MATHEMATICAL-MODEL FOR GAS-PARTICLE PARTITIONING OF SECONDARY ORGANICAEROSOLS

A dynamic model is developed for gas-particle absorptive partitioning of semi-volatile organic aerosols. The model is applied to simulate a pair of m-xylene/NOx outdoor smog chamber experiments. In the presence of an inorganic seed aerosol a threshold for aerosol formation is pre dicted. An examination of characteristic times suggests conditions whe re an assumption of instantaneous gas-particle equilibrium is justifie d. Semi-volatile products that are second-generation, rather than firs t-generation, products of a parent hydrocarbon cause a delay in aeroso l formation due to the delayed rate at which the second-generation pro ducts are formed. The gas-particle accommodation coefficient is the pr incipal transport parameter and is estimated to have a value between 1 .0 and 0.1 for the m-xylene aerosol. (C) 1997 Elsevier Science Ltd.