Effects of salts on water evaporation and soil fracture development
Revealing the drying and cracking mechanism of saline alkali soil can provide a theoretical basis for the formulation of precise irrigation systems based on crack networks in arid and semi-arid saline alkali areas.This study set up 5 types of soil salt content (0,0.3%,0.6%,1%,2%,respectively recorded as CK,T3,T6,T10,T20) treatments to conduct constant temperature soil evaporation experiments,explore the impact of salt content on soil evaporation process,and quantitatively analyze the geometric characteristics of soil shrinkage crack network during evaporation process using digital image processing technology.The results showed that:(1) The evaporation processes of different treatments had similarities,that is,the evaporation process included a linear stage and a nonlin-ear stage,but the proportion of each evaporation stage to the total evaporation stage was different.T20 entered the de-celeration rate stage at the earliest,indicating that salt causes a decrease in soil permeability.(2) The cumulative evap-oration decreased with the increase of soil salt content,namely CK>T3>T6>T10>T20,indicating that salt can inhibit soil evaporation.(3) As the soil salt content increased,the water content of the cracking decreased,and the crack area and crack length gradually decreased and then stabilization.The interaction between water evaporation and surface cracking was manifested by the chemical effects of free Na+on soil particles during water loss and the physical effects of precipita-ted Na2SO4 crystals on soil pores.(4) Correlation analysis showed that cumulative evaporation and soil moisture was sig-nificantly positively and negatively correlated with surface crack,respectively.The correlations between cumulative evap-oration and crack parameters were overall higher than that between soil water content and crack parameters.
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