Profiles of dissolved gaseous mercury concentration in the Mediterranean seawater

Profiles of dissolved gaseous mercury (DGM) concentration were systematically measured on a wide geographical scale for the first time in the Mediterranean basin during the international oceanographic cruise MED-OCEANOR on board the R/V Urania of the National Research Council of Italy from 14 July to 10 August 2000. Generally, DGM levels increase from the surface to the first hundred meters and remain constant down to the bottom, suggesting that DGM is produced not only in surface water via photo-induced reactions, but also in deep water as a consequence of bacterial activity, even if it is not possible to exclude a contribution of the geothermal activity at the bottom. The Western Mediterranean basin resulted to be characterised by an average DGM concentration value (0.088 pM) in surface water, lower than that observed in the Eastern basin (0.211 pM).