THE CA-41 BOMB PULSE AND ATMOSPHERIC TRANSPORT OF RADIONUCLIDES

For the first time, the Ca-41 signal from the nuclear weapon tests has been measured. Calcium 41 concentrations have been determined in alpi ne ice of the Fiescherhorn glacier (Switzerland) with accelerator mass spectrometry. The peak concentrations have been observed to be about 3x10(6) atoms of Ca-41 per kilogram of ice in the 1950s. It has been f ound that Ca-41 is produced essentially by the atoll bombs. A universa l box model, able to describe atmospheric transport of radionuclides t hat are in gaseous form or attached to aerosols, has been developed. T he model has been applied to calculate the bomb pulses of C-14, Cl-36, Ca-41, Sr-90, and Cs-137. For the transport of radionuclides that are attached to aerosols such as Ca-41, Sr-90, and Cs-137, sedimentation (gravitational settling) in tile upper stratosphere has been taken int o account. It has been found that the deposition of bomb-produced Cl-3 6 on the Earth's surface is delayed compared to that of Sr-90 by about 1 year because Cl-36 stays gaseous in the stratosphere. The model can also be used to calculate the deposition of cosmogenic radionuclides, e. g. Cl-36 and Be-10, in their natural archives, such as polar ice s heets.