Austausch von Schwermetallen an der Grenzfläche Wasser/Sediment in Gewässern und Baggergutdeponien

[Einführung:] Die Gewässergüte-Wirtschaft in der Bundesrepublik Deutschland (und in anderen Industrieländern) steht derzeit vor einem Widerspruch: einerseits können Erfolge bei der Verringerung von Schadstoffeinträgen in vielen Oberflächengewässern verzeichnet werden (...); andererseits nehmen die Probleme bei der Beseitigung von kontaminierten Gewässersedimenten eher zu (...)Subsequent to the desciption of characteristic exchange processes including examples from both literature and own research the alternatives for the treatment of dredged sludges were evaluated under the aspect of heavy metal mobilization (including changes of typical associations) as follows: (1) During handling of contaminated sediments under water oxidation processes may affect an enhanced consumption of oxygen and a reducction of the bonding strength of metals. (2) Following open water field or diked disposal of less buffered sludges the oxidation of sulfide minearals leads to lowering of pH-Values and partially to significant remobilisation of metals. (3) After dumping in estuarine, coastal, and shallow marine areas both oxidation of sulfides and organic substances takes place; metals released are partly kept in solution by complexation processes. (4) Regarding the heaplike deposition of dredged sludges on land, which is favourable because of the better control and repair facilities, stabilization measures should be optimized also with respect to the fixation of heavy metals. (5) Due to the formation of sparingly soluble sulfide phases of heavy metals the marine environment, e.g. in the form of a near-shore subsediment deposit, could provide a noteworthy alternative for solving the problems with dredged materials, as has been demonstrated by the example of a peninsula project in the North Sea coast of Rotterdam