细沟水蚀动态过程的稳定性稀土元素示踪研究

Study on dynamic tracing of rill erosion process with rare earth element tracer

本文利用稳定性稀土元素(RareEarthElement)REE示踪法探讨了坡面水蚀动态过程的试验方法,根据细沟侵蚀沿坡长的产沙特点,给出了元素的施放方法、施放深度和浓度的数学表述及计算方法,并进行了室内细沟侵蚀模拟实验。试验采用3个流量(2、4、8L min)5种坡度(5°、10°、15°、20°、25°),3次重复。试验采用8m土槽,分区段施用10种不同的稀土元素进行示踪,每个施放区长0 8m,宽0 1m,不同坡段根据侵蚀特点采用不同的施放深度。给出了根据收集到的侵蚀土壤样本中不同稀土元素的含量及总的土壤侵蚀量计算坡面不同部位的侵蚀产沙量的方法,由试验数据计算了不同水动力条件下的土壤侵蚀量沿细沟的分布,并分析了坡度和流量对坡面侵蚀量随坡长变化的影响。结果表明,REE示踪法可以示踪细沟土壤侵蚀的动态过程,且可保证一定的精度要求。由示踪方法得到的细沟土壤侵蚀量,在一定坡度和流量下,产沙量随着沟长的增加而增加,但增加的幅度越来越小,且渐趋于一个稳定值。侵蚀产沙量随着坡度和流量的增加而增加,但坡度较流量对产沙变化的影响更大。

The method for tracing of rill erosion process by means of rare earth element (REE) tracer was developed. In accordance with the sediment detachment along a rill, the application method, optimal application depth and suitable concentration of REE were investigated and the computational formula for application dosage of REE was given. Laboratory rill simulation experiments were conducted. The method for determining the sediment yield at different locations of slope according to the REE concentration of eroded soil and the total amount of erosion was established. The distributions of eroded amounts along the rills were calculated from the experimental data and the effects of slope length and flow rate on erosion amount were analyzed. It is found that the proposed REE tracing method can used to trace the whole formation process of erosion with enough accuracy. The experimental result shows the sediment concentration increases with rill length and tends to a stable amount. The sediment yield increases with the increase of slope gradient and flow rate. But the slope gradient has greater influence on sediment yield than flow rate.