Journal
ATMOSPHERIC ENVIRONMENT
Volume 45, Issue 2, Pages 318-325Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.atmosenv.2010.10.021
Keywords
Acid catalyzed reaction; OC; EC; WSOC; Acidity; SOA
Funding
- National Basic Research Program of China [2005CB422203]
- Hong Kong Polytechnic University [1-BB94, G-YX0K]
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Although laboratory studies suggest that aerosol acidity ([H+]) significantly enhances the production of secondary organic aerosol (SOA) through heterogeneous chemistry, field studies have provided limited evidence of such enhancement. In this study, correlation of strong aerosol acidity with WSOC was investigated using the 24-hr PM2.5 samples collected at sites near four major cities of China - Beijing (BJ), Shanghai (SH), Lanzhou (LZ), and Guangzhou (GZ) - during the summers of 2004-2006. PM2.5 samples were characterized by high atmospheric loadings of PM2.5, OC, EC, sulfate, nitrate, aerosol acidity, and aerosol-water, especially in Beijing and Shanghai. On average, OC and EC were distributed in the ratio of approximately 2:1 among carbonaceous aerosols (TC = OC + EC) in all four cities. However, the WSOC fraction in DC differed across the four cities (BJ similar to 55% of OC; SH similar to 35%; LZ similar to 40%; GZ similar to 32%). We found an increased WSOC content in organic carbon (OC) fraction in the samples with elevated aerosol acidity (H+) and the WSOC was thought to be influenced by aerosol acidity. The WSOC/OC ratio showed a strong positive correlation with the normalized strong acid concentration ([H+]/[OC]) in the four cities. The higher WSOC fraction in DC at higher strong acidity is postulated to be linked to the conversion of DC to WSOC via heterogeneous acid-catalyzed chemistry. (C) 2010 Elsevier Ltd. All rights reserved.
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