Fine paniculate matter was sampled in Shanghai urban area during two air pollution events, from October 10th to 21", 2009. Based on the analysis of the pollution episode, characteristics of PM2.5 and its chemical composition were analyzed to discuss the pollution sources and formation mechanism. The haze event, which occurred on October 14th, was mainly caused by the secondary transformation of local air pollutants. The ratio of PM2.5 to PM10 exceeded 60% and the concentrations of water soluble ions in PM2.5 were very high. During the floating dust event from October 17th to 19th, concentration of coarse paniculate matter rose and the proportion of PM2.5 decreased. The secondary ions transferred from fine particles to coarse particles and concentration of Ca2+ was high. Meanwhile, concentrations of K+, EC and OC in PM2.3 were high due to the straw burning in Yangtze Delta. Therefore, together with local emission control, the control of secondary fine paniculate matter and its precursors should be also emphasized.%采集了上海城区2009年10月10～21日期间2次空气污染过程的样品,在对污染过程分析的基础上,着重分析了PM2.5及其化学组分的变化,探讨了污染源及形成机制.研究表明,14日的灰霾过程主要由本地排放的污染物二次转化形成,PM2.5占PM10比重超过60％且PM2.5中离子组分含量高.17～19日的浮尘过程中,受北方沙尘影响本市粗颗粒浓度上升,PM2.5所占比重下降,二次离子组分从细颗粒物向粗颗粒物转移且Ca2+浓度上升,同时受到长江三角洲区域秸秆焚烧的影响,细颗粒物中K+,EC和OC含量高.因此,应在控制本地源排放的同时,加强对细颗粒尤其是二次细颗粒污染及其前体物的协同控制.
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