The temperature profiles of soil columns during infiltration

Abstract

Liquid front movement and temperature profile development during infiltration were determined for columns of aggregates of a non-swelling kraznozem and a swelling chernozemic soil at two initial moisture regimes. The temperature front can be divided into three zones: (a) A zone of vapour condensation and temperature rise; (b) a zone between (a) and (c) where temperature falls and heat is lost by conduction to the Liquid Wetting Front; (c) a zone starting at the liquid wetting front and with temperature decreasing to ambient. The mechanisms of vapour diffusion under a vapour pressure gradient, of liquid flow under a potential gradient, of heat conduction under a temperature gradient, and of transport of heat by convection by water and by vapour condensation occur simultaneously and qualitatively explain all the observed results, without recourse to other models. In one soil, there is also transfer of heat ahead of the condensation front as hot air. Heat balance procedures are used to show that the thermodynamic heat of wetting obtained from the adsorption isotherms is the dominant quantity in each experiment, if corrections are made for the radiant heat loss by the columns. The results are discussed in terms of infiltration into unstable soils. It is concluded that the multiple-transfer mechanisms first collectively discussed by Philip and de Vries can be applied directly to these systems.