Abstract
The concentration of aerosols during quiet snowfalls was measured by a minute particle detector of Gardner Assoc. type simultaneously with other relating factors in Sapporo in March 1972, selecting periods from midnight to early morning when the emission rate of aerosols due to human life is small and the effect of sideward divergence was negligible.
As a result, the collection efficiency of aerosols by falling snow crystals, the surface emission rate and the dissipation coefficient were determined. The values of collection efficiency determined, were several ten percent. These values are one or two order greater than expected from simple aerodynamical consideration. Accordingly it is considered that the main mechanism in which aerosols are collected by falling snow crystals is the thermal turbulence including Brownian motion and ventilation effect.
The apparent scavenging effect by snowfall was one order greater than those reported in foreign countries. The reasons for the great difference were considered.
