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A re-evaluation on the atmospheric significance of octanal vapor uptake by acidic particles: Roles of particle acidity and gas-phase octanal concentration

Authors Lee, Alex K.Y. HKUST affiliated (currently or previously)
Li, Yong Jie
Lau, Arthur P.S. HKUST affiliated (currently or previously)
Chan, Chak Keung View this author's profile
Issue Date 2008
Source Aerosol science and technology , v. 42, (12), 2008, p. 992-1000
Summary An electrodynamic balance was used to investigate the uptake of octanal vapor by single sulfuric acid droplets levitated under various relative humidity (RH) conditions and gas-phase octanal concentrations. In the high octanal concentration experiments (200300 ppm), we observed that the organic mass yield depended on the acidity of the sulfuric acid droplets and significant uptake of octanal only occurred when the RH was about 10\% (H2SO4 wt\% similar to 64\%). Furthermore, repartitioning of only a portion of condensed organic compounds was observed after active dilution with octanal-free compressed air, indicating that low-volatility products had formed and that repartitioning is important in affecting the organic mass fraction and chemical composition of atmospheric organic aerosols. When a relatively lower octanal concentration (700-900 ppb) was used, no significant uptake of octanal vapor by the sulfuric acid droplets was observed even at 10\% RH with long exposure time (> 25 h). Our findings suggest that both particle acidity and gas-phase octanal concentration are the critical factors that influence the organic mass yield of levitated acidic droplets. Because of the severe conditions of low RH and high octanal conditions required to effect the reactions, the reactive uptake of aldehydes, especially those that have chemical structures and properties very similar to octanal, into acidic particles may not be an important pathway in secondary organic aerosol formation under actual atmospheric conditions.
ISSN 0278-6826
Rights This is an electronic version of an article published in Aerosol Science and Technology, v. 42, no. 12, December 2008, p. 992-1000. Aerosol Science and Technology is available online at
Language English
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