蓄水和蒸发条件下土壤过渡层中水盐运移规律研究

在国内外有关土壤水盐运移规律研究成果的基础上,应用陕西省卤泊滩综合治理和谐生态模式,分析了在蓄水和蒸发条件下,土壤饱和层与非饱和层之间的过渡层中盐分变化规律以及对土壤饱和层和非饱和层盐分的影响。针对3组不同初始条件,分别开展了室内试验和数值模拟。结果表明,在地下水位基本稳定情况下,土壤非饱和层与饱和层之间存在一个10～20cm的过渡层。在蒸发条件下,由于土壤毛管的水分蒸发作用的最低范围在过渡层内,所以过渡层有隔离下层盐分作用。如果土壤非饱和层含盐量高,蒸发可能呈返盐;如果土壤非饱和层含盐量不高,但过渡层含盐量高,蒸发也可能呈返盐;过渡层如果含盐量低,蒸发返盐的可能性很小;但过渡层以下的饱和层盐分,不管含盐量高低,均处于相对稳定状态。过渡层对下层高含盐的隔离作用显著。

Experiment and numerical simulation on salt movement in the transition layer of soil under ponding and evaporating conditions

The change law of salt in transition layer and its effects on salt in unsaturated zone and saturated zone under ponding and evaporating conditions in Lubotan, Shaanxi province were studied. Both laboratory experiment and numerical simulation have been done for three kinds of initial condition. The results show that there exists a transition layer with thickness 10～20cm. This layer is the lowest limit of evaporation capillary, it can isolate the salt movement. If unsaturated zone has high salt content, the soil will be resalinized under evaporation. If unsaturated zone has low salt content and transition layer has high salt content, the soil will also be resalinized under evaporation; when transition layer has low salt content, the possibility of soil resalinization is small. But the salt of saturated zone is relatively stable whenever the salt content in high or low. Therefore, the transition layer has a remarkable isolation effect of salt movement.