MODELING OF RADIOCESIUM IN LAKES - THE VAMP MODEL

The objective of this work is to present a new, state-of-the-art model for predicting radiocesium in lakes. The target variables to model an d predict are Cs concentrations in lake water and in predatory fish. T hese results emanate from IAEA's VAMP project, initiated after the Che rnobyl accident in 1986. The sites included in this work cover a wide range of lake and catchment characteristics. This new VAMP model has n ine specific components (see below), which are meant to increase the p redictive accuracy of the model and make it easy to apply for lakes in general. (1) A seasonal variability moderator for water discharge. (2 ) A dimensionless moderator for the water retention rate. (3) A season al variability moderator for epilimnetic and hypolimnetic temperatures , which influence lake stratification and redox-induced internal loadi ng of radiocesium from sediments. (4) A transfer coefficient to calcul ate relationships between biomasses. (5) An outflow rate function for the transport of cesium from the catchment to the lake. (6) A dimensio nless moderator for planktonic uptake of radiocesium, i.e. for the tra nsfer of cesium in dissolved phase in the lake water to phytoplankton. (7) An algorithm for the lake partition coefficient (Kd). (8) A sub-m odel to express biological half-lives. (9) An approach to quantify int ernal loading. Empirical validations, and critical sensitivity tests, have shown that the VAMP model in many lakes yields just as good predi ctions as parallel sets of empirical data, and this is as goon as any model can yield. rt should be possible to improve the VAMP model furth er if and when more field data become available, for both the VAMP lak es and other sites. Copyright (C) 1996 Elsevier Science Limited