Yield of SO 2 and formation of aerosol in the photo-oxidation of DMS under atmospheric conditions

Abstract

Photo-oxidation of DMS under atmospheric conditions was studied both in dry ( [H 2O] < 1 ppm ) and in humid air (relative humidity ~ 35%at 30°C). Yield of SO 2was 21 ± 5% at the early stage of reaction and finally increased to 29 ± 7%. Formation of aerosols were also measured. In dry air number concentration of aerosols was low (max. ~ 3.0 × 10 -3 cm −3 ). but geometrical mean diameter was large (~ 0.4 μm). In humid air number density of aerosols was high (max. ~ 3 × 10 5 cm -3 ), but geometrical mean diameter was small (~ 0.2 μm). Dimensionless parameter ( A/(N 1 3 V 2 3 ) ) was calculated to be 4.35 for the humid air system. Both methanesulfonic acid (CH 3SO 3H, MSA) and sulfuric acid were detected in sampled aerosols.