西安市市政污水厂剩余污泥中重金属形态特征及潜在生态风险评价

Morphological Characteristics of Heavy Metals in Sewage Sludge and Their Potential Ecological Risk Assessment in Xi'An,(Shaanxi)

采用现场采样及室内分析方法,研究了西安市剩余污泥的基本理化性质,污泥中重金属元素的含量、赋存形态及迁移特征,并对市政污泥土地利用的潜在生态风险进行了评价。结果表明：西安市剩余污泥整体pH呈中性（6.24~8.12）,具有高有机质（46.71%~72.41%）、高N（6.18%~6.94%）、高P（1.71%~4.21%）、低K（1.02%~2.03%）的特点,具有很好的土地利用价值;污泥中重金属（除Pb、Mn、Co外）及As整体含量高于《土壤环境质量标准》的二类标准（pH=6.5~7.5）,但除Zn、Ni、Hg超过《农用污泥中污染物控制标准》酸性土壤（pH〈6.5）最高允许含量外,其余重金属及As均低于该标准值;西安市污泥中重金属的形态分布主要由重金属元素的性质决定,污泥中各重金属的迁移或稳定性顺序（F1＋F2）为Cu（19.38%）〈Cr（21.2%）〈Pb（47.76%）〈Co（50.22%）〈Ni（54.63%）〈Mn（61.53%）〈Zn（74.21%）;修正潜在生态风险评价结果表明,西安市剩余污泥重金属综合污染程度处于重度水平,污泥土地利用时重金属污染的潜在生态风险水平为严重,其中Hg为其首要贡献者,其次是Zn和Ni。

In this paper, with the methods of on-site sampling and laboratory analysis, physicochemical properties of sewage sludge, concentrations, form of existence and transfer characteristics of heavy metals in the sewage sludge were studied in Xi＇an, Shanxi. Subsequently, the potential ecological risk of heavy metals in municipal sludge for land application was evaluated. Results showed that the sludge had neutral pH（6.24 ~ 8.12）, and contained rich organic matter（46.71% ~ 72.41%）, high N（6.18% ~ 6.94%）, high P（1.71% ~ 4.21%）, low K（1.02% ~ 2.03%）,which was suitable for land application. The concentrations of all heavy metals and As, except Pb, Mn, Co were higher than the values of the secondary standard（pH = 6.5 ~ 7.5） of soil environmental quality standard（GB15618-1995） of China, and did not exceed the pollution control standards of agricultural application sludge of China, except that Zn, Ni, and Hg exceeded the threshold in acid soil（pH 6.5）. The morphological distribution of heavy metals in the sludge of Xi＇an was mainly determined by their nature. The ability of migration of heavy metals in sewage sludge when applied in soil was in the order of Cu（19.38%） Cr（21.2%） Pb（47.76%） Co（50.22%） Ni（54.63%） Mn（61.53%） Zn（74.21%）. After amendment,the potential ecological risk assessment results showed that the comprehensive pollution level of heavy metals in the sludge of Xi＇an was at a degree of severity, and the potentialecological risk of heavy metals by sludge land application was at a degree of high severity with primary contribution from Hg, followed by Zn and Ni.