细河流域土壤中重金属的污染现状及潜在生态风险

分别以《土壤环境质量标准》(GB15618—1995)中的二级标准和沈阳市土壤环境背景值作为参比值, 调查沈阳市细河流域表层(0~20 cm)土壤中的重金属含量与富集情况,对细河流域重金属富集系数和超标率进行探讨,并结合Müller地累积指数法和Hkanson潜在生态风险指数法对污染情况进行生态风险评价.结果表明,细河流域土壤w(Hg), w(Cd), w(Pb)和w(Zn)差异显著,4种重金属含量显著正相关.流域内土壤中w(Cd)严重超出土壤环境标准值,超标样品数量占67.88%;其次为Zn和Hg,超标样品数量分别占4.87%和3.41%, Pb未超标. 4种重金属含量均高于土壤背景值,表现出明显的累积效应,重金属的富集顺序为Cd>Hg>Pb>Zn;细河流域土壤中Hg, Cd, Pb和Zn具有不同程度的潜在生态风险; Pb除在细河上游流域局部污染区土壤中具有高风险外,其余均为一般风险; Zn在全流域污染区均属于一般风险; Hg和Cd在全流域污染区均为极高风险. 

Pollution Conditions and Potential Ecological Risks of Heavy Metals in Soil of the Xihe Watershed

Concentrations and accumulation of heavy metals in the surface soil (0-20 cm) of the Shenyang Xihe watershed were investigated. The reference values ofthe Second Grade for Environmental Quality Standard for Soils (GB15618-1995) and the environmental background values of Shenyang City were used to analyze the accumulation coefficient and rates beyond the soil standard. The Müller land accumulation index and Hkanson potential ecological risk index methods were applied to assess the ecological risk. The results showed that the contents of Hg, Cd, Pb and Zn in the Xihe watershed soil were apparently different, and the four heavy metals were correlated with each other using Pearson correlative analysis. The percentage of samples with Cd content exceeding the national standard was the largest, reaching 67.88% of the total soil area. The percentages of samples with Zn and Hg contents exceeding the standard were 4.87% and 3.41%, respectively.Moreover, Pb content was within what the standard demands. Hg, Cd, Pb and Zn contents in the soil were wholly higher than background values, which reflected the accumulation effects, and the accumulated order for these heavy metals was Cd>Hg>Pb>Zn. The obtained results of potential ecological risk assessment showed that Hg, Cd, Pb and Zn in the Xihe watershed possessed different potential ecological risks. Pb appeared to have very high risk in the upriver polluted area, and general risk in the other polluted areas. Zn appeared to have general risk, and Hg and Cd appeared to have very high risk in the entire polluted watershed.