Modeling Solute Transport by Centrifugation

Abstract

Measurements of physical and chemical solute transport properties of soil/waste systems are necessary to predict pollutant migration in soils. The sorption distribution coefficient is most often determined in the laboratory by performing column studies or batch equilibrium tests. Both of these methods suffer from disadvantages. For fine‐grained soils, which have small permeabilities, column studies require long periods of time to conduct and batch tests usually overestimate the sorption distribution coefficient because of the solids effect. An alternative method is developed that uses a constant head permeameter spinning in a centrifuge. As the permeameter spins, larger confining stresses are imposed on the soil sample and pore water velocities are increased relative to ordinary column studies. The utility of the method was demonstrated by conducting miscible displacement experiments for a range of column sizes and inertial accelerations. Sorption distribution coefficients, based on the local equilibrium assumption, were computed from experimental breakthrough curves using an analytical solution to the solute transport equation.