Mean residence time of radioactive aerosols in the upper layers of the atmosphere based on fallout of high-altitude tracers

Abstract

The concentrations of 109Cd in fallout and in surface air at observation points in the Soviet Union during 1964–1967 are summarized. Analysis of these data and their comparison with results from experiments on 102Rh suggest that the mean residence time of finely divided aerosols in the atmosphere above 21 km from sources above 100 km is 14 years. Analysis of the 238Pu fallout data indicates that the mean residence time of aerosols injected at about 40–60 km altitude is significantly lower, possibly about 4 years.