Worldwide Deposition of 90 Sr Through 1976

Each year since 1958 the annual worldwide deposition and the cumulative deposit of strontium-90 have been estimated. Samples were collected at several sites by using either a steep walled, stainless steel pot or a plastic funnel that drains a column containing dowex-50 ion exchange resin. At the end of each month, the total material collected was analyzed radiochemically for strontium-90. In 1976, the annual rate of deposition of strontium-90 from atmospheric tests of nuclear weapons reached its lowest value since the systematic measurement of radioactive fallout began in the 1950's.