BIOGEOCHEMICAL PROCESSES AFFECTING SELENIUM CYCLING IN WETLANDS

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