Estimation of the Volume Fraction of Water Soluble Material in Submicron Aerosols in the Atmosphere

Abstract

In order to obtain the knowledge of the dependence of the volume fraction of water soluble material (ε) in atmospheric aerosols on their size, an experimental study was carried out for aerosols with radii between 0.02 and 0.lμm. By means of a differential mobility separator, nearly monodisperse aerosols were extracted from the atmospheric aerosols in dry condition, and then they were humidified to grow to larger particles under some relative humidity conditions. The particle sizes before and after the humidification were measured by a second order differential mobility analyzer. From these experimental data, the value of ε was estimated as a function of particle radius on the assumption that water soluble material in particles was ammonium sulfate.
The measurements were made in December 1981 and in February 1982. It was found that the value of ε was in the range of 0.2-1, and had a tendency to increase with increasing particle radius from 0.02 to 0.lμm.