Temporal and spatial variations of radioactive cesium levels in Northeast Japan following the Fukushima nuclear accident.

Radioactive emissions into the environment from the Fukushima Daiichi Nuclear Power Plant accident led to global contamination. Radionuclides such as 131I, 134Cs, and 137Cs were further transported to North America and Europe. Thus, the Fukushima Daiichi Nuclear Power Plant accident is a global concern for both human health and the ecosystem because a number of countries ban or impose restrictions the import of Japanese products. In the present study, three-year (May 2011 to May 2014) fluctuations and accumulations of Cs, 134Cs, and 137Cs in two salmonid fish, white-spotted char and masu salmon were examined in Northeast Japan. The total Cs, 134Cs, and 137Cs levels in the fish gradually decreased throughout the three-year studied period after the Fukushima Daiichi Nuclear Power Plant accident; however, higher levels (more than 100 Bq kg-1) were still detected in the Fukushima prefecture and neighboring prefectures in Japan 3 years after the Fukushima Daiichi Nuclear Power Plant accident. Spatial radiocesium levels gradually decreased with increasing distance from the Fukushima Daiichi Nuclear Power Plant (Fukushima prefecture). The radiocesium levels facing the Pacific Ocean area were generally higher than those facing the Sea of Japan area. These results suggest that radionuclides from Fukushima Daiichi Nuclear Power Plant are still widely distributed and remain in the natural environment in Northeast Japan.