宁南黄土高原土壤137Cs分布与相关影响因子研究

利用137Cs示踪方法,对宁南黄土高原阳洼流域纵断面土壤137Cs分布及相关影响因子进行了初步研究。结果表明:流域纵断面137Cs面积活度随坡面海拔和水平距离的变化,表现为一种不规则的波动振荡趋势。随海拔降低,纵断面上、中部137Cs面积活度逐步下降,有明显的土壤侵蚀发生;坡面下部137Cs面积活度最高,泥沙沉积的再分布现象明显。流域内林草地剖面土壤137Cs呈指数型分布,坡耕地、梯田137Cs在耕层内呈均一分布,其分布模式与各土地类型土壤有机质的分布状态完全一致。相关分析表明,两者在P<0.01水平达到极显著相关(r2=0.336,n=417)。土壤137Cs的损失和土壤有机质的移动具有相同的物理路径和运移机制;农耕坡地土壤137Cs面积活度随坡度增加有逐步降低的趋势;土地利用方式、坡度、耕作活动是影响纵断面土壤137Cs空间异质性的主要因素。137Cs示踪方法是研究土壤侵蚀空间分布的一种有效工具。

Study on Distribution of Cesium-137 and Relative Influencing Factors in Loess Plateau of South Ningxia

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.