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Tracking the Pathways and Anticipating Impacts of Selenium
Twenty years ago Dennis Lemly started tracking selenium and its impacts on fish and wildlife. An elemental contaminant released through a variety of industrial and in agricultural activities, selenium bioaccumulates. It degrades water quality and travels into the food chain, where it reaches fish and birds. Selenium contamination does not result in sudden fish kills. It causes deterioration and deformity in fish and wildlife over time, working almost invisibly. Lemly, Southern Research Station senior scientist for aquatic toxicology, refers to selenium as an insidious killer.
Sources of selenium contamination include:
- Coal, gold, silver, nickel, and phosphate mining
- Metal smelting
- Municipal landfills
- Oil transport, refining, and utilization
- Agricultural irrigation
As a trace element, selenium cannot be eliminated. It moves from one form or environmental compartment to another, often becoming more concentrated in the process. Consider that a coal storage-pile leachate contains 1-30 µg/L selenium. As coal-cleaning process water, the concentration increases to 15-63 µg/L. As coal ash slurry, the selenium concentration increases to 50-1500 µg/L. Lemly says, “There are serious implications for industrial waste management and environmental safety. As society’s need for electric power increases, so does the volume of seleniferous coal wastes that are produced. In the United States alone, over 120 million tons of fly ash are produced annually, and the disposal of this material is creating a new selenium issue because of contaminated landfill leachate.”
When an oil spill occurs, publicity focuses on impacts of heavy oil coating of wildlife and beaches and the aquatic toxicity of the hydrocarbon fraction. Long-term risks from selenium go largely unrecognized, even though it may bioaccumulate and persist in the environment. Lemly says, “The oil industry transports and disposes huge volumes of selenium-laden materials on a global scale. At any point in this process it can become a major contributor to elevated selenium concentrations in aquatic ecosystems.”
Lemly, a member of the Coldwater Streams and Trout Habitat in the Southern Appalachians research unit in Blacksburg, VA, focuses on selenium research. He wrote Selenium Assessment in Aquatic Ecosystems: A Guide for Hazard Evaluation and Water Quality Criteria as a handbook for field personnel to perform site–by–site assessment of potentially contaminated areas. Three recently published journal articles address separate aspects of selenium toxicity. Lemly discusses the effects of selenium on 20 resident fish species in Symptoms and Implications of Selenium Toxicity in Fish: The Belews Lake Example. Selenium contamination fed into the lake in wastewater from a coal-fired power plant from 1974–1986, and 19 species were eliminated. Perhaps because selenium kills slowly, nationally it lacks a high-profile image as a contaminant.
In Regulatory Implications of Using Constructed Wetlands to Treat Selenium-laden Wastewater, Lemly and ecologist Harry M. Ohlendorf address ecological, environmental, and liability issues. For two decades, constructed wetlands have been used to treat industrial, municipal, and agricultural wastewater nationally and internationally. Constructed wetlands provide a cost-effective alternative to conventional wastewater treatment. They also portray an environmentally friendly image. Actually, the converse might be true on both points. Lemly and Ohlendorf state that owners and managers of constructed wetlands bear legal responsibility for toxic hazards to fish and wildlife, even if the wetlands are not designed as habitat. The authors track the major pathways for selenium movement in an aquatic ecosystem. They provide a framework for a wetland-specific ecological risk assessment, considering the perils of selenium as it accumulates in plants and animals.
The United States Environmental Protection Agency (EPA) may require Total Maximum Daily Loads (TMDLs) on impaired water bodies to provide watershed-level improvement in water quality. Establishing TMDLs would set a limit on the total aggregate amount of a contaminant allowed in an aquatic system. In A Procedure for Setting Environmentally Safe Total Maximum Daily Loads (TMDLs) for Selenium, Lemly offers a program of seven steps structured to answer two questions:
- Is selenium impairing the water body based on biological criteria?
- If so, what amount of selenium load reduction is necessary to correct the problem?
The seven-step procedure aims to keep selenium concentrations below levels that threaten the reproduction of fish and aquatic birds. Lemly stresses the significance of identifying and using a hydrological unit (States and the EPA use the term “water body”] when evaluating potential selenium transport and bioaccumulation. Lemly cautions that dietary selenium in eggs can cause reproductive failure in fish even though there is little direct damage or toxicity to the spawning fish themselves. Unlike the nesting birds whose chicks’ could not mature in the DDT-thinned shells, the selenium-contaminated fish do not witness their reproductive failure because their eggs successfully hatch.
Lemly works with scientists in Canada, Brazil, Australia, Japan, and Russia on efforts to assess and mitigate selenium toxicity. Causes for contamination include diamond mining and volcanic ash. The international community expresses high interest in Lemly’s research, demonstrated by publication requests from 64 countries in the last year.
Springer-Verlag New York published Selenium Assessment in Aquatic Ecosystems: A Guide for Hazard Evaluation and Water Quality Criteria. You can download the journal articles referenced below when visiting the Southern Research Station Web site: / .
Lemly, A. Dennis. 2002. A procedure for setting environmentally safe total maximum daily loads (TMDLs) for selenium. Ecotoxicology and Environmental Safety. 52: 123-127.
Lemly, A. Dennis. 2002. Symptoms and implications of selenium toxicity in fish: the Belews Lake case example. Aquatic Toxicology. 57: 29-49.
Lemly, A. Dennis; Ohlendorf, Harry M. 2002. Regulatory implications of using constructed wetlands to treat selenium-laden wastewater. Ecotoxicology and Environmental Safety. 52: 46-56.
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