ABSTRACT
Biomethylation of mercury (Hg) in sediments depends on its chemical form as well as the chemical and physical characteristics of the sediment. The cycling, transformation, deposition, and availabilities of the various forms of Hg and other metals and metalloids in the aquatic ecosystem depend not only on their physicochemical natures but also on the metabolic interactions of the transforming microbes with other microbial species. The volatility of many naturally formed compounds leads to their rapid discharge from the environment, but both methylated arsenicals and tetraalkyllead have been detected in aquatic organisms, and both bioaccumulate in fish to some extent. Morphological and chemical factors play important roles in determining the rate of adsorption and sedimentation of Hg in aquatic systems. The partitioning of lead between the aqueous and solid phases in aquatic environments is affected by input from diverse sources as well as biological activities and a variety of other factors.
