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Proc Natl Acad Sci U S A

Title:		Quantitative constraints on autoxidation and dimer formation from direct probing of monoterpene-derived peroxy radical chemistry
Author(s):		Zhao Y; Thornton JA; Pye HOT;
Address:		"School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; yuezhao20@sjtu.edu.cn thornton@atmos.washington.edu. Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195. Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195; yuezhao20@sjtu.edu.cn thornton@atmos.washington.edu. National Exposure Research Laboratory, US Environmental Protection Agency, Research Triangle Park, NC 27711"
Journal Title:		Proc Natl Acad Sci U S A
Year:		2018
Volume:		20181109
Issue:		48
Page Number:		12142 - 12147
DOI:		10.1073/pnas.1812147115
ISSN/ISBN:		1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking)
Abstract:		"Organic peroxy radicals (RO(2)) are key intermediates in the atmospheric degradation of organic matter and fuel combustion, but to date, few direct studies of specific RO(2) in complex reaction systems exist, leading to large gaps in our understanding of their fate. We show, using direct, speciated measurements of a suite of RO(2) and gas-phase dimers from O(3)-initiated oxidation of alpha-pinene, that approximately 150 gaseous dimers (C(16-20)H(24-34)O(4-13)) are primarily formed through RO(2) cross-reactions, with a typical rate constant of 0.75-2 x 10(-12) cm(3) molecule(-1) s(-1) and a lower-limit dimer formation branching ratio of 4%. These findings imply a gaseous dimer yield that varies strongly with nitric oxide (NO) concentrations, of at least 0.2-2.5% by mole (0.5-6.6% by mass) for conditions typical of forested regions with low to moderate anthropogenic influence (i.e., /=1 s(-1), respectively, confirming both oxidation pathways produce HOM efficiently, even at higher NO concentrations typical of urban areas. Thus, gas-phase dimer formation and RO(2) autoxidation are ubiquitous sources of low-volatility organic compounds capable of driving atmospheric particle formation and growth"
Keywords:		autoxidation dimers monoterpenes particle formation peroxy radicals;
Notes:		"PubMed-not-MEDLINEZhao, Yue Thornton, Joel A Pye, Havala O T eng Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2018/11/11 Proc Natl Acad Sci U S A. 2018 Nov 27; 115(48):12142-12147. doi: 10.1073/pnas.1812147115. Epub 2018 Nov 9"