云南某冶炼厂周围农田土壤重金属污染状况及生态风险评价

通过现场采样和实验室分析,在分析冶炼厂周边区域不同深度土壤中重金属含量的基础上,利用单因子和内梅罗指数法对其污染程度进行评价,结果表明,表层土壤中镉、铅、汞、锌和铜均超过云南背景值和二级标准,且内梅罗综合指数均大于5,说明表层土壤受到重金属镉、铅、汞、锌和铜的重度污染。综合不同深度土壤重金属污染程度,如按综合指数法依次排序应为:铜汞锌镉铅砷铬。数据统计分析可知,锌与镉在土壤中均呈现极显著正相关,汞与锌、镉均呈现显著正相关,说明该冶炼厂周边村庄与农田土壤中锌和镉的污染可能有相同的来源,而汞也与锌和镉的来源相近,区域内的锌冶炼生产可能是导致研究区域农用土壤重金属含量升高的主要原因。从重金属的综合潜在生态风险指数看,表层土壤中潜在生态风险指数RI平均值为2 049.01,其中镉的贡献率最大,占比约为90.34%,汞的占比约为6.96%,这表明该区域土壤中镉和汞的潜在生态风险较大。

Heavy metals pollution and potential ecological risk in paddy soils around historical mining plant in Yunnan Province

Heavy metals concentrations and their potential relationships in paddy soil around mining plants were analyzed by field sampling and laboratory testing. The results showed that the top soils were contaminated by Cd, Pb, Hg, Zn and Cu with a relatively higher Nemerow pollution index (>5). The pollution levels of heavy metals in soil are in the order: Cu>Hg>Zn>Cd>Pb>As>Cr. Statistical Analysis of the heavy metals data shown that Zn and Cd were in a significant positive correlation, while Hg and Zn/Cd were in positive correlation, which indicated the elevated Zn and Cd were from the same contamination sources (nearby historical mining activities). The average RI in the topsoil was about 2049.01, and Cd occupied about 90.34% and Hg was about 6.96%, which indicated that the paddy soil exhibited a higher potential ecological risk, especially from Cd and Hg.