Study of metal sorption/desorption processes on competing sediment components with a multichamber device

A new multichamber device was developed to study sorption/desorption reactions of metals on different competing sediment components and the influence of environmental factors on these reactions. The system consists of a central chamber connected with six external chambers and separated by 0.45-μm-diameter membranes. The diffusion kinetics of metals between the single chambers were determined. Equilibrium was attained within 24 h. Algal cell walls (Scenedesmus quadricauda), bentonite, aluminium oxide, managese oxide, quartz powder, and goethite were used as model sediment components. Determination of metal sorption on the solid phases resulted in a significant enrichment on the algal cell walls, particularly for Cu and Cd. It was concluded that sorption depends not only on ion exchange but also on complexing reactions which lead to relatively stable surface binding. A second series of experiments investigated the effect of seawater on sediment components and dredged mud. Cadmium was remobilized from all solid components, but Cu was not remobilized from algal cell walls and bentonite. The dominant role of organic substrates in the binding of metals such as Cd andCu is of particular relevance for the transfer of these elements into biological systems. Even relatively small percentages of organic substrates, if involved in metabolic processes, may constitute a major pathway by which metals are transferred within the food chain.