US Fish & Wildlife Service


Date of this Version



Published by the U.S. Fish and Wildlife Service, 1-28, (1989)


Selenium is a widely distributed element generally found at low concentrations in surface waters and soils (Cooper et. al. 1974. Kubota 1980. Raptis et. al. 1983. Trelease 1945). Selenium has received recent attention from the Department of the Interior and the U.S. Fish and Wildlife Service (Service) because high levels of selenium borne by irrigation return flows have caused serious problems for fish and wildlife (Clark 1987. Hoffman et. al. 1988. Lemly 1987. Ohlendorf et. al. 1986a,b, 1987, 1988, Saiki and Lowe 1987). Because selenium concentrations can occur in coal deposits, ash from coal-fired powerplants has caused serious selenium contamination problems in several places (Guthrie and Cherry 1979. Lemly 1987. Sorenson et. al. 1982).

Selenium occurs at high levels in many Cretaceous sedimentary rocks, such as some limestones, sandstones, phosphate rocks, and shales. It is common in sulfide ores of heavy metals. Across the great plains of the United States there are numerous areas where the soils are high in selenium. In nature, selenium occurs in four important oxidation states: elemental selenium (Se). Se-2, which is often associated with metals, Se+4 (selenite), and Se+6 (selenate). A variety of natural chemical processes can convert selenium from one inorganic form to another [Callahan et. al. 1979. Cutter 1978, 1982, Environmental Protection Agency (EPA) 1987]. The alkaline soils of much of the western United States provide conditions which result in the oxidation of selenium to selenate, which is very soluble and is easily leached from soils. Selenite and selenate are the principal forms of inorganic selenium entering good chains because these forms are taken up by plants [Kansas Department of Health and Environment (KDHE) 1986]. Also, in many cases there are considerable differences in uptake and biological effects of the different forms of selenium (e.g. Butler and Peterson 1967. Kumar and Prakash 1971. Lindstrom 1983). Because selenium is chemically similar to sulfur, selenium taken up by photosynthetic organisms can be converted to an organic form such as selenomethionine, selenocystine, or selenocysteine (e.g. Bottino et al. 1984. Burau 1985. Doran and Alexander 1977. National Research Council 1976. Stadtman 1974. Wrench 1978. 1979). These substituted amino acids are readily incorporated into tissues of consumers, and therefore may be more toxic than the inorganic forms (e.g. Burau 1985. EPA 1987). Selenomethionine is a particularly hazardous organic form (Heinz et al. 1987. Hoffman and Heinz 1988).

Apparently, there is little information about selenium concentrations in Kansas soils. However, in much of the state Cretaceous rocks or soils derived from Cretaceous rocks are ator near the surface. Water percolating through those rocks or soils can carry selenium to groundwaters (KDHE 1986).

Selenium is an essential trace nutrient for terrestrial and freshwater organisms. However, proper selenium levels in animals fall within narrow ranges, and the acute and chronic effects of organic and inorganic forms of selenium differ on aquatic and terrestrial plants and animals (EPA 1987). Selenium deficiency can produce a variety of symptoms, as can selenium toxicosis. Many of the symptoms are the same (Marier and Jaworski 1983). Numerous cases of selenium poisoning of fish, mammals, and birds have been documented (e.g. Clark 1987. Cumbie and Van Horn 1978. EPA 1987. Hoffman et. al. 1988. Lemly 1987. Ohlendorf et. al. 1986a,b, 1988, Saiki and Lowe 1987). In contrast. selenium can reduce the toxic effects of arsenic, mercury, and some other environmental contaminants (EPA 1987).

Selenium bioaccumulation occurs in some settings (Cherry and Guthrie 1977. DuBowy 1989 Lemly 1985, 1987, Lemly and Smith 1987. Saiki 1986), and concentrations in plants and animals may be progressively greater in organisms higher in the food chain. However, Adams and Johnson (1977) and Kay (1984) suggested that selenium biomagnification does not occur. Whether it does or not, monitoring selenium levels in habitats important to fish or wildlife and in the animals themselves is necessary to determine if selenium concentrations are detrimental to fish or wildlife.

The most recent EPA water quality criteria to protect aquatic life are 5 mcg/l maximum for a 4 day average and 20 mcg/l for a 1 hour average (EPA 1987). Neither value is to be exceeded more than once every three years on the average.

A draft report of the KDHE (1986) indicated that between 1978 and 1985, a site on Rattlesnake Creek near Raymond had a mean selenium concentration of 18.7 mcg/l. The selenium concentration was of concern to the Service because Quivira National Wildlife Refuge is a few miles upstream from the sampling site. Water samples from the Creek above the refuge did not have elevated selenium levels. Therefore, sampling was conducted on the refuge in 1987 to determine if a source of selenium contamination was located on the refuge or if selenium levels on the refuge were hazardous to fish or wildlife.