An experimental study of the scavenging of aerosol particles by natural snow crystals

Abstract

An experimental study of the scavenging of aerosol particles of mean radius 0.75 μm by natural snow crystals of a few millimeters is carried out. Aerosol particles are spherical indium acetylacetonate particles generated by a modified La Mer generator. Snow crystals are obtained during natural snowfalls. Shapes of snow crystals include needles, columns, broad-branched crystals, stellar crystals, and hexagonal plates. Aerosol particles are dispersed into an aerosol chamber and snow crystals fall through the chamber to scavenge aerosol particles. The collection efficiency of aerosol particles by snow crystals is found to decrease with increasing crystal size for all shapes. This can be explained by the relative strength of the inertial force of particles and the hydrodynamic drag force created by the fall of the snow crystal. Larger crystals would create greater drags during the fall and force the aerosol particles to follow more closely to streamlines and hence reduce the collection efficiency.