ESTIMATES OF RESIDENCE TIMES OF SULFATE AEROSOLS IN AMBIENT AIR

The aerodynamic size distribution of sulfates in ambient aerosol particles were measured using a high-resolution. submicron region low-pressure cascade impactor. In continental areas the mass (volume) distribution of sulfates determined by ion chromatography, was largely associated with submicron aerosols in the accumulation mode (0.1-2 mum) peaking in the 0.2-0.5 mum size range. The mass median aerodynamic diameter (MMAD) varied from 0.25 to 0.31 mum (mean 0.28 mum). The mean value of the geometric standard deviation sigma(g) was 2.06. In estimating lifetimes of sulfate aerosols, the residence times of 12 days applies to aerosols of approximately 0.3 mum MMAD size.