TERRAPUB Geochemical Journal
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Geochemical Journal, Vol. 52, 2018
doi:10.2343/geochemj.2.0505

Temporal variation of iodine-129 in rainwater at Tsukuba before and after the Fukushima Daiichi Nuclear Power Plant accident

Masumi Matsumura,1* Kimikazu Sasa,1 Tetsuya Matsunaka,1 Keisuke Sueki,2 Tsutomu Takahashi1 and Hiroyuki Matsuzaki3

1Tandem Accelerator Complex, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
2Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
3The University Museum, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-0032, Japan

(Received May 3, 2017; Accepted October 12, 2017)

Abstract: Rainwater has been sampled on a monthly basis at the University of Tsukuba, Japan, since 2009. The serious accident at the Fukushima Daiichi Nuclear Power Plant in March 2011 resulted in the atmospheric emission of large quantities of radionuclides. Monthly 129I deposition was monitored for 19 months before and 41 months after the accident to estimate its influence at Tsukuba. Before the accident, 129I concentration in rainwater was in the range (0.19−2.6) × 108 atoms L−1. There was a rapid increase after the accident, with the highest 129I concentration recorded in March 2011 as (5.4 ± 0.8) × 1010 atoms L−1. It took approximately 1 y for the 129I concentration to return to pre-accident background levels, due to continuing resuspension and deposition. Measured decreases in 129I concentration in rainfall showed good agreement with double-exponential modeling.
Key words: Iodine-129; rainwater; Fukushima Daiichi Nuclear Power Plant accident; AMS; Modeling atmospheric concentrations


*Corresponding author E-mail: masumi@tac.tsukuba.ac.jp

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