A BOX-MODEL OF METAL FLOWS THROUGH THE SCHELDT ESTUARY (1981-1983 AND1992-1995)

The behaviour of Cu, Zn, Cd and Pb in the Scheldt estuary was investig ated in the periods 1981 to 1983 and 1995. The Hg behaviour was studie d between 1992 and 1994. A box model was used to establish the relatio nship between the trace metal inputs and the fate of these pollutants in the Scheldt estuary. Annual budgets were calculated for particulate and dissolved trace metals. For Hg, seasonal budgets of the various s pecies (inorganic Hg, methylmercury, Hg degrees) could also be calcula ted. These budgets allow an evaluation of the consistency of each indi vidual flux or process, such as the inputs of the various metals into the North Sea, the sedimentation flux of particulate metals in the are a of high turbidity, the evasional fluxes and the formation rates of H g degrees, etc, in relation to the other ones.