LEAD IN THE NORTH-SEA AND THE NORTH-EAST ATLANTIC-OCEAN

Lead has been determined in 105 water samples from the northeast Atlantic and from the North Sea. Rigorous precautions were applied to avoid contamination during sampling and analysis. Two different analytical methods were used: anodic stripping voltammetric-technique (ASV) and atomic adsorption spectral photometry (AAS). Determinations with ASV were carried out on board, directly after sampling. After 2 mo. storage, acidified samples were analysed by AAS after freon dithiocarbamate extraction and nitric acid back extraction. Particulate Pb was determined by AAS after an acid digestion. The profiles of Pb concentration vs. depth show around 160 ppm at the surface and around 20 ppm at the bottom, both in the Atlantic and in the Norwegian Sea. The shapes of the profiles are different depending on the hydrography of the area sampled. The profiles from the northeast Atlantic coincide with a profile from the Northwest Atlantic. These profiles have Pb concentrations about a factor of 3 higher than those in the pacific. Considering the high Pb input in the North Sea, the Pb concentrations found there are remarkably low, probably because of scavenging effects in estuaries leading to a short residence time in the water column. The dominant Pb input in offshore regions is from the atmosphere. The highest Pb levels are found in the northern North Seas, around 300 ppm in surface water. In the Atlantic, particulate Pb is a minor part of the total Pb; in the North Sea the particulate fraction is larger, up to 40%.