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Cs in the ocean following the Fukushima Daiichi Nuclear Power Station accidentTsumune, Daisuke*; Tsubono, Takaki*; Misumi, Kazuhiro*; Sakuma, Kazuyuki; Onda, Yuichi*
Pure and Applied Chemistry, 16 Pages, 2024/00
Times Cited Count：0Twelve years after the Fukushima Daiichi Nuclear Power Station (F1NPS) accident, Cs activity concentrations have not yet decreased to pre-accident levels because of direct release from the site and fluvial discharges of Cs deposited on land. It is necessary to consider dispersion processes in the coastal area to understand the impact of multiple river discharges and direct release. To achieve this goal, we carried out oceanic dispersion simulations that considered direct release and fluvial discharges and compared the results with the annual averages of observed data. We assumed that particulate Cs discharged from rivers to the ocean quickly resuspended and re-leached after coagulation and precipitation and that all of the Cs were dispersed. The reproducibility of results was improved by considering fluvial discharges of particulate Cs at all sites between 2013 and 2016, except near the F1NPS. In other words, particulate Cs discharged from rivers was found to influence the results of ocean surface activity concentrations within a relatively short period of time. The impact of direct release was dominant for the observed Cs activity concentrations adjacent to the F1NPS, which was used to estimate direct releases.
Cs in seabed sediment off the Fukushima coast; Implications from numerical simulationsMisumi, Kazuhiro*; Tsumune, Daisuke*; Tsubono, Takaki*; Tateda, Yutaka*; Aoyama, Michio*; Kobayashi, Takuya; Hirose, Katsumi*
Journal of Environmental Radioactivity, 136, p.218 - 228, 2014/10
Times Cited Count：22 Percentile：54.1(Environmental Sciences)Major controls on spatiotemporal variations of Cs activity in seabed sediments derived from the Fukushima Dai-ichi Nuclear Power Plant accident during the first year after the accident were investigated by using numerical simulations. The model successfully reproduced major features of the observed spatiotemporal variations of Cs activity in sediments. The spatial pattern of Cs in sediments, which mainly reflected the history of Cs activity in the bottom water overlying the sediment and the sediment particle size distribution, became established during the first several months after the accident. Taking Cs activities in sediments in the coastal area and in the vicinity of the power plant into account, increased the simulated total inventory of Cs in sediments off the Fukushima coast to a value on the order of 10
Bq.
Cs released from the Fukushima Daiichi Nuclear Power PlantMasumoto, Yukio*; Miyazawa, Yasumasa*; Tsumune, Daisuke*; Tsubono, Takaki*; Kobayashi, Takuya; Kawamura, Hideyuki; Estournel, C.*; Marsaleix, P.*; Lanerolle, L.*; Mehra, A.*; et al.
Elements, 8(3), p.207 - 212, 2012/06
Times Cited Count：82 Percentile：92.24(Geochemistry & Geophysics)Present status of oceanic dispersion simulations of cesium 137 (Cs) directly discharged from Fukushima Daiichi Nuclear Power Plant are reviewed using five model outputs and other available informations, focusing on estimations of discharged amount of Cs and subsequent dispersion in a region off Fukushima during March and April, 2011. Common aspects and discrepancies among the simulated results are described. While the discharged amount spreads from about 1 to 27 P Bq of Cs among the estimates, the values obtained from the five models indicate 2 to 4 P Bq. With these total amounts and time evolutions of the discharge rate, mimicking observed Cs concentration near FDNPP, as a source for the dispersion calculation, all the five models simulated the Cs dispersion in the ocean reasonably well corresponding to the observed distributions.
