Annual report of the Surface Air Sampling Program

Abstract

Measurements of the concentrations of atmospheric radionuclides in filter samples collected for the Environmental Measurements Laboratory's Surface Air Sampling Program indicate that the tropospheric concentrations of radioactive debris from nuclear weapons tests continued to decrease during 1981 to 1983. A springtime peak in the concentrations of fission products was still discernible in the Northern Hemisphere during 1983, but in both hemispheres the concentrations were approaching the lower limits of detection of the analytical techniques that we use to measure them. During 1970 to 1981 we had included sites at the Rocky Flats Plant, Colorado within our sampling program. We were especially interested in monitoring atmospheric concentrations of plutonium that had contaminated some soil there during the 1960's. We ceased sampling at Rocky Flats in 1981 because we believed that our measurements were biased toward high levels by the location of our samplers, and no longer reflected the true levels of atmospheric contamination at the plant. During recent years, the decreasing atmospheric concentrations of debris from nuclear weapons tests have limited the accuracy and precision of the data that we report for such debris. 3 refs., 17 tabs.