广州市污水污泥中的重金属及其农用探讨

分析了广州市6种污水污泥中重金属(Zn,Cu,Pb,Cr,Mn和Ni)质量分数及其存在形态,并对污泥农业利用过程中施用的最大量进行了估算.结果表明:广州不同来源污水污泥中.(Cu),w(Zn),w(Mn)和,(Ni)较高,变幅较大,而w( Ph )和w( Cr)低.除一种污泥中w(Cu)超标外,其他重金属基本符合国家农用控制标准(G1318918-2002),但所有污泥中重金属质量分数都超过广州市农田土壤平均值.不同重金属以及同一重金属在不同污泥中的形态分布也不同,其中Zn,Mn和Ni的潜在迁移性强,Cu和Cr中的还原态占有很大的比例,污泥中Pb主要以还原态和残渣态存在.根据广州市主要旱地赤红色土壤静态环境容量和动态环境容量计算表明,污泥农用过程中Cu和Zn是主要监控污染元素,不同来源污泥的最大施用量有明显差异.为保证土壤环境的安全,建议将Cu和Zn作为控制城市污水污泥农用过程中最高施用量的计算参考指标.

Content and Fraction of Heavy Metals in Sewage Sludge and Its Farmland Application in Guangzhou

The content and fraction of six heavy metals (Zn,Cu,Pb,Cr,Mn and Ni) in four kinds of sewage sludge from the city of Guangzhou were investigated,and the maximum amount of sewage sludge that could be applied to agricultural soil was calculated.The results showed that the contents of Cu,Zn,Mn and Ni in the sewage sludge from various sources in Guangzhou were higher and had wide ranges,while the contents of Pb and Cr were low.Although the contents of these heavy metals in all four sewage sludges exceeded their average values in Guangzhou crop soil,they met the national control standards for pollutants in sludge for agricultural use (GB18918-2002) on the whole,with the exception of the Cu content in one kind of sludge.The results also revealed that different heavy metals,as well as the same heavy metal in different kinds of sludge,were present in different chemical forms.The active proportions of Zn,Mn and Ni were larger.Cu and Cr existed mainly in reducible form.Pb was in a state of reducible and residual fractions.As calculated by the static environmental capacity and dynamic environmental capacity of latosolic red soil in Guangzhou dry land,the main detected harmful heavy metals were Cu and Zn in the course of agricultural utilization of sludge.The maximum application amount of sludge from various sources was significantly different.Therefore,we suggested that the contents of Cu and Zn in sewage sludge could be used as a reference index for calculating the maximal application rate in the control of application rate of sewage sludge for agricultural land for the protection of soil environment of Guangzhou.