AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Chemical Characterization of Submicron Aerosol Particles and Light Extinction Apportionment before and during Heating Season in Beijing, China
QINGQING WANG, Yele Sun, Qi Jiang, Wei Du, Chengzhu Sun, Pingqing Fu, Zifa Wang, Institute of Atmospheric Physics, CAS
Abstract Number: 158 Working Group: Combustion
Abstract Despite extensive efforts into characterization of the sources and formation mechanisms of severe haze pollution in the megacity of Beijing, the response of aerosol composition and optical properties to coal combustion emissions in the heating season remain poorly understood. Here, we conducted a 3-month real-time measurement of submicron aerosol (PM1) composition by an Aerosol Chemical Speciation Monitor and particle light extinction by a Cavity Attenuated Phase Shift extinction monitor in Beijing, China from 1 October to 31 December 2012. The average (±σ) PM1 concentration was 82.4 (±73.1) µg/m3 during heating period (HP, 15 November – 31 December), which was nearly 50% higher than that before HP (1 October – 14 November). While nitrate and secondary organic aerosol (SOA) showed relatively small changes, organics, sulfate and chloride were observed to have significant increases during HP, indicating the dominant impacts of coal combustion sources on these three species. The relative humidity - dependent composition further illustrated an important role of aqueous-phase processing for the sulfate enhancement during HP. We also observed great increases of hydrocarbon-like OA (HOA) and coal combustion OA (CCOA) during HP, which was attributed to higher emissions at lower temperatures and coal combustion emissions, respectively. The relationship between light extinction and chemical composition was investigated using a multiple linear regression model. Our results showed that the largest contributor to particle extinction was ammonium nitrate (32%) and ammonium sulfate (28%) before and during HP, respectively. In addition, the contributions of SOA and primary OA to particle light extinction were quantified. The results showed that the OA extinction was mainly caused by SOA before HP, and by SOA and CCOA during HP, yet with small contributions from HOA and cooking aerosol for the entire study period. Our results elucidate substantial changes of aerosol composition, formation mechanisms, and optical properties due to coal combustion emissions and meteorological changes in the heating season.