Atmos. Chem. Phys. Discuss., 3, 6147-6178, 2003
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Modelling the formation of organic particles in the atmosphere
T. Anttila1,2, V.-M. Kerminen1, M. Kulmala2, A. Laaksonen3, and C. O’Dowd4
1Finnish Meteorological Institute, Air Quality Research, Sahaajankatu 20E, FIN-00880 Helsinki, Finland
2University of Helsinki, Department of Physical Sciences, P.O. Box 6, FIN-00014 University of Helsinki, Helsinki, Finland
3University of Kuopio, Department of Applied Physics, P.O. Box 1627, FIN-70211, Kuopio, Finland
44Department of Experimental Physics, National University of Ireland, Galway, University Road, Galway, Ireland

Abstract. A modelling study investigating the formation of organic particles from inorganic, thermodynamically stable clusters was carried out. A recently-developed theory, the so-called nano-Köhler theory, which describes a thermodynamic equilibrium between a nanometer-size cluster, water and water-soluble organic compound, was implemented in a dynamical model along with a treatment of the appropriate aerosol and gas-phase processes. The obtained results suggest that both gaseous sulphuric acid and organic vapours contribute to organic particle formation. The initial growth of freshly-nucleated clusters having a diameter around 1 nm is driven by condensation of gaseous sulphuric acid and by a lesser extent cluster self-coagulation. After the clusters have reached sizes of around 2 nm in diameter, low-volatile organic vapours start to condense spontaneously into the clusters, thereby accelerating their growth to detectable sizes. A shortage of gaseous sulphuric acid or organic vapours limit, or suppress altogether, the particle formation, since freshly-nucleated clusters are rapidly coagulated away by pre-existing particles. The obtained modelling results were applied to explaining the observed seasonal cycle in the number of aerosol formation events in a continental forest site.

Citation: Anttila, T., Kerminen, V.-M., Kulmala, M., Laaksonen, A., and O’Dowd, C.: Modelling the formation of organic particles in the atmosphere, Atmos. Chem. Phys. Discuss., 3, 6147-6178, doi:10.5194/acpd-3-6147-2003, 2003.
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