Four grain size correction procedures were tested for their applicability for comparing concentrations of heavy metals and organic micropollutants (PCBs, PAHs) in sediments . A simple and straightforward procedure proved best : wet sieving of fresh sediment, isolating and analysing the < 63 ,um grain size fraction and expressing the pollutant concentration as a proportion of the fraction's dry weight . The total analytical errors, expressed as the variation coefficient of the average concentrations, were 3 .8-7 .6% for heavy metals, 12-24% for PCBs and 5 .3-9 .9% for PAHs .

No abstract

No abstract

From literature data it is calculated that on an annual basis, 11 to 17 tonnes of PCBs enter the North Sea. Largest sources are the Atlantic Ocean and the atmosphere: together they account for 60-79% of the total input. Sources with greatest impact are the rivers, sewers and sludge. Highest concentrations are found close to the Dutch shore and in the German Bight. The PCB levels result in adverse effects on the seal population in the Wadden Sea. Of the total world PCB production, at least 57% is still in use and their future dispersal into the oceans cannot easily be controlled. If the increase in ocean PCB concentration continues, it may ultimately result in the extinction of fish-eating marine mammals.

No abstract