A respected national journal this week reported that there is evidence of long-term water quality degradation tied to mountaintop mining in a West Virginia watershed.
"Our analysis of water samples from 23 sites along West Virginia's Upper Mud River and its tributaries shows that salinity and trace element concentrations, including selenium, increased at a rate directly proportional to the cumulative amount of surface mining in the watershed," said lead researcher Ty Lindberg. "We found a strong linear correlation."
The study, "Cumulative impacts of mountaintop mining on an Appalachian watershed," was conducted by researchers at Duke University and appears this week in the peer-reviewed online Early Edition of the Proceedings of the National Academy of Sciences.
The West Virginia Coal Association, contacted for comment, had not yet seen the study.
Companies conducting mountaintop coal mining use explosives and heavy machinery to clear away surface rocks and extract underlying deposits of coal. They dispose of the waste rock in adjacent valleys.
To assess the cumulative impact of more than 100 permitted discharge outlets draining about 11 square miles of active and reclaimed mountaintop mines in the Upper Mud watershed, the Duke researchers collected more than 150 sets of samples from 23 sites — including two sites upstream of all of the surface mines — between May and December 2010.
They sampled for electrical conductivity, a measure of salinity, and for concentrations of major ions and trace elements derived from coal or the rock that contains it.
Conductivity measurements taken downstream of mine discharge outlets exceeded levels harmful to aquatic life, said Richard Di Giulio, professor of environmental toxicology, in a media release. At the two sampling sites upstream of any mines, conductivity levels were within an acceptable range.
Changes in water quality due to increased salinity in the Upper Mud from mine runoff were found to be "exceptionally persistent," Lindberg said. "Mines reclaimed almost two decades ago are continuing to release effluents with salinity similar to active mines in the region."
Selenium, which research has shown to be toxic to fish at high concentrations, followed a similar pattern, Di Giulio said. The researchers observed deformities typical of selenium exposure in fish collected from downstream waters.
In general, contaminant concentrations increased with the amount of mining upstream, indicating cumulative effects that may be overlooked in individual permitting decisions, according to the researchers.
"As eight separate mining-impacted tributaries flowed into the Upper Mud, conductivity and concentrations of selenium, sulfate, magnesium and other inorganic solutes increased proportionately," said Avner Vengosh, professor of geochemistry and water quality. "Nearly 90 percent of the variation in trace elements