Coupled Heat and Mass Transfer In Wettable and Non-Wettable Salinized Soils.

Coupled heat and mass transfer occurs in unsaturated conditions near the soil surface.  Thermal gradients cause water to move and water redistribution influences temperature and solute distributions.  Some dry soil surfaces can become water repellent if the soil moisture content becomes less than the critical soil moisture content.  Previous work has only considered the effects of solutes and wettability separately on coupled heat and mass transfer in soil.  The objective of this study is to determine coupled heat and mass transfers in salinized, wettable and salinized, non-wettable soils.

Two wetting conditions (natural wettable and chemically-treated non-wettable) were  used with a salinized silt loam soil to establish two soil treatments.  The soils were packed into closed soil columns and temperature gradients (30 ^oC mean temperature; 150 ^oC m^-1 gradient) were applied for 25 days.  Thermo-TDR probes installed at various depths within the soil columns were used to provide in-situ measurements of soil temperature, thermal properties, volumetric water content, and bulk electrical conductivity.  Temperature and soil thermal conductivity distributions were similar for the wettable and non-wettable salinized soils.  Net water transfers to the cold ends of the soil columns was small for both the wettable and non-wettable soils.  Coupled heat and mass transfer was similar in the wettable and non-wettable salinized soils.