Mass balance of mercury in the Mediterranean Sea

The Mediterranean Basin is rich in mercury from natural and anthropogenic sources. During an extensive research from 2002–2005, measurements of different mercury forms were carried out in the Mediterranean Sea by the Italian research vessel Urania as a part of the Med Oceanor and MERCYMS projects funded by the EU Framework programme. Further on, transport and fate of mercury forms was simulated in water and air compartments by two different models, and an approximate coupling of both models was performed. The new 3-dimensional model PCFLOW3D was completed with the first version of a biogeochemical module which deals with various mercury species in dissolved and particulate forms. Exchange with the bottom and the atmosphere, methylation, demethylation, reduction and oxidation were taken into account. Based on the integrated hydrodynamic-atmospheric model and results of field measurements the mass balance of total mercury in the Mediterranean Sea was determined in order to estimate main sources and sinks and simulate future trends of mercury contamination in the Mediterranean. The following terms were taken into account: sources of mercury from major rivers and from point sources, exchange with the Atlantic Ocean and the Black Sea, estimated natural sources from geotectonic active areas in the sea, exchange with bottom sediments, and evasion to and deposition from the atmosphere.