YVES BALKANSKI - Academia.edu (original) (raw)

Papers by YVES BALKANSKI

Geophysical research letters, Jan 28, 2018

There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that s... more There is high uncertainty in the direct radiative forcing of black carbon (BC), an aerosol that strongly absorbs solar radiation. The observation-constrained estimate, which is several times larger than the bottom-up estimate, is influenced by the spatial representativeness error due to the mesoscale inhomogeneity of the aerosol fields and the relatively low resolution of global chemistry-transport models. Here we evaluated the spatial representativeness error for two widely used observational networks (AErosol RObotic NETwork and Global Atmosphere Watch) by downscaling the geospatial grid in a global model of BC aerosol absorption optical depth to 0.1° × 0.1°. Comparing the models at a spatial resolution of 2° × 2° with BC aerosol absorption at AErosol RObotic NETwork sites (which are commonly located near emission hot spots) tends to cause a global spatial representativeness error of 30%, as a positive bias for the current top-down estimate of global BC direct radiative forcing. B...

Proceedings of the National Academy of Sciences, 2016

Journal of Environmental Radioactivity, 2015

In this study we conduct a detailed comparison of the modelling response of the Fukushima Dai-ich... more In this study we conduct a detailed comparison of the modelling response of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident with global and local observations. We use five different model versions characterized by different horizontal and vertical resolutions of the same General Circulation Model (GCM). Transport efficiencies of 137 Cs across the world are presented as an indication of the expected radioactive impact. Activity concentrations were well represented showing lower Normalized Mean Biases (NMBs) when the better resolved versions of the GCM were used. About 95% of the results using the zoom configuration over Europe (zEur) remained within a factor of 10 from the observations. Close to Japan, the model reproduced well 137 Cs concentrations using the zoom version over Asia (zAsia) showing high correlations, while more than 64% of the modelling results were found within a factor of two from the observations and more than 92% within a factor of 10. Labile and refractory rare radionuclides calculated indirectly showed larger deviations, with about 60% of the simulated concentrations within a factor of 10 from the observations. We estimate that around 23% of the released 137 Cs remained into Japan, while 76% deposited in the oceans. Around 163 TBq deposited over North America, among which 95 TBq over USA, 40 TBq over Canada and 5 TBq over Greenland). About 14 TBq deposited over Europe (mostly in the European part of Russia, Sweden and Norway) and 47 TBq over Asia (mostly in the Asian part of Russia, Philippines and South Korea), while traces were observed over Africa, Oceania and Antarctica. Since the radioactive plume followed a northward direction before its arrival to USA and then to Europe, a significant amount of about 69 TBq deposited in the Arctic, as well. These patterns of deposition are fully consistent with the most recent reports for the accident.

Atmospheric and Oceanic Optics, 2012

ABSTRACT Road transport and shipping are copious sources of aerosols, which exert a significant r... more ABSTRACT Road transport and shipping are copious sources of aerosols, which exert a significant radiative forcing, compared to, for example, the CO2 emitted by these sectors. An advanced atmospheric general circulation model, coupled to a mixed-layer ocean, is used to calculate the climate response to the direct radiative forcing from such aerosols. The cases considered include imposed distributions of black carbon and sulphate aerosols from road transport, and sulphate aerosols from shipping; these are compared to the climate response due to CO2 increases. The difficulties in calculating the climate response due to small forcings are discussed, as the actual forcings have to be scaled by large amounts to enable a climate response to be easily detected. Despite the much greater geographical inhomogeneity in the sulphate forcing, the patterns of zonal and annual-mean surface temperature response (although opposite in sign) closely resembles that resulting from homogeneous changes in CO2. The surface temperature response to black carbon aerosols from road transport is shown to be notably non-linear in scaling applied, probably due to the semi-direct response of clouds to these aerosols. For the aerosol forcings considered here, the most widespread method of calculating radiative forcing significantly overestimates their effect, relative to CO2, compared to surface temperature changes calculated using the climate model.

