A sediment trap and radioisotope study to determine resuspension of particle reactive substances in the sound between Sweden and Denmark

摘要

Sediment traps and the radioisotopes Cs-137, Pb-210, Be-7, Th-234 and Th-228 were used to study downward fluxes and resuspension of sediments in the shallow sound (Oresund) between Sweden and Denmark connecting the Baltic Sea with the North Sea. The water transport through Oresund covers approximately 30% of the total water transport between the North Sea and the Baltic Sea. The heavy boat traffic and the densely populated surroundings coupled to a shallow Sound makes resuspension events ail important factor in transporting released pollutants. Over the time period studied massfluxes recorded by the sediment traps ranged between 175 g m(-2) day(-1) near bottom during winter time to less than 1 g m(-2) day(-1) during late spring when the water column was stratified. A combination of sediment traps at different levels in the water column and radioisotope ratios shows that resuspended seabed sediments accounts for a large portion of the collected trap material, ranging from nearly 100% during the winter period to some 50% during stratified periods in late spring.