The coupling of long-term trace metal trends to internal trace metal fluxes at the oxic-anoxic interface in the Gotland Basin (57°19,20′N; 20°03,00′E) Baltic Sea

Highly resolved vertical profiles of trace metals (Pb, Cd, Zn, Cu, Co, Fe, Mn) have been carried out between December 1999 and February 2001 on a seasonal base. Calculations of dissolved trace metal fluxes using the vertical turbulent mixing coefficient according to the seasonal movement of the redoxcline gave information about the diffusive flux and quantitative transport of trace metals into the anoxic water body. For Cddiss, Cudiss and Zndiss, elevated downward fluxes were observed during winter season, and by a factor 1.5-2 reduced fluxes during summer. Codiss, Fediss and Mndiss show no seasonal flux variations. About 25% of Cd, 12% of Cu and 8% of Zn which has been supplied by rivers and by the atmosphere are eliminated by diffusive exchange, due to sulfide precipitation, across the oxic-anoxic interface in the Gotland Basin. For dissolved lead, the diffusive exchange is negligible.