Simulation and prediction of anthropogenic lead perturbation in the Mediterranean Sea

Simulations of Pb biogeochemical cycles were carried out based on a box model previously developed and tested by in-situ measurements. It has been demonstrated that the different evolutions of the fluxes determining the Pb budget lead to disequilibrium in Pb biogeochemical cycles in the Mediterranean Sea, particularly the anthropogenic perturbation governed by economical development and political regulations. Such a disequilibrium resulted in an increase in the concentration of lead between 1950 and 1976. Pb concentrations have decreased since 1976 in the Western Basin thanks to the application of limited Pb consumption regulations in the western countries. However Pb concentrations will increase again and the critical concentration for marine organisms will be reached by the middle of the next century if Pb consumption is not limited in the eastern countries. In relation to the exchange with the North Atlantic, the Mediterranean Sea acted as a sink for Pb before 1980, but since 1981, has become a source. Concerning the accumulation in the sediments, about half of the total external input was estimated to have been deposited between 1950 and 1992.