季节性冻融期不同潜水位埋深下土壤蒸发规律模拟研究

为了揭示季节性冻融期不同潜水位埋深和土壤质地对土壤蒸发的影响,通过连续2个冻融期的蒸渗计土壤剖面含水率和土壤温度的监测,利用水热耦合运移模型模拟研究了4种不同潜水位埋深(0.5、1.0、1.5、2.0 m)下砂壤土和壤砂土的土壤蒸发规律。结果表明:不稳定冻结阶段和消融解冻阶段地表土壤均出现昼融夜冻的特征,土壤液态水分较多,砂壤土和壤砂土蒸发量分别占整个冻融期的91.7%和81.8%以上。稳定冻结阶段的土壤蒸发量随着潜水位埋深的增加而增大,但小于0.31 mm。潜水位埋深为0.5 m时冻融期土壤蒸发量最大,砂壤土和壤砂土分别为47.28 mm和25.60 mm,随着潜水位埋深的增加,冻融期土壤蒸发量呈指数型减少,土壤颗粒直径相对较大的壤砂土土壤蒸发量随潜水位埋深的增加而衰减的幅度较为明显。该研究可为地下水浅埋区土壤盐渍化的防治和地下水资源量的科学评价提供依据。

Simulation of Soil Moisture Evaporation under Different Groundwater Level Depths during Seasonal Freeze-thaw Period

At present, many studies are carried out on influencing factors of soil moisture evaporation (SME), mechanism and controlling technology of SME at non-freezing period. However, the researches about SME during freeze-thaw period are few because the monitoring on SME is difficult. In order to reveal the influence of groundwater level depth and soil texture on SME during seasonal freeze-thaw period, based on two successive freeze-thaw period monitoring of soil water content and temperature of the lysimeter, SME of sandy loam and loamy sand under four kinds of groundwater level depths (0.5m, 1.0m, 1.5m, 2.0m) was simulated by using SHAW model. The results show that the soil is thawing in day and freezing at night, and then liquid water is more during unsteady freezing stage and thawing stage. SME of sandy loam and loamy sand are more than 91.7% and 81.8% respectively during freezing and thawing periods. SME was increasing with the increase of groundwater level depth while it was lower than 0.31mm during steady freezing stage. SME was 47.28mm for sandy loam and 25.60mm for loamy sand when the groundwater level depth was 0.5m. SME decreases exponentially with the increasing groundwater level depth during freeze-thaw period, and the decreasing amplitude of SME for loamy sand is more obvious for its larger soil particle diameter.