Chemical reaction and Co-60 retardation in unsteady, unsaturated soil water flow: the effect of clay content

Abstract

The ability of the regolith to adsorb and retard radioactive and other noxious chemicals is important when selecting repository sites. Because of its surface charge and great specific surface, the clay in soil contributes significantly to this retardation. This paper illustrates a novel analysis of unsteady water and solute flow in unsaturated soil that quantifies these effects. Analysis and experiments suggest that the use of a clay-based space-like coordinate permits us to generalise results to account for variation in clay content and soil structure across many materials. Results imply that clay content, mineralogy, and charge permit quantitative material classification according to their ability to retard cationic wastes. The approach appears to offer significant economies in selecting materials where adsorption and retardation of cation pollutants is desired.