Analysis of effective diffusion and transport of inorganic solute through a landfill liner system

Abstract.

Diffusion characteristics of clayey soil under a representative waste landfill in Korea were evaluated by a laboratory diffusion column test. Then, a numerical analysis of solute transport under the landfill was performed using parameters obtained from the test. From the analysis, the influence of the effective diffusion and the advection of solute migration, as well as the efficiency of the hardened barrier layer with various hydraulic conductivities of the underlying clayey soil, were examined. The results of the experiment showed that the effective diffusion coefficients, D*, for chloride ions from three inorganic chemicals ranged from 2.5×10^{– 10} to 5.5×10^–10 m²/s. From the numerical transport analysis, it was found that effective diffusion contributes more to the depth of transport under the landfill without the hardened barrier at hydraulic conductivities of clay of 1×10^–7 cm/s, and the depth of transport of Cl^– was confined to the upper 5 m of the clayey layer. The depth of transport for K_clay=1×10^–6 cm/s was highly dependent on advection and the importance of the hardened barrier becomes significant for preventing the migration of solute transport.