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Published July 18, 2011 | Supplemental Material + Published
Journal Article Open

Explicit modelling of SOA formation from α-pinene photooxidation: sensitivity to vapour pressure estimation


The sensitivity of the formation of secondary organic aerosol (SOA) to the estimated vapour pressures of the condensable oxidation products is explored. A highly detailed reaction scheme was generated for α-pinene photooxidation using the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Vapour pressures (Pᵛᵃᵖ) were estimated with three commonly used structure activity relationships. The values of Pᵛᵃᵖ were compared for the set of secondary species generated by GECKO-A to describe α-pinene oxidation. Discrepancies in the predicted vapour pressures were found to increase with the number of functional groups borne by the species. For semi-volatile organic compounds (i.e. organic species of interest for SOA formation), differences in the predicted Pᵛᵃᵖ range between a factor of 5 to 200 on average. The simulated SOA concentrations were compared to SOA observations in the Caltech chamber during three experiments performed under a range of NO_x conditions. While the model captures the qualitative features of SOA formation for the chamber experiments, SOA concentrations are systematically overestimated. For the conditions simulated, the modelled SOA speciation appears to be rather insensitive to the Pᵛᵃᵖ estimation method.

Additional Information

© Author(s) 2011. This work is distributed under the Creative Commons Attribution 3.0 License. Received: 24 Mar 2011 – Discussion started: 29 Mar 2011 – Revised: 28 Jun 2011 – Accepted: 08 Jul 2011 – Published: 18 Jul 2011. NCAR is sponsored by the National Science Foundation. JLT was supported and SM was supported in part by a grant from the US Department of Energy, Office of Science, ER, DE-FG02-ER63993. Edited by: G. McFiggans. The publication of this article is financed by CNRS-INSU.

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Published - acp-11-6895-2011.pdf

Supplemental Material - acp-11-6895-2011-supplement.pdf


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