济南市机动车排气污染特征及对市区PM2.5的影响

从济南市机动车年检线上利用稀释通道方法采集了小型汽油车、中型汽油车、中型柴油车和大型柴油车4类机动车排气载带PM_(2.5),分析测量了样品中水溶性离子、金属元素、有机C(OC)和元素C(EC)的含量,明确了济南市机动车排气的化学组分特征,得到了济南市机动车排气污染现状以及排放特征.计算了4类机动车排气载带颗粒物的OC/EC值,小型汽油车、中型汽油车、中型柴油车和大型柴油车排气载带颗粒物中OC/EC值分别为15.79、4.34、1.93和0.39,其中小型汽油车、中型汽油车的OC/EC值均大于2,表明汽油车的尾气大于柴油车的尾气污染.而小型汽油车OC/EC值高达15.79,说明小型汽油车尾气中存在严重的二次污染.金属元素特征分析表明Ti、Mn、Fe、Al在济南市机动车尾气颗粒物PM_(2.5)中含量较高,尤其是Mn和Ti,因此,这4种金属元素可作为济南市机动车尾气源的标志元素.PMF模型解析表明,机动车排气源对济南市环境空气PM_(2.5)的贡献率为17.5%,由此可以通过控制济南市小、中型汽油机动车数量、改善油品和改善机动车排气系统来降低对PM_(2.5)的贡献率,从而减少市区空气中PM_(2.5)的浓度.

Study on characteristics of vehicle exhaust and the influence on PM2.5 in Jinan City

PM_2.5 samples were collected from annual inspection line, using dilution tunnel method, for four categories of vehicles, including small gasoline vehicles, medium gasoline vehicles, medium diesel vehicles, and large diesel vehicles. Water-soluble ions, metal elements, organic carbon (OC), and element carbon (EC) in the particles were quantitatively analyzed to identify the chemical components of the vehicle emission in Jinan City and characterize the pollution level. The value of OC/EC in PM_2.5 for four categories of vehicles was 15.79, 4.34, 1.93 and 0.39, respectively. These values of small and medium gasoline vehicles were large than 2, indicating that the pollution intensity of both were severer than that of diesel vehicles, especially for small gasoline vehicles with the value of 15.79, implying high possibility of serous secondary pollution. The analysis of metal elements showed that the contents of Ti, Mn, Fe, and Al in the PM_2.5 were relatively higher than others, and Mn and Ti dominated the element profile. Therefore, the four metal elements can be used as tracer elements to track the sources of vehicles emission. PMF analysis shows that the contribution rate of vehicle exhaust source was about 17.5% in Jinan City. It makes it possible to reduce the occurrence of ambient PM_2.5 in Jinan City by limiting the number of vehicles or improving the exhaust system of motor vehicles.