HR: 0800h
AN: H11D-1299    [Abstracts]
TI: Modeling in-situ uranium(VI) bioreduction at Oak Ridge, TN
AU: * Luo, J
EM: jianluo@stanford.edu
AF: Stanford University, Department of Civil and Envirnomental Engineering, Stanford, CA 94305-4020 United States
AU: Weber, F
EM: frank-andreas.weber@env.ethz.ch
AF: Swiss Federal Institute of Technology (ETH) Z�rich, Institute of Terrestrial Ecology, ETH Zentrum CHN, Z�rich, CH-8092 Switzerland
AU: Cirpka, O A
EM: olaf.cirpka@eawag.ch
AF: Swiss Federal Institute for Environmental Science and Technology (EAWAG), Department of Water Resources and Drinking Water, šberlandstrasse 133, D�bendorf, CH-8600 Switzerland
AU: Wu, W
EM: wei-min.wu@stanford.edu
AF: Stanford University, Department of Civil and Envirnomental Engineering, Stanford, CA 94305-4020 United States
AU: Nyman, J L
EM: jnyman@stanford.edu
AF: Stanford University, Department of Civil and Envirnomental Engineering, Stanford, CA 94305-4020 United States
AU: Carley, J M
EM: carleyjm@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Science Division, Oak Ridge, TN 37831-6038 United States
AU: Jardine, P M
EM: jardinepm@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Science Division, Oak Ridge, TN 37831-6038 United States
AU: Criddle, C S
EM: ccriddle@stanford.edu
AF: Stanford University, Department of Civil and Envirnomental Engineering, Stanford, CA 94305-4020 United States
AU: Kitanidis, P K
EM: peterk@stanford.edu
AF: Stanford University, Department of Civil and Envirnomental Engineering, Stanford, CA 94305-4020 United States
AB: A travel-time based reactive-transport model is developed to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI) at Oak Ridge, TN. The space to travel-time transformation is obtained from a conservative-tracer test. Reactive transport is solved numerically in time and travel-time coordinates. Reaction kinetics include aquatic equilibrium geochemistry, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). U(VI) sorption/desorption is described by a surface-complexation model and the characteristics of kinetic sorption/desorption is described by mass transfer between stagnant micro-pores and mobile flow zones. The model characterizes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results indicate that (1) nitrate inhibits U(VI) reduction at the site; (2) the effective reduction rate of U(VI) is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption is kinetically controlled; (4) pH and bicarbonate concentration varies over the experimental period, significantly influencing the U(VI) sorption/desorption; and (5) calcium concentration influences the concentrations of biodegradable U(VI) species.
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1849 Numerical approximations and analysis
SC: Hydrology [H]
MN: Fall Meeting 2005