Plutonium isotopes and 241Am in surface sediments off the coast of the Japanese islands before and soon after the Fukushima Dai-ichi nuclear power plant accident
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The concentrations of 239+240Pu, 241Pu and 241Am in the sediments at the coast of Japanese islands from 2008 to 2011 varied widely from one sampling site to another and were generally lower in sandy sediments at shallower sites, and higher in clayey sediments at deeper sites. In contrast, there seemed to be no temporal variation in the concentrations during the survey period. The 241Am/239+240Pu activity ratio was relatively higher than the global fallout presumably owing to the ingrowth of 241Am from the ancestor, 241Pu originating mainly from the hydrogen bomb explosion tests in the Marshall Islands in the 1950s.
KeywordsPu isotopes 241Am Sediment Fukushima Dai-ichi nuclear power plant accident
We sincerely thank our colleagues at the Marine Ecology Research Institute for their help with sampling and for logistical support for the survey. We also acknowledge the crews of the R/Vs and technicians who assisted greatly with onboard fieldwork. This research was conducted under contract with the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of the Japanese Government.