-9Attempts to interpret the data obtained by these projects have raised a steady crop of questions regarding mechanisms. The planning of the opera- tional programs has always been strongly influericed by current ideas about these mechanisms. An increasing effort is being supported by the AEC in the area of basic mechanism studies. These studies make use of radioisotopes as tracers, non= radioactive tracers such as ozone and water vapor, or the methods of classical synoptic and dynamic meteorology. The mechanisms being investigated can be grouped under: (1) global atmospheric transport and mixing processes (2) aerosol behavior including scavenging by precipitation. A list of those projects involving sampling and analysis of atmospheric radioactivity follows (Table II). DOE ARCHIVES it