Research Of Freeze-Thaw Soil Evaporation Under Airtight Laboratory Experiment

Evaporation is the most important water balance item in arid and semi-arid ecosystems.During the seasonal freeze-thaw period,there is less rain and more soil evaporation,exacerbating the shortage of water resources.The law and factors influencing soil evaporation during freezing and thawing period are relatively complex.Exploring the law and factors influencing soil evaporation under freezing and thawing is of practical significance for alleviating the shortage of water resources in arid and semi-arid areas.An airtight laboratory experiment with 48 h freezing and 33 h natural thawing under-22? and-15? constant freezing temperature scheme were conducted to study the laws of soil temperature and soil evaporation with five soil water contents and four soil textures including sandy soil,loamy sand,sandy loam and silt loam.The main results are as follows:(1)Soil water content affects the change of soil temperature.The higher the soil water content,the slower the soil freezing and thawing speed,and the smaller the soil temperature change.The soil texture affects the thermal conductivity of the soil,and the soil with a lot of sand is easy to freeze and thaw.Different constant freezing temperatures affect the temperature gradient between the soil and the external environment.The soil temperature under the-22?constant freezing temperature scheme is significantly lower than the-15? constant freezing temperature scheme.(2)During the freezing and thawing process,the soil moisture content has a significant effect on soil evaporation.The soil evaporation and evaporation rate in freezing stages increase with the increase of the soil moisture content,while the law is the opposite in thawing stage.(3)The effect of soil texture on soil evaporation during freezing and thawing.Under the-22? constant temperature freezing scheme,the cumulative evaporation of sand is 1.29 mm,which is 0.151 mm,0.402 mm,and 0.523 mm higher than loamy sand,sandy loam,and silty loam respectively.Under the-15? constant temperature freezing scheme,the cumulative evaporation of sand is 1.47 mm,which is 0.125 mm,0.239 mm and 0.360 mm higher than loamy sand,sandy loam and silt loam respectively.In different freezing and thawing stages,the evaporation rate of sand is the largest,and the silt loam has the smallest evaporation rate.(4)Effects of different constant temperature freezing scheme on soil evaporation.Under the-22 ? constant temperature freezing scheme,the cumulative evaporation of sand,loamy sand,sandy loam and silty loam were 1.29 mm,1.14 mm,0.89 mm and 0.77 mm,which were reduced 12.24%,15.32%,27.86% and 30.90% compared with the-15? constant temperature freezing scheme.During different freezing and thawing stages,the soil evaporation rate under the-22? constant temperature freezing scheme is less than the-15? constant temperature freezing scheme.