Atmospheric Chemistry and Physics, 2014

We applied a climate-chemistry global model to evaluate the impact of black carbon (BC) depositio... more We applied a climate-chemistry global model to evaluate the impact of black carbon (BC) deposition on the Himalayan snow cover from 1998 to 2008. Using a stretched grid with a resolution of 50 km over this complex topography, the model reproduces reasonably well the remotely sensed observations of the snow cover duration. Similar to observations, modelled atmospheric BC concentrations in the central Himalayas reach a minimum during the monsoon and a maximum during the post-and pre-monsoon periods. Comparing the simulated BC concentrations in the snow with observations is more challenging because of their high spatial variability and complex vertical distribution. We simulated spring BC concentrations in surface snow varying from tens to hundreds of µg kg −1 , higher by one to two orders of magnitude than those observed in ice cores extracted from central Himalayan glaciers at high elevations (> 6000 m a.s.l.), but typical for seasonal snow cover sampled in middle elevation regions (< 6000 m a.s.l.). In these areas, we estimate that both wet and dry BC depositions affect the Himalayan snow cover reducing its annual duration by 1 to 8 days. In our simulations, the effect of anthropogenic BC deposition on snow is quite low over the Tibetan Plateau because this area is only sparsely snow covered. However, the impact becomes larger along the entire Hindu-Kush, Karakorum and Himalayan mountain ranges. In these regions, BC in snow induces an increase of the net shortwave radiation at the surface with an annual mean of 1 to 3 W m −2 leading to a localised warming between 0.05 and 0.3 • C. 1 Introduction Black carbon (BC) is one of the major anthropogenic pollutants affecting the climate system. Bond et al. (2013) estimated the global climate forcing of BC through all forcing mechanisms to be about +1.1 W m −2 with a 90 % probability to be included in a range of +0.17 to +2.1 W m −2. This value includes the net effect of BC on radiation and clouds, but Published by Copernicus Publications on behalf of the European Geosciences Union.

Quaternary Science Reviews, 2009

Western European loess sequences of the last glaciation (w100,000-15,000 years BP) exhibit strong... more Western European loess sequences of the last glaciation (w100,000-15,000 years BP) exhibit strong, cyclic variations of the sedimentation rate, which are coeval to the Greenland stadial/interstadial cycles and the Heinrich events. These North-Atlantic rapid climate changes appear, thus, as a potential cause for the sedimentation variations, via changes in dust intensity cycle. Here we make a first step in testing this hypothesis, by modelling the impact of the North-Atlantic abrupt climate variations on dust emission. Our dust emission calculations use meteorological fields generated by the LMDZ atmospheric general circulation model at a resolution down to 60 km over Western Europe. Three numerical experiments are run, representing a Greenland stadial, an interstadial and a Heinrich event. Orbital parameters and icesheet configuration correspond to conditions from Marine Isotope Stage 3 (w60,000-25,000 years BP), a period characterized by strong millennial-scale climate variability. The only differences we impose in the boundary conditions regard the North-Atlantic surface temperature and sea-ice cover in the latitudinal band 30-63 N. The changes in wind, precipitation, soil moisture and snow cover from one simulated state to another result in small differences in dust emission intensity. In contrast, when the inhibition of the aeolian erosion by vegetation is taken into account, the dust fluxes for the cold climate states (Greenland stadial and Heinrich event) become generally more than twice higher than those for the relatively warmer Greenland interstadial, in agreement with the loess data. These results support the hypothesis that the North-Atlantic millennial-scale variability is imprinted in Western European loess profiles, and point to vegetation changes as the main factor responsible for millennial-scale sedimentation variations. An analysis for the English Channel and southern North Sea areas, major potential dust sources, shows that the seasonality of dust emission is not controlled by the wind speed, as in modern large deserts, but by the surface conditions. Consequently, the dusty season lasts from late winter to early summer, with maximum activity in April-May, and is shifted towards summer when the climate is colder.

Tellus B: Chemical and Physical Meteorology, 1999

Sulfur hexafluoride (SF 6) is an excellent tracer of large-scale atmospheric transport, because i... more Sulfur hexafluoride (SF 6) is an excellent tracer of large-scale atmospheric transport, because it has slowly increasing sources mostly confined to northern midlatitudes, and has a lifetime of thousands of years. We have simulated the emissions, transport, and concentration of SF 6

