Biogeochemical processes affecting selenium cycling in wetlands

Important selenium data in the literature are discussed with reference to the biogeochem-ical processes affecting selenium cycling in wetlands. Selenium oxidation-reduction reactions are shown to be the most important biogeochemical processes controlling speciation, precipitation/dissolution, sorption/desorption, methylation, and volatilization of selenium. Furthermore, bioavailability and toxicity of selenium, with reference to wetland ecosystems, are summarized. Based on the information available in the literature, a conceptual model depicting selenium chemistry and behavior in wetlands is described.