城市地表颗粒物重金属分布特征及其影响因素分析

城市地表颗粒物作为重金属的重要载体，严重危害城市人群和水体，已成为城市环境的重要研究对象。阐述了对地表颗粒物重金属的空间、粒径、赋存形态等分布特征及其影响因素进行系统分析的意义。通过对国内不同城市不同功能区的重金属（主要为：Zn、Cu、Cd、Pb）数据进行对比分析，各功能区重金属污染情况为：Cu、Pb：工业区〉商业区〉交通区〉居民区〉休闲区；Zn：工业区〉交通区〉商业区〉居民区〉休闲区；Cd：交通区〉工业区〉商业区〉居民区〉休闲区，同时各功能区中Zn、Pb含量波动性较大。整体上国内工业区、交通区和商业区地表颗粒物重金属污染严重。与我国的土壤重金属背景值相比，4种金属中Cd污染程度最为严重。探讨了与国外部分城市地表颗粒重金属污染特征之间的差异，指出国内城市重金属含量均值整体上低于欧美发达城市，而国内一线城市重金属含量明显偏高。系统分析了颗粒物重金属的粒级效应，赋存形态以及生物有效性。综述了城市交通活动（主要为交通流量、车辆行驶速度、变速频率、车辆类型、道路特征等）、降雨冲刷事件、雨前干燥期、大气风力作用、和其他因素对地表颗粒物重金属分布特征的影响。某种程度上，道路车辆的行驶速度和变速对颗粒物重金属累积的影响作用大于交通流量。不同降雨事件和雨前干燥期对重金属分布特征影响的研究结论不一，但地表颗粒对大气PM2.5重金属贡献较大。今后应在以下方面进一步加强对城市地表颗粒物重金属的研究：建立颗粒物粒径划分标准；加强重金属在降雨冲刷过程变化规律的分析；探讨地表颗粒物与大气颗粒物重金属转换关系；还应开展中小型城市，城乡结合部（城中村）地表颗粒物重金属污染特性研究。

Distribution Characteristics and Their Influencing Factors of Heavy Metals in Urban Road Sediments

As the important carrier of heavy metals, urban road sediments may threaten humans health and urban water systems, thus they have been the important research object in the field of environmental sciences. In this paper, the research significances of spatial, particle size and speciation distribution characteristics as well as their influencing factors on heavy metals in road sediments was reviewed and discussed. This study pointed out the distribution characteristics of heavy metals （i.e., Zn, Cu, Cd and Pb） based on the comparative analysis of heavy metal concentrations in different functional areas among domestic cities. The results showed that Cu and Pb concentration in urban road sediments decreased in the order of industrial area, commercial area, traffic area, residential area and leisure area;the content of Zn followed the order as industrial area〉traffic area〉commercial area〉residential area〉leisure area;Cd concentration decreased in the order of traffic area〉industrial area〉commercial area〉residential area〉leisure area, and the concentrations of Zn and Pb fluctuated obviously. In general, the heavy metal contamination of industrial, traffic and commercial areas were more serious than other functional zones in China. Moreover, compared with the corresponding heavy metals＆#39; background concentration in soil of China, Cd was found to be the most serious one among these four metals. The differences of heavy metal accumulation in road sediments between domestic and foreign cities were systematically investigated, and the results revealed that the mean concentrations of heavy metals in China were lower than the values in the developed cities in Europe and America, while the contents of these metals in large-scaled cities were higher than the mean concentration in China. Particle size distribution, chemical fraction and bioavailability of heavy metals in urban sediments were analyzed. The impact of traffic activities （i.e., traffic flow, vehicle speed, the frequency of brake use and ve