土壤剖面中~(210)Pb_(ex)的分布特征及其在土壤侵蚀示踪中的应用

210Pb由于在环境中特殊的分配关系及其在土壤中迁移性小、极易被土壤细颗粒吸附等特性而被视为良好的示踪剂,210Pb的沉降具有连续性和相对稳定性,可示踪百年尺度的平均土壤侵蚀速率。具有初始分布及其在未扰动土壤剖面中均呈现出土表含量最高,随深度增加含量减少的分布特征。在耕作土壤中由于耕作混合作用210Pbex呈均匀分布。评述了目前用到的210Pbex侵蚀模型重量逼近模型和质量平衡模型,210Pbex与其它核素(137Cs、7Be)复合示踪研究土壤侵蚀和泥沙来源是核素示踪的一大亮点。提出了210Pbex示踪土壤的优点和应用210Pbex示踪应注意的问题。

The Distribution of 210Pbex in Soils and Its Application in Estimating Soil Erosion

~(210) Pb is often regarded as a good tracer because of its special distribution in the environment and its characteristics in soils. The deposition of fallout 210Pb is continued and relatively constant with time, thus it has the potential for estimating long-term rates of soil redistribution.The concentration of 210Pbex is greatest in the surface and decreases with increasing depth in topsoils, where 210Pbex is initially distributed and in undisturbed soils.While in cultivated soils, 210Pbex is distributed uniformly,the models of 210Pbex applied currently are evaluated respectively.The promising trend in the application of 210Pbex and other nuclides (such as 137Cs and 7 Be) in studying soil erosion is discussed. The advantages and problems of using 210Pbex are also mentioned in the paper.