HR: 0800h
AN: H21C-0707    [Abstracts]
TI: Characterization of Transient Transport Behavior During Biostimulation Field Experiments Using Novel Breakthrough Analysis Approaches
AU: * Englert, A
EM: alenglert@lbl.gov
AF: Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Kowalsky, M
EM: MBKowalsky@lbl.gov
AF: Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Li, L
EM: LILi@lbl.gov
AF: Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AU: Long, P
EM: philip.long@pnl.gov
AF: Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, United States
AU: Hubbard, S
EM: SSHubbard@lbl.gov
AF: Earth Science Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, United States
AB: Biostimulation experiments were performed to immobilize uranium within a shallow, unconsolidated, and unconfined aquifer at the DOE Integrated Field Challenge Site (IFC) in Rifle, CO. During experiments conducted in 2002 and 2003, twenty wells were used to deliver acetate and bromide to the contaminated aquifer over a 111 and 119 day period, respectively. Due to changes in the injection rate, the injection concentration and the groundwater level during the injection period, the mean concentration of the bromide injected to the aquifer was temporally variable. Although a dense dataset of bromide concentrations was collected from fifteen downgradient monitoring wells, interpretation of the bromide breakthrough datasets in terms of hydrological heterogeneity was difficult using conventional tracer test analysis methods due to the complex bromide input function. We developed two novel approaches for analyzing and interpreting breakthrough curves (BTC) in the presence of a complex tracer injection function. The first approach is based on conventional temporal moment analysis. It estimates the effective velocity and dispersivity based on changes of the first and second moment along the distance between the injection and the monitoring well. The second approach is based on the analytical solution of the one dimensional convection dispersion equation. To account for the complex injection function, here each step in the injection function is represented by an analytical solution of the one dimensional convection dispersion equation. These are weighted by the concentration of each step and combined based on superposition. Fit of this function to the BTCs permits the estimation of the effective velocity and dispersivity. We applied the developed approaches to the bromide BTCs at the IFC to characterize the flow and transport processes in the sense of a stream tube model. This analysis suggested that the novel BTC analysis approach greatly improved our ability to quantitatively interpret the bromide breakthrough datasets, and that velocity and dispersivity varied over space and time in response to the biostimulation treatment.
DE: 0418 Bioremediation
DE: 1816 Estimation and forecasting
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: 2007 Fall Meeting