PARENT SESSION
SA5 - Selenium: Toxicity Investigations of Ecological Risks
Chair: Harb, John1, 1 nharb@do.usbr.gov
8:00 AM to 12:00 PM - Sunday, 17 November 2002
Room Ballroom D
(046) Derivation Of A Site-Specific Effluent Standard For Selenium In The Great Salt Lake, Utah.
Adams, William*,1, Brix, Kevin2, DeForest, David3, 1 Rio Tinto, Salt Lake City, UT, USA2 EcoTox, Newport, OR, USA3 Parametrix, Inc., Kirkland, WA
ABSTRACT- A site-specific effluent standard for selenium in the Great Salt Lake, Utah was developed by assessing bioavailabilty and toxicity of selenium to resident biota in the lake and by considering the potential for dietary selenium exposure to aquatic dependent birds. Because of its high salinity, the lake has limited biological diversity with bacteria, algae, diatoms, brine shrimp and brine flies being the only organisms always present in the lake. To evaluate their sensitivity to selenium, a series of acute and chronic toxicity studies were conducted on the brine shrimp, Artemia franciscana, the brine fly, Ephydra cinerea, and the hypersaline algae, Dunaliella viridis. The resulting acute LC50 and chronic values were relatively high compared with many freshwater species. This is thought to be the result of the high ambient sulfate concentrations (8,500 mg/L) in the lake, as sulfate is known to reduce selenate bioavailability (the predominant form of selenium in the lake). Acute and chronic test results were compared to selenium concentrations expected to occur in a mining effluent discharged at the south end of the lake. Based on the toxicity test results and the effluent selenium concentrations, no appreciable risks to resident aquatic biota are expected from selenium in the discharge. Field and laboratory data collected on selenium bioaccumulation in brine shrimp and brine fly larvae demonstrated a linear relationship between water and tissue selenium concentrations. Applying a dietary selenium threshold of 5 mg/kg dw for aquatic birds to this relationship resulted in an estimate of 27 mg/L Se in water as a safe concentration for the exposure pathway and an appropriate site-specific water quality standard. The data indicate a discharge limit of 27 ug/L would not result in direct toxicity to aquatic organisms or result in dietary selenium concentrations that would affect hatchability or survival of sensitive birds species.
Key words: selenium, Great Salt Lake, brine shrimp, good guys