HR: 0800h
AN: H21A-0993    [Abstracts]
TI: Microbial Heterogeneity in the Subsurface and its Effects on DNAPL Interfacial Properties
AU: Bertrand, L J
EM: bertralj@clarkson.edu
AF: Clarkson University, 8 Clarkson Avenue Department Civil Environmental Engineering, Potsdam, NY 13699-5710 United States
AU: * Grimberg, S J
EM: grimberg@clarkson.edu
AF: Clarkson University, 8 Clarkson Avenue Department Civil Environmental Engineering, Potsdam, NY 13699-5710 United States
AU: Powers, S E
EM: sep@clarkson.edu
AF: Clarkson University, 8 Clarkson Avenue Department Civil Environmental Engineering, Potsdam, NY 13699-5710 United States
AU: Denham, M
EM: Miles.Deham@srs.gov
AF: Savannah River Technology Center, Bldg. 773-42A, Aiken, SC 29808 United States
AU: Doty, T D
AF: Clarkson University, 8 Clarkson Avenue Department Civil Environmental Engineering, Potsdam, NY 13699-5710 United States
AB: Remediation of dense non-aqueous phase liquid (DNAPL) is affected by the heterogeneous spatial distribution of the DNAPL in the subsurface. This distribution is contingent upon porous media properties such as grain size, mineral composition as well as hydrodynamic and capillary forces on the DNAPL. Processes resulting in reduced interfacial tension (IFT) and, thus, capillary forces, may affect DNAPL distribution in the subsurface. The goal of this research is to determine the effect of heterogeneous microbial distributions on the DNAPL interfacial properties at A-14 Outfall Area of the DOE Savannah River Site (SRS). Soil cores were collected from both PCE contaminated areas and background locations near the A-14 outfall. Cores were characterized for microbial concentrations, volatile compounds, and grain size and mineral content. Anaerobic enrichment cultures were grown to assess the effects of microbial activity on the IFT. Results show that bacterial distributions vary significantly with depth but are well correlated with the PCE and TCE concentration in the contaminated area. In the non-contaminated area, bacterial concentrations also vary significantly with depth and are at least 1-2 orders of magnitude lower than concentrations in the DNAPL contaminated borings. These results indicate that the bacterial distribution is predominantly affected by the presence of DNAPL and secondarily by the pore space and soil moisture. Anaerobic enrichments cultures generated from the site reduced PCE/water IFT as much as 50% when the culture was stressed with oxygen or elevated PCE concentrations. The decrease in IFT was predominantly attributed to bacterial adhesion at the PCE/water interface. Anaerobic enrichment cultures using background cores have been developed to determine whether this observed effect on IFT is unique to anaerobic PCE degrading organisms and what bacterial concentrations at the DNAPL interface are required to observe significant IFT reductions. Results of these experiments will be presented at the conference.
DE: 1831 Groundwater quality
DE: 1875 Unsaturated zone
DE: 0614 Biological effects
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting