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International Journal of Earth & Environmental Sciences Volume 2 (2017), Article ID 2:IJEES-125, 7 pages
https://doi.org/10.15344/2456-351X/2017/125
Original Article
Temporal Variations of Global Fallout-Derived Plutonium and 137Cs in River Water in Japan

Katsumi Hirose1* and Michio Aoyama2

1Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan
2Institute of Environmental Radioactivity, Fukushima University, 1 Kanayagawa, Fukushima 960-1296, Japan
Prof. Katsumi Hirose, Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan; E-mail: hirose45037@mail2.accsnet.ne.jp
02 November 2016; 16 January 2017; 18 January 2017
Hirose K, Aoyama M (2017) Temporal variations of global falloutderived plutonium and 137Cs in river water in Japan. Int J Earth Environ Sci 2: 125. doi: https://doi.org/10.15344/2456-351X/2017/125
This research is supported by funding from the Ministry of Education, Culture, Science and Technology, Japan..

Abstract

Temporal variations of global fallout-derived plutonium and 137Cs concentrations in river water in Japan were examined using a composite dataset for 1966–1987 (1966-1987 for 239,240Pu, 1978-1987 for 137Cs). Plutonium and 137Cs concentrations in Japanese river water exhibited exponential decreases during the sampling periods, with the exception of 137Cs concentrations immediately after the Chernobyl nuclear reactor accident in 1986. The apparent half-decrease time of dissolved 137Cs (1.9 ± 0.3 years), which means a time that radionuclide concentrations in river water decrease to a half, was similar to that for dissolved 239,240Pu for the same period, whereas the apparent half-decrease time of particulate 239,240Pu (4.5 ± 2.2years) was longer. Temporal changes in dissolved 239,240Pu and 137Cs in river water can be explained by direct contribution of radionuclides from rainwater and leaching of radionuclides from surface-layer soil particles on land.