Time-dependent radioactive concentrations of fallout following the Chernobyl reactor accident.

The levels of Chernobyl-derived 137Cs, 134Cs, 106Ru and 103Ru were measured at Thessaloniki, Greece, in air, rain, soil, grass and milk samples for more than 2 years after the accident. The data were analysed in conjunction with 7Be (produced in the atmosphere by cosmic rays) measurements and show that significant variations were observed, particularly in the spring and in the autumn measurements. In interpreting these variations we took into consideration the tropospheric, or possibly stratospheric, fallout injections into the atmosphere due to the Chernobyl accident, nuclear weapons testing or other releases from nuclear reactors operating world-wide. Useful information can be derived for determining the periodicity of global circulation of the fallout radionuclides.