Heat, water, and solute transfer in unsaturated porous media .2. Compacted soil beneath plastic cover

Soil surface dynamics involve coupled transfer of heat, water, and solute. An experimental and theoretical study of heat, water, and solute transfer in closed compacted soil columns under surface temperature wave amplitudes is presented. The temperature wave amplitudes ranged from 17.9 to 21.0 degrees C. Potassium chloride solution was used to moisten Clarinda clay and Fayette silty clay loam soils. Initial water contents of 0.403 and 0.279 and initial solute concentrations of 0.062 and 0.052 mol kg(-1) were used in Clarinda and Fayette soils, respectively. The moistened soils were packed and compacted in PVC columns (0.075 m diameter and 0.30 m high). Bulk densities of the compacted Clarinda and Fayette soils were 1403 and 1585 kg m(-3), respectively. The columns were buried in soil such that column surfaces were exposed to natural as well as artificial radiation and thermal conditions. The coupled nonsteady-state balance equations of mass and energy were solved numerically to predict soil temperature, water content, and solute concentration distributions. The theoretical model described soil temperature, water content, and solute concentration well as compared with the measured values. The Fickian diffusive solute flux was one or two orders of magnitude greater than salt-sieving and thermal-diffusion solute fluxes.