Copper and cadmium uptake by estuarine sedimentary phases

An understanding of the distribution of toxic trace metals and other materials of environmental interest among the different sedimentary phases is necessary to assess the hazard associated with pollution of aquatic sediments.A simple model, analogous to speciation in solution among soluble ligands, was developed to enable the distribution of metals within sediments to be estimated.The model requires the conditional metal binding constants (slopes of the linear portions of the adsorption isotherms) to be evaluated for a small number of model sedimentary phases in isolation, as well as knowledge of the composition of the sediment and water.The model has been applied to the distributions of copper and cadmium in estuarine sediments and predicts that iron and organic matter are the sedimentary constituents of greatest importance for these metals.Manganese phases may contribute to cadmium binding, but clay minerals and (probably) aluminosilicates are insignificant sinks for both copper and cadmium.The model predictions for copper and cadmium in estuarine sediments are in good semi- quantitative agreement with the results of selective ex- traction studies on natural sediments reported in the literature and studies reported here of cadmium uptake by natural sediments.