Modelling the formation of organic particles in the atmosphere

T. Anttila (1, 2) , V.-M. Kerminen (1) , M. Kulmala (2) , A. Laaksonen (3) , C. O'Dowd (4)

1 FMI - Finnish Meteorological Institute
2 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
3 University of Kuopio
4 Department of Experimental Physics

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.

Domaines: Océan, Atmosphère

T. Anttila, V.-M. Kerminen, M. Kulmala, A. Laaksonen, C. O'Dowd. Modelling the formation of organic particles in the atmosphere. Atmospheric Chemistry and Physics Discussions, 2003, 3 (6), pp.6147-6178. ⟨hal-00301396⟩