基于^137Cs技术的西汉水流域坡耕地侵蚀示踪研究

Soil erosion of cultivated lands in the Xihanshui River Basin

为了说明西汉水流域坡耕地侵蚀特征,为流域泥沙管理提供依据,采用^137Cs土壤侵蚀核素示踪技术,按野外采样、核素检测、模型计算3步开展研究。结果表明：6块坡耕地剖面的^137Cs比活度在某一深度范围内呈较均匀分布,在坡面中上部,^137Cs均匀分布的范围与耕层深度接近;6块坡耕地的平均侵蚀模数为2 643-6 419 t/（km^2·a）,其中1块为强度侵蚀、5块为中度侵蚀;沿坡面自上而下,侵蚀强度从大到小递减;影响坡耕地侵蚀的主要因素是坡度和耕作强度,通常坡度越大,侵蚀模数越大,而耕作强度越小甚至退耕还林,侵蚀模数越小。

Cesium-137 measurements in the Xihanshui River Basin were used to quantify soil erosion on cultivated lands to give data for sediment management in the basin.The cesium-137 measurements used field sampling,nuclide content determination,and erosion rate calculations.Measurements on the 6 cultivated lands showed a homogenised Cesium-137 distribution within a depth approximately equal to the depth of the plough layer on the top and middle slopes.The average soil erosion rates ranged between 2 643 to 6 419 t/（km^2·a） which indicates moderate and intense erosion.On one slope,the soil erosion rate decreased from the top to bottom.The slope gradient and farming method affect the soil erosion rate and the rate of soil erosion is in general proportional to the slope and inversely proportional to the farming intensity.