An Attempt for Obtaining the Aerosol Size Distribution

Abstract

A method is proposed for the detection of the size distribution of atmospheric aerosols that have a radius from 5×10^-7 to 5×10^-6cm.
To make a charge equilibrium of aerosols in which the fraction of charged particles depends on the size of the aerosols, the sample air containing the aerosols was irradiated with Po²¹⁰ (α ray, approximately 100μ Ci) and the ion mobility distributions were obtained by the ion analyzer.
The relation between the size (electrical mobility) and the charged fraction of the aerosols irradiated with Po²¹⁰ was measured. From the result it was known that the Boltzmann distribution law was not valid for the small size.
On the basis of this result, the ion mobility distribution was transferred to the size distribution of the particles. This irradiation method was applied to the measurement of diurnal variation in the size distribution in the urban atmosphere.