Parametric study of selective removal of atmospheric aerosol by coagulation, condensation and gravitational settling.

This work studies the scavenging efficiencies of aerosol particles after a given mechanism of removal (coagulation, heterogeneous nucleation and gravitational settling) as a function of time. It also analyses the health impact of the aerosol before and after the above dynamic mechanisms by comparing the respirable dust fractions. The well-known equations of scavenging are applied to three atmospheric environments (clear, hazy and urban) that represent the aerosol PSDs in the countryside, industry and the city, respectively. From this study it is inferred that respirable dust is hardly scavenged and when compared with the initial volume of respirable aerosol, roughly 10% remains after 18 h of gravitational settling. Therefore, gravitational settling is the main removal mechanism of respirable aerosol compared to condensation and coagulation and is almost six times better than rainout.