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J Phys Chem A

Title:		Radical product yields from the ozonolysis of short chain alkenes under atmospheric boundary layer conditions
Author(s):		Alam MS; Rickard AR; Camredon M; Wyche KP; Carr T; Hornsby KE; Monks PS; Bloss WJ;
Address:		"School of Geography, Earth & Environmental Sciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K"
Journal Title:		J Phys Chem A
Year:		2013
Volume:		20131115
Issue:		47
Page Number:		12468 - 12483
DOI:		10.1021/jp408745h
ISSN/ISBN:		1520-5215 (Electronic) 1089-5639 (Linking)
Abstract:		"The gas-phase reaction of ozone with unsaturated volatile organic compounds (VOCs), alkenes, is an important source of the critical atmospheric oxidant OH, especially at night when other photolytic radical initiation routes cannot occur. Alkene ozonolysis is also known to directly form HO2 radicals, which may be readily converted to OH through reaction with NO, but whose formation is poorly understood. We report a study of the radical (OH, HO2, and RO2) production from a series of small alkenes (propene, 1-butene, cis-2-butene, trans-2-butene, 2-methylpropene, 2,3-dimethyl-2-butene (tetramethyl ethene, TME), and isoprene). Experiments were performed in the European Photoreactor (EUPHORE) atmospheric simulation chamber, with OH and HO2 levels directly measured by laser-induced fluorescence (LIF) and HO2 + SigmaRO2 levels measured by peroxy-radical chemical amplification (PERCA). OH yields were found to be in good agreement with the majority of previous studies performed under comparable conditions (atmospheric pressure, long time scales) using tracer and scavenger approaches. HO2 yields ranged from 4% (trans-2-butene) to 34% (2-methylpropene), lower than previous experimental determinations. Increasing humidity further reduced the HO2 yields obtained, by typically 50% for an RH increase from 0.5 to 30%, suggesting that HOx production from alkene ozonolysis may be lower than current models suggest under (humid) ambient atmospheric boundary layer conditions. The mechanistic origin of the OH and HO2 production observed is discussed in the context of previous experimental and theoretical studies"
Keywords:		Alkenes/*chemistry Atmosphere/*chemistry Hydroxyl Radical/*chemical synthesis/chemistry Molecular Structure Ozone/*chemistry Peroxides/*chemical synthesis/chemistry;
Notes:		"MedlineAlam, Mohammed S Rickard, Andrew R Camredon, Marie Wyche, Kevin P Carr, Timo Hornsby, Karen E Monks, Paul S Bloss, William J eng Research Support, Non-U.S. Gov't 2013/11/01 J Phys Chem A. 2013 Nov 27; 117(47):12468-83. doi: 10.1021/jp408745h. Epub 2013 Nov 15"