US Fish & Wildlife Service


Date of this Version



Published by the U.S. Fish and Wildlife Service, 1-70, (1999)


The objectives of this study were to determine background concentrations of metals and organic compounds in biotic and abiotic components of the Fort NiobraralValentine National Wildlife Refuge (NWR) Complex and document these results to utilize as baseline information for future contaminants investigations. To establish this baseline, sediment, water, and biotic samples (fish, double crested cormorant eggs, and vegetation) were collected from Fort Niobrara and Valentine National Wildlife Refuge in 1995 and tested for inorganic and organic contaminants. lnorganics were determined by inductively coupled plasma atomic emission spectrophotometer (lCP) scans. Arsenic and selenium were analyzed by atomic absorption spectrophotometry (AAS). Mercury levels were determined by cold vapor atomic absorption. Organochlorine scans were performed by capillary gas chromatography with an electron capture detector to determine organic contaminant levels.

Elevated inorganic contaminant concentrations were detected in water, sediment, plant, and fish samples collected from each refuge. Only aluminum appeared elevated in water samples collected from Valentine NWR. Aluminum and arsenic appeared elevated at Fort Niobrara NWR. At Valentine NWR, elevated concentrations of metals in sediment were limited to one of the three sediment samples from Pelican Lake (Valentine NWR), which contained elevated levels in 11 of 19 metals analyzed. Aquatic plants collected from Valentine NWR showed very limited contamination; only boron was elevated in the common star duckweed collected from Marsh Lake. Concentrations of boron and selenium were elevated in aquatic macrophytes collected from Fort Niobrara NWR. Elevated concentrations of copper, molybdenum, and zinc were detected in fish collected from Valentine NWR. Concentrations of aluminum, copper, selenium, and zinc appeared elevated in fish collected from Fort Niobrara NWR. None of the concentrations detected in double~crested cormorant eggs appeared elevated.

Concentrations of organics did not appear to be elevated in any of the media sampled from both refuges. The lack of intensive agriculture and absence of industrial development have likely allowed these refuges to remain in fairly pristine condition.