title: Variations of fine particle physiochemical properties during a heavy haze episode in the winter of Beijing.
abstract: 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 118μgm(-3) to 402μgm(-3) within 12h. In contrast, it was less than 10μgm(-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 0.2-1.1μm 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 0.7μm, and the mode size of the post-haze particles was 0.4μm, 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.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; Hebei Collaborative Innovation Center of Coal Exploitation, Hebei University of Engineering, Handan 056038, Hebei, China.
authors.forename: Hongya
authors.initials: H
authors.lastname: Niu
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China; Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan.
authors.forename: Wei
authors.initials: W
authors.lastname: Hu
authors.affiliation: Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan.
authors.forename: Daizhou
authors.initials: D
authors.lastname: Zhang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Wu
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
authors.forename: Song
authors.initials: S
authors.lastname: Guo
authors.affiliation: Hebei Collaborative Innovation Center of Coal Exploitation, Hebei University of Engineering, Handan 056038, Hebei, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Pian
authors.affiliation: Hebei Collaborative Innovation Center of Coal Exploitation, Hebei University of Engineering, Handan 056038, Hebei, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Cheng
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China. Electronic address: minhu@pku.edu.cn.
authors.forename: Min
authors.initials: M
authors.lastname: Hu
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000068476:Beijing; D004784:Environmental Monitoring; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012621:Seasons
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Aging; Core-shell structure; Morphology; Secondary particles; Size; Soot particles