Physical, Chemical and Optical Properties of Atmospheric Aerosols

Abstract

Atmospheric aerosols are complicated suspensions of multicomponent particles of different sizes in air. This section provides an overview of the fundamental physical, chemical and optical properties of these particles. We begin with the discussion of the aerosol shape and density and we then focus on the ability of these particles to deliquesce, that is to absorb moisture from the atmosphere and grow from solid particles to aqueous droplets. The effect of the aerosol chemical composition and temperature on this hygroscopic behavior is outlined based on first thermodynamic principles. The ability of a lot of these particles to act as cloud condensation nuclei and form cloud droplets is also discussed. Aerosol particles can be viewed as atmospheric micro-reactors, that is as the medium where heterogeneous chemical reactions can take place. Our present understanding of these heterogeneous reactions is reviewed. Finally the fundamental principles governing atmospheric aerosol scattering and absorption of radiation are reviewed, including a brief description of the instrumentation used to measure these optical properties.