Atmos. Chem. Phys. Discuss., 13, 2759-2793, 2013
www.atmos-chem-phys-discuss.net/13/2759/2013/
doi:10.5194/acpd-13-2759-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Modeling organic aerosol from the oxidation of α-pinene in a Potential Aerosol Mass (PAM) chamber
S. Chen1, W. H. Brune1, A. Lambe2,3, P. Davidovits2, and T. Onasch2,3
1Department of Meteorology, Pennsylvania State University, University Park, PA, USA
2Chemistry Department, Boston College, Chestnut Hill, MA, USA
3Aerodyne Research Inc., Billerica, MA, USA

Abstract. A model has been developed to simulate the formation and evolution of secondary organic aerosol (SOA) and was tested against data produced in a Potential Aerosol Mass (PAM) flow reactor and a large environmental chamber. The model framework is based on the two-dimensional volatility basis set approach (2D-VBS), in which SOA oxidation products in the model are distributed on the 2-D space of effective saturation concentration (Ci*) and oxygen-to-carbon ratio (O : C). The modeled organic aerosol mass concentrations (COA) and O : C agree with laboratory measurements within estimated uncertainties. However, while both measured and modeled O : C increase with increasing OH exposure as expected, the increase of modeled O : C is rapid at low OH exposure and then slows as OH exposure increases while the increase of measured O : C is initially slow and then accelerates as OH exposure increases. A global sensitivity analysis indicates that modeled COA values are most sensitive to the assumed values for the number of Ci* bins, the heterogeneous OH reaction rate coefficient, and the yield of first-generation products. Modeled SOA O : C values are most sensitive to the assumed O : C of first-generation oxidation products, the number of Ci* bins, the heterogeneous OH reaction rate coefficient, and the number of O : C bins. All these sensitivities vary as a function of OH exposure. The sensitivity analysis indicates that the 2D-VBS model framework may require modifications to resolve discrepancies between modeled and measured O : C as a function of OH exposure.

Citation: Chen, S., Brune, W. H., Lambe, A., Davidovits, P., and Onasch, T.: Modeling organic aerosol from the oxidation of α-pinene in a Potential Aerosol Mass (PAM) chamber, Atmos. Chem. Phys. Discuss., 13, 2759-2793, doi:10.5194/acpd-13-2759-2013, 2013.
 
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