DO DECREASED TRACE-METAL CONCENTRATIONS IN SURFICIAL SKAGERRAK SEDIMENTS OVER THE LAST 15-30 YEARS INDICATE DECREASED POLLUTION

Varying concentrations of Zn, Pb and Cu over the last 15-30 years (199 1-1963) have been found in two undisturbed cores with preserved sedime nt-water interfaces from the Skagerrak (Station A: 645 m, Station B: 4 05 m water depth). Mass Accumulation Rates (MAR) in g/m2/year were use d to resolve the question of increased or decreased supply. Station A- MAR increased exponentially: Zn from 0.05 to 0.28, Cu from 0.009 to 0. 044, and Pb from 0.003 to 0.114 g/m2/year, while concentrations did no t show this increase over the last 15-30 years. Station B-MAR increase d exponentially: Zn from 0.07 to 0.29, Cu from 0.013 to 0.049, and Pb from 0.014 to 0.114 g/m2/year, while concentrations decreased over the same period. MAR indicated that both stations received similar trace metal flux. Release of trace metals from the sediment to the water col umn and/or dilution by water and organic matter within the upper few c entimetres of the sediment accounted for the concentration decrease at both stations. MAR revealed an increase in trace metal supply, and th us an increase in pollution, over the last 15-30 years, although conce ntrations indicated the opposite.