确定侵蚀细沟土壤临界抗剪应力的REE示踪方法

近年来兴起的REE示踪方法 ,可以研究土壤侵蚀的发生和发展的过程 ,及其沿坡面变化的规律。本研究采用Dy、La、Sm、Yb、Ce、Eu、Nd、Tb等 8个REE、3个雨强 (50mmh- 1,10 0mmh- 1和 150mmh- 1)和4个坡度 (8.74% ,17.63 % ,3 6.4%和 46.63 % )进行了一系列人工模拟降雨试验 ,展示了土壤侵蚀沿坡面变化与坡面细沟发展的关系 ,分析了土壤表面水流动力特征与土壤侵蚀之间的动态平衡。由土壤侵蚀沿坡面的变化 ,确定了土壤细沟侵蚀发生的临界距离 ,并由此得到侵蚀细沟土壤临界剪应力。对不同试验条件下最大细沟侵蚀率与径流剪应力和细流力之间的关系进行了回归分析

A METHOD FOR DETERMINING CRITICAL SHEAR STRESS OF SOIL IN ERODING RILL WITH REETRACERS

In recent years, the tracing method of rare earth element ( REE) has been used to study the dynamic processes of soil erosion, such as its i nitiation, development and distribution upon the hill slope. A series of laborat ory rainfall simulation experiments were conducted with eight REEs, namely Dy, L a, Sm, Yb, Ce, Eu, Nd and Tb. The experiments involved 3 rainfall intensities: 5 0 mm h -1 , 100 mm h -1 and 150 mm h -1 ; 4 slope gradients: 8.74%, 17.63%, 36.4% and 46.63%, with 3 replicates. The REE experiments revealed soil erosion distrib ution and its relation to the development of eroding rills. Analysis was made to relate the fluctuation in soil erosion upon the slope to the energy in the runo ff flow. With quantitative determination of soil erosion along slope by REE trac ers, the critical distance at which rill erosion initiated was determined, and t he critical shear stress of soil were estimated accordingly. Regression analyses of maximum rill detachment rate and shear stress and stream power of runoff wer e made.