Coupled Heat, Water, and Solute Transfer in a Wettable and Non-Wettable Soil.

The presence of temperature gradients in soil causes water to move.  Soil water can move in both the liquid and vapor phases.  Some dry soil surfaces become water repellent if the moisture content is less than a critical moisture content.  The existence of a water repellent layer of soil can suppress soil water evaporation.   The occurrence of temperature and soil water repellency can affect the coupled processes of heat and water transfer in unsaturated soil, particularly near the soil surface.  The effect of soil water repellency on soil water redistribution and thermal properties due to imposed temperature gradients has not been studied extensively.  The objective of this research is to compare soil water redistribution and thermal properties in wettable and non-wettable soils in response to temperature gradients. 

Two wettable soils (silt loam and sand) at two conditions (wettable and  non-wettable) were packed into four closed soil columns.  Temperature gradients were applied to the closed soil columns.  Transient soil water content and temperature distributions were measured with thermo-TDR probes installed at various depths within the soils.  The effect of soil wettability on water redistribution in closed soil columns will be reported.