Modeling organic aerosol from the oxidation of α-pinene in a Potential Aerosol Mass (PAM) chamber

S. Chen, W. H. Brune, A. T. Lambe, P. Davidovits, T. B. Onasch

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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.

Original languageEnglish (US)
Pages (from-to)5017-5031
Number of pages15
JournalAtmospheric Chemistry and Physics
Volume13
Issue number9
DOIs
StatePublished - May 15 2013

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All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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