Mobilization and transfer of heavy metals to major sediment components after changes of typical estuarine conditions (salinity, redox potential/pH) have been studied in a newly developed experimental device, consisting of a central chamber connected with six external chambers and separated by membranes of 0.45-µm pore diameter. Algal cell walls (Scenedesmus quadricauda), bentonite, Al-oxide, Mn-oxide, quartz powder and goethite were used as model sediment components. Significant metal enrichment was found on algal cell walls, and on freshly precipitated iron hydroxide. Oxidation of anoxic mud from Hamburg harbour causes lowering of pH and remobilization of cadmium and zinc. The experiments of the effect of seawater on sediment components and dredged mud indicate the dominant role of organic substrates in the binding of metals such as cadmium and copper, suggesting that even at relatively small percentages of organic substrates these materials are primarily involved in metabolic processes and thus may constitute the major carriers by which metals are transferred within the food chain. These results demonstrate that is particularly problematic to disperse waste materials in ecologically productive, high-energy environments such as estuaries. [Presented at the 10th International Symposium "Chemistry of the Mediterranean" May 1988, Primosten, Yugoslavia.]