Migration Parameters of Chloride and Potassium in GCLs from Diffusion and Column Tests

Prediction of contaminant transport through barrier systems requires entering the solute transport parameters (e.g. diffusion coefficients and retardation factors) into analytical or numerical transport models. In low permeability hydraulic barriersfor containment applications (e.g. GCLs), molecular diffusion often is the dominant solute transport mechanism. The paper describes the determination of solute transport parameters of a GCL by means of through-diffusion (diffusive transport only) and column tests (diffusive and advective transport). Diffusion tests were performed at two stress levels (70 kPa and 241 kPa) while a column test was performed at 70 kPa, using a 20 mM KCl solution. Very close transport parameters for Cland K+ were obtained by the different testing approaches. The results confirmed the dominant effect of diffusion in transport through GCLs and, besides the reduction in steady-state osmotic efficiency shown in previous studies, also highlighted the enhancing effect of consolidation on effective diffusion coefficients and retardation factors.