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Published February 7, 2014 | Supplemental Material + Published
Journal Article Open

Secondary organic aerosol yields of 12-carbon alkanes


Secondary organic aerosol (SOA) yields were measured for cyclododecane, hexylcyclohexane, n-dodecane, and 2-methylundecane under high-NOx conditions, in which alkyl proxy radicals (RO_2) react primarily with NO, and under low-NO_x conditions, in which RO2 reacts primarily with HO2. Experiments were run until 95–100% of the initial alkane had reacted. Particle wall loss was evaluated as two limiting cases using a new approach that requires only suspended particle number-size distribution data and accounts for size-dependent particle wall losses and condensation. SOA yield differed by a factor of 2 between the two limiting cases, but the same trends among alkane precursors were observed for both limiting cases. Vapor-phase wall losses were addressed through a modeling study and increased SOA yield uncertainty by approximately 30%. SOA yields were highest from cyclododecane under both NOx conditions. SOA yields ranged from 3.3% (dodecane, low-NO_x conditions) to 160% (cyclododecane, high-NO_x conditions). Under high-NO_x conditions, SOA yields increased from 2-methylundecane < dodecane ~ hexylcyclohexane < cyclododecane, consistent with previous studies. Under low-NO_x conditions, SOA yields increased from 2-methylundecane ~ dodecane < hexylcyclohexane < cyclododecane. The presence of cyclization in the parent alkane structure increased SOA yields, whereas the presence of branch points decreased SOA yields due to increased vapor-phase fragmentation. Vapor-phase fragmentation was found to be more prevalent under high-NO_x conditions than under low-NO_x conditions. For different initial mixing ratios of the same alkane and same NO_x conditions, SOA yield did not correlate with SOA mass throughout SOA growth, suggesting kinetically limited SOA growth for these systems.

Additional Information

© 2014 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 29 June 2013; Published in Atmos. Chem. Phys. Discuss.: 7 August 2013; Revised: 13 December 2013; Accepted: 23 December 2013; Published: 7 February 2014. This work was supported by the Office of Science (Biological and Environmental Research), US Department of Energy grant DE-SC 0006626 and National Science Foundation grants AGS-1057183 and ATM-0650061. We thank M. Chan for experimental assistance and A. Matsunaga for information regarding Tenax tube preparation and sampling procedures. C. Loza, L. Yee, and J. Craven were supported by National Science Foundation Graduate Research Fellowships. Manabu Shiraiwa was supported by the Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellowship for Research Abroad. Edited by: J. B. Burkholder

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Published - acp-14-1423-2014.pdf

Supplemental Material - acp-14-1423-2014-supplement.pdf


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