In-cloud processes of methacrolein~under simulated conditions - Part 2: Formation of Secondary Organic Aerosol

• Published in: Atmospheric chemistry and physics discussions Vol. 9; no. 2; pp. 6425 - 6449
• Main Authors: Haddad, IEl, Liu, Y, Nieto-Gligorovski, L, Michaud, V, Temime-Roussel, B, Quivet, E, Marchand, N, Sellegri, K, Monod, A
• Format: Journal Article
• Language: English
• Published: 10.03.2009
• ISSN: 1680-7367; 1680-7375

The fate of methacrolein in cloud evapo-condensation cycles was experimentally investigated. To this end, aqueous-phase reactions of methacrolein with OH radicals were performed (as described in Liu et al., 2009), and the obtained solutions were then nebulized and dried into a mixing chamber. The ESI-MS and ESI-MS/MS analyses of the aqueous phase composition denoted the formation of high molecular weight multifunctional products containing hydroxyl, carbonyl and carboxylic acid moieties. The time profiles of these products suggest that their formation can imply radical pathways. These high molecular weight organic products are certainly responsible for the formation of SOA observed during the nebulization experiments. The size, number and mass concentration of these particles increased significantly with the reaction time: after 22 h of reaction, the aerosol mass concentration was about three orders of magnitude higher than the initial aerosol quantity. The evaluated SOA yield ranged from 2 to 12%. This provides, for the first time to our knowledge, strong experimental evidence that cloud processes can act as important contributors to secondary organic aerosol formation in the troposphere. The hygroscopic properties of these secondary organic aerosols are analysed in Michaud et al. (2009).