ESTIMATES OF RESIDENCE TIMES OF SULFATE AEROSOLS IN AMBIENT AIR

The aerodynamic size distribution of sulfates in ambient aerosol parti cles were measured using a high-resolution. submicron region low-press ure cascade impactor. In continental areas the mass (volume) distribut ion of sulfates determined by ion chromatography, was largely associat ed with submicron aerosols in the accumulation mode (0.1-2 mum) peakin g 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 lif etimes of sulfate aerosols, the residence times of 12 days applies to aerosols of approximately 0.3 mum MMAD size.