摘要
以土壤水和溶质运移的动力学原理为基础 ,采用数值模拟方法 ,研究了在浅层地下水和蒸发条件下含有粘土层土壤的水和Cl-的运移状况 ,重点探讨了两种粘土的层位和层厚对水和Cl-运移影响的差别及原因。研究结果表明 ,粘土层对土壤的水和溶质运移影响的程度 ,与层状土壤中该粘土及其组合土壤的水力学性质有关。本文模拟的重粘土 (简称Y粘土 )与轻壤土所组成的层状土壤 ,其基本情况为 ,随粘土层层位的升高和层厚加大 ,土壤水分蒸发和地下水补给速率降低 ,Cl-积累减少。而轻粘土 (简称R粘土 )与轻壤土所组成的层状土壤 ,由于它们的导水率曲线在压力水头h约 - 10 0 0cm处相交 ,当h低于此值时 ,R粘土的导水率就大于轻壤土的。因此 ,蒸发、补给速率和Cl-积累强度出现以顶位最高 ,甚至高于均质轻壤土 ,其次为底位 ,最低为中部层位的现象。在蒸发条件下Cl-在剖面中的积聚部位主要是土表。粘土层的存在 ,起到了阻滞作用 ,而阻滞程度则与该粘土水力学性质、层位。
On the basis of dynamics principle for soil water and solutes transport, the numerical modeling is used for analyzing the regularity of the transport of water and Cl - in the soil with clay layer under evaporation in this paper. The layered soils used for simulation are composed of loam and two kinds of clay layer respectively. The depth of groundwater is 1.5 m. The differences and causes in the effects of the position and thickness of the clay layer on the transport of soil water and solute between two kinds of clay layer are focused. The results show that the degree of the effects depends on the soil hydraulic properties of the clay and loam in the layered soil. In case 1 where the layered soil is composed of loam and heavy clay Y, the basic condition is, the higher the position of the clay layer and the thicker the clay layer are, the lower the evaporation, up inflow rate and the accumulation of Cl - in soil are. In case 2, where the layered soil is composed of the same loam as above and light clay R, the highest evaporation and up inflow rate and accumulation of Cl - appear in the layered soil with clay layer at the top position. The next higher level appears in the case where the clay layer locates in the bottom of the soil and the lowest appears in the soil with clay layer in the middle position. The causes of above differences are resulted from the different hydraulic properties of the two clays. The hydraulic conductivity curves ( K versus h ) of clay R and loam cross at about -1 000 cm of h . Therefore, when the surface soil is drying and h drops to less than -1 000 cm, the K of clay R will be higher than that of loam. But the h value of the intersecting point for clay Y and loam is rather lower than above value. The accumulation position of Cl - in soil profile under evaporation is mainly at the soil surface, clay layer in soil profile only plays the role of retardation in the transport of solutes to the surface and of temporal accumulation place.
出处
《土壤学报》
CAS
CSCD
北大核心
2004年第4期493-502,共10页
Acta Pedologica Sinica
基金
国家重点基础研究发展规划项目(G1999011709资助
