The solute diffusion coefficient in variably compacted, unsaturated volcanic ash soils

Abstract

The solute diffusion coefficient in soil (Ds) and its dependency on the soil water content (θ), soil type, and compaction govern the transport and fate of dissolved chemicals in the soil vadose zone. Only a few studies have quantified solute diffusivity (Ds/D0, where Ds and D0 are the solute diffusion coefficients in soil and pure water, respectively) for variably compacted soils with different textures. We measured the Ds for KCl on five different soils from Japan: two volcanic ash soils (Andisols) at different bulk densities, two sandy soils, and a loamy soil. The Ds was measured across a wide range of θ using the half-cell method. The Ds/D0 values for Andisols with bimodal pore size distr..