Journal of Geophysical Research, 2007

The large spatial and temporal variability of atmospheric aerosol load makes it a challenge to qu... more The large spatial and temporal variability of atmospheric aerosol load makes it a challenge to quantify aerosol effect on climate. This study is one of the first attempts to apply data assimilation for the analysis of global aerosol distribution. Aerosol optical thickness (AOT) observed from the Polarization and Directionality of the Earth Reflectances (POLDER) spaceborne instrument are assimilated into a three-dimensional chemistry model. POLDER capabilities to distinguish between fine and coarse AOT are used to constrain them separately in the model. Observation and model errors are a key component of such a system and are carefully estimated on a regional basis using some of the high-quality surface observations from the Aerosol Robotic Network (AERONET). Other AERONET data provide an independent evaluation of the a posteriori fields. Results for the fine mode show improvements, in terms of reduction of root-mean-square errors, in most regions with the largest improvements found in the Mediterranean Sea and Eurasia. We emphasize the results for the Arctic, where there is growing evidence of a strong aerosol impact on climate, but a lack of regional and continuous aerosol monitoring. The a posteriori fields noticeably well reproduce the winterspring ''Arctic Haze'' peak measured in Longyearbyen (15°E, 78°N) and typical seasonal variations in the Arctic region, where AOT increase by up to a factor of three between a posteriori and a priori. Enhanced AOT are found over a longer period in spring 2003 than in 1997, suggesting that the large Russian fires in 2003 have influenced the Arctic aerosol load.

Journal of Geophysical Research: Atmospheres, 2012

The CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) layer product is used for a multimo... more The CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) layer product is used for a multimodel evaluation of the vertical distribution of aerosols. Annual and seasonal aerosol extinction profiles are analyzed over 13 sub-continental regions representative of industrial, dust, and biomass burning pollution, from CALIOP 2007-2009 observations and from AeroCom (Aerosol Comparisons between Observations and Models) 2000 simulations. An extinction mean height diagnostic (Z a) is defined to quantitatively assess the models' performance. It is calculated over the 0-6 km and 0-10 km altitude ranges by weighting the altitude of each 100 m altitude layer by its aerosol extinction coefficient. The mean extinction profiles derived from CALIOP layer products provide consistent regional and seasonal specificities and a low inter-annual variability. While the outputs from most models are significantly correlated with the observed Z a climatologies, some do better than others, and 2 of the 12 models perform particularly well in all seasons. Over industrial and maritime regions, most models show higher Z a than observed by CALIOP, whereas over the African and Chinese dust source regions, Z a is underestimated during Northern Hemisphere Spring and Summer. The positive model bias in Z a is mainly due to an overestimate of the extinction above 6 km. Potential CALIOP and model limitations, and methodological factors that might contribute to the differences are discussed.

Journal of Geophysical Research, 2005

The global cycle of multicomponent aerosols including sulfate, black carbon (BC), organic matter ... more The global cycle of multicomponent aerosols including sulfate, black carbon (BC), organic matter (OM), mineral dust, and sea salt is simulated in the Laboratoire de Météorologie Dynamique general circulation model (LMDZT GCM). The seasonal open biomass burning emissions for simulation years 2000-2001 are scaled from climatological emissions in proportion to satellite detected fire counts. The emissions of dust and sea salt are parameterized online in the model. The comparison of model-predicted monthly mean aerosol optical depth (AOD) at 500 nm with Aerosol Robotic Network (AERONET) shows good agreement with a correlation coefficient of 0.57(N = 1324) and 76% of data points falling within a factor of 2 deviation. The correlation coefficient for daily mean values drops to 0.49 (N = 23,680). The absorption AOD (t a at 670 nm) estimated in the model is poorly correlated with measurements (r = 0.27, N = 349). It is biased low by 24% as compared to AERONET. The model reproduces the prominent features in the monthly mean AOD retrievals from Moderate Resolution Imaging Spectroradiometer (MODIS). The agreement between the model and MODIS is better over source and outflow regions (i.e., within a factor of 2). There is an underestimation of the model by up to a factor of 3 to 5 over some remote oceans. The largest contribution to global annual average AOD (0.12 at 550 nm) is from sulfate (0.043 or 35%), followed by sea salt (0.027 or 23%), dust (0.026 or 22%), OM (0.021 or 17%), and BC (0.004 or 3%). The atmospheric aerosol absorption is predominantly contributed by BC and is about 3% of the total AOD. The globally and annually averaged shortwave (SW) direct aerosol radiative perturbation (DARP) in clear-sky conditions is À2.17 Wm À2 and is about a factor of 2 larger than in all-sky conditions (À1.04 Wm À2). The net DARP (SW + LW) by all aerosols is À1.46 and À0.59 Wm À2 in clear-and all-sky conditions, respectively. Use of realistic, less absorbing in SW, optical properties for dust results in negative forcing over the dust-dominated regions.

