HR: 0801h
AN: NS11B-0496    [Abstracts]
TI: A Laboratory Tank Experiment to Investigate the Effects of Microbial Growth on Water Flow and GPR Wave Propagation
AU: * Patterson, E
EM: elisha04@ku.edu
AF: Dept. of Geology University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66045, United States
AU: Schillig, P
EM: schillig@ku.edu
AF: Dept. of Geology University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66045, United States
AU: Tsoflias, G P
EM: tsoflias@ku.edu
AF: Dept. of Geology University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66045, United States
AU: Devlin, J
EM: jfdevlin@ku.edu
AF: Dept. of Geology University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66045, United States
AU: Roberts, J A
EM: jaroberts@ku.edu
AF: Dept. of Geology University of Kansas, Lindley Hall, rm 120 1475 Jayhawk Blvd., Lawrence, KS 66045, United States
AB: A detailed laboratory tank experiment was conducted, as follow-up to preliminary findings from an earlier experiment, to investigate the effects of microbial growth on groundwater flow, and the sensitivity of GPR to measure changes in the aquifer resulting from that growth. The preliminary work involved the biostimulation of saturated sand in a Plexiglas® tank measuring 1.0 m high by 1.0 m long by 0.3 m wide. Bacteria were stimulated with a solution of tryptic soy broth and sodium acetate that served as a carbon and nutrient source. Twice weekly, GPR data were acquired in a transillumination survey mode through the sand, across the width of the tank. The experiment indicated that GPR wave velocities were highly variable in the bioactive zone compared to the non- stimulated zone in the tank. In particular, the effect of microbial growth appeared to produce a net decrease in GPR wave velocity. In order to assess the validity of these findings, the experiment was repeated with a higher sampling density and additional monitored parameters. As before, the experiment was conducted in a large flow-through sandbox reactor using groundwater acquired from a local, shallow aquifer, amended with a carbon source. Measured parameters included two-way GPR travel time and amplitude, pH, electrical conductivity, and temperature, all collected twice daily both upstream and downstream of the nutrient injection ports. This was maintained over the period that biological activity became established. Groundwater velocity (multilevel point velocity probes), and attached biomass were evaluated at the beginning and end of the experiment. Baseline conditions were documented over a period of about a month, before nutrient injections were begun. During this time, a dye tracer experiment was performed to visualize the flow paths within the porous medium prior to biostimulation. At the time of writing the experiment was underway with final results pending.
DE: 0416 Biogeophysics
DE: 0418 Bioremediation
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting