西昌普诗碎屑岩地区紫色土剖面重金属迁移富集特征与生态风险评价

Migration and enrichment characteristics of heavy metals in purple soil of a profile in the Pushi clastic rock area, Xichang region, Sichuan, China and their ecological risk assessment

为探究西昌普诗碎屑岩地区紫色土中8种重(类)金属元素(Cu、Cd、Ni、Pb、Zn、Hg、As、Cr)的迁移富集特征及潜在生态风险,选取白垩系小坝组4个典型岩石-土壤剖面进行了系统的采样、测试和分析。结果表明,研究区土壤呈酸性—弱酸性,重金属元素Cd、Pb、Zn在剖面表层富集,与外源重金属元素叠加有关。此外,重金属元素的迁移富集特征还受到剖面风化程度、淋溶淀积作用、黏土矿物吸附作用及大气降尘等多种因素共同影响。单因子指数评价和内梅罗综合指数评价表明,研究区4个剖面均不存在土壤重金属元素污染问题。潜在生态风险评价表明研究区土壤整体处于低潜在生态污染水平,Hg和Cd元素存在中度潜在生态风险等级。建议相关部门加强土壤重金属元素的检测和监控力度,科学降低土壤重金属潜在生态风险。

In order to explore the migration and enrichment characteristics and potential ecological risks of eight heavy(quasi) metal elements( Cu, Cd, Ni, Pb, Zn, Hg, As, Cr) in purple soil in Pushi clastic rock area of Xichang, four typical rock-soil profiles of Cretaceous Xiaoba Formation were selected for systematic sampling, testing and analysis. The results showed that the soil in the study area was acidic-weakly acidic, and the heavy metal elements Cd, Pb and Zn were enriched in the surface layer of the profile, which was related to the superposition of exogenous heavy metal elements. In addition, the migration and enrichment characteristics of heavy metal elements are also affected by many factors, such as profile weathering degree, leaching deposition, clay mineral adsorption and atmospheric dust fall. The single factor index evaluation and Nemero comprehensive index evaluation showed that there was no soil heavy metal pollution in the four sections of the study area. The potential ecological risk assessment showed that the soil in the study area was at a low potential ecological pollution level, and Hg and Cd had a moderate potential ecological risk level. It is suggested that the relevant departments should strengthen the detection and monitoring of soil heavy metals to reduce the potential ecological risk of soil heavy metals scientifically.