TERRAPUB Geochemical Journal
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Geochemical Journal, Vol. 46 (No. 4), pp. 361-369, 2012

Distribution of Pu isotopes in marine sediments in the Pacific 30 km off Fukushima after the Fukushima Daiichi nuclear power plant accident

Jian Zheng,1 Tatsuo Aono,1 Shigeo Uchida,1 Jing Zhang2 and Makio C. Honda3

1Research Center for Radiation Protection, National Institute of Radiological Sciences, 491 Anagawa, Inage, Chiba 263-8555, Japan
2Department of Environmental Sciences, The University of Toyama, 3190 Gofuku, Toyama 930-0887, Japan
3Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka 237-0061, Japan

(Received February 24, 2012; Accepted May 17, 2012)

Abstract: The Fukushima Dai-ichi Nuclear Power Plant (DNPP) accident has caused serious contamination of the marine environment from atmospheric fallout deposition and the direct discharges of highly radioactive liquid wastes. In contrast to the immediate intensive studies on the distributions of released fission products, such as 131I, 134Cs and 137Cs, information on the possible contamination by actinides in the marine environment is quite limited. In this study, we report the first data-set on the distribution of Pu isotopes in surface sediments in the Pacific 30 km off Fukushima after the Fukushima DNPP accident. Activities of 239+240Pu and 241Pu, and atom ratios of 240Pu/239Pu and 241Pu/239Pu in surface sediments collected in July-August, 2011 were analyzed to make a quick assessment on the environmental impact of the possible Pu contamination. The observed 239+240Pu activities and 240Pu/239Pu atom ratios are comparable to those previously reported in marine sediments in the western North Pacific and its marginal seas, and in Japanese estuaries before the accident. The Pu contamination from the Fukushima DNPP accident was not observed in marine sediments outside the 30 km zone.
Key words: Fukushima, plutonium isotopes, western North Pacific, marine sediments, SF-ICP-MS


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