AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Effect of Functional Groups on Composition and Yields of SOA Formed from Reactions of VOCs with OH Radicals in the Presence of NOx
LUCAS ALGRIM, Paul Ziemann, University of Colorado
Abstract Number: 480 Working Group: Aerosol Chemistry
Abstract In a series of environmental chamber experiments we have identified major products and measured the yields of secondary organic aerosol (SOA) formed from the reactions of C$_(12) ketone, C$_(10) alcohol, and C$_(10) nitrate position-isomers with OH radicals in the presence of NO$_x . Gas- and particle-phase products were analyzed using real-time and offline mass spectrometry as well as gas and liquid chromatography. Although particle composition was similar for different VOC isomers containing a particular functional group, SOA yields depended on functional group position on the carbon chain. The effect of functional groups on yields can be explained by differences in vapor pressures of parent VOCs and the fate of alkoxy radical intermediates. For example, in the case of ketones important observed differences from alkane chemistry were enhanced decomposition via alpha-cleavage from alpha-ketoalkoxy radicals, and the ability of the added keto group to allow particle-phase cyclic hemiacetal formation. Results also indicate that both 1,5- and 1,6-H shift isomerizations are significantly hindered when the keto group is part of the transition state ring. Effects of hydroxyl and nitrooxy groups have also been determined and will be discussed. These results will be used to help evaluate and improve VOC oxidation and SOA formation mechanisms and models used to predict SOA formation in the atmosphere.