Abstract:Samples of atmospheric particles were collected in August at four monitoring stations (Yunqi, Zhaohui, Hanggang, Xiasha )in Hangzhou City. Size distributions of the main extinction components were quantified, including SO42-, NO3-, NH4+, OC and EC. Meanwhile, a wide range of gaseous pollutants and meteorological elements were observed simultaneously on Zhaohui station in order to assess the influence factors of visibility degradation. PM2.5, RH, SO2 and NO2 were negatively correlated with visibility. The peaks of particles concentration appeared in the size of 0.4~0.7μm and 9.0~10μm. SO42-,NO3-,NH4+ and OC exhibited the single modal. The peaks of SO42- and NH4+ were in the size of 0.4~1.1μm, while the peak of NO3- appeared in the size of 5.8~10μm and the peak of OC was in 0.4~0.7μm. EC exhibited the bi-modal and the peaks were in 0.4~0.7μm and 2.1~3.3μm. In order to solve the visibility problem of Hangzhou, the fine particles, especially the size that less than 1.1μm should be reduced primarily. EC was the dominant extinction component in this study and the pollution sources of EC, such as vehicle exhausts should be primarily controlled in Hangzhou to improve the visibility and reduce the haze days.