Assessment of Thermo‐Induced Solute Transport in Saturated Layered Soil With Effective Porosity

ABSTRACT A numerical investigation is performed on one‐dimensional coupled heat transfer and solute transport in saturated, incompressible layered soils, incorporating the effects of three soil phases: solid particles, mobile pore fluid, and immobile pore fluid. The finite difference method is employed to solve the coupled governing equations for heat transfer and solute transport. The thermal module of the model assumes local thermal equilibrium between solid and fluid phases, and incorporates heat transfer through conduction, advection, and mechanical dispersion. The solute transport module accounts for diffusion, advection, mechanical dispersion, and sorption processes. The proposed model is first developed and subsequently subjected to verification. Numerical simulations demonstrate that heat transfer considerably influences solute transport, affecting key metrics including breakthrough time, mass flux, cumulative mass outflow, and concentration distribution within the soil stratum. These effects persist not only during active heat transfer but also long after its cessation. Furthermore, effective porosity significantly impacts both heat and solute transport processes, and the Soret coefficient also notably affects solute transport through thermodiffusion. Conventional solute transport analyses that neglect the coupled effects of heat transfer and effective porosity may yield substantially divergent results.