EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Open Access Open Access Natural Hazards Natural Hazards and Earth System and Earth System Sciences Sciences Discussions Open Access Open Access Atmos. Chem. Phys., 13, 1425–1438, 2013 Atmospheric Atmospheric www.atmos-chem-phys.net/13/1425/2013/ doi:10.5194/acp-13-1425-2013 Chemistry Chemistry © Author(s) 2013. CC Attribution 3.0 License. and Physics and Physics Discussions Open Access Open Access Atmospheric Atmospheric Measurement Measurement Techniques Techniques Discussions Open Access Modelling the global atmospheric transport and deposition of Open Access radionuclides from the Fukushima Dai-ichi nuclear accident Biogeosciences Biogeosciences Discussions T. Christoudias1 and J. Lelieveld1,2 1The Cyprus Institute, Nicosia, Cyprus Open Access 2Max Planck Institute of Chemistry, Mainz, Germany Open Access Climate Correspondence to: T. Christoudias ([email protected]) Climate of the Past of the Past Received: 24 August 2012 – Published in Atmos. Chem. Phys. Discuss.: 19 September 2012 Discussions Revised: 7 January 2013 – Accepted: 22 January 2013 – Published: 5 February 2013 Open Access Open Access Earth System Abstract. We modeled the global atmospheric dispersion level 7 events. This causedEarth the release System of large amounts of and deposition of radionuclides released from the Fukushima radionuclides to the atmosphereDynamics (Butler, 2011; Chino et al., Dynamics Dai-ichi nuclear power plant accident. The EMAC atmo- 2011; Stohl et al., 2012). In particular the isotopes of io- Discussions spheric chemistry – general circulation model was used, with dine and caesium adversely affect human health through the circulation dynamics nudged towards ERA-Interim reanaly- large-scale contamination of air, water, soils and agricul- Open Access Open Access sis data. We applied a resolution of approximately 0.5 de- tural products (Anspaugh etGeoscientific al., 1988). Although both ra- Geoscientific grees in latitude and longitude (T255). The model accounts dionuclides are releasedInstrumentation as gases, caesium has a low volatil- Instrumentation for emissions and transport of the radioactive isotopes 131I ity and partitions into ambientMethods aerosol and particles, whereas 137 Methods and and Cs, and removal processes through precipitation, par- in our model iodine largelyData remains Systems in the gas phase. Re- ticle sedimentation and dry deposition. In addition, we sim- moval of these compounds from the atmosphere is governed Data Systems ulated the release of 133Xe, a noble gas that can be regarded by dry and wet deposition processes. Several initial stud- Discussions Open Access Open Access as a passive transport tracer of contaminated air. The source ies of the atmospheric behaviour and budgets of radioactive Geoscientific terms are based on Chino et al. (2011) and Stohl et al. (2012); species, notably 131I and 137GeoscientificCs, were conducted using chem- 131 Model Development especially the emission estimates of I are associated with istry transportModel models. For Development example, the Austrian Weather a high degree of uncertainty. The calculated concentrations Service (ZAMG) performed a daily forecast of the disper- Discussions have been compared to station observations by the Com- sion of radioactivity in the atmosphere. Morino et al. (2011) Open Access prehensive Nuclear-Test-Ban Treaty Organisation (CTBTO). simulated the transport and deposition of the radionuclidesOpen Access We calculated that about 80 % of the radioactivity from over Japan using an off-lineHydrology regional model.and A numerical Hydrology and Fukushima which was released to the atmosphere deposited simulation for the long-rangeEarth transport System from the plant to the Earth System into the Pacific Ocean. In Japan a large inhabited land area US and even Europe with a global aerosol transport model was contaminated by more than 40 kBqm−2. We also esti- was conducted by Takemura et al.Sciences(2011). Ten Hoeve and Ja- Sciences 137 134 mated the inhalation and 50-year dose by Cs, Cs and cobson (2012) quantified worldwide health effects using the Discussions 131 Open Access I to which the people in Japan are exposed. GATOR-GCMOM global model. Open Access The objective of the present study is to model the global Ocean Science atmospheric dispersionOcean of radionuclides Science from the Fukushima accident and compute the deposition patterns using an at- Discussions 1 Introduction mospheric chemistry-general circulation model, initialized by estimated source terms. The emission strengths have Open Access On the 11 March 2011 an earthquake occurred off the Pa- been determined through inverse modelling byOpen Access Stohl et al. cific coast of Tohoku,¯ which triggered a powerful tsunami. (2012). The temporal emission profiles of the radioactive iso- Solid Earth The tsunami damaged the Fukushima Dai-ichi nuclear power topes 133Xe and 137Cs were estimatedSolid Earth at three reference re- plant complex, followed by a series of major accidents, giv- lease heights using the Lagrangian transport model FLEX- Discussions ing rise to three INES (International Nuclear Event Scale) Open Access Open Access Published by Copernicus Publications on behalf of the European Geosciences Union. The Cryosphere The Cryosphere Discussions 1426 T. Christoudias and J. Lelieveld: Global atmospheric modeling of Fukushima radioactivity PART (Stohl et al., 1998), driven by operational meteoro- freely and consistently according to the model dynamics. logical data from the European Centre for Medium-Range Therefore, the precipitation field is not necessarily identical Weather Forecasts (ECMWF) and the National Center for with that of the ERA-Interim dataset, which is relevant for Environmental Prediction (NCEP) Global Forecast System the transport and wet deposition of soluble tracers, notably (GFS) analyses, and constrained by a large number of avail- 137Cs. In Fig. 1 we present a comparison between the time able concentration and deposition data from Japan, North integrated precipitation from ERA-Interim and our model America and Europe. over the simulated period from 11 March onward. It shows Furthermore, we incorporated the preliminary estimates of that precipitation patterns downwind of Japan are very simi- release amounts of 131I by Chino et al. (2011). A reverse lar, whereas in the tropics (e.g., the intertropical convergence estimation of the source term was conducted by coupling zone) differences are more evident. We do not expect that Japanese Environmental monitoring data with regional at- this significantly influences our results. Both ERA-Interim mospheric dispersion simulations. Emission inventories are and EMAC results indicate that during the first week after further discussed in Sect. 2.1. the accident (11–18 March 2011; Fig. 1) some precipitation We briefly describe the model in Sect. 2, including the occurred in the northern part of the main island of Japan, emissions of radionuclides and the representation of removal mainly along the east coast (37◦–40◦ N). mechanisms. The analysis of our results regarding the global The applied model setup comprises the submodels deposition (Sect. 3.2) and a comparison of surface concen- RAD4ALL for radiation and atmospheric heating processes, trations to station measurements (Sect. 3.1) are discussed in CLOUD for cloud formation and microphysical processes in- Sect. 3. Estimates of doses from the inhalation and ground cluding precipitation, and CONVECT for the vertical trans- deposition of radionuclides are given in Sect. 3.3. A sum- ports of trace species associated with convection. The DRY- mary and conclusions are presented in Sect. 4. DEP (Kerkweg et al., 2006) and SCAV (Tost et al., 2006, 2007) submodels were used to simulate aerosol dry and wet deposition processes, respectively. The SEDI submodel was 2 Model simulation used to simulate particle sedimentation, of which the results will be presented below as part of the simulated dry deposi- The global ECHAM5/MESSy Atmospheric Chemistry tion. (EMAC) general circulation model includes sub-models de- We focus on the radionuclides that were emitted as gases scribing tropospheric and middle atmospheric processes and and partly attached to ambient aerosol particles: the semi- their interactions with oceans, land and vegetation, and volatile isotopes of iodine 131I (with a half-life of 8 days) trace species emissions of natural and anthropogenic origin and caesium 137Cs (with a half-life of ∼30 years). We also (Jockel¨ et al., 2005). It uses the first version of the Modular modeled the emission of the isotope 133Xe (with a half-life Earth Submodel System (MESSy1) to link multi-institutional of 5.25 days). Since xenon is an unreactive noble gas and is computer codes. The core atmospheric model is the 5th gen- not removed by deposition processes, it serves as a passive eration European Centre Hamburg general circulation model tracer of atmospheric transport. 137Cs is modeled as a water- (ECHAM5; Roeckner et al., 2003, 2006). soluble aerosol with a standard lognormal distribution with For the present study we applied EMAC version 1.9 (based mean radius 0.25 µm and a Henry’s law coefficient equal to on ECHAM5 version 5.3) at the T255L31 resolution, i.e., 1.0 molL−1 atm−1 and a density of 1000.0 kgm−3. Due to with a spherical spectral truncation of T255 (corresponding the long decay lifetime of 137Cs compared to the simulation to a quadratic