ABSTRACT

Particles abound in the atmosphere, ranging in size from approximately one-half millimeter (the size of sand or drizzle) down to molecular dimensions. Atmospheric particles are made up of an amazing variety of materials and discrete objects that may consist of either solids or liquid droplets. A number of terms are commonly used to describe atmospheric particles; the more important of these are summarized in Table 9.1. Particulates is a term that has come to stand for particles in the atmosphere, although particulate matter or simply particles is preferred usage.