Simulation of radionuclide fluxes from the Dnieper-Bug Estuary into the Black Sea

To simulate the radionuclide flux from the Dnieper-Bug Estuary into the Bla ck Sea the three-dimensional time-dependent flow and transport code THREETO X was used. The prognostic variables of the model are the three components of the velocity field, temperature, salinity, surface elevation, suspended sediment concentration and the rajionuclide concentrations in the solute, s uspended sediments and bottom deposition. The dispersion of Cs-137 and Sr-9 0 in the estuary and adjacent shelf area of the Black Sea over the first tw o years following the Chernobyl accident was reconstructed. The fluxes of r adionuclides from the Dnieper-Bug Estuary into the Black Sea were estimated . The results are in reasonable agreement with the available measurements. It is shown that the differences between the Cs-137 and Sr-90 distributions specific to the Dnieper-Bug Estuary were due to the different geochemical behaviours of these radionuclides. The deviation from a linear correlation between salinity and dissolved Cs-137 concentration in the estuary was show n to be due to exchange processes with contaminated bottom sediments, (C) 1 999 Elsevier Science Ltd. All rights reserved.