Mass balance of trace metals in the Adriatic Sea

A first order mass balance of six different trace metals (Mn, Fe, Pb, Zn, C u, Ni) was presented for a 1-year period for the different compartments of the Adriatic Sea: compartment 1 (northern Adriatic Sea), compartment 2 (cen tral Adriatic Sea and surface layer of the southern Adriatic Sea) and compa rtment 3 (deep water of the southern Adriatic Sea). The Adriatic Sea appear ed to be a source of dissolved Cu, Mn and Fe for the Mediterranean Sea thro ugh the Strait of Otranto whereas for dissolved Zn and Pb the Adriatic Sea appeared to be a net sink. For dissolved Ni, inputs and outputs through the Strait of Otranto balanced each other. The: residence times of all metals in compartment 1 were significantly shorter than that of water indicating s ignificant removal. Tn compartments 2 and 3, residence times of Mn and Fe w ere relatively short suggesting removal from the water column whereas for t he other metals their residence limes were similar to that of water. Calcul ations of turnover times of metals with respect to different processes show ed that in compartments 1 and 2, sedimentation was the main process that af fected the content of the reservoirs whereas in compartment 3, the water fl ux exchanges played an important role for Zn, Cu and Ni. Most of the metals clearly undergo a very dynamic cycle of sedimentation/re mobilization particularly in the Northern Adriatic Sea. Tn the northern Adr iatic Sea, most of the Mn and Fe in deposited sediment were remobilized. Th is was related to diagenetic processes involving the utilisation and solubi lisation of Mn and Fe oxides, which occur in the surface of the sediment in the northern Adriatic Sea. In the central Adriatic Sea, remobilization of Mn and Fe was less than in the northern Adriatic Sea, suggesting that diage nesis processes appear deeper in the sediment. Advective transport of sedim ent was a major sourer of metals for the deep basin. As much as 80% of the sediments in the South Adriatic Pit might be advected from the shelf. Remob ilization fluxes in the South Adriatic Pit were significantly less than in the Northern and Central Adriatic Sea reflecting hemi-pelagic sediments. (C ) 2000 Elsevier Science B.V. All rights reserved.