Impact of the Fukushima Dai-ichi Nuclear Power Plant Accident on the neon flying squids in the Northwest Pacific from 2011 to 2018

Following nine years since the Fukushima Dai-ichi Nuclear Power Plant Acciden (FDNPPA), it might be the time to draw a much clearer conclusion for the impact of FDNPPA on marine biota. In this work, the evolution of the FDNPPA derived Cs-134, Cs-137 and Ag-110m in the neon flying squids in the Northwest Pacific from 2011 to 2018 were studied. The background level of Cs-137 in neon flying squids (<0.10 Bq/kg(fresh) (weight)) with the average of 0.017 Bq/kg(fresh) (weight)) before FDNPPA were estimated. The radioactive levels of Cs-134, Cs-137 and Ag-110m in neon flying squids decreased with time. Cs-134 and Ag-110m decreased at the halflives of 7.6 months and 5.7 months at the population level, respectively. After May 2014, Cs-134 and Ag-110m cannot be detected and Cs-137 activities returned to the background level before FDNPPA. BCFs of cesium isotopes (3.7-17.7 with the average of 10.8) and Ag-110m (similar to 7 x 10(4)) for neon flying squids were estimated. The amount of Ag-110m released into the Northwest Pacific (similar to 20-similar to 26 TBq) were firstly calculated using a Cs-134/Ag-110m(activity) (ratio) method. Radiation dose assessment demonstrated that it was far from causing radiation harm to neon flying squids in the open ocean of Northwest Pacific and humans who ingested these neon flying squids. (C) 2020 Elsevier Ltd. All rights reserved.