Migration of salt bands through a porous medium

In order to improve agricultural conditions in saline and sodic soils, we must better understand salt precipitation dynamics and the limiting kinetic mechanisms associated with the salinization process. We used laboratory techniques to monitor salt crystal formation in porous media cells under highly controlled conditions to examine the temporal evolution of salt crystallization. We found that salt crusts first precipitate on the surface and then move down through the porous media towards the water source forming bands collinear with equipotential moisture planes. We compare the kinetic data with a salt crystal formation and transport model and conclude that salt band formation and transport occurs via a cycle of vapor transport, osmotic deposition and deliquescence in the moving front, followed by evaporation and recrystallization in the receding front. Vapor density gradients and deliquescence kinetics controls the transport rate of salt bands through porous media.