240Pu/239Pu and 242Pu/239Pu atom ratios of Japanese monthly atmospheric deposition samples during 1963–1966

• Published in: Scientific reports Vol. 9; no. 1
• Main Authors: Ohtsuka, Yoshihito, Aoyama, Michio, Takaku, Yuichi, Igarashi, Yasuhito, Hattori, Michinari, Hirose, Katsumi, Hisamatsu, Shun’ichi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 30-05-2019; Nature Publishing Group
• Subjects: 704/172/169/824; 704/172/169/895; Environmental science; Environmental tracers; Fallout; Humanities and Social Sciences; multidisciplinary; Nuclear power plants; Nuclear weapons; Plutonium; Science; Science (multidisciplinary); Scientific imaging; Stratosphere; Tracers; Troposphere
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-44352-7

Global fallout plutonium isotopic ratios from the 1960s are important for the use of Pu as environmental tracers. We measured the
240
Pu/
239
Pu and
242
Pu/
239
Pu atomic ratios of monthly atmospheric deposition samples collected in Tokyo and Akita, Japan during March 1963 to May 1966. To our knowledge, our results represent the first data measured for actual atmospheric deposition samples collected continuously during the 1960s. Both atomic ratios increased rapidly from March 1963 to June 1963, followed by a gradual increase until September 1963. Then, both ratios declined with a half-life of approximately 5.6 months. The observed temporal changes of the ratios were likely caused by the upper-stratospheric input of nuclear debris from high-yield atmospheric nuclear weapon testing during 1961–62, followed by its downward transport to the troposphere.