Appropriate Material Properties for Advective–Diffusive Solute Flux in Membrane Soil

A generalized advective–diffusive equation for describing electrolytic solute transport in fine-grained soil (clay) membranes is presented. Clarification is made between the current theory and the widely cited coupled-flow theory by Yeung and Mitchell. Results of recently published experimental data are evaluated to demonstrate that the effective diffusion coefficient associated with Fick’s first law is not an appropriate independent material property for solute transport considerations in membrane soil. Three independent and experimentally attainable material properties are identified, specifically: osmotic efficiency, membrane diffusion coefficient, and hydraulic conductivity. Simple physical experiments by which these properties may be measured are described.