湖南省某冶炼厂周边农田土壤重金属污染及生态风险评价

Heavy Metal Pollution and Ecological Risk Assessment of the Paddy Soils near a Smelting Area in Hunan Province

利用野外采样与实验室分析相结合的方法，以湖南省某冶炼厂周边农田土壤（0～20cm）为研究对象，监测了Cd、As、Pb、Cr、Cu、Zn、Hg等7种重金属的含量，并对重金属污染程度与潜在生态风险进行了评价。结果表明，7种重金属都存在不同程度的超标或污染，其中Cd、As、Pb等的污染较为严重。统计学分析结果表明，Pb、As、Hg、Zn、Cd等来源相同，可能主要都来自于人为污染，即冶炼作业造成的污染。7种重金属化学形态不尽相同：在重金属有效态中，Cd的水溶态和可提取态较高；Ph、Cu、Zn可还原态、可氧化态这两部分含量较高。而Hg、As、Cr的残渣态含量较高。风险评价代码评价结果表明．cd的生态风险较高，4．5％的样点cd为极高生态风险，52．8％的样点cd为高生态风险，42．7％的样点cd为中度生态风险；100％的样点Zn为中度生态风险；Cu有60．1％的样点属于低生态风险，39．9％的样点属于中度生态风险；As、Pb主要以低生态风险为主（所占比例分别为77．2％、80％）；Hg主要以无生态风险为主（所占94．3％）。Hakanson潜在生态风险指数法计算的综合潜在生态风险指数（RI）的范围为46．4～1627．5，表明研究区域农田土壤存在很高的生态风险。上述各项结果综合表明，研究区农田土壤受到了严重的重金属污染，由此引起的重金属生态风险应引起高度关注。

The concentrations of Cd, Hg, As, Pb , Cr , Cu and Zn in the topsoil of paddy fields near a smelting area located in the Hunan province were analyzed by field sampling and laboratory analysis, aiming to evaluate the pollution degrees and potential ecological risks of soil heavy metals. The experimental data indicate that the soil was seriously polluted by heavy metals, especially by Pb, As, Cd. Additionally, cluster analyses suggested that metals such as Pb, As, Hg, Zn and Cd could be from the same sources probably related to acid mine drainage and the mining complexes located in the area.. The chemical speciation analysis of heavy metal showed Cd mainly existed in exchangeable form. Pb, Cu and Zn were distributed mainly in acid extractable fractions and Fe/Mn oxide fractions, and Hg, As, Cr was mainly associated with residual fraction. The results of risk assessment code （RAC） showed Cd was medium, high and extremely high risk （42.7% , 52. 8% and 4.5% ） , Zn was medium risk （ 100% ） , Cu was low and medium risk （60. 1% and 39. 9% ）, Hg was mainly no risk （94. 3% ） , As and Pb was mainly low risk （77.2% and 80% ）. The range of the potential ecological risk of soil calculated by risk index （RI） was 46.4-1 627.5, revealed a considerable-high ecological risk in study area. All the results indicated that research area is seriously polluted by heavy metals.