HR: 1340h
AN: H33H-1724    [Abstracts]
TI: Study of Uranium Transport Utilizing Reactive Numerical Modeling and Experimental Data from Heterogeneous Intermediate-Scale Tanks
AU: * Rodriguez, D
EM: drrodrig@mines.edu
AF: Colorado School of Mines, 1500 Illinois St ESE Division, Golden, CO 80401, United States
AU: Miller, A
EM: amiller@mines.edu
AF: Colorado School of Mines, 1500 Illinois St ESE Division, Golden, CO 80401, United States
AU: Honeyman, B
EM: bhoneyma@minesedu
AF: Colorado School of Mines, 1500 Illinois St ESE Division, Golden, CO 80401, United States
AB: The study of the transport of contaminants in groundwater is critical in order to mitigate risks to downstream receptors from sites where past releases of these contaminants has resulted in the degradation of the water quality of the underlying aquifer. In most cases, the fate and transport of these contaminants occurs in a chemically and physically heterogeneous environment; thereby making the prediction of the ultimate fate of these contaminants difficult. In order to better understand the fundamental processes that have the greatest effect on the transport of these contaminants, careful laboratory study must be completed in a controlled environment. Once the experimental data has been generated, the validation of numerical models may then be achieved. Questions on the management of contaminated sites may center on the long-term release (e.g., desorption, dissolution) behavior of contaminated geomedia. Data on the release of contaminants is often derived from bench-scale experiments or, in rare cases, through field-scale experiments. A central question, however, is how molecular-scale processes (e.g., bond breaking) are expressed at the macroscale. This presentation describes part of a collaborative study between the Colorado School of Mines, the USGS and Lawrence Berkeley National Lab on upscaling pore-scale processes to understanding field-scale observations. In the work described here, two experiments were conducted in two intermediate-scale tanks (2.44 m x 1.22 m x 7.6 cm and 2.44 m x 0.61 m x 7.6 cm) to generate data to quantify the processes of uranium dissolution and transport in fully saturated conditions, and to evaluate the ability of two reactive transport models to capture the relevant processes and predict U behavior at the intermediate scale. Each tank was designed so that spatial samples could be collected from the side of the tank, as well as samples from the effluent end of the tank. The larger tank was packed with a less than 2mm fraction of a composite field material collected from Naturita, Colorado, a Uranium Mill Tailings Remedial Action (UMTRA) Site. The smaller tank was heterogeneously packed into varying layers representing a subdivision of the less than 2mm fraction into two fractions consisting of 0 to 0.250 mm and 0.250 mm to 2 mm. Various physical and chemical parameters were measured in each tank. This paper presents the results from these tank studies as they pertain to a model comparison analysis that was completed. Reactive transport simulations were carried out with the code CrunchFlow and compared with the United States Geologic Service code RATEQ. Both codes were developed to simulate reactive transport, although their code structures are different. RATEQ utilizes MODFLOW to simulate groundwater flow and the framework of MT3DMS to incorporate a reactive transport module. CrunchFlow is self-contained in that the flow and transport portions of the code are solved within the same multicomponent model. The model analysis demonstrated that the incorporation of a kinetic module into RATEQ had the ability to capture the non-equilibrium behavior of the uranium migration in the system as was observed in both intermediate-scale tank experiments.
UR: http://laer.mines.edu/projects/uranium.html
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting