Abstract
Abstract. We modeled the global atmospheric dispersion and deposition of radionuclides released from the Fukushima Dai-ichi nuclear power plant accident. The EMAC atmospheric chemistry – general circulation model was used, with circulation dynamics nudged towards ERA-Interim reanalysis data. We applied a resolution of approximately 0.5 degrees in latitude and longitude (T255). The model accounts for emissions and transport of the radioactive isotopes 131I and 137Cs, and removal processes through precipitation, particle sedimentation and dry deposition. In addition, we simulated the release of 133Xe, a noble gas that can be regarded as a passive transport tracer of contaminated air. The source terms are based on Chino et al. (2011) and Stohl et al. (2012); especially the emission estimates of 131I are associated with a high degree of uncertainty. The calculated concentrations have been compared to station observations by the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO). We calculated that about 80% of the radioactivity from Fukushima which was released to the atmosphere deposited into the Pacific Ocean. In Japan a large inhabited land area was contaminated by more than 40 kBq m-2. We also estimated the inhalation and 50-year dose by 137Cs, 134Cs and 131I to which the people in Japan are exposed.
Highlights
Introduction atmospheric dispersionOofcreadaionnuSclicdeies fnrocmetheFukushima accident and compute the deposition patterns using an atmospheric chemistry-general circulation model, initializedOn the 11 March 2011 an earthquake occurred off the Pacific coast of Tohoku, which triggered a powerful tsunami
We focus on the radionuclides that were emitted as gases and partly attached to ambient aerosol particles: the semivolatile isotopes of iodine 131I and caesium 137Cs
We estimated the cumulative doses due to inhalation over the simulation period (11 March–31 May 2011) as well as the effective doses over 50 years from ground contamination by applying conversion factors for 137Cs, 134Cs and 131I recommended by the International Atomic Energy Agency (IAEA, 2009, Appendix I)
Summary
The global ECHAM5/MESSy Atmospheric Chemistry (EMAC) general circulation model includes sub-models describing tropospheric and middle atmospheric processes and their interactions with oceans, land and vegetation, and trace species emissions of natural and anthropogenic origin (Jockel et al, 2005). It uses the first version of the Modular Earth Submodel System (MESSy1) to link multi-institutional computer codes. The precipitation field is not necessarily identical with that of the ERA-Interim dataset, which is relevant for the transport and wet deposition of soluble tracers, notably 137Cs. In Fig. 1 we present a comparison between the time integrated precipitation from ERA-Interim and our model over the simulated period from 11 March onward. Due to the long decay lifetime of 137Cs compared to the simulation period and the short timescales of the atmospheric removal processes considered, its radioactive decay is not taken into account in the simulation
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