Upscaling of Long-Term U(VI) Desorption from Pore Scale Kinetics to Field-Scale Reactive Transport Models
James A. Davis, PI
Gary P. Curtis, Co-PI
Bruce D. Honeyman, Co-PI
Douglas B. Kent, Co-PI
Carl I. Steefel, Co-PI
Abstract - The focus of the proposed project is the development of scientifically defensible approaches for upscaling reactive transport models (RTM) through a detailed understanding of U(VI) desorption across several spatial scales: bench-, intermediate-, and field-scales. Our target system is the DOE UMTRA site near Naturita, CO. Processes that control U(VI) desorption and transport at the pore scale will be incorporated into a multicomponent RTM that is used to evaluate the outcome of intermediate- scale experiments. The intermediate-scale experiments will be designed to study U(VI) desorption from U-contaminated sediments with known physical and chemical heterogeneity structure, similar in scale and distribution to that observed at the Naturita field site. These results will be used to examine the upscaling of RTM to the intermediate-scale, based on a detailed understanding of the pore-scale processes. Natural and forced-gradient field-scale transport experiments and a geostatistical study of field data will be conducted to extend the upscaling of RTM to the field scale. The findings from this investigation will provide a basis for a methodology to upscale the knowledge of processes at the pore scale to effective rates of the same processes occurring at the field scale. Development of this methodology will lead to a scientifically defensible approach for conceptual model development for multicomponent RTM at contaminated DOE sites, leading to predictive U(VI) transport simulations with reduced uncertainty.
