ACCUMULATION OF HEAVY-METALS IN THE ODER ESTUARY AND ITS OFFSHORE BASINS

The river Oder drains a highly polluted industrial area of Eastern Eur ope and enters the Baltic Sea through a system of shallow water lagoon s. Heavy metal distribution pattern in sediments of the Oder lagoon an d its off-shore basins reflect the influence of heavy metal pollution on the estuarine and open Baltic environment. Heavy metal concentratio ns in surficial sediments of the Oderhaff are up to 5-times higher com pared to other subareas within the study area. Enrichment factors of C o, Ni, Cu, Zn and Pb in surficial sediments over the preindustrial bac kground are highest in the inner lagoon of the Oderhaff and decrease c loser to the open Baltic. Cu, Zn, and Pb concentrations increase stron gly at a distinct depth (between 5 and 40 cm) towards the sediment sur face in all sediment cores, while other metals, such as Co and Ni, rem ain almost unchanged. One of the investigated sediment cores (IOW #180 19, Arkona Basin) shows an undisturbed sediment accumulation pattern a nd yielded a historical record of heavy metal accumulation for the Sou thern Baltic. Heavy metal accumulation rates in sediments indicate tha t pollutants at present bypass the Oderhaff lagoon, whereas the off-sh ore basins act as final sinks for the heavy metals. The data point to a 2 to 3-times higher heavy metal accumulation in the Arkona Basin com pared to the Bornholm Basin. This reflects the prefered NW-direction o utflow of the Oder river during spring time, when the river load is hi ghest, and the weak exchange of water masses between the Arkona and Bo rnholm Basin. Since the beginning of industrialization, the anthropoge nic Cu is about 30% of the total Cu-accumulation, for Zn about 40% and for Pb about 50%.