An international comparison of models and approaches for the estimation of the radiological exposure of non-human biota.
ABSTRACT Over the last decade a number of models and approaches have been developed for the estimation of the exposure of non-human biota to ionising radiations. In some countries these are now being used in regulatory assessments. However, to date there has been no attempt to compare the outputs of the different models used. This paper presents the work of the International Atomic Energy Agency's EMRAS Biota Working Group which compares the predictions of a number of such models in model-model and model-data inter-comparisons.
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ABSTRACT: Concentration ratios (CRwo-media) are used in most radioecological models to predict whole-body radionuclide activity concentrations in wildlife from those in environmental media. This simplistic approach amalgamates the various factors influencing transfer within a single generic value and, as a result, comparisons of model predictions with site-specific measurements can vary by orders of magnitude. To improve model predictions, the development of 'condition-specific' CRwo-media values has been proposed (e.g. for a specific habitat). However, the underlying datasets for most CRwo-media value databases, such as the wildlife transfer database (WTD) developed within the IAEA EMRAS II programme, include summarised data. This presents challenges for the calculation and subsequent statistical evaluation of condition-specific CRwo-media values. A further complication is the common use of arithmetic summary statistics to summarise data in source references, even though CRwo-media values generally tend towards a lognormal distribution and should, therefore, be summarised using geometric statistics. In this paper, we propose a statistically-defensible and robust method for reconstructing underlying datasets to calculate condition-specific CRwo-media values from summarised data and deriving geometric summary statistics. This method is applied to terrestrial datasets from the WTD. Statistically significant differences in sub-category CRwo-media values (e.g. mammals categorised by feeding strategy) were identified, which may justify the use of these CRwo-media values for specific assessment contexts. However, biases and limitations within the underlying datasets of the WTD explain some of these differences. Given the uncertainty in the summarised CRwo-media values, we suggest that the CRwo-media approach to estimating transfer is used with caution above screening-level assessments.Journal of Environmental Radioactivity 09/2013; · 3.67 Impact Factor
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ABSTRACT: The application of the concentration ratio (CR) to predict radionuclide activity concentrations in wildlife from those in soil or water has become the widely accepted approach for environmental assessments. Recently both the ICRP and IAEA have produced compilations of CR values for application in environmental assessment. However, the CR approach has many limitations, most notably, that the transfer of most radionuclides is largely determined by site-specific factors (e.g. water or soil chemistry). Furthermore, there are few, if any, CR values for many radionuclide-organism combinations. In this paper, we propose an alternative approach and, as an example, demonstrate and test this for caesium and freshwater fish. Using a Residual Maximum Likelihood (REML) mixed-model regression we analysed a dataset comprising 597 entries for 53 freshwater fish species from 67 sites. The REML analysis generated a mean value for each species on a common scale after REML adjustment taking account of the effect of the inter-site variation. Using an independent dataset, we subsequently test the hypothesis that the REML model outputs can be used to predict radionuclide, in this case radiocaesium, activity concentrations in unknown species from the results of a species which has been sampled at a specific site. The outputs of the REML analysis accurately predicted (137)Cs activity concentrations in different species of fish from 27 Finnish lakes; these data had not been used in our initial analyses. We recommend that this alternative approach be further investigated for other radionuclides and ecosystems.Science of The Total Environment 06/2013; 463-464C:284-292. · 3.26 Impact Factor
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ABSTRACT: An environmental risk assessment (ERA) was performed to evaluate the impact on non-human biota from liquid and atmospheric radioactive discharges by the Belgian Nuclear Power Plants (NPP) of Doel and Tihange. For both sites, characterisation of the source term and wildlife population around the NPPs was provided, whereupon the selection of reference organisms and the general approach taken for the environmental risk assessment was established. A deterministic risk assessment for aquatic and terrestrial ecosystems was performed using the ERICA assessment tool and applying the ERICA screening value of 10 μGy h(-1). The study was performed for the radioactive discharge limits and for the actual releases (maxima and averages over the period 1999-2008 or 2000-2009). It is concluded that the current discharge limits for the Belgian NPPs considered do not result in significant risks to the aquatic and terrestrial environment and that the actual discharges, which are a fraction of the release limits, are unlikely to harm the environment.Journal of Environmental Radioactivity 08/2013; 126C:61-76. · 3.67 Impact Factor