陕西长武黄土剖面S_1—L_4土层入渗率与成因

PERMEABILITY AND ORIGIN OF S_1-L_4 SOIL LAYERS IN CHANGWU LOESS SECTION IN SHAANXI

根据渗水实验、空隙度,粒度和磁化率等测定,研究了长武黄土剖面S1-L4土层的渗透性及其成因。结果表明,长武黄土与红褐色古土壤前20min入渗速率大,变化大,为剧变入渗速率阶段,20min之后入渗速率变化较小,为弱变入渗速率阶段。黄土层入渗率较大,所研究的3层黄土平均入渗系数为2.02mm/min,红褐色古土壤层入渗率较低,所研究的3层古土壤平均入渗系数为0.71mm/min。黄土层空隙度较高,含水空间发育较好,利于构成含水层。红色古土壤层空隙度较低,含水空间发育较弱,利于构成隔水层。由于红褐色古土壤也有一定的渗透性,其隔水性较弱,这是黄土地下水具有多层性的原因。磁化率与粒度成分分析表明,黄土层与红褐色古土壤层渗透性、含水空间与隔水性的差异主要是冰期与间冰期的气候变化决定的成壤作用强弱造成的。研究表明第四纪气候变化对黄土地层土壤水和地下水资源富集条件、富集规律具有重要控制作用,在黄土水资源开发利用中有重要应用价值。

Using the methods such as infiltrating water experiment, total porosity, measurement of susceptibility and magnetic susceptibility, we did some research on the permeability of S1-L4 layers in the Changwu loess section and on its mechanism of formation. The research result shows that the infiltration rate of the loess and red-brown paleosol layers changed greatly. During the first 20 minutes, the change was extreme and we called it an enormous change stage. In about twenty minutes the infiltration rate changed less than before and we called it a gradual change stage. The infiltration rate of the loess is larger than the red-brown paleosol layers. For example, the steady infiltration rate of loess layers is 2. 01 mm/min and that of red- brown paleosol layers is 0.71 mm/min. Porosity and moisture space of the loess layers are also larger than those of red-brown paleosol layers,so the loess layers can form water-bearing layers more easily than the red-brown paleosol ones and the latter can form water-resistant layers more easily than the former. The red-brown paleosol layers have definite permeability and the nature of water-resistance is stronger than that of the loess layers. It is the reason why the groundwater of loess has many layers. The susceptibility of loess layers is lower while that of the red-brown paleosol layers is higher, which shows that the difference between the red-brown paleosol layers and loess layers in permeability was mostly determined by climate changes during ice age and interglacial stage. The result showed that conditions and laws of enrichment of the loess groundwater were controlled by climate changes during Quaternary. This has an important appli- cation value to development and utilization of loess water resources.