Journal of Geophysical Research: Atmospheres, 2001

Three different sea salt generation functions are investigated for use in global three-dimensiona... more Three different sea salt generation functions are investigated for use in global three-dimensional atmospheric models. Complementary observational data are used to validate an annual simulation of the whole size range (film, jet, and spume droplet derived particles). Aerosol concentrations are corrected for humidity growth and sampler inlet characteristics. Data from the North American deposition network are corrected for mineral dust to derive sea salt wet fluxes. We find that sea salt transport to inner continental areas requires substantial mass in the jet droplet range, which is best reproduced with the source of Monahan et al. [1986]. The results from this source formulation also shows the best agreement with aerosol concentration seasonality and sea salt size distributions below 4 m dry radius. Measured wind speed dependence of coarse particle occurrence suggests that above 4 m the source from Smith and Harrison [1998] is most appropriate. Such sea salt simulations are relevant for assessing heterogeneous chemistry and radiative effects. Sea salt aerosol provides on an annual average, in marine regions, an aggregate surface area equal to 1-10% of the area of the underlying Earth's surface. Together with mineral dust, sulfate, and carbonaceous aerosol the total aerosol surface area globally amounts to 13% of that of the Earth's surface. On the basis of atmospheric column burdens, sea salt represents 21% of the total global aerosol surface area. Equal partitioning of the aerosol surface area among the four components suggests that one has to consider all of them if the global aerosol impact is to be fully determined.

Journal of Geophysical Research: Atmospheres, 1998

An off-line global three-dimensional tracer model based on analyzed wind fields was augmented to ... more An off-line global three-dimensional tracer model based on analyzed wind fields was augmented to simulate the atmospheric transport of mineral dust. The model describes the evolution of the aerosol size distribution and hence allows to compute aerosol number and mass concentrations. In this study we describe the parameterization of the sedimentation process and include a preliminary source formulation but exclude wet deposition. Validation of the model is done during a 16-day period in June-July 1988 with very scarce precipitation. It is based on a comparison of every model grid box with daily satellite-derived optical thickness observations of Saharan dust plumes over the North Atlantic and the Mediterranean. The model reproduces accurately the daily position of the dust plumes over the ocean, with the exception of Atlantic regions remote from the African coast. By systematic analysis of transport and aerosol components we show that the largest uncertainty in reproducing the position of the dust clouds is the correct localization of the source regions. The model simulation is also very sensitive to the inclusion of convection and to an accurate treatment of the sedimentation process. Only the combination of source activation, rapid transport of dust to higher altitudes by convective updraft and long-range transport allows the simulation of thc dust plumes position. This study shows that a mineral dust transport model is only constrained if both the sourcc strength and the aerosol size distribution are known. The satellite observation of optical thic •kness over the Mediterranean and assumptions about the size distribution indicate that the dust emission flux was of the order of 17x 106 t for the 16-day period under invcstigation. The simulations suggest that a major aerosol mode initially around 2.5 [tm with a standard deviation of 2.0 plays the dominant role in long-range transport of mineral dust.

Journal of Geophysical Research: Atmospheres, 1999

Mineral dust aerosols in the atmosphere have the potential to affect the global climate by influe... more Mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean. Ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2-20 times greater during glacial periods, raising the possibility that mineral aerosols might have contributed to climate change on glacialinterglacial time scales. To address this question, we have used linked terrestrial biosphere, dust source, and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum (LGM) climates. We obtain a 2.5-fold higher dust loading in the entire atmosphere and a twenty-fold higher loading in high latitudes, in LGM relative to present. Comparisons to a compilation of atmospheric dust deposition flux estimates for LGM and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations; differences suggest where further improvements in the simple dust model could be made. The simulated increase in highlatitude dustiness depends on the expansion of unvegetated areas, especially in the high latitudes and in central Asia, caused by a combination of increased aridity and low atmospheric [CO2]. The existence of these dust source areas at the LGM is supported by pollen data and loess distribution in the northern continents. These results point to a role for vegetation feedbacks, including climate effects and physiological effects of low [CO2], in modulating the atmospheric distribution of dust. 1988; Overpeck et al., 1996]. Ice core and marine sediment records suggest that average eolian deposition rates were approximately 2-20 times higher during glacial periods than during interglacial periods [e.g.,

