黔北坡面林地土壤侵蚀与微量元素迁移研究

Study on the Relationships Between Soil Erosion and Trace Elements Migration on Sloping Land in Zunyi Region,Guizhou Province

选择黔北遵义地区岩溶坡面林地作为研究对象,研究岩溶坡面林地土壤侵蚀空间分布特征,深入揭示碳酸盐岩岩溶地区在地表水力侵蚀作用下土壤表层(0-30cm)微量元素再分配及迁移机理,利用137 Cs示踪技术研究区域内各个采样点的土壤物理侵蚀强度,并结合地球化学方法,以Ti作为不活化参比元素,获得坡面林地土壤微量元素在地表侵蚀作用下迁移和富集特点。结果表明:坡顶、坡中和坡脚土壤剖面137Cs面积活度分别为100.52,846.74,1 626.23Bq/m2,坡顶、坡中小于本底值,坡脚大于本底值;坡顶和坡中侵蚀速率分别为4 854,1 922t/(km2·a),坡脚沉积速率为3 160t/(km2·a);Li、Cs、Cu、Cd等元素迁移系数均值顺坡降低;Co、Pb、U、Ta和Nb顺坡升高;Ti、Th、Cr、W顺坡变化不明显。137 Cs面积活度从坡顶到坡脚呈上升趋势,坡顶和坡中土壤侵蚀强度分别属于中度侵蚀和轻度侵蚀,坡脚属于沉积点。Li、Be、Rb、Cs、Ba、V、Cu、Cd易在坡顶富集,以化学迁移为主;Co、Pb、Sb、U、Zr、Hf、Ta、Nb易在山底富集,Co、Pb、Sb、U存在一定的化学迁移,但以物理迁移为主,Zr、Hf、Ta、Nb为物理迁移;Ti、Th、W没有明显的富集现象,未发生迁移。

To study the characteristics of spatial distribution of soil erosion karstic slope in Guizhou province analyzed the influence of organic matter and clay mineral on trace element＇s erosional migration,to deeply analyse the mechanism of trace element distribution and migration（0-30cm）under the effect of surface water erosion in the karstic region.The karstic slope forest land in Zunyi,north of Guizhou was the research object.The ^137Cs tracer technique was applied to study the soil erosion and evaluate the soil erosion intensity of each sample site.Combined with the geochemical methods and titannium（Ti）as the inactive reference element,got the trace element＇s migration and enrichment characteristics of the slope soil from horizontal and vertical directions under the effect of erosion.The results showed that：The activities per unit area of ^137Cs were 100.52Bq/m^2,846.74Bq/m^2 and 1 626.23Bq/m^2 on top of slope,in middle of slope and downhill of slope,respectively.The values of the top and middle slopes were less than the background values and that of the downhill was greater than the background value.The average erosion rates of the top and middle slopes were 4 854t/（km^2·a）and 1 922t/（km^2·a）respectively,the average deposit rate of the downhill was3 160t/（km^2·a）.The migration coefficients of Li,Cs,Cu,Cd decreased with the slope downward,Co,Pb,U,Ta,Nb increased along with the slope downward and other elements,such as Ti,Th,Cr,W were not changed significantly.The activity per unit area of ^137Cs increased with the slope downward,the soil erosion intensities of slope top and slope middle were moderate erosion and mild erosion,respectively,and downhill of the slope was sedimentary points.Li,Be,Rb,Cs,Ba,V,Cu,Cd were prone to enrichmentmainly by chemical migration on the slope top.Co,Pb,Sb,U,Zr,Hf,Ta,Nb were prone to enrichment in the slope downhill and there was a certain chemical migration and physical migration with Co,Pb,Sb,U,but the physical migration was the dominant way.The physical migration was dominant way for Zr,Hf,Ta,Nb.There was not significant enrichment and migration of Ti,Th,W.