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| Titel |
One-year, regional-scale simulation of 137Cs radioactivity in the ocean following the Fukushima Dai-ichi Nuclear Power Plant accident |
| VerfasserIn |
D. Tsumune, T. Tsubono, M. Aoyama, M. Uematsu, K. Misumi, Y. Maeda, Y. Yoshida, H. Hayami |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 8 ; Nr. 10, no. 8 (2013-08-23), S.5601-5617 |
| Datensatznummer |
250085306
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| Publikation (Nr.) |
 copernicus.org/bg-10-5601-2013.pdf |
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| Zusammenfassung |
| A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant following
the Great East Japan Earthquake
and tsunami of 11 March 2011 resulted in the release of radioactive materials
to the ocean by two major pathways: direct release from the accident site and
atmospheric deposition. A 1 yr, regional-scale simulation of 137Cs
activity in the ocean offshore of Fukushima was carried out, the sources of
radioactivity being direct release, atmospheric deposition, and the inflow of
137Cs deposited into the ocean by atmospheric deposition outside the
domain of the model.
Direct releases of 137Cs were estimated for 1 yr after the accident by
comparing simulated results and measured activities adjacent to the accident
site. The contributions of each source were estimated by analysis of
131I/137Cs and 134Cs/137Cs activity ratios and
comparisons between simulated results and measured activities of 137Cs.
The estimated total amounts of directly released 131I, 137Cs, and
137Cs were 11.1 ± 2.2 PBq, 3.5 ± 0.7 PBq, and
3.6 ± 0.7 PBq, respectively. Simulated 137Cs activities
attributable to direct release were in good agreement with measured
137Cs activities not only adjacent to the accident site, but also in a
wide area in the model domain, therefore this implies that the estimated
direct release rate was reasonable. Employment of improved nudging data by
JCOPE2 improved both the offshore transport result and the reproducibility of
137Cs activities 30 km offshore. On the other hand, simulated
137Cs activities attributable to atmospheric deposition were low
compared to measured activities. The rate of atmospheric deposition into the
ocean was underestimated because of a lack of measurements of deposition into
the ocean when atmospheric deposition rates were being estimated. Simulated
137Cs activities attributable to the inflow of 137Cs deposited into
the ocean outside the domain of the model were in good agreement with
measured activities in the open ocean within the model domain after June
2012. The consideration of inflow is important to simulate the 137Cs
activity in this model region in the later period of the simulation. The
contribution of inflow increased with time and was dominant (more than
99%) by the end of February 2012. The activity of directly released
137Cs, however, decreased exponentially with time and was detectable
only in the coastal zone by the end of February 2012. |
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