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Large-scale extraction of metals presents hazardous waste management problems worldwide. Projections show that by the year 2000 mining will hgve directly disturbed about 240,000 km of the Earth's surface (1), an area about the size of Oregon; copper mining alone is projected to totally disrupt about 1600 km2 of land. Milling and smelting presently release an estimated 7 to 70 x 103 metric tons (MT) of metals to the aquatic environment (1,2). Metal production has increased over the last century although the grade of ore has declined (3), and the richest metal reserves are now in less developed countries (4) where legislative protection from environmental damage often is limited.Coping with hazardous waste problems is an immense challenge (5). In the United States, EPA has identified over 31,000 hazardous waste sites (6); about 1200 of these need immediate response, and only a small proportion have been cleaned up (6, 7). The largest complex

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Selenium fractionation and speciation in Benton Lake National Wildlife Refuge (Montana), a wetland system containing moderate levels of selenium, were studied to determine the biogeochemical processes of selenium in wetlands. Results showed that selenate was a major selenium species of dissolved selenium in drainage water. It decreased substantially through the pond system as the relative percentages of organic selenium and selenite increased. Elemental selenium and selenium associated with organic materials were the major fractions in sediments, accounting for a mean of 46% and 33% of total selenium, respectively. Concentrations of soluble selenium and adsorbed selenium were relatively low, respectively accounting for a mean of 5% and 13%. Within the soluble and adsorbed fraction of selenium in sediment, selenate and organic selenium were the major selenium species. Selenium associated with oxides was very low (less than 4%). In this wetland environment, microbial reduction of selenate to elemental selenium, selenium uptake by wetland organisms, and incorporation of these organisms into wetland sediment are the major processes removing selenium from the water column; selenium adsorption is relatively less important.