ON THE ACCUMULATION-DISPERSION PROCESSES OF THE TRACER CS-137 IN THE ITALIAN SEAS

This paper addresses the study of accumulation-dispersion processes, i n the Italian Seas, of radionuclides due to fall-out on to the surface of the sea. Two periods are considered. 1960-1984, during which the f all-out was caused by large scale nuclear explosions in the atmosphere ; 1986-1992, during which the fall-out was caused by the Chernobyl acc ident. We focus on the analysis of vertical dispersion processes by me ans of mathematical models: a lumped parameter model (a depth-averaged model) for the sui;face layer and a depth dependent model for the dee p laver. A regression analysis performed by fitting the experimental d ata (fall-out and activities in sea waters) to the model equations all ows us to estimate the parameters introduced in the models. Fallout da ta are used as an input flux for the lumped parameter model to simulat e the dispersion processes in a surface layer. This model also produce s the output Jinx at the lower interface, which is used as input flux in a depth-dependent model for the deep layer. For sufficiently slow p rocesses, as during the period 1960-1984, the experimental data are we ll described and interpreted by these models. On the contrary, for rap id processes, as during the period 1986-1992, and when the experimenta l data are not complete, the analysis carried our with these models ca nnot be satisfactory. (C) 1997 Elsevier Science Ltd.