Modeling organic aerosol from the oxidation of α-pinene in a Potential Aerosol Mass (PAM) chamber 1Department of Meteorology, Pennsylvania State University, University Park, PA, USA
15 May 2013
2Chemistry Department, Boston College, Chestnut Hill, MA, USA
3Aerodyne Research Inc., Billerica, MA, USA
Received: 09 January 2013 – Published in Atmos. Chem. Phys. Discuss.: 25 January 2013 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.
Revised: 22 April 2013 – Accepted: 23 April 2013 – Published: 15 May 2013
Citation: Chen, S., Brune, W. H., Lambe, A. T., Davidovits, P., and Onasch, T. B.: Modeling organic aerosol from the oxidation of α-pinene in a Potential Aerosol Mass (PAM) chamber, Atmos. Chem. Phys., 13, 5017-5031, doi:10.5194/acp-13-5017-2013, 2013.