PARTITIONING OF TRACE-METALS IN SUSPENDED MATTER FROM THE ELBE ESTUARY FRACTIONED BY A SEDIMENTATION METHOD

The particulate matter in water samples from the freshwater region of the Elbe estuary was fractioned by its setting characteristics. The se dimenting and the permanently suspended fractions of the particulate m atter were analysed separately for trace metals (Cd, Pb, Cu, Cr, Co, N i) and organic composition. The two fractions differed significantly i n organic and metal content and C-13 in organic matter. Permanently su spended particles rich in riverine biogenic material contained amounts of trace metals enhanced by a factor of about three in comparison to the sedimented fraction. Also, 80% of the total particulate trace meta ls was transported downstream by this fraction. Along the profile of t he Elbe from km 630 to km 670 a decrease in suspended particulate trac e metals occurred in both fractions, which amounted to a reduction of approximately 50% between March and June. The largest decrease was det ected just below Hamburg harbour and was explained by mixing of highly polluted riverine SPM with less polluted sedimenting SPM from downstr eam regions. The specific loading of the particulates with trace metal s was linked to the particulate organic matter content which was in pa rt degraded during the transport downstream. The adsorption characteri stics of the organic matter remained quite constant both over the fres hwater profile and at different times of the year and accumulation [C/ Metal (g.mg-1)] varied mostly between 0.5 and 1 for Cu, Pb, Cr and Ni and 15 to 30 for Cd. The results indicate that even small changes in t he particulate organic matter composition might produce great differen ces in the total particulate trace-metal content.