Uncertainties in SOA Formation from the Photooxidation of α-pinene

Monday, 14 December 2015: 10:45
3004 (Moscone West)
Renee McVay1, Xuan Zhang1, Bernard Aumont2, Richard Valorso2, Marie Camredon3, Stéphanie La3 and John Seinfeld1, (1)California Institute of Technology, Pasadena, CA, United States, (2)University Paris-Est Créteil Val de Marne, Créteil Cedex, France, (3)LISA, UMR CNRS 7583, Universités Paris Est Creteil et Paris Diderot, France, Créteil, France
Explicit chemical models such as GECKO-A (the Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) enable detailed modeling of gas-phase photooxidation and secondary organic aerosol (SOA) formation. Comparison between these explicit models and chamber experiments can provide insight into processes that are missing or unknown in these models. GECKO-A is used to model seven SOA formation experiments from α-pinene photooxidation conducted at varying seed particle concentrations with varying oxidation rates. We investigate various physical and chemical processes to evaluate the extent of agreement between the experiments and the model predictions. We examine the effect of vapor wall loss on SOA formation and how the importance of this effect changes at different oxidation rates. Proposed gas-phase autoxidation mechanisms are shown to significantly affect SOA predictions. The potential effects of particle-phase dimerization and condensed-phase photolysis are investigated. We demonstrate the extent to which SOA predictions in the α-pinene photooxidation system depend on uncertainties in the chemical mechanism.