Evaluation of a detailed model of secondary organic aerosol formation from α-pinene against dark ozonolysis experiments

BOREAM a detailed model for the gas-phase oxidation of alpha-pinene and Its subsequent formation of Secondary Organic Aerosol (SOA) is tested against a large set of SOA yield measurements obtained in dark ozonolysis experiments For the majority of experiments modelled SOA yields are found to agree with measured yields to within a factor 2 However the comparisons point to a general underestimation of modelled SOA yields at high temperatures (above 30 C) reaching an order of magnitude or more in the worst cases whereas modelled SOA yields are often overestimated at lower temperature (by a factor of about 2) Comparisons of results obtained using four different vapour pressure prediction methods indicate a strong sensitivity to the choice of the method although the overestimated temperature dependence of the yields is found in all cases Accounting for non-ideality of the aerosol mixture (based on an adapted UNIFAC method) has significant effects especially at low yields Our simulations show that the formation of oligomers through the gas-phase reactions of Stabilised Criegee Intermediates (SCI) with other molecular organic products could increase the SOA yield significantly only at very low relative humidity (below 1%) Further tests show that the agreement between model and measurements is improved when the ozonolysis mechanism includes additional production of non-volatile compounds (c) 2010 Elsevier Ltd All rights reserved