喀什污水处理厂污泥中重金属Cd和Pb的形态分析及风险评价

Morphological Analyses and Risk evaluation of Heavy Metals Cd and Pb in Sewage Sludge from Kashgar Sewage Plant

分析了新疆喀什市污水处理厂污泥的基本性质、污泥中重金属Cd和Pb的含量及形态,并利用地累积指数(Igeo)法和内梅罗指数法(PI)评估了污泥在土地利用过程中重金属的潜在生态风险。结果表明,该污泥有良好的农用价值。但是污泥中Cd的总量为5.48 mg/kg,此结果超过中国农用污泥中重金属的控制标准(酸性土壤中),主要形态为残渣态和可交换态,分别占44.34%和23.18%,生物可利用态含量较高,易被植物吸收利用,所以农用具有较大的风险。Pb含量在我国农用污泥中重金属的控制标准范围内,存在形态主要为残渣态,占82.64%,在污泥中较稳定;地累积指数法和内梅罗单项指数法的评估结果表明,污泥农用对土壤环境存在严重的潜在生态风险。

The basic properties, total contents and speciation of heavy metals Cd ＆ Pb in sewage sludge from kashgar sewage plant were analyzed. The potential ecological risk of heavy metals for sludge land application was evaluated by geo- accumulation pollution index （Igeo） and Nemerow .index method（PI）. The results showed that the sludge was organic fertilizer with good value for farmland. The total content of Cd was 5.48 mg/kg, above the Chinese sewage sludge criteria for agricultural use. The main speciation was residual and exchangeable form, accounting for 44.34% and 23.18%, respectively. The proportion of bioavailable forms of Cd can be easily absorbed by plants. Appropriate treatment should be carried out before using in farmland. The total content of Pb was less than the Chinese sewage sludge criteria for agricultural use and its main speciation was residual form accounting for 82.64%. The results of Nemerow and geo-accumulation pollution index showed that heavy metals in sewage sludge caused serious ecological risk when they were directly utilized as fertilizer.