中国城市污泥中汞含量的时空分布特征

为全面了解中国城市污水处理厂脱水污泥中汞的赋存状况,从全国40个城市污水处理厂采集315个污泥样品,使用DMA-80直接测汞仪测定了样品中汞的含量.结果表明,全国城市污泥样品中的汞含量范围为0.45~15.42 mg·kg~(-1),汞含量符合对数正态分布,几何平均值为(2.19±3.16)mg·kg~(-1).所有污泥样品中的汞含量均满足《城镇污水处理厂污泥处置混合填埋用泥质》(GB/T 23485-2009)规定的污泥填埋标准;97.8%的城市污泥汞含量均满足土地改良用泥质标准(中性、碱性土壤);86.7%的城市污泥汞含量满足土地改良用泥质标准(酸性土壤).不同城市的污泥样品汞含量存在较大差异(变异系数105%),同一个污水处理厂污泥汞含量也不稳定(7d变异系数0.6%~53.6%).污泥中汞含量中位数呈现华北地区东北地区西北地区西南地区华东地区华中地区华南地区的空间分布趋势.以相应城市的土壤背景值为参比,利用地累积指数法,对于城市污泥中的汞污染现状进行了评价,发现汞重度污染以上的省份比例达到60%以上.与历史数据对比发现,全国城市污泥中汞含量呈现先升高后降低的趋势,峰值出现于2000~2009年.研究结果为城市污水和污泥汞污染的防治工作提供了数据支持.

Spatial and Temporal Variation of Mercury in Municipal Sewage Sludge in China

In order to determine the occurrence of mercury (Hg) in the dewatered sewage sludge (SS) from municipal wastewater treatment plants (MWTPs) in China, 315 SS samples were collected from 40 MWTPs. The total Hg (THg) contents of the sludge samples were analyzed using a DMA-80 Hg analyzer. It was found that THg in the samples ranged from 0.45-15.42 mg ·kg^-1. The THg data followed a log-normal distribution with a geometric mean of (2.19±3.16) mg ·kg^-1. THg contents in all the sludge samples meet the criteria set for disposal (by co-landfilling) of MWTPs sludge (GB/T 23485-2009). In terms of THg contents, 97.8% of the sludge was suitable for land application in neutral and alkaline soils, while 86.7% of the sludge was suitable for land application in acidic soil. THg in SS varied greatly, not only among cities (variation coefficient of 105%), but also in the same MWTP (variation coefficient of 0.6%-53.6% over seven days). Mercury contents in SS of China showed a descending trend of North > Northeast > Northwest > Southwest > East > Central > South China. Using the corresponding urban soil background values of THg as references, Hg pollution levels of SS were evaluated using the geological cumulative index method. It was found that SS from more than 60% of the cities sampled were heavily polluted by Hg. Mercury contents in the SS of China showed a temporal trend of increasing then decreasing, with 2000-2009 being the peak period. Results of the present study provide significant data support for the prevention and control of mercury pollution in sewage and SS in China.