应用受体模型(CMB)对北京市大气PM_(2.5)来源的解析研究

为研究影响北京市大气环境PM2.5污染水平的主要来源,于2012年8月—2013年7月,依托北京市大气地面观测网络在10个监测点采集的491 d(次)大气PM2.5有效样本,对其化学组分进行了测试分析;从城市大气污染源组成出发,建立和完善了5类固定点源、2类流动源、4类无组织面源的PM2.5排放成分谱.应用受体模型(CMB)开展了来源解析研究.结果显示:1观测期间大气环境PM2.5的来源主要包括:一次来源机动车(16%)、燃煤(15%)、土壤尘(6%)、二次硫酸铵和硝酸铵(36%),以及有机物(20%)和其他未识别来源(7%);与历史解析结果相比,燃煤源分担率有所下降,二次无机盐与有机物分担率上升,且二次硝酸盐有赶超二次硫酸盐之势;2从主要组分的来源看,观测期间环境大气PM2.5中近25%的硫酸盐来自于燃煤锅炉和电厂排放,17%的有机物来自机动车排放;3北京市PM2.5来源类型大致相同,但各点位PM2.5来源种类和分担率具有一定差异,对一些排放量较大的局地排放源有比较明确的响应.研究表明,开展区域性PM2.5治理、大力削减前体物、严格控制本地机动车、燃煤等PM2.5排放都是改善北京市空气质量的重要途径.

Source apportionment of PM2.5 in Beijing by the chemical mass balance

In the study, 491 PM_2.5 samples from 10 sites in Beijing were collected in the campaign from August 2012 to July 2013 and used to analyze the major sources of PM_2.5. Five types of point source emissions, two types of mobile emissions and four types of fugitive emissions were defined and the chemical mass balance (CMB) model was used to conduct source apportionment analysis. Results indicated that the major sources of PM_2.5 were organic matter (20%), secondary nitrate (20%), secondary sulfate (16%), motor vehicle (16%), coal burning (15%),soil dust (6%) and unidentified (7%). Compared with the previous results, the contribution from coal burning declined, while that of secondary inorganic matter and organic matter increased. Source apportionment of the key components showed that 25% of sulfates came from coal-burning boiler emission and 17% of OM emitted by motor vehicle. The source of each site was quite different, showing the characteristics of local pollutant source emission. To improve the air quality in Beijing City, it is important to take action regionally to reduce PM_2.5 and precursor gases emissions. In the meanwhile, the local traffic and coal-burning emission should be more strictly controlled.