广西都安县耕地土壤重金属污染风险评价

Risk Assessment of Heavy Metal Contamination in Farmland Soil in Du'an Autonomous County of Guangxi Zhuang Autonomous Region,China

为全面了解广西都安瑶族自治县耕地土壤重金属污染特征和生态风险状况,通过实地调查采样及土壤重金属含量分析,利用单因子指数、内梅罗综合指数、Hakanson潜在生态危害指数对都安县耕地土壤中Cd、As、Ni、Zn、Cr、Sb、Cu、Pb这8种重金属进行污染和生态风险评价.结果表明,都安县耕地土壤重金属总体污染严重,74.6%的耕地土壤点位超标,Cd、As、Ni、Zn、Cr、Sb、Cu、Pb的超标率依次为70.6%、42.9%、34.9%、19.8%、19.6%、2.94%、1.59%、0.79%,其中Cd和As超标率远远超过全国和广西水平,是都安县主要的污染元素.都安县耕地土壤总体呈现"中度"生态风险,其中Cd对生态风险贡献率达到88%;九渡乡东南部和保安乡与东庙乡结合部存在高生态风险.都安县耕地土壤重金属污染来自两个主要污染源,其中刁江流域两岸受污灌耕地土壤中As、Sb污染可能主要来源于刁江上游的矿业活动.

For a comprehensive understanding of the pollution characteristics and ecological risk of heavy metals of farmland soil in Du’an Autonomous County of Guangxi Zhuang Autonomous Region,China,this study evaluated the cadmium( Cd),arsenic( As),nickel( Ni),zinc( Zn),chromium( Cr),antimony( Sb),copper( Cu) and lead( Pb) pollution situation using the single factor index,the Nemerow pollution index and the Hakanson ecological risk index. The results showed that heavy-metal pollution of farmland soil in Du’an County was serious. 74. 6% of the soil samples had heavy metals concentrations higher than the Grade Ⅱ of National Soil Environmental Quality Standard( GB 15618-1995). The over standard rates of Cd,As,Ni,Zn,Cr,Sb,Cu,Pb were 70. 6%,42. 9%,34. 9%,19. 8%,19. 6%,2. 94%,1. 59%,0. 79%,respectively. Cd and As were the main contaminants in Du’an County,the pollution was far more serious than those of the national and Guangxi Zhuang Autonomous Region. In terms of the ecological risk,heavy metals of farmland soil in Du’an County showed a 'middle'ecological risk,with Cd accounting for 88% of the total ecological risk. The north-west of Jiudu Town and the zone between Bao’an Town and Dongmiao Town were two areas with high ecological risk in Du’an County. The contamination of farmland soils in Du’an County was caused by two main sources,whereas the pollution of As and Sb of farmland soils near Diaojiang River was mainly caused by the upstream mining industry.