Radionuclide Release from Slag and Concrete Waste Materials. Part 2: Relationship Between Laboratory Tests and Field Leaching

摘要

Technical literature has been evaluated to assess the several-orders-of-magnitude discrepancy that is commonly reported between the mineral dissolution rates that are inferred from mass-balance calculations for natural systems and those measured in laboratory experiments. This was done to gain insights that may be useful for modeling the weathering behaviors and contaminant releases from waste materials in surface disposal sites. Predicting the concentrations and movement of contaminants in groundwater requires an understanding of (1) groundwater flow, (2) processes affecting contaminant dispersal and groundwater mixing, and (3) physical and chemical reaction processes that affect the concentration of a contaminant in groundwater. Inverse modeling of field measurements to extract mineral dissolution rates is affected by uncertainties in all three of these factors, whereas most laboratory measurements used in direct modeling address only the dissolution of an isolated material in a well-constrained system. Both approaches and the origins of uncertainties in each that are likely to contribute to the differences between the dissolution rates that are determined are evaluated. Information and insights pertinent to assessing the longterm weathering of waste materials under subaerial conditions are provided by each approach, and several aspects are evaluated in detail to support the use of inverse and direct modeling in future applications.