北京城市污泥中铅砷镉形态浓度的ICP-MS分析

城市污泥中重金属的难降解和高毒性限制了污泥的资源化利用。以北京G和Q污水处理厂的压滤出厂污泥为实验材料，采用BCR三步浸提法对污泥中铅砷镉Pb，As，Cd的三种形态进行提取，以HNO₃-HClO₄进行全量消解，利用ICP-MS检测Pb，As，Cd的全量和各形态的含量，从而为北京城市污泥的资源开发研究提供基础数据。实验结果表明，北京城市污泥中Pb和Cd含量比上世纪末明显降低：其中，G污泥中Pb，As，Cd的全量(干重)分别为19.60，37.96和1.34 mg·kg-1,而Q污泥中分别为19.58，23.46和2.30 mg·kg-1;两种污泥中Pb含量相差甚微，G污泥中As明显高于Q污泥，而Cd则显著低于后者;两种污泥中相应金属的三种形态的变化趋势基本一致：Pb与As以HAc酸溶态为主，H₂O₂可氧化态最少;而Cd主要以NH₂OH-HCl可还原态存在，HAc酸溶态最少。三种重金属中生物毒性大的形态均占70％以上。

Content Determination of Different Species of Pb,As, and Cd in the Municipal Sewage Sludge of Beijing with ICP-MS

Heavy metals in municipal sewage sludge can limit the utilization of sludge resources, due to their recalcitrant characteristics and harmful effects. Here, ICP-MS was used to determine the total and special content of Pb, As and Cd in the sewage sludge from G and Q Wastewater Treatment Plants, Beijing. The air-dried samples were dissolved in HNO₃-HClO₄ before the total content determination, or, sequentially extracted with BCR three-step method before special content determination for the heavy metals. The total contents are 19.60, 37.96 and 1.34 mg·kg-1 dry weight (DW) for Pb, As and Cd in the sewage sludge from G Plant, respectively; or, 19.58, 23.46 and 2.30 mg·kg-1 DW in that from Q Plant, respectively. Pb and Cd decreased dramatically in the total contents, compared to the corresponding data in the late 20th century. Both G and Q sludge samples show similar patterns in the species distribution for the three heavy metals: most of Pb and As are HAc soluble, and least are H₂O₂ oxidative; while Cd mainly exists in NH₂OH-HCl reductive state, seldom in HAc soluble state. Species with high ecotoxicity account for a major part (over 70%) of the three species for all the metals on the whole. The authors’ results provide basic data for the ecological risk assessment and utilization of municipal sewage sludge from Beijing.