Chemical composition, morphology, size and mixture of fine particles were measured in a heavy haze and the post-haze air in Beijing in January 2012. With the occurrence of haze, the concentrations of gaseous and particulate pollutants including organics, sulfate, nitrate, and ammonium grew gradually. The hourly averaged PM2.5 concentration increased from 118 mu g m(-3) to 402 mu g m(-3) within 12 h. In contrast, it was less than 10 mu g m(-3) in the post-haze air. Occupying approximately 46% in mass, organics were the major component of PM1 in both the haze and post-haze air. Analysis of individual particles in the size range of 0.2-1.1 mu m revealed that secondary-like particles and soot particles were always the majority, and most soot particles had a core-shell structure. The number ratio of secondary-like particles to soot particles in accumulation mode in the haze air was about 2:1, and that in the post-haze air was 8:1. These results indicate both secondary particle formation and primary emission contributed substantially to the haze. The mode size of the haze particles was about 0.7 mu m, and the mode size of the post-haze particles was 0.4 mu m, indicating the remarkable growth of particles in haze. However, the ratios of the core size to shell size of core-shell structure soot particles in the haze were similar to those in the post-haze air, suggesting a quick aging of soot particles in either the haze air or the post-haze air. (C) 2016 Elsevier B.V. All rights reserved.
ISI Document Delivery No.: DW8UGTimes Cited: 8Cited Reference Count: 45Niu, Hongya Hu, Wei Zhang, Daizhou Wu, Zhijun Guo, Song Pian, Wei Cheng, Wenjing Hu, MinHU, Wei/M-4751-2018; Guo, Song/D-9218-2012; Wu, Zhijun/A-7041-2012HU, Wei/0000-0002-0416-1130; Guo, Song/0000-0002-9661-2313; Zhang, Daizhou/0000-0002-1448-2325National Basic Research Program of China [2013CB228503]; National Natural Science Foundation of China [91544214, 41541038]; Natural Science Foundation of Hebei Province [D2016402120]; Education Bureau of Hebei Province for Excellent Young Scholars [YQ2014020]; special fund of the State Key Joint Laboratory of Environment Simulation and Pollution Control [14K05ESPCP]; Chinese Scholarship Council (CSC)This work was supported by the National Basic Research Program of China (2013CB228503), the National Natural Science Foundation of China (91544214 and 41541038), the Natural Science Foundation of Hebei Province (D2016402120), the Education Bureau of Hebei Province for Excellent Young Scholars (YQ2014020), and special fund of the State Key Joint Laboratory of Environment Simulation and Pollution Control (14K05ESPCP). The Chinese Scholarship Council (CSC) supported Mr. Wei Hu's study in Prefectural University of Kumamoto, Japan. The authors would like to thank Nicholas James O'Connor for his assistance in the word and grammar editing. Any errors are the responsibility of the authors.85132Elsevier science bvAmsterdam1879-1026