Physical Behavior of Aerosol Particles

In this chapter we want to discuss the physical behavior of aerosol particles in the atmosphere. Except where noted otherwise, this discussion pertains to aerosols in general, whether radioactive or not. Foremost is the subject of the motion of aerosol particles relative to a surrounding air mass. How does an aerosol particle get from one position to another? What are the laws that control this movement? This discussion will involve two important classes of motion, which we call uniform motion and diffusive motion. There is a third major process by which aerosol particles get transported about the earth’s surface: this is by motion of the air mass itself (wind, turbulence, convective air currents, fan-induced circulation, etc.). However, motion of air masses is really a separate subject since it is not directly dependent on their aerosol content. The effect of such motion on aerosol transport will be left for discussion in later chapters.