title: Effects of Aqueous-Phase and Photochemical Processing on Secondary Organic Aerosol Formation and Evolution in Beijing, China.
abstract: Secondary organic aerosol (SOA) constitutes a large fraction of OA, yet remains a source of significant uncertainties in climate models due to incomplete understanding of its formation mechanisms and evolutionary processes. Here we evaluated the effects of photochemical and aqueous-phase processing on SOA composition and oxidation degrees in three seasons in Beijing, China, using high-resolution aerosol mass spectrometer measurements along with positive matrix factorization. Our results show that aqueous-phase processing has a dominant impact on the formation of more oxidized SOA (MO-OOA), and the contribution of MO-OOA to OA increases substantially as a function of relative humidity or liquid water content. In contrast, photochemical processing plays a major role in the formation of less oxidized SOA (LO-OOA), as indicated by the strong correlations between LO-OOA and odd oxygen (Ox= O3+ NO2) during periods of photochemical production (R2= 0.59-0.80). Higher oxygen-to-carbon ratios of SOA during periods with higher RH were also found indicating a major role of aqueous-phase processing in changing the oxidation degree of SOA in Beijing. Episodes analyses further highlight that LO-OOA plays a more important role during the early stage of the formation of autumn/winter haze episodes while MO-OOA is more significant during the later evolution period.
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Weiqi
authors.initials: W
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Tingting
authors.initials: T
authors.lastname: Han
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Du
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology , Nanjing 210044, China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.
authors.forename: Pingqing
authors.initials: P
authors.lastname: Fu
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.
authors.forename: Zifa
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Aerodyne Research, Inc. , Billerica, Massachusetts 01821, United States.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
authors.affiliation: State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences , Beijing 100029, China.|Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences , Xiamen 361021, China.|Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology , Nanjing 210044, China.
authors.forename: Yele
authors.identifier: 0000-0003-2354-0221
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000336:Aerosols; D000393:Air Pollutants; D000068476:Beijing; D002681:China; D009930:Organic Chemicals / Q000737:chemistry*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D009930:Organic Chemicals