浑善达克沙地东南缘坡地风蚀速率变化的137Cs与210Pb复合示踪研究

Tracing Wind Erosion Rates with 137Cs and 210Pb in a Typical Slope on the Southeast Margin of Hunshandake Sandy Land, Inner Mongolia

  • 摘要:
      目的  坡地是人为活动频繁而生态较脆弱的地区,土壤侵蚀是造成丘陵区坡地土地流失的主要方式,因此探究丘陵区坡地不同位置和不同时间尺度风蚀速率的变化具有重要意义。
      方法  以位于浑善达克沙地东南缘农牧交错带、生态环境脆弱、易受到土壤风蚀影响的内蒙古多伦县为研究区,选择一个植被类型为沙化草地的典型坡地,通过测量其坡顶、坡肩、背坡、坡麓等不同位置剖面的137Cs和210Pb比活度,探讨坡地不同位置的剖面137Cs、210Pb含量及分布特征,计算坡地不同位置的土壤侵蚀速率。
      结果  坡地137Cs分布较深,210Pb含量随深度增加呈负指数递减,137Cs、210Pb平均活度值较低,受长期风蚀的影响,样品中砂含量高。
      结论  除坡麓处于沉积状态外,坡地不同位置均受到轻度或微度风蚀作用的影响,风蚀速率相对大小为:坡肩 > 坡顶 > 背坡 > 坡麓。20世纪60年代以来土壤侵蚀速率显著降低,生态环境质量总体向好。

     

    Abstract:
      Objective  Slope land is the fragile ecology area because of frequent human activities. Soil erosion is the main reason for causing the loss of slope land in hilly areas. The paper’s aim was to study the variation of wind erosion rate in different positions and time scales of slope land in hilly area.
      Method  Duolun County, Inner Mongolia has been chosen as the research area, which is located in the farming-pastoral zone in the southeast margin of Hunshandake Sandy Land. The ecology environment is fragile and easy to be damaged by soil wind erosion here. A typical slope land with sandy grassland was selected. By measuring the activities of 137Cs and 210Pb in different position of the slope, such as summit, shoulder, backslope and footslope, the contents and distribution were discussed. The soil erosion rates of different positions on slope land were calculated.
      Result  Finally, we concluded that the distribution depth of 137Cs in slope land was deeper, and the content of 210Pb decreased negatively exponential with the increasing of depth. At the same time, the average activities of 137Cs and 210Pb were lower, but the sand content in samples was high because of wind erosion for long time.
      Conclusion  Except for the sedimentary state of the footslope, the different positions of the slope land were affected by mild or slight wind erosion. The wind erosion rates followed a descending order of shoulder, summit, backslope, footslope. Since 1960s, the soil erosion rate has decreased significantly, and the quality of ecological environment is better than before.

     

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