珠江广州段鸦岗断面底泥中重金属的生态危害评价

Heavy Metals in Sediment in Yagang Spot of Guangzhou Reach in Pearl River and Its Ecological Risk

目的为研究镉、铬、铜、铅在珠江广州段的环境影响提供依据。方法于2006年4月在珠江广州段鸦岗断面采集了表层底泥,测定了该断面底泥中的重金属镉、铬、铜、铅的含量,并采用Tessier形态分类法对镉、铬、铜、铅在底泥中的存在形态进行了提取和测定。结果该断面底泥中镉、铬、铜、铅含量分别为2.29、217.97、320.60和124.44 mg/kg,均高于全国湖泊底泥的平均值,分别为广东省土壤背景值的57.25,6.26倍,28.63倍,4.31倍。其中,镉以可交换态为主,占总量比例为55.02%;铬以铁锰态为主,占总量的58.55%;铜以有机态为主,占总量的48.69%;铅以铁￣锰态和残渣态为主,占总量的比例分别32.52%和38.77%。结论依据瑞典学者Hakanson提出的潜在生态危害指数法对该断面底泥中的镉、铬、铜、铅进行了潜在生态危害评价,表明镉潜在生态危害强,铬、铅的潜在生态危害轻微,铜的潜在生态危害中等。

Objective To investigate the contamination of Cd, Pb, Cu and Cr in the sediment of Guangzhou reach in Pearl River. Methods The sediments were collected in Yagang spot in April, 2006. The content of heavy metals were determined, the heavy metals in the sediment were extracted with Tcssier five stage sequential extraction procedure, and AAS was applied to determine the concentration of heavy metals in the sediment and extracts. Results The level of Cd, Pb, Cu, Cr were 2.29 mg/kg, 217.97 mg/kg,320.60 mg/kg and 124.44 mg/kg respectively in the sediment in Yagang spot. They were higher than the background values of soil of Guangdong, and different heavy metals had different values of five forms. Cd existed as exchanged form mainly, and Cr, Pb existed as stable form mainly, so, Cd was easy to be resolved into water, Cr, Pb were relatively stable in the sediment. Conclusion The ecological risk of the four heavy metals is assessed with Hakanson potential ecological harmful index, the ecological risk of Cd is high, Cr, Pb is lower, Cu is moderate.