A multiple-porosity finite-element model of reactive contaminants in soils

Abstract

This chapter proposes a finite-element algorithm for a multiple-porosity model of contaminant transport. The model combines three contaminant porosities—the primary porosity of the intact soil, the secondary porosity of the mobile water in the fissures, and the tertiary porosity of immobile solutions in the fissures. Sorption on the fissure walls can be instantaneous or time-dependent. Hence, the same formulation can be used to solve four types of mass-transfer problems and their combinations—intact soils, intact soils containing immobile solutions, intact soils with nonequilibrium sorption, and contaminant migration in soils with regularly spaced fractures. When the soil is fractured, the model's secondary porosity represents transport in the fractures. However, when the soil is intact, the primary porosity disappears and the model's secondary porosity represents transport processes in the soil.