广州城市污泥中重金属的存在特征及其农用生态风险评价

分析了广州7种城市污泥中Zn、Cu、Pb、Cr、Mn、Ni的含量，研究了其中5种污泥中重金属的形态特征，并利用地累积指数（Igeo）和潜在生态危害指数法（RI）对污泥农用过程中重金属的潜在生态风险进行了综合性评价. 结果表明，广州不同来源城市污泥中Cu、Zn、Mn、Ni含量较高，变化幅度较大，而Pb、Cr含量较低. 除一种污泥中Cu超标外，其他重金属基本符合国家农用控制标准（GB18918-2002）,但所有污泥中重金属含量都超过珠江三角洲耕地土壤均值.不同重金属在不同污泥中的形态分布差异较大. 其中，含工业污水污泥中Cu、Cr还原态占很大的比例，Pb、Fe主要以还原态和残渣态存在；生活污水污泥中重金属主要以可氧化态和残渣态存在，酸可交换态中Mn的比例较高，易还原态中Zn的比例较高；5种污泥中Cu、Zn、Mn潜在迁移性最强.Igeo和RI评价结果表明，污泥中Cu、Zn、Mn是潜在的强生态风险元素,污泥在农用过程中具有一定生态风险性. Igeo和RI用于污泥农用过程中重金属的生态风险评价是可行的,与其它评价方法相比较, RI能更好地反映污泥中重金属对生态环境的综合影响.

Heavy metal characteristics in sewage sludge and its potential ecological risk assessment for agriculture use in Guangzhou

The contents of heavy metals (Zn、Cu、Pb、Cr、Mn、Ni) in different sludges were analyzed and their speciution was determined. The index of geoaccumulation (I_(geo)) and potential ecological risk (RI) were used to evaluate the potential ecological risk of heavy metals in sludge intended for agriculture use in Guangzhou. The results showed that the contents of Cu, Zn, Mn, Ni were high, but Pb, and Cr were much lower. Although the contents of heavy metals were higher than the background values of Pearl River Delta crop soil, except for Cu contents in the selected sludge samples, the other elements meet the controlled standards of pollutants in sludge for agricultural uses (GB18918-2002). Different heavy metals in different selected sludges had different forms. In the industrial sewage sludge, Cu, Cr existed mainly in reduced forms, but Pb and Fe were in the state of reducible and residual fractions. In the domestic sewage sludge, the heavy metals exist mainly in oxidizable and residual fractions, but the percentage of Mn in the exchangeable fraction and Zn in the reducible fraction. In all, the active proportion of Cu ,Zn .Mn was large and their potential transformation was strong.Assessed by the results of I_(geo) and RI, use of the sludge for agricultural purposes has a certain ecological risk because Cu, Zn and Mn pose a potential risk. The I_(geo) and RI methods are feasible for evaluation of the ecological risk of heavy metals in sludge. In comparison with other assessment methods, RI can better reflect potential eco-environmental risk for agriculture process due to the combination of total contents, toxicity and bioavailability of heavy metals.