Sediment surface geochemistry of three Baltic Sea Deep Basins.

Three deep basins were chosen for this study and the most recent changes that are reflected in the uppermost 15 to 35 cm are reported. The Gotland Basin, the largest continuous sedimentation basin in the southern Baltic Sea, was chosen for the present study. Simultaneously, a quite large basin, the North Central Baltic Basin was investigated and chemical data are reported for the first time. In the southern Baltic Sea the Bornholm Basin was investigated. All 3 basins are different as regards the physicochemical conditions in the area. The investigated elements were divided into different groups according to their origin and geochemical behavior: elements of natural terrestrial origin; nutrients; elements that are confined to early diagenetic minerals; and in the near-surface zone the anthropogenic elements including several harmful metals. Although there seems to be a decreasing trend in the surface zone the metal concentrations are still clearly elevated.