AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Primary and Secondary Organic Aerosol during Severe Haze Episodes in January 2013 in Beijing, China
CAIQING YAN, Mei Zheng, Xiaoying Li, Huaiyu Fu, Xiang Ding, Quanfu He, Xinming Wang, Peking University
Abstract Number: 82 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract During January 2013, a significant large area in North China Plain experienced several severe hazes including Beijing, the capital city of China. The haze resulted in very poor visibility and it was clearly associated with high PM2.5 mass concentration. The hourly PM2.5 mass concentration measured by Tapered Element Oscillating Microbalance (TEOM) during these episodes was as high as 828µg/m3, and offline 24-h average PM2.5 mass concentration also showed the highest value as 500µg/m3. Characteristics and sources of organic aerosol during these high PM2.5 pollution episodes were discussed. Offline filter samples were analyzed for organic carbon (OC), elemental carbon (EC) by the Sunset ECOC analyzer and various individual organic compounds including some important tracers for carbonaceous aerosol by gas chromatography-mass spectrometry (GC-MS). OC, one of the most important major components in PM2.5, varied from 4 to 80µg/m3. OC concentration increased during haze episode days but its relative importance in PM2.5 decreased (a lower percentage). OC/EC ratio ranged from 2.7 to 10.9, which showed higher influence by secondary organic aerosol during haze periods. The result agreed well with the estimate of secondary organic aerosol from the organic tracer-based method. The contributions of various sources to primary and secondary organic aerosol during our study period were estimated. Sources of primary OA (e.g. dust, biomass burning, coal combustion, vehicular emission etc.) were quantified by the chemical mass balance (CMB) model. Sources of secondary organic aerosols were estimated based on the tracer method with SOA from different VOCs precursors (e.g. isoprene, α-pinene, ß-caryophyllene, and toluene). Our findings indicate that these haze periods were associated with high relative humidity, and inorganic ions such as sulfate, nitrate and ammonium increased significantly and became more important in PM2.5. During these haze events, organic aerosol was dominated by secondary organic aerosol while in clean days, primary organic aerosol was more important in OA, providing supportive evidence that secondary components played a very important role in haze episodes.