陕西紫阳富硒土元素迁移特征及其质量评估

Element migration characteristics and quality assessment of selenium-rich soils in Ziyang,Shaanxi

本文以陕西省紫阳县北部为研究区,以富硒土壤为研究对象,按照岩石-母质-土壤结构,系统测定微量元素硒(Se)和有害元素砷(As)、汞(Hg)、铬(Cr)、镉(Cd)、铅(Pb)的含量,并对各元素迁移累积特征及土地质量进行评价。测定结果表明:(1)从岩石到土壤部分,主要有害元素含量呈升高趋势,其中,As为12.570 mg/kg、Hg为0.068 mg/kg、Cd为1.162 mg/kg、Pb为24.754 mg/kg,而Cr和Se的含量则有所下降,分别为89.510 mg/kg和1.445 mg/kg;(2)从岩石到母质部分,Cd、As、Se和Hg呈现明显富集,迁移积累系数分别为7.612、3.900、3.854和3.175;(3)从母质到土壤部分,Cd、Se、As呈现富集,迁移积累系数分别为4.070、2.644和2.502;(4)Cr的风化淋溶系数高达41.847,Pb的风化淋溶系数为7.983,说明两者在渗漏水作用下容易流失,富集程度不高;(5)6种元素土壤克里金插值空间分布特征与地层、构造等具有很好的一致性,构成高硒土壤的地质背景区;(6)工作区富硒土壤与寒武纪-奥陶纪-志留纪的黑色含碳岩系关系密切,是土壤中硒元素的主要来源。本文依据土壤富硒程度、有害元素污染程度以及有机质含量等因素将研究区的富硒土地划分为5个等级,为当地富硒特色农业区划提供技术参考。

In this paper,Se and the contents of As,Hg,Cr,Cd,Pb in the selenium-rich soils in the northern part of Ziyang County,Shaanxi Province are measured according to rock parent material soil structure,and the migration and accumulation characteristics of each element and the land risk are evaluated.The results show that the content of As,Hg,Cd and Pb in soil is increase(As 12.570 mg/kg,Hg 0.068 mg/kg,Cd 1.162 mg/kg,Pb 24.754 mg/kg),while the content of Cr and Se is decrease to 89.510 mg/kg and 1.445 mg/kg.Cd,As,Se and Hg are obviously enriched from rock to parent material,and the migration and accumulation coefficients are 7.612,3.900,3.854 and 3.175,respectively.Cd,Se and As from parent material to soil are also enriched,with migration and accumulation coefficients of 4.070,2.644 and 2.502,respectively.The weathering leaching coefficient of Cr and Pb is as high as 41.847 and 7.983,indicating that the two elements are easy to be lost and enriched under the action of water leakage.The Krigin interpolation spatial distribution characteristics of the six elements are consistent with the strata and structures.It is found that the heavy metal accumulation in the high selenium geological background area is largely controlled by regional geological factors.The selenium-rich soil in the working area is closely related to the black carbon-bearing rock series of Cambrian-Ordovician-Silurian,which is the main source of soil selenium.In this paper,five grades of land risk assessment zones are divided according to the selenium enrichment degree,harmful elements pollution degree,organic matter content and other factors,providing technical support for the development of local selenium-rich characteristic agriculture.