Air pollution surveillance systems.

Atmospheric surveillance is necessary in order to identify airborne pollutants, to establish ambient concentrations of these pollutants, and to record their trends and patterns. Air pollutants may occur in the form of gases, liquids, and solids, both singly and in combination. Gaseous pollutants make up about 90 percent of the total mass emitted to the atmosphere with particulates and aerosols accounting for the remaining 10 percent. Small particulates are of particular importance because they may be in the respirable size range. These small particles may contain biologically active elements and compounds. Furthermore, they tend to remain in the atmosphere where they interfere with both solar and terrestrial infrared radiation, which may affect climate on a global basis.