Most knowledge of the biogeochemistry, food chain transport, bioaccumulation, toxicity, and aquatic ecosystem effects of selenium derives from research conducted in reservoirs and lakes (lentic systems). The few studies of selenium in streams (lotic systems) indicate that differences in the biogeochemistry, speciation, bioavailability, and food chain transport of selenium result in lower toxic effects than would be predicted from available lake data. Nevertheless, permits for selenium-containing effluents that are discharged to streams typically are based on the chronic criterion (5 ppb), which is based on data from lakes. This criterion concentration is likely to be lowered by EPA before year-end 2004, making permitting more difficult for all selenium dischargers. EPA, however, is receptive to proposals for site-specific permitting methods.

The goals of this research are to: (1) delineate selenium cycling, speciation, bioaccumulation, and toxic effects in streams receiving selenium discharges, (2) compare and contrast selenium dynamics in lakes and streams, and (3) develop, in collaboration with EPA and various industries, site-specific permitting methods for point-source discharges to running waters. Features include:

• understanding of selenium biogeochemistry in running waters;
  
• delineation of the role of selenium speciation in bioaccumulation, food chain transport, and toxicity in running waters;
  
• demonstration of the need for a site-specific approach to discharge permits for streams; and
  
• guidance for site-specific permitting of selenium discharges to streams.