AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Characteristics and Sources of Submicron Aerosols above Urban Canopy (260 m) in Urban Beijing, China during 2014 APEC Summit
CHEN CHEN, Wei Du, Weiqi Xu, Zifa Wang, Tingting Han, Qingqing Wang, Zhiqiu Gao, Yele Sun, Inst. of Atmospheric Physics, Chinese Academy of Sciences
Abstract Number: 165 Working Group: Urban Aerosols
Abstract Beijing, the capital of China, experiences frequent severe haze pollution in recent years. Despite extensive efforts in characterization of fine particles at ground surface, real-time characterization of aerosol particle composition above urban canopy has never been performed in megacity Beijing. Here we conducted the first real-time measurements of submicron aerosol composition using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM) at 260 m on a 325-m meteorological tower from 5 October to 12 November, 2014. Simultaneously, a High-resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed at the ground surface to measure size-resolved non-refractory submicron aerosol composition at the same location. The Asia-Pacific Economic Cooperation (APEC) summit with the most strict emission controls in Beijing and surrounding regions provides a great opportunity to study the impacts of emission controls on aerosol chemistry. The measurements above canopy are ideal to evaluate the roles of emission controls in reducing particulate matter levels by minimizing the influences of local point sources. The average mass concentration of NR-PM$_1 showed a significant decrease from 65.8 micrograms per cubic meter to 24.8 micrograms per cubic meter during APEC, suggesting that emission controls over regional scales reduced the particulate matter levels substantially. However, the bulk NR-PM$_1 compositions was rather similar before and during APEC, both of which were dominated by organics followed by nitrate and sulfate. These results elucidate the impacts of synergistic controls of precursors over regional scales on reducing secondary organic and inorganic aerosols. In addition, the roles of meteorological conditions, particularly mountain valley breeze, in affecting PM levels were also explored. Finally, the comparisons of aerosol particle composition between the ground surface and 260 m will be discussed.