期刊
ENVIRONMENTAL SCIENCE & TECHNOLOGY
卷 51, 期 2, 页码 762-770出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.6b04498
关键词
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资金
- National Natural Science Foundation of China [41575120]
- National Key Basic Research Program of China [2014CB447900]
- Strategic Priority Research Program (B) of the Chinese Academy of Sciences [XDB05020501]
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 (O-x = O-3 + NO2) during periods of photochemical production (R-2 = 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.
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