Articles | Volume 17, issue 12
Atmos. Chem. Phys., 17, 7345–7364, 2017
https://doi.org/10.5194/acp-17-7345-2017

Special issue: The Modular Earth Submodel System (MESSy) (ACP/GMD inter-journal...

Atmos. Chem. Phys., 17, 7345–7364, 2017
https://doi.org/10.5194/acp-17-7345-2017

Research article 20 Jun 2017

Research article | 20 Jun 2017

Global-scale combustion sources of organic aerosols: sensitivity to formation and removal mechanisms

Alexandra P. Tsimpidi1, Vlassis A. Karydis1, Spyros N. Pandis2,3, and Jos Lelieveld1,4 Alexandra P. Tsimpidi et al.
  • 1Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz, Germany
  • 2Department of Chemical Engineering, University of Patras, Patras, Greece
  • 3Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
  • 4Energy, Environment and Water Research Center, Cyprus Institute, Nicosia, Cyprus

Abstract. Organic compounds from combustion sources such as biomass burning and fossil fuel use are major contributors to the global atmospheric load of aerosols. We analyzed the sensitivity of model-predicted global-scale organic aerosols (OA) to parameters that control primary emissions, photochemical aging, and the scavenging efficiency of organic vapors. We used a computationally efficient module for the description of OA composition and evolution in the atmosphere (ORACLE) of the global chemistry–climate model EMAC (ECHAM/MESSy Atmospheric Chemistry). A global dataset of aerosol mass spectrometer (AMS) measurements was used to evaluate simulated primary (POA) and secondary (SOA) OA concentrations. Model results are sensitive to the emission rates of intermediate-volatility organic compounds (IVOCs) and POA. Assuming enhanced reactivity of semi-volatile organic compounds (SVOCs) and IVOCs with OH substantially improved the model performance for SOA. The use of a hybrid approach for the parameterization of the aging of IVOCs had a small effect on predicted SOA levels. The model performance improved by assuming that freshly emitted organic compounds are relatively hydrophobic and become increasingly hygroscopic due to oxidation.

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We analyzed the sensitivity of model-predicted global-scale OA to parameters and assumptions that control primary emissions, photochemical aging, and the scavenging efficiency of LVOCs, SVOCs, and IVOCs. The simulated OA concentrations were evaluated against a global dataset of AMS measurements. According to our analysis, a combination of increased IVOCs and decreased hygroscopicity of the freshly emitted IVOCs can help reduce discrepancies between simulated SOA and observed OOA concentrations.
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