PICES SCIENTIFIC REPORT No. 60, 2020 Report of Working Group 30 on

In order to better evaluate the impact of the FDNPP accident on the marine environment in the North Pacific, the Working Group on Assessment of Marine Environmental Quality of Radiation around the North Pacific (WG 30) was established in 2013 under the auspices of the Marine Environmental Quality (MEQ) committee, and co-chaired by Prof. [...] 60 1 Monitoring the Coastal Waters of Japan Section 2 2 Monitoring the Coastal Waters of Japan 2.1 Environmental monitoring strategies The 2011 accident at the FDNPP of the Tokyo Electric Power Company (TEPCO) focused concerns on radioactivity contamination of the environment and the general radiological safety of the public. [...] To confirm the level of the radionuclide concentration before the FDNPP accident in the offshore area of East Japan, we summarized the 137Cs and 90Sr concentration data off the coast of Fukushima and adjacent prefectures in East Japan. [...] The difference reflects the structure of a long tail in the high concentration region of frequency distribution (Figure 2.9), and is thought to be caused by the differences in the quality of the sea sediment among the sampling areas (Oikawa et al., 2013b). [...] The 137Cs/90Sr activity ratio at the beginning of the FDNPP accident and the amount of 137Cs directly released into the ocean indicated that the inventory of 90Sr in the wastewater was about 0.04 PBq (Povinec et al., 2012).