Modelling radioactivity dispersion in the Alborán Sea, western Mediterranean

Abstract
A numerical model which simulates the dispersion of non-conservative radionuclides in the Alboran Sea has been developed. Water currents are obtained from two hydrodynamic models working on the same domain: a 2D depth-averaged model is used two calculate tides and a 2-layer has been applied to obtain the residual (mean) circulation. The output of the hydrodynamic models is first applied to calculate suspended particle concentrations and sedimentation rates over the domain, which are also required by the radionuclide transport model. This assumes that radionuclides may be present in three phases: dissolved, suspended matter and bed sediments. Exchanges between the liquid and solid phases are described through kinetic transfer coefficients. The model has been applied to simulate the dispersion of 137-Cs and 239,240-Pu introduced in the sea from atmospheric fallout. Measured and computed radionuclide concentrations in the water column and in bed sediments are, in general, in good agreement.