Journal of Geophysical Research: Atmospheres, 2000

A global climatological distribution of tropospheric OH is computed using observed distributions ... more A global climatological distribution of tropospheric OH is computed using observed distributions of 03, H20, NOt (NO2+NO+2N2Os+NO3 +HNO2+HNO4), CO, hydrocarbons, temperature, and cloud optical depth. Globa.1 annual mean OH is 1.16 x 10 • molecules crn-3 (integrated with respect to mass of air up to 100 hPa within 4-32 ø latitude and up to 200 hPa outside that region). Mean hemispheric concentrations of OH are nearly equal. While global mean OH increased by 33% compared to that from Spivakovsky et al. [1990], mean loss frequencies of CH3CCi3 and CH4 increased by only 23% because a lower fraction of total OH resides in the lower troposphere in the present distribution. The value for temperature used for determining lifetimes of hydrochlorofiuorocarbons (HCFCs) by scaling r•te constants [Prather and Spivakovsky, 1990] is revised from 277 K to 272 K. The present distribution of OH is consistent within a few percent with the current budgets of CH3CC13 and HCFC-22. For CH3CC13, it results in a lifetime of 4.6 years, including stratospheric and ocean sinks with atmospheric lifetimes of 43 and 80 years, respectively. For HCFC-22, the lifetime is 11.4 years, allowing for the stratospheric sink with an atmospheric lifetime of 229 years. Corrections suggested by observed levels of CH2C12 (•nnu•l means) depend strongly on the rate of interhemispheric mixing in the model. An increase in OH in the Northern Hemisphere by 20% combined with a decrease in the southern tropics by 25% is suggested if this rate is at its upper limit consistent with observations of CFCs •nd SSKr. For the lower limit, observations of CH2C12 imply •n increase in OH in the Northern Hemisphere by 35% combi'ned with a decrease in OH in the southern tropics by 60%. However, such large corrections are inconsistent with observations for 14CO in the tropics and for the interhemispheric gradient of CH3CC13. Industrial sources of CH2C12 are sufficient for balancing its budget. The available tests do not establish significant errors in OH except for a possible underestimate in winter in the northern and southern tropics by 15-20% and 10-15%, respectively, and an overestimate in southern extratropics by ,-•25%. Observations of seasonal variations of CH3CC13, CH2C12, 14CO, and C2H6 offer no evidence for higher levels of OH in the southern than in the northern extratropics. It is expected that in the next few years the latitudinal distribution and •nnu•l cycle of CH3CC13 will be determined primarily by its loss frequency, allowing for additional constraints for OH on scales smaller than global. its concentration in the troposphere [e.g., McConnell

Journal of Geophysical Research, 1998

Wet deposition in a global size-dependent aerosol transport model 2. Influence of the scavenging ... more Wet deposition in a global size-dependent aerosol transport model 2. Influence of the scavenging scheme on vertical profiles, surface concentrations, and deposition W. Guelle, 1 y. j. Balkanski, 1 j. E. Dibb, 2 M. Schulz, 3 and F. Dulac • Abstract. The main atmospheric sink for submicron aerosols is wet removal. Lead 210, the radioactive decay product of 222Rn, attaches immediately after being formed to submicron particles. Here we compare the effects of three different wet-scavenging schemes used in global aerosol simulations on the 2•øPb aerosol distribution using an off-line, size-resolved, global atmospheric transport model. We highlight the merits and shortcomings of each scavenging scheme at reproducing available measurements, which include concentrations in surface air and deposition, as well as vertical profiles observed over North America and western and central North Pacific. We show that model-measurement comparison of total deposition does not allow to distinguish between scavenging schemes because compensation effects can hide the differences in their respective scavenging efficiencies. Differences in scavenging parameterization affect the aerosol vertical distribution to a much greater extent than the surface concentration. Zonally averaged concentrations at different altitudes derived from the model vary by more than a factor of 3 according to the scavenging formulation, and only one scheme enables us to reproduce reliably the individual profiles observed. This study shows that ground measurements alone are insufficient to validate a global aerosol transport model. 1. Introduction Very little has been done to evaluate tropospheric aerosol vertical distribution predicted from models against actual measurements. This represents a clear gap in our ability to adequately represent aerosol mass and number concentrations, to assess their direct radiative effect, and to estimate the heterogeneous reactions that take place at their surfaces. A description of the processes that affect aerosol number concentration necessitates a good representation of the fate of the aerosol in and below clouds. Boucher [1995, p. 87] highlighted the differences that arise in sulfate distributions between the models MO-GUNTIA and IMAGE. Not only are the amplitude of the resulting radiative forcings different, but the tim-1Laboratoire des Sciences du Climat et de l'Environnement, Laboratoire mixte Commissariat k l'Energie Atom

Journal of Geophysical Research: Atmospheres, 2002

We present simulations of the dust cycle during present and glacial climate states, using a model... more We present simulations of the dust cycle during present and glacial climate states, using a model, which explicitly simulates the control of dust emissions as a function of seasonal and interannual changes in vegetation cover. The model produces lower absolute amounts of dust emissions and deposition than previous simulations of the Last Glacial Maximum (LGM) dust cycle. However, the simulated 2-to 3-fold increase in emissions and deposition at the LGM compared to today, is in agreement with marine-and ice-core observations, and consistent with previous simulations. The mean changes are accompanied by a prolongation of the length of the season of dust emissions in most source regions. The increase is most pronounced in Asia, where LGM dust emissions are high throughout the winter, spring and summer rather than occurring primarily in spring as they do today. Changes in the seasonality of dust emissions, and hence atmospheric loading, interact with changes in the seasonality of precipitation, and hence of the relative importance of wet and dry deposition processes at high northern latitudes. As a result, simulated dust deposition rates in the high northern latitudes show high interannual variability. Our results suggest that the high dust concentration variability shown by the Greenland ice core records during the LGM is a consequence of changes in atmospheric circulation and precipitation locally rather than a result of changes in the variability of dust emissions.

Global Biogeochemical Cycles, 1999

Recently, very precise measurements have detected the seasonal variability in the atmospheric O•/... more Recently, very precise measurements have detected the seasonal variability in the atmospheric O•/N• ratio at several sites in the northern and southern hemispheres. In this paper, we derive marine primary productivity (PP) from satellite ocean color data. To infer air-sea oxygen fluxes, a simple one-dimensional •diagnostic model of ocean biology has been developed that depends on only two parameters: a time delay between organic production and oxidation (set to 2 weeks) and an export scale length (50 m). This model gives a global net community production of 4.3 mol C m ': yr '• in the euphotic zone and 3.2 mol C m-• yr-• in the mixed layer. This last value corresponds to a global fratio (net community production (NCP)/PP) at the base of the mixed layer of 0.37. The air-sea fluxes derived from this model are then used at the base of a three-dimensional atmospheric model to compare the atmospheric seasonal cycle of O•/N• at five sites: Cape Grim (40.6øS, 144.6E), Baring Head (41.3øS, 174.8øE), Mauna Loa (19.5øN,154•8øW), La Jolla (32.9øN, 117.3øW), and Barrow (71.3øN, 156.6øW). The agreement between model and observations is very encouraging. We infer from the agreement that the seasonal variations in O•/N• are largely controlled by the photosynthesis rate but also by the remineralization linked to the deepening and shoaling of the mixed layer. Lateral ventilation to high latitudes may also be an important factor controlling the amplitude of the seasonal cycle. plant respiration, soil respiration, changes in land use, and fossil fuel combustion. In the ocean, processes causing •5(O2/N2) = 106 [(O2/N2)sampie/(O2fN2)referenc (1)

Environmental Science & Technology, 2013

The earthquake and the subsequent tsunami that occurred offshore of Japan resulted in an importan... more The earthquake and the subsequent tsunami that occurred offshore of Japan resulted in an important loss of life and a serious accident at the nuclear facility of Fukushima. The "hot spots" of the release are evaluated here applying the model LMDZORINCA for 137 Cs. Moreover, an assessment is attempted for the population and the environment using the dosimetric scheme of the WHO and the interactive tool ERICA, respectively. Cesium-137 was deposited mostly in Pacific and Atlantic Oceans and North Pole (80%), whereas the rest in the continental areas of North America and Eurasia contributed slightly to the natural background (0.5−5.0 kBq m −2). The effective dose from 137 Cs and 134 Cs (radiocesium) irradiation during the first 3 months was estimated between 1−5 mSv in Fukushima and the neighboring prefectures. In the rest of Japan, the respective doses were found to be less than 0.5 mSv, whereas in the rest of the world it was less than 0.1 mSv. Such doses are equivalent with the obtained dose from a simple X-ray; for the highly contaminated regions, they are close to the dose limit for exposure due to radon inhalation (10 mSv). The calculated dose rates from radiocesium exposure on reference organisms ranged from 0.03 to 0.18 μGy h −1 , which are 2 orders of magnitude below the screening dose limit (10 μGy h −1) that could result in obvious effects on the population. However, these results may underestimate the real situation, since stable soil density was used in the calculations, a zero radiocesium background was assumed, and dose only from two radionuclides was estimated, while more that 40 radionuclides have been deposited in the vicinity of the facility. When monitoring data applied, much higher dose rates were estimated certifying ecological risk for small mammals and reptiles in terms of cytogenetic damage and reproduction.