OVERVIEW

The atmospheric aerosol has profound effects on the nature of the air environment. Effects on human health have led to the establishment of ambient air quality standards by the United States and other industrial nations. The optical properties of the aerosol affect local and regional visibility and Earth's radiation balance, hence global climate. There is evidence that reactions that take place on the surface of the stratospheric aerosol play a major role in the destruction of the stratospheric ozone layer. Particularly complex (and poorly understood) are the indirect effects of the aerosol serving as condensation nuclei for the formation of clouds which in turn affect the radiation balance. For an extensive review of the properties of the atmospheric aerosol and its effects, especially health related, the reader is referred to the document prepared by the U.S. EPA (1996) for use in setting the ambient air quality standard for particulate matter. Atmospheric aerosol properties and dynamics are reviewed in detail by Seinfeld and Pandis (1998).

The effects of the atmospheric aerosol are largely determined by the size and chemical composition of the individual particles and their morphology (shape and/or fractal character). For many applications, the aerosol can be characterized sufficiently by measuring the particle size distribution function and the average distribution of chemical components with respect to particle size. Particle-to-particle variations in chemical composition and particle structure are less often measured, although they may have significant effects on biochemical and nucleation phenomena. In this chapter we focus on certain important...