阳洼流域土壤137Cs的空间分布及侵蚀研究

利用137Cs示踪技术,研究了宁南黄土高原阳洼流域土壤137Cs的空间分布和侵蚀特征.研究结果表明,流域137Cs背景值为1 966.99 Bq/m2,流域内不同土地利用方式下土壤137Cs比活度不同,且有比较明显的137Cs比活度分异.流域内林草地土壤剖面137Cs呈现指数分布模式,坡耕地剖面的137Cs则呈均匀分布模式.不同土地利用方式下土壤137Cs的面积活度表现为沟台＞林草地＞农耕坡地,其中农耕坡地、沟台地土壤侵蚀、沉积表现出较大的变异,变异系数达65%以上.阳洼流域土壤侵蚀模数与137Cs比活度呈现出相反的分布趋势,但都明显具有斑块状和条带状分布的特点.流域土壤以中、强度侵蚀为主,中、强度侵蚀面积占流域总面积的46%,在流域土壤侵蚀防治中坡耕地仍是治理的关键.

Spatial Distribution of Cesium-137 and Characteristics of Soil Erosion in Yangwa Watershed

Spatial distribution of Cesium-137 and characteristics of soil erosion were studied using 137Cs trace technology in the Yangwa watershed on the Loess Plateau of the southern Ningxia Hui Automous Region.The 137Cs inventory was 1 966.99 Bq/m² in the watershed.Special activities of 137Cs were different in plough layers under different land uses.It could be expressed by an exponential function for the soil profile of forest and grassland and by a uniform distribution for the soil profile of sloping land.In terms of area activities of 137Cs,tableland,forest and grassland,and sloping land were ranked in descending order.Sedimentation and soil erosion on cultivated sloping land and tableland had a great variance,with the variation coefficient being over 65%.The change trends of soil erosion module and distribution of 137Cs were adverse,but both of them were distributed as a strip or patch under different land uses.The moderate and serious erosion types were the main types of soil erosion and their area accounts for 46% of the total area of Yangwa watershed.Therefore,controlling soil erosion on sloping land is the key to the watershed management.