REE示踪研究坡面侵蚀时空演变过程

Using Rare Earth Element as Tracers for Studying Spatial and Temporal Process of Soil Erosion in Sloping Land

在室内人工模拟降雨条件下,通过沿坡面垂直分段和分层结合布设不同的稀土元素,研究坡面侵蚀的时空演变规律。结果表明:次降雨条件下在产流开始20min内,坡面片蚀和细沟侵蚀的平均侵蚀加速度、平均侵蚀率和累积侵蚀量之比分别为1∶1,1∶1.5和1∶1.3,坡面下1/3区域的平均侵蚀加速度、平均侵蚀率和累积侵蚀量分别是坡面中部的5,12,13倍;后期细沟平均侵蚀加速度、平均侵蚀率和累积侵蚀量分别为片蚀的43,7,5倍。连续小雨强降雨条件下,产流35min内,细沟侵蚀平均加速度是片蚀的7～10倍,35min后,坡面处于稳定状态;降雨产流10min内,坡面下1/3区域平均侵蚀加速度是坡面中部的5倍,沟头激活后,坡面中部的平均侵蚀加速度达到坡面下1/3区域的4倍;坡顶部存在一个相对稳定区。说明REE示踪技术能够同时量化随时间和空间变化的坡面侵蚀过程。

By placing different rare earth elements into different soil depth and different section across a slope in an indoor plot, simulated consecutive rainfall was applied to study the temporal and spatial process of erosion. Under first artificial rainfall simulation, the results indicate that the ratios of sheet to rill average erosion acceleration, sheet to rill average erosion velocity and cumulated erosion was 1∶1, 1∶1.5 and 1∶1.3 respectively within earlier 20 min runoff. Viewing the erosion process of different section on sloping land, the average erosion acceleration, average erosion velocity and cumulated erosion of slope bottom occupied about 1/3 slope area are 5, 12 and 13 times of that of middle slope respectively. However, within the following runoff, average acceleration, average velocity and cumulated erosion of rill erosion are 43, 7 and 5 times of that of sheet erosion respectively. Under gentle intensity consecutive rainfall, from beginning to 35 min of runoff, rill average erosion acceleration is 7～10 times of that of sheet erosion. Then in the following period, the slope becomes stable. On the section aspect, within 10 minutes of earlier runoff under gentle intensity consecutive rainfall, the average erosion acceleration of this area is 5 times of that of middle section. Then the average erosion acceleration of middle section is 4 times of that of bottom section contrarily along with rill head activated again. Above all, the results prove that REE tracer technology could be used to quantify the slope erosion change with time and space.