The distribution of Cesium-137 in the different slope vertical section and the relative influencing factors of soil erosion were studied by using 137Cs tracer technology in Yangwa watershed of loess plateau of south Ningxia.The result showed that the change trend of 137Cs area activity were an irregularly waved oscillations

when the 137Cs area activity in the different slope vertical section were changed with the elevation increasing and the slope level distance extending.There were the highest 137Cs area activity on the bottom of sloping land

137Cs area activity in the up and middle of sloping land were gradually decreased with elevation decline

and there were an obviously sediment deposition on the bottom of sloping land.137Cs were uniformly distributed within the plough layer for cultivated fields and terrace

but there were an exponential tendency in the vertical distribution of 137Cs activity from an undistributed site.All change trend of 137Cs activity were harmonious with the distribution of soil organic matter in the soil depth under the different land use pattern.There were a significant correlations between the 137Cs and organic matter content under the P<0.01 level(r2=0.336

n=417).So

we concluded that there were a same physical pathway and move mechanism of 137Cs and soil organic matter.The 137Cs area activity was also gradually decreased with the farming sloping gradient increasing.The spatial heterogeneity of 137Cs area activity in the different vertical section of sloping land were effected by land use pattern

slope gradient

farming activity

which induced soil and sediments movement in the sloping land.The 137Cs tracer technology was an effective method to study the soil deposition and movement in spatial scale.