侵蚀泥沙颗粒中^(137)Cs的含量特征及其示踪意义

Character of ^(137)Cs concentration in erosive sediment and its tracing meaning

通过对黄土丘陵区典型小流域—燕沟的林地、坡耕地与沟口洪水泥沙的颗粒组成分析 ,发现其颗粒组成有明显的差异 ,表明该研究区在侵蚀过程中发生了一定程度的颗粒分选 ,而在泥沙输移过程中颗粒分选不明显 ,在应用1 37Cs示踪流域侵蚀速率或利用沟口泥沙推算流域侵蚀模数时应适当进行颗粒校正。通过对坝地沉积泥沙1 37Cs含量进行分析 ,结果表明 ,1 37Cs含量、沉积厚度与次降雨侵蚀强度、侵蚀类型之间存在密切关系 ,同时运用沉积样中核素含量特征可望解决流域尺度坡面侵蚀与沟谷侵蚀的比重关系这一研究难题。

The relationship between the concentration of 137 Cs and the grain size of soil was analyzed. 137 Cs concentrations in clay layer and sand layer in a dam land were also compared. The results show the higher concentration of 137 Cs, the smaller the soil grain. The mechanical composition of the sediment at the outlet of the watershed has significant difference compared with that of soil in woodland and cropping slope fields, which indicates that there is soil particle selectivity occurred in the course of erosion, but not in the process of sediment transmitting. All these mean that the results need to be revised if 137 Cs in sediment of the outlet is used to estimate erosion modulus of the watershed. 137 Cs concentration in sediment in dam land was analyzed and the result shows that there is a close relationship among 137 Cs concentration, sediment thickness and erosion intensity of per rainfall, erosion types. Applying the characteristic of radionuclide in sediment samples, it is possible to solve the proportion relationship between slope erosion and gully erosion at watershed scale.