污泥中重金属的环境活性及生态风险评估

研究了湖南省长沙市、株洲市和常德市10个污水处理厂剩余污泥中As,Cd,Cu,Ni,Pb,Zn的含量和形态特征,并利用潜在生态危害指数法对污泥农用过程中重金属的生态风险进行了综合评价。结果表明,城市污泥中富含有机质及N,P,K等养分,然而,污泥表现为以Cd为主的多金属污染,不能直接农用。污泥中Cd含量为1.43～260mg/kg,以可还原态为主,占全量比例高于28.9%;As,Pb的可还原态,Ni,Zn的酸可溶态和可还原态,Cu可还原态和氧化态所占比例较高,表明污泥中重金属的潜在环境活性较高。风险指数评价结果表明,污泥中Cd和As是潜在的强生态风险元素;以工业废水处理为主的污水处理厂污泥重金属单因子生态风险相对较高,且综合潜在生态风险严重。

Environmental Availability and Ecological Risks of Heavy Metals in Sewage Sludge

The contents and speciation of heavy metals in sewage sludge from 10wastewater treatment plants in the cities of Changsha,Zhuzhou and Changde of Hu′nan Province were addressed.The potential ecological risk index(IR)was used to evaluate the ecological risk of heavy metals in the sludge intended for agriculture.The results showed that the sewage sludge was rich in organic matter,nitrogen,phosphorous,and potassium.As sewage sludge could potentially cause multi-metal contamination,especially Cd,sewage sludge should not be directly used for agriculture.The total content of Cd in sewage sludge ranged from 1.43to 260 mg/kg and the major speciation of Cd was in reducible form with percentage as high as 28.9%.The major speciations of As and Pb in sludge were also in reducible form,those of Ni and Zn were in acid soluble and reducible forms,while those of Cu were in reducible and oxidizable forms,respectively.The results demonstrated that the environmental availability of heavy metals in sewage sludge was high.Based on the results of IR,Cd and As in the sewage sludge imposed a potentially severe risk.Both the single and comprehensive potential ecological risks of the heavy metals in the sewage sludge from the industrial areas were extremely serious.