Index Geophysics

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

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 (<i>C</i>_<i>i</i>*) and oxygen-to-carbon ratio (O : C). The modeled organic aerosol mass concentrations (<i>C</i>_OA) 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 <i>C</i>_OA values are most sensitive to the assumed values for the number of <i>C</i>_<i>i</i>* 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 <i>C</i>_<i>i</i>* 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.

Chen, S.

Brune, W. H.

Lambe, A. T.

Davidovits, P.

Onasch, T. B.

2018-01-15

Text

application/pdf

10.5194/acp-13-5017-2013

https://acp.copernicus.org/articles/13/5017/2013/

eISSN: 1680-7324

eng