黄土坡面细沟侵蚀过程的REE示踪

利用REE示踪技术探讨了坡面细沟侵蚀的发育过程。试验结果表明：在细沟发育过程中，各坡段细沟侵蚀量呈动态变化趋势；细沟发育过程可以分为起始、发展、稳定3个阶段，在不同阶段，侵蚀方式、发育特征迥异。总的看来，在坡顶部、上部、中部、下部4个坡段上，细沟发育过程中，坡面下部的侵蚀量较大。但随着放水流量的增加，坡面上部侵蚀量的比重增加。由于溯源侵蚀，最下部坡段的相对侵蚀量从92％减少到37％，呈显著下降趋势，其它3个坡段则分别从4．7％、0．25％、2．14％增加到29％、17％和23％。试验结果还表明，REE示踪法不仅可定量测定不同坡位的侵蚀量，还可以揭示冲刷过程中各坡位相对侵蚀量的变化趋势。

The REE Tracer Method for the Study of Rill Erosion Process on Loess Sloping Surface

By the rare earth elements (REE) tracer method, four REE (Ce, Sm, Nd, Dy) were used to study the changeable process of rill erosion on loess sloping surface in runoff scouring experiments. During different stages, the erosion pattern and characteristics are different. Generally, hi the process of the rill development, the soil erosion amount hi the bottom section was larger, and it decreased with the increase of the flow discharge, but the situation is on the contrary to the top section, which indicated that the influence of flow discharge outweighed the gradient on the rill erosion; the rill relative erosion amount hi the bottom section obviously decreased from 92% to 37%, but the other three sections gradually increased from 4.7%, 0.25%, 2.14% to 29 %, 17% and 23% respectively because of the headcut erosion. Results from the experiments have also shown that the REE tracer method can be used not only quantitatively to determine rill erosion amounts in different slope sections, but also to reveal the changeable trend of rill relative erosion amounts. It provides a reliable and effective method for the research on rill erosion process.