北京市地表土重金属污染特征及潜在生态风险

摘要

为研究北京市地表土重金属污染特征及潜在生态风险,于2013年11~12月采集了北京市不同功能区的表土样品,用沉析法进行沉降和分级,共得到49组不同粒径的地表土样,并用ICP-MS测试了样品中Cr、Ni、Cu、Zn、Mo、Cd、Ba和Pb等8种重金属的浓度.北京地表土中Cd、Cu、Zn和Pb的平均浓度分别为1.4mg/kg、85mg/kg、333mg/kg、69mg/kg,且4种重金属在道路交通中的污染均明显重于其他功能区.Cd、Cu、Mo、Ni、Pb和Zn的地累积指数随粒径的减小而升高,粒径越小,其污染程度越高.道路交通表土重金属总的潜在生态风险远高于其他功能区,程度很强;工业区和城乡结合部的总的潜在生态风险次之,程度较强.北京不同粒径地表土总的重金属潜在生态指数随粒径的减小而增大,粒径越小,其生态健康风险越大.北京地表土重金属潜在生态风险以Cd的为主.%In order to study the pollution characteristics and potential ecological risk of heavy metals in topsoil of Beijing, topsoil samples were collected in different functional areas of Beijing during November 2013 to December 2013. And 49groups of topsoil samples with different particle sizes were obtained using settling-out method after the settlement and classification from the initial samples. Then the concentrations of 8heavy metals Cr, Ni, Cu, Zn, Mo, Cd, Ba and Pb were measured by ICP-MS. The results showed that the average concentrations of Cd, Cu, Zn and Pb were respectively 1.4mg/kg, 85mg/kg, 333mg/kg and 69mg/kg in topsoil of Beijing, and the pollution of those heavy metals in traffic areas was significantly heavier than that in other functional areas. Geo-accumulation indexes of Cd, Cu, Mo, Ni, Pb and Zn were negatively correlated with the particle size. That is to say, the smaller the particle size was, the higher the corresponding value would be, and the higher its pollution degree would be. The total potential ecological risks of heavy metals in traffic areas were much higher than those in other functional areas. And the total potential ecological risks of heavy metals in industrial zones and urban-rural fringe areas were the second highest. The smaller the particle size was, the higher the potential ecological indexes would be, and the bigger its potential ecological risk would be. In addition, the potential ecological risk of Cd accounted for the most part of the total potential ecological risks.