沘江流域耕地土壤重金属分布及生态风险评价

地处兰坪铅锌矿下游的沘江流域土壤重金属污染问题倍受关注。本文在沘江流域采集了35个耕地土壤样品，分析测定了砷、铜、锌、镉、铅、汞6种重金属污染物累积量，并应用内梅罗综合污染指数法及Hacanson潜在生态风险指数法，对耕地土壤污染状况及生态风险进行评价。结果表明：（1）沘江流域沿岸耕地重金属铅、锌、镉累积量相对处于极高水平，均值分别为1 146.97、579.15、4.85 mg·kg^-1，污染十分严重；砷的累积量也较大，均值为26.85 mg·kg^-1；铜、汞累积量较小，污染程度轻；（2）地统计分析结果表明，兰坪周边流域是土壤重金属砷、锌、铅、镉污染的一个主要点源污染源，而铜、汞污染没有显著点源污染源，均来自不同面源污染；（3）流域内梅罗指数均值为17.69（远大于3），存在极其严重重金属污染，同时综合潜在生态风险指数均值为773.38，有很强潜在生态风险。污染物贡献表现为镉 > 铅 > 锌 > 砷 > 汞 > 铜；（4）沘江流域耕地土壤总体表现为水田重金属污染略高于旱地。

Distribution and Ecological Risk Assessment of Heavy Metals in Arable Soils in Bijiang Watershed, China

It has been paid much attention to soil heavy metal pollution in the Bijiang watershed caused by the Lanping lead-zinc mine. We collected 35 arable soil samples along Bijiang, then sampled and tested the contents of As, Cu, Zn, Cd, Pb, Hg. And then with Nemerow Multi-Factor Index and the Potential Ecological Risk Index method, we evaluated the heavy metal pollution risk. The results showed:(1)The accumulation of Pb, Zn, Cd was in a relatively high level, the average was 1 146.97, 579.15, 4.85 mg·kg^-1 respectively, which was seriously polluted; the average accumulation of As was 26.85 mg·kg^-1; but Cu, Hg was slightly polluted. (2)Statistical analysis showed that Lanping area was a main point source pollution of As, Zn, Pb, Cd, while Cu, Hg was pollution caused by different non-point source pollution.(3)Within this basin, the Nemerow index was 17.69, which was serious heavy metal pollution, while the comprehensive potential ecological risk index was 773.38, which was a strong potential ecological risk. The contribution of pollutants was Cd > Pb > Zn> As> Hg > Cu. (4)As a whole, the soil heavy metal pollution of paddy field was higher than of the dry land.