An experimental study on behaviors of water and chemicals in a non-uniform soil layer and its mechanism under evaporation

In arid and semi-arid areas，evaporation和salinization becomes quite important phenomena which must be to clarified. In thisstudy,Akadama-soil layers with a dual pore structure (macro-pores and micro-pores) were focused on anon - uniform soil,与评估实验使用layers moistened by distilled water and enriched NaCl solution在25℃和20%的temperature和humidity controlled room . To examine effects ofa solar radiation, water-table and turbulent surface wind to evaporation, in some cases，such conditions were applied to the layer. Through the evaporation experiments1.Micro-pores play a role of transmission route of underlying soil-waterto an evaporation zone2.Turbulence of applied surface wind to the exposed surfacepenetrates easily into soil through macro-poresand it affects vapor transfer in the soil layer significantly. Therefore，in the vapor transfer in the soil layer，不只是molecular diffusion，但也有turbulent one caused by the surface wind must be takenaccount3.The heating on the upper surface leads a characteristic vapor density profile in the soilwith a peak at the evaporation zone is located. Water vapor created by evaporation istransported in the upper and lower directions. the downward moving vapor condenses in a deeptherefore soil-water is carried to a deep zone via evaporation，vapor transfer and condensation process.4.Enrichment of soil-water appears in an upper zone of thesoil layer,where the concentrations of Na+ and Cl start to increase abruptly with decreasing depth. Thislocation is more or less consistent with the upper end of drying front. the concentrations belowdepth, as a result，become lower than initial ones this may be due to absorption and ion exchange on the soil-particles。

In arid and semi-arid areas, evaporation and salinization becomes quite important phenomena which must be to clarified. In this study, Akadama-soil layers with a dual pore structure (macro-pores and micro-pores) were focused on as a non-uniform soil, and evaporation experiments using the layers moistened by distilled water and enriched NaCl solution were undertaken in a temperature and humidity controlled room at 25℃ and 20%. To examine effects of a solar radiation, water-table and turbulent surface wind to evaporation, in some cases, such conditions were applied to the layer. Through the evaporation experiments, the following are clarified.1.Micro-pores play a role of transmission route of underlying soil-water to an evaporation zone, and it causes evaporation rate higher.2.Turbulence of applied surface wind to the exposed surface penetrates easily into soil through macro-pores, and it affects vapor transfer in the soil layer significantly. Therefore, in the vapor transfer in the soil layer, not only molecular diffusion but also turbulent one caused by the surface wind must be taken account3.The heating on the upper surface leads a characteristic vapor density profile in the soil with a peak at which the evaporation zone is located. Water vapor created by evaporation is transported in the upper and lower directions. The downward moving vapor condenses in a deep location, therefore soil-water is carried to a deep zone via evaporation, vapor transfer and condensation process.4.Enrichment of soil-water appears in an upper zone of the soil layer, where the concentrations of Na+ and Cl start to increase abruptly with decreasing depth. This location is more or less consistent with the upper end of drying front. The concentrations below that depth, as a result, become lower than initial ones・this may be due to absorption and ion exchange on the soil-particles.