The distributions of Cs, Cs and Sr in the northwest Pacific seawater in the winter of 2012.

To understand the status of the radionuclides released during the Fukushima Dai-ichi Nuclear Power Plant accident, the Cs, Cs and Sr in the seawater in the public area of the northwest Pacific Ocean were analyzed in November-December 2012. The radioactivity of Cs, Cs and Sr decreased sharply from June 2011 to November-December 2012. The highest average values of Cs and Cs were found at a depth of 500 m, suggesting that Cs and Cs had been transported to a depth of 500 m or deeper by the end of 2012. Total inventories of 0.80 ± 0.20 pBq for Cs from the surface to a depth of 500 m and 0.07 ± 0.02 pBq for Sr from the surface to a depth of 100 m were obtained in the waters southeast of Fukushima. Cs was detectable in the Chinese exclusive economic zone, and the seawater quality was much lower than the target level for China.