Clay mineral and heavy metal distributions in the northeastern North Sea

Abstract

Clay mineralogy and heavy metal distribution of surface sediments of the northeastern North Sea have been analysed in order to show the origin and transport pathways of fine-grained sediments. The distribution patterns of clay minerals largely reflect regional current patterns. Fine material enriched in smectite, derived mostly from the German Bight sector in the south, is transported by the Jutland current parallel to the west coast of Denmark into the Skagerrak, where a decreasing proportion of smectite indicates the increasing influence of the central and northern North Sea currents. Illite and chlorite have identical distribution patterns in the northeastern North Sea which suggests a common origin for both clay minerals. This origin is located in Pleistocene relict sediments of the northern North Sea rather than in a contribution from the North Atlantic. Zinc, cadmium, copper and lead in surface sediments of the North Sea, when compared to background values, are significantly enriched. Sediments of the Inner German Bight are in comparison with other North Sea sediments highly polluted. A zone of high heavy metal contents (Zn, Cd and Cu) is found along the German and Danish coasts comparable to the smectite distribution indicating the transport of fine-grained polluted sediments to the north. Further to the north these sediments are diluted by less polluted sediments. Finally in the Skagerrak and the Norwegian Trench a relatively low stage of pollution is reached.