Modelling surface radioactive, chemical and oil spills in the Strait of Gibraltar

A model that simulates the dispersion of chemical/radioactive and oil spills in the Strait of Gibraltar has been developed. Water currents over the Strait have been obtained from a hydrodynamic model. Computed tides and residual currents have been compared with observations in the area. The dispersion model, based on a particle-tracking technique, is solved off-line. Standard tidal analysis, carried out over results provided by the hydrodynamic model, is applied to obtain currents at any time and position of the Strait. Specific processes for each contaminant (decay of radioactive material, oil evaporation and decomposition) are included and simulated by means of a stochastic method. A Monte Carlo method is applied for turbulent diffusion. The model can deal with instantaneous and continuous releases. MatLab graphic user interfaces have been developed to introduce input data and visualize simulation results. Some dispersion calculations have been carried out. In general, contaminants are flushed towards the east due to the residual currents. Nevertheless, dominant east winds tend to retain contamination in the Strait and to enhance mixing. This is also the case if the release occurs close to the coast, where currents are weaker than in the central part of the Strait.