Analysis of the 50-year records of the atmospheric deposition of long-lived radionuclides in Japan

Long-lived anthropogenic radionuclides (137Cs, 90Sr, and Pu isotopes) have been determined in monthly atmospheric deposition samples collected in Japan since 1956. The maximum annual deposition occurred in 1963 after the large-scale atmospheric nuclear weapons testing of 1961–1962. In the 1980s, the fallout from the Chinese nuclear weapons tests was observed and the released radionuclides from the Chernobyl accident affected radioactive deposition in Japan until the early 1990s. Recently, the deposition rates have been boosted by the resuspension of radionuclides in deposited particles, the 239,240Pu content of which may originate from dusts from the East Asian continent deserts and arid areas.