SEDIMENT TRANSPORT PATHWAYS IN THE SKAGERRAK AND KATTEGAT AS INDICATED BY SEDIMENT CHERNOBYL RADIOACTIVITY AND HEAVY-METAL CONCENTRATIONS

The concentration of the heavy metals Hg, Cu, Pb and Zn as well as Che rnobyl Cs-137 radioactivity was determined in surface sediments from t he Skagerrak and Kattegat. Sediment samples from adjacent Swedish fjor ds were analysed as well. The sampling was carried out between spring 1988 and autumn 1990. Highest concentrations of heavy metals and large st Cs- 137 activities occur in fine-grained organic-rich (> 2% C(org)) sediment from Swedish inshore waters and locally also in the Kattegat . Regional trends of relative enrichment of the various heavy metals a nd Chernobyl Cs-137 with respect to organic carbon was used to determi ne transport patterns of material enriched with respective elements. I t can be proven that deposition of fine-grained material transported f rom the (southern) North Sea by the Jutland Current is the main mechan ism determining the regional accumulation of lead and Chernobyl-derive d Cs-137. This mechanism principally controlls the areal distribution of mercury-enriched material as well, but it is regionally of less imp ortance as far as the accumulation of Cu and Zn concerns. The Chernoby l Cs-137 data show that a large proportion of the fine-grained materia l transported by the Jutland Current originally is river-borne suspens ion load from (central) westem Europe. The areal enrichment pattern of copper, and on a smaller scale those of mercury and zinc too, points to westerly directed suspension load transport across the Kattegat. Ma terial enriched with these elements apparently is being discharged fro m Swedish industrial and urban centers, in particular the Goteborg are a.