Oxidation of sulphur dioxide in water droplets in the presence of ammonia

SO2 oxidation by oxygen in monodisperse water droplets was studied in a cylindrical chamber, without and in the presence of ammonia. The range of SO2 concentration was from about 10(-2) to 5 ppmv, while the NH3 input concentration was kept constant at about 4.7 x 10(-2) ppmv. The contact time between gases and droplets was 210 s. The experimental results were compared with the theoretical values predicted by the kinetics of Larson et al. (Atmos. Environ., 12 (1978) 1597) and McKay (Atmos. Environ., 5 (1971) 7). Much higher sulphate concentrations were obtained in experiments pun in the presence of NH3, as opposed to those without NH3. The experimental results agree with the values predicted by McKay's kinetics and are higher than Larson's.