SIZE DISTRIBUTION OF THE URBAN AEROSOL IN VIENNA

Two instruments have been developed recently which permit to measure the size distribution of urban aerosols in the size range from 0.002 to 16 μm, a special cloud chamber and a low pressure cascade impactor. The cloud chamber is a computer-controlled condensation nuclei counter which measures aerosols in the range between 0.002 and 0.1 μm by exposing the aerosol stepwise to well-defined supersaturations; the instrument is capable of measuring the nucleation mode. The cascade impactor samples the aerosol through nine stages. The stages for the smaller sizes operate between pressure considerably below atmospheric pressure and permit the extension of the size range down to 0.06 μm providing in this way a sufficient overlap to the cloud chamber. The impactor measures the accumulation mode completely. Both instruments have been applied to the Viennese urban aerosol and the accumulation mode as well as the nucleation mode were measured. © 1979.