Modelling of radiocaesium in lakes. Results from the VAMP project

The paper provides an overview of the main results from the IAEA VAMP (Validation of Environmental Model Predictions) project, which will be presented in a comprehensive technical report that will be published by the IAEA. Seven models for radiocaesium in lakes have been critically examined. The predictions (137Cs in water, sediments and biota) have been validated with data from seven European lakes covering very wide ranges in most limnological characteristics and Chernobyl fallout. The models differ widely in terms of size (number of variables and processes accounted for) and set-up (definitions of fundamental model variables, such as retention of water and radiocaesium, bio-uptake rates, internal loading, seasonal variability, etc.). Much work has been done on critical evaluations of the models (e.g. sensitivity and uncertainty tests). An important objective has been to identify the most fundamental processes regulating the distribution and bio-uptake of radiocaesium in lakes. A new model for predicting radiocaesium in water and predatory fish has been developed. A definition of the important concept of 'predictive power' is presented. The paper discusses the 'sensitivity' of lakes to radiocaesium as well as various remedial strategies. (author). 2 refs, 6 figs, 2 tabs