ENVIRONMENTAL-CONDITIONS CONTROLLING SELENIUM VOLATILIZATION FROM A WETLAND SYSTEM

Natural selenium volatilization from Benton Lake, MT, a wetland system containing moderate levels of selenium, was studied in water-sediment , water-sediment with a flooding-drying cycle, and plant-water-sedimen t microcosms. Results showed that selenium volatilization occurred fro m water, sediment, and wetland plants. Sediment and plants were the ma jor producers of volatile selenium from the system. The rate of seleni um volatilization from algae and high-selenium sediment was much highe r than that from watermilfoil and low-selenium sediment. The rate was also controlled by various environmental factors. Higher temperature, higher air flow, flooding-drying and the decomposition of wetland plan ts greatly increased the removal rates of selenium through selenium vo latilization. Our results suggest that natural selenium volatilization can be an important process removing selenium from wetland systems.