Phase partitioning for different aerosol species in fog

Abstract

Simultaneous measurements of several non-volatile species in unscavenged aerosol particles and in fog droplets have revealed differences in partitioning for different chemical species. The average scavenged fraction of sulphate was 18% and the corresponding fraction of elemental carbon was only 6%. This suggests that the aerosol was externally mixed, and that the chemical mixture of the aerosol as a function of size is important in the context of nucleation scavenging. The measurements obtained could not distinguish between the two primary hypotheses for explaining the observed differences, (a) that the particles had the same size distribution and their chemical composition was the controlling factor, and (b) that the elemental carbon was associated with smaller particles than the sulphate, so that the difference in scavenging efficiency was controlled by the size distribution of the particles.