Selenium pollution
In high concentrations, selenium acts as an environmental contaminant. Sources of pollution include waste materials from certain mining, agricultural, petrochemical, and industrial manufacturing operations. In Belews Lake North Carolina, 19 species of fish were eliminated from the lake due to 150-200 μg Se/L wastewater discharged from 1974 to 1986 from a Duke Energy coal-fired power plant. At the Kesterson National Wildlife Refuge in California, thousands of fish and waterbirds were poisoned by selenium in agricultural irrigation drainage.
Substantial physiological changes may occur in fish with high tissue concentrations of selenium. Fish affected by selenium may experience swelling of the gill lamellae, which impedes oxygen diffusion across the gills and blood flow within the gills. Respiratory capacity is further reduced due to selenium binding to hemoglobin. Other problems include degeneration of liver tissue, swelling around the heart, damaged egg follicles in ovaries, cataracts, and accumulation of fluid in the body cavity and head. Selenium often causes a malformed fish fetus which may have problems feeding or respirating, distortion of the fins or spine is also common. Adult fish may appear healthy despite their inability to produce viable offspring.
Selenium is bioaccumulated in aquatic habitats, this results in higher concentrations in organisms than the surrounding water. Organoselenium compounds can be concentrated over 200,000 times by zooplankton when water concentrations are in the 0.5 to 0.8 μg Se/L range. Inorganic selenium bioaccumulates more readily in phytoplankton than zooplankton. Phytoplankton can concentrate inorganic selenium by a factor of 3000. Further concentration through bioaccumulation occurs along the food chain, as predators consume selenium rich prey. It is recommended that a water concentration of 2 μg Se/L be considered highly hazardous to sensitive fish and aquatic birds. Selenium poisoning can be passed from parents to offspring through the egg, and selenium poisoning may persist for many generations.Reproduction of mallard ducks is impaired at dietary concentrations of 7 ug Se/L. Many benthic invertebrates can tolerate selenium concentrations up to 300 μg Se/L in their diet.[1]
References
- ↑ Lemly, Dennis (1998). Selenium Assessment in Aquatic Ecosystems: A guide for hazard evaluation and water quality criteria. Springer. ISBN 0-387-95346-9.