HR: 1340h
AN: H13G-1666    [Abstracts]
TI: A metabolism-based modeling approach to redox transformations in a nitrate- and uranium- contaminated aquifer at Oak Ridge, Tennessee, USA
AU: * Jin, Q
EM: qjin@uoregon.edu
AF: University of Oregon, 1272 University of Oregon, Eugene, OR 97403, United States
AB: Microbial metabolisms control groundwater chemistry and influence the fate of both natural and anthropogenic contaminants in aquifers. Recent advances in groundwater microbiology revealed diverse microorganisms competing for limited energy resources in aquifers. To predict accurately the kinetics of redox transformations, we took into account both microbial metabolic diversity and limited energy resources and developed a new biogeochemical reaction model for microbially catalyzed redox reactions in a nitrate- and uranium-contaminated aquifer at the FRC site, Oak Ridge, east Tennessee. The new model describes the metabolisms of diverse microorganisms in the aquifer as a network of metabolic reactions. It considers various interactions among the pathways, such as inhibition, syntrophism, and competition. The model predicts the rates of each pathway by taking into account the balance of electrons, energy, and nutrients during microbial metabolisms. To incorporate the close interactions between microorganisms and aquifer environments, the new model also considers geochemical reactions pertinent to microbial metabolisms, including abiotic redox reactions, mineral precipitation and dissolution, surface adsorption, and ion exchange. The catalytic capacity of individual branch of the network (i.e., kinetic parameters and biomass concentration of functional groups) is then determined by fitting the modeling results to a laboratory microcosm experiment on sediments from the FRC site. The best-fit model is then applied to predict the kinetics of microbial metabolisms during a field push-pull test on the aquifer. The new model predicts well the progress of redox transformations observed during the field experiment, including denitrfication, ammonification, iron reduction, sulfate reduction, and methanogenesis. The results revealed the key roles of metabolic diversity and energy availability in controlling the kinetics of redox reactions in aquifers. These results also demonstrated the potential of the new model to extrapolate the results of laboratory experiments directly to natural environments.
DE: 0412 Biogeochemical kinetics and reaction modeling (0414, 0793, 1615, 4805, 4912)
DE: 0418 Bioremediation
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1831 Groundwater quality
SC: Hydrology [H]
MN: 2007 Fall Meeting