations. This suggests that both the acids and salts may contribute similarly to the ionic strength of the solution. The magnitude of the conductivity of formic acid was observed to be up to four times that of other acids at the same concentration. We infer from these observations, that depending on the type of organic acid, different organic acids may contribute more to the fluid conductivity than other acids of the same concentration. Finally, the data from the current study was compared to fluid conductivity and organic acid concentration data from a hydrocarbon contaminated site in Michigan. Preliminary calculations suggest that the direct presence of organic acids in the groundwater at the site may contribute to more than half of the total fluid conductivity measured at the site.
DE: 0400 Biogeosciences
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly