Changes in Metal Speciation Following Alteration of Sediment Redox Status

Abstract

This chapter discusses studies documenting changes in metal speciation following changes in sediment Eh status, emphasizing the concepts of redox intensity and capacity. Changes in metal speciation are affected by both redox intensity and capacity. Changes in oxidation-reduction potential can result from natural and anthropogenic alterations of sediment conditions. Changes in metal and metalloid speciation generally follow these changes in sediment Eh and pH conditions. The use of specific analytical techniques for speciation of the metals and metalloids in sediments will be presented. Sediments can serve as sinks or sources of toxic heavy metals to overlying water bodies. The exchange of metals across the sediment-water interface depends on a complex interplay of physical, chemical, and biological processes that control metal speciation, solubility, and the development of concentration gradients. Chromium, selenium and arsenic represent a class of metals and metalloids that exist in multiple valence states in the sediment environment.