Date of this Version
Water, soil, vegetation, grasshoppers (Family Acrididae), bird eggs and bird livers collected at a 23.5 hectare (58 acres) grassland irrigated with wastewater from an in situ uranium mine (Study Area) and a reference site in 1998 were analyzed for selenium and other trace elements. Bird surveys were conducted at the irrigated grassland at the in situ uranium mine to determine species use, relative abundance and behavior. We observed 23 species of birds using the Study Area. Western meadowlarks (Sturnella neglecta), red-winged blackbirds (Agelaius phoeniceus), lark buntings (Calamospiza melanocorys) and horned larks (Eremophila alpestris) were the most common avian species using the Study Area and were observed feeding and drinking at this site. Meadowlarks, redwinged blackbirds and lark buntings were observed nesting at the Study Area. Selenium concentrations in the uranium mine wastewater applied onto the grassland ranged from 340 to 450 μg/L. Selenium in the upper 15 cm (6 in) of soil from the irrigated grassland at the mine ranged from 2.6 to 4.2 μg/g dry weight (dw). Mean selenium concentrations in soil and water were 5 and 15 times higher at the Study Area than at the reference site. Selenium concentrations in grasses and grasshoppers ranged from 6.8 to 24 μg/g and 11 to 20 μg/g dw, respectively. Selenium in red-winged blackbird eggs and livers collected from the Study Area ranged from 13.2 to 22 μg/g and 33 to 53 μg/g dw, respectively, and concentrations were well in excess of toxic thresholds. Two composite samples of gizzard contents taken from red-winged blackbirds collected at the Study Area had selenium concentrations of 12 and 83 μg/g dw. Mean selenium concentrations in grasses, grasshoppers, and bird eggs and livers were 5.8 to 30 times higher at the Study Area than at the reference site. Elevated selenium concentrations in water, soil, grasshoppers, and red-winged blackbird eggs and livers collected from the Study Area demonstrate that selenium is being mobilized and is bioaccumulating in the food chain.