ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-12-4743-2012 Global modeling of SOA formation from dicarbonyls, epoxides, organic nitrates and peroxides Lin G. 1 Penner J. E. 1 Sillman S. 1 Taraborrelli D. 2 Lelieveld J. 2 3 Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA Department of Atmospheric Chemistry, Max Planck Institute for Chemistry, Mainz, Germany The Cyprus Institute, Nicosia, Cyprus 31 05 2012 12 10 4743 4774 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/12/4743/2012/acp-12-4743-2012.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/4743/2012/acp-12-4743-2012.pdf

Recent experimental findings indicate that secondary organic aerosol (SOA) represents an important and, under many circumstances, the major fraction of the organic aerosol burden. Here, we use a global 3-D model (IMPACT) to test the results of different mechanisms for the production of SOA. The basic mechanism includes SOA formation from organic nitrates and peroxides produced from an explicit chemical formulation, using partition coefficients based on thermodynamic principles together with assumptions for the rate of formation of low-volatility oligomers. We also include the formation of low-volatility SOA from the reaction of glyoxal and methylglyoxal on aqueous aerosols and cloud droplets as well as from the reaction of epoxides on aqueous aerosols. A model simulation including these SOA formation mechanisms gives an annual global SOA production of 120.5 Tg. The global production of SOA is decreased substantially to 90.8 Tg yr<sup>−1</sup> if the HO<sub>x</sub> regeneration mechanism proposed by Peeters et al. (2009) is used. Model predictions with and without this HO<sub>x</sub> (OH and HO<sub>2</sub> regeneration scheme are compared with multiple surface observation datasets, namely: the Interagency Monitoring of Protected Visual Environments (IMPROVE) for the United States, the European Monitoring and Evaluation Programme (EMEP), and aerosol mass spectrometry (AMS) data measured in both the Northern Hemisphere and tropical forest regions. All model simulations show reasonable agreement with the organic carbon mass observed in the IMPROVE network and the AMS dataset, however observations in Europe are significantly underestimated, which may be caused by an underestimation of primary organic aerosol emissions (POA) in winter and of emissions and/or SOA production in the summer. The modeled organic aerosol concentrations tend to be higher by roughly a factor of three when compared with measurements at three tropical forest sites. This overestimate suggests that more measurements and model studies are needed to examine the formation of organic aerosols in the tropics. The modeled organic carbon (OC) in the free troposphere is in agreement with measurements in the ITCT-2K4 aircraft campaign over North America and in pollution layers off Asia during the INTEX-B campaign, although the model underestimates OC in the free troposphere in comparison with the ACE-Asia campaign off the coast of Japan.

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