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

(048) Remediation of a selenium-contaminated backwater channel in the upper Colorado River.

Hamilton, Steven^*,1, Holley, K.M.², Buhl, K.J.¹, Bullard, F.A.¹, ¹ U.S. Geological Survey, Yankton, SD² U.S. Bureau of Reclamation, Grand Junction, CO

ABSTRACT- A study was conducted in 1995-1998 to determine if operation of a water control structure allowing Colorado River flow through a channel area at Walter Walker State Wildlife Area could reduce selenium concentrations in aquatic ecosystem components. Selenium and other inorganic elements, were measured in water, sediment, aquatic invertebrates, and forage fish. Colorado pikeminnow were collected and muscle plug samples taken for selenium analysis. Selenium concentrations in filtered water were 21.0 g/L in 1995, 23.5 g/L in 1996, 2.1 g/L in 1997, and 2.1 g/L in 1998; in sediment were 8.5 g/g in 1995, 8.2 g/g in 1996, 4.8 g/g in 1997, and 1.1 g/g in 1998; aquatic invertebrates were 27.4 g/g in 1996, 15.5 g/g in 1997, and 4.9 g/g in 1998; in forage fish 27.2 g/g in 1996, 20.2 g/g in 1997, and 8.6 g/g in 1998. Selenium concentrations in muscle plugs of Colorado pikeminnow were 9.8 g/g in 1995, 9.5 g/g in 1996, 9.0 g/g in 1997, and 10.3 g/g in 1998. Although selenium concentrations in water, sediment, aquatic invertebrates, and forage fish decreased substantially after operation of the water control structure, a corresponding change in Colorado pikeminnow did not seem to occur. Selenium concentrations in muscle plugs decreased with increasing fish total length and weight, but did not different in subsequent years. A hazard assessment of potential effects on Colorado pikeminnow suggested a high hazard in 1995, 1996, and 1997, and a moderate hazard in 1998.

Key words: drainage, selenium, fish, hazard