MODELLING OF PARTICLE FORMATION FROM NO3 OXIDATION OF SELECTED MONOTERPENES

A model, containing homogeneous homomolecular nucleation, condensation/evaporation and coagulation was used to reproduce aerosol size distributions measured during nitrate radical-initiated oxidation of selected monoterpenes. One set of parameters was fitted for each terpene to represent experiments at different concentration levels. The model accounts for the main aspects of particle formation and growth. Nucleation rate and yield of condensable products, in essence, control the appearance of size distributions. In order to obtain the necessary nucleation rates, at least a small yield of one product with a vapour pressure in the 10^7-10^-8Pa region is needed. Nucleation rates were estimated from total particle concentration measurements and parameters of the classical nucleation theory were fitted to the data by help of the model. Apparent vapour pressures of the main condensing products from (alpha)-pinene, (beta)-pinene and (delta)3-carene were estimated from aerosol yields obtained from experiments and found to fall in the 10^4Pa region.