Issues in aerosol dynamics

Abstract

Aerosol systems evolved in time due to coagulation, evaporation and condensation, nucleation, and chemical reactions. Theoretical descriptions of the dynamics of aerosol systems require a thorough understanding of the physical and chemical processes involved. In many cases of practical interest, the fundamental processes are now well enough understood that quantitative predictions of aerosol properties can be made. Still, many questions central to aerosol science remain unresolved. Homogeneous nucleation has been the subject of many investigations over the years, yet the established theories are unable to predict the nucleation rate within orders of magnitude. Models of coagulation are generally predicated on the assumption that particles coalesce immediately after they agglomerate, yet many aerosols under study today consist of solid particles. When solid particles formed by vapor nucleation coagulate, low density flocs are generated. The structures of these particles are remarkably similar for a broad spectrum of particles formed in widely different systems and from materials with significantly different properties. Some aspects of this similarity are explained by models of diffusion limited aggregation and fractals, but these models cannot explain why the different agglomerates have similar fine scale structure sizes. Many aerosol systems involve complex interactions between the particulate material and the surrounding atmosphere. The solution thermodynamics of the concentrated solutions that occur in aqueous atmospheric aerosols has received relatively little attention.

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