View article

PM 2.5 with its major chemical components were measured and analyzed during a concurrent haze in Jan. 1–19, 2013 at three sites (Shanghai, Beijing, and Huaniao, a remote isle over the East China Sea) to probe the sources and formation process of such a severe haze over three typical regions in China. The mean PM 2.5 concentrations during the severely polluted days reached 180.8 μg m− 3, 299.2 μg m− 3, and 131.1 μg m− 3 in Shanghai, Beijing, and the Huaniao Isle, respectively. The mass ratio of the sum of SO 4 2−, NO 3−, and NH 4+ to PM 2.5 were over 1/3 during the polluted days at all the three sites. Promoted gas-to-particle transformations from acidic SO 2 and NO x to SO 4 2− and NO 3− under high relative humidity conditions played a major role in the formation of this severe haze. Significant contribution of traffic emissions to the haze formation over China was suggested to be one of the major …