Deformation of the Size Distribution of Aerosol Particles Dispersing from Land to Ocean

Abstract

When the aerosols originated on land are dispersed over the ocean, they are not only decreased in the concentration, but deformed in the pattern of size distribution. This deformation was ascertained by the experiments aboard an observation ship in 1972 and 1974.

From the mobility spectrometry of atmospheric ions using the apparata we have developed, and the concurrent size spectrometry of large particles using a Royco Optical Counter, the whole size distribution of aerosol particles covering the radius range from 3 nm to 5 µn was determined over the cruising course of 1000 km from Tokyo.

With the aid of the result of ²²²Rn concentration measurements, the effect of dilution by the spatial dispersion was estimated. Subtracting the dilution factor from the apparent decay rate of the aerosol concentration, the residence time of aerosols was determined in relation to the particle size.

In both the expeditions in 1972 and 1974, the deformation of the size distribution was found to take place in such a way that the center of gravity of the distribution is shifted towards smaller size with the increasing age of aerosols.