1.1 ,Relevance of Sediment Contamination—,Sediment provides habitat for many aquatic organisms and is a major repository for many of the more persistent chemicals that are introduced into surface waters. In the aquatic environment, both organic and inorganic chemicals may accumulate in sediment, which can in turn serve as a source of exposure for organisms living on or in sediment. Contaminated sediments may be directly toxic to aquatic life or can be a source of contaminants for bioaccumulation in the food chain.