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Volume 18, issue 12 | Copyright
Atmos. Chem. Phys., 18, 8469-8489, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 18 Jun 2018

Research article | 18 Jun 2018

Source apportionment of organic aerosol from 2-year highly time-resolved measurements by an aerosol chemical speciation monitor in Beijing, China

Yele Sun1,2,3, Weiqi Xu1,3, Qi Zhang4, Qi Jiang1,a, Francesco Canonaco5, André S. H. Prévôt5, Pingqing Fu1,2,3, Jie Li1, John Jayne6, Douglas R. Worsnop6, and Zifa Wang1,2,3 Yele Sun et al.
  • 1State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
  • 2Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
  • 4Department of Environmental Toxicology, University of California, 1 Shields Ave., Davis, CA 95616, USA
  • 5Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen PSI 5232, Switzerland
  • 6Aerodyne Research, Inc., Billerica, MA 01821, USA
  • anow at: National Meteorological Centre, Beijing 100081, China

Abstract. Organic aerosol (OA) represents a large fraction of submicron aerosols in the megacity of Beijing, yet long-term characterization of its sources and variations is very limited. Here we present an analysis of in situ measurements of OA in submicrometer particles with an aerosol chemical speciation monitor (ACSM) for 2 years from July 2011 to May 2013. The sources of OA are analyzed with a multilinear engine (ME-2) by constraining three primary OA factors including fossil-fuel-related OA (FFOA), cooking OA (COA), and biomass burning OA (BBOA). Two secondary OAs (SOA), representing a less oxidized oxygenated OA (LO-OOA) and a more oxidized (MO-OOA), are identified during all seasons. The monthly average concentration OA varied from 13.6 to 46.7µgm−3 with a strong seasonal pattern that is usually highest in winter and lowest in summer. FFOA and BBOA show similarly pronounced seasonal variations with much higher concentrations and contributions in winter due to enhanced coal combustion and biomass burning emissions. The contribution of COA to OA, however, is relatively stable (10–15%) across different seasons, yet presents significantly higher values at low relative humidity levels (RH<30%), highlighting the important role of COA during clean periods. The two SOA factors present very different seasonal variations. The pronounced enhancement of LO-OOA concentrations in winter indicates that emissions from combustion-related primary emissions could be a considerable source of SOA under low-temperature (T) conditions. Comparatively, MO-OOA shows high concentrations consistently at high RH levels across different T levels, and the contribution of MO-OOA to OA is different seasonally with lower values occurring more in winter (30–34%) than other seasons (47–64%). Overall, SOA ( = LO-OOA+MO-OOA) dominates OA composition during all seasons by contributing 52–64% of the total OA mass in the heating season and 65–75% in non-heating seasons. The variations in OA composition as a function of OA mass loading further illustrate the dominant role of SOA in OA across different mass loading scenarios during all seasons. However, we also observed a large increase in FFOA associated with a corresponding decrease in MO-OOA during periods with high OA mass loadings in the heating season, illustrating an enhanced role of coal combustion emissions during highly polluted episodes. Potential source contribution function analysis further shows that the transport from the regions located to the south and southwest of Beijing within  ∼ 250km can contribute substantially to high FFOA and BBOA concentrations in the heating season.

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Short summary
We present a 2–year analysis of organic aerosol (OA) from highly time–resolved measurements by an aerosol chemical speciation monitor in the megacity of Beijing. The sources of OA were analyzed with the advanced factor analysis of a multilinear engine (ME-2). Our results showed very different seasonal patterns, relative humidity and temperature dependence, and sources regions among different OA factors. The sources and processes of OA factors, and their roles in haze pollution are elucidated.
We present a 2–year analysis of organic aerosol (OA) from highly time–resolved measurements...