Atmospheric radioactivity along the HASL ground-level sampling network, 1968 to mid-1970, as an indicator of tropospheric and stratospheric sources

Radioactivity concentrations and activity ratios in air sampled at ground-level locations are useful in correlating the latitudinal spread of nuclear debris with a tropospheric or stratospheric source. In late 1968 and again in late 1969, China detonated a high-yield nuclear device in the northern hemisphere (40°N), and France conducted a nuclear test series (22°S) in mid-1968 and in mid-1970. An examination of the Zr-95 concentrations and Zr-95 to Ce-144 activity ratios indicates several time and space regions with similar radioactivity characteristics that can be related to one of these specific sources of debris.