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Title: A re-evaluation on the atmospheric significance of octanal vapor uptake by acidic particles: roles of particle acidity and gas-phase octanal concentrations
Authors: Lee, Alex King Yin
Li, Yong Jie
Lau, Arthur P. S.
Chan, Chak-Keung
Keywords: Secondary organic aerosol (SOA)
Acid-catalyzed reaction
Sulfuric acid
Gas-particle partitioning
Issue Date: Dec-2008
Citation: Aerosol science and technology, v. 42, no. 12, December 2008, p. 992-1000
Abstract: 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 (200–300 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% ~ 64%). Furthermore, reversible partitioning of a portion of condensed organic compounds was observed after active dilution with octanal-free compressed air. This finding indicates the potential importance of repartitioning of condensed organics 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 hrs). 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.
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
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CBME Journal/Magazine Articles
IENV Journal/Magazine Articles

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