Temporal distribution of plutonium isotopes in marine sediments off Fukushima after the Fukushima Dai-ichi Nuclear Power Plant accident

The characterization of Pu isotopes in a sediment core collected in the western North Pacific off Fukushima in January 2013 was determined. We compared the results with that of the marine sediments collected from July 2011 to July 2012. Both the Pu239+240 activities and the Pu-240/Pu-239 atom ratios showed no variation in the marine sediments in the last 2 years since the FDNPP accident. Pu contamination in the marine sediments in the investigated areas still originated from global fallout and the Pacific Proving Ground close-in fallout.