AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Formation and Sources: Seasonal Haze Episodes in Beijing, China in 2013
YANJUN ZHANG, Jing Cai, Mei Zheng, Peking University
Abstract Number: 303 Working Group: Haze in China: Sources, Formation Mechanisms, and Current Challenges
Abstract China, especially North China Plain, nowadays frequently gets hit by haze episodes characterized with high PM2.5 concentration. Due to significant visibility decrease and health threat during hazy days, there is an urgent need to better understand sources and formation mechanisms of haze. This study will present seasonal characteristics of PM2.5 chemical components from Beijing in 2013, and reveal causes for haze episodes in four seasons.
Both major and trace components of PM2.5 are analyzed using multiple techniques. As PM2.5 concentration in Beijing increases, the fraction of sulfate and nitrate increase while that of organic matter decreases significantly. One episode in each season is selected for detailed analysis according to its PM2.5 mass concentration. Beside chemical characterization, source apportionment by chemical mass balance (CMB) and positive matrix factorization (PMF) are also conducted to understand sources of these episodes. Measured and PMF-calculated source profiles agree well with each other. Results of both CMB and PMF analyses indicate coal combustion, traffic emission, road dust, biomass burning and secondary sources are major contributors. Different sources show distinct characteristics in seasonal episodes.
To better understand the contribution of local emission and regional transport in an episode, back trajectory analysis, potential source function (PSCF) and concentration weighted trajectory (CWT) are also applied in this study. During haze periods, the frequency of southward winds is found to increase significantly, especially in summer. More discussion about differences of episodes in four seasons based on its chemical characteristics, sources and the degree of regional transport will be discussed and presented.