EFFECT OF MULTIPLE CONTAMINANT MIGRATION ON DIFFUSION AND ADSORPTION OF SOME DOMESTIC WASTE CONTAMINANTS IN A NATURAL CLAYEY SOIL

This paper describes laboratory model tests involving the placement of domestic landfill leachate on top of a layer of saturated undisturbed clayey soil and allowing chemical constituents to migrate into the soil by diffusion only. During the testing period (15 days), samples from the overlying leachate were regularly collected and analyzed for the chemical constituents of interest (i.e., Cl−, Na+, K+, Mg++, and Ca++). At the end of the test, the soil layer was sectioned to determine the pore-water and adsorbed concentration variations with depth for each species. Mathematical model POLLUTE was then used to back-figure both the diffusion coefficient (D) and the adsorption term (ρK). The measured diffusion coefficients at a temperature of 10 °C were determined to be , , and . The corresponding adsorption terms were , , and .Ca++ and Mg++, originally predominant on the clay exchange sites, were heavily desorbed to accommodate the adsorption of migrating Na+, K+, and possibly NH4+, causing hardness halo effe...