The Radioactive Waste Management Complex (RWMC), similar to other DOE mixed-waste burial grounds, contains mixtures of metals, radionuclides, volatile organic chemicals, chelators, and other contaminants. These wastes are located in the vadose zone and consequently subject to complex biogeochemical interactions which affect the redox speciation, the mobility of contaminants, etc.
Because of the existence of a discrete and mobile gas phase in the vadose zone, transport of molecules in both the aqueous and gas phase can occur. The partitioning of compounds between dissolved, solid, and gaseous forms can lead to the development of spatially variable pH and associated variability in contaminant behavior. The presence of organic carbon, as either disposed waste or as natural materials, can promote microbial mineralization. Microbial activity in turn will be a function of available electron acceptors, such as oxygen in the vadose zone gas phase and free water (water that microorganisms can access). The non linear relationship between movement of the gas and aqueous phases and their effect on microbial activity will ultimately influence contaminant mobility. The vadose zone chemical cycles, the subsurface transport of reactive gases, and their effects on radionuclide mobility are poorly understood. These coupled processes will be investigated in variably-saturated, mesoscale experiments using RWMC soils. Field observations at the RWMC will be used to bound the range of conditions considered in the mesoscale experiment and will serve as a check on experimental results. Supporting laboratory experiments will use uranium to assess the effects of varying carbon dioxide concentrations on contaminant mobility. Additional laboratory studies will assess processes controlling the migration of carbon dioxide and volatile organic chemicals through the vadose zones. Results from these experimental efforts will be integrated through the development of conceptual models of the coupled processes and their embodiment in numerical simulators.
- Contacts:
- Mark Ankeny, (208) 526-5748, Send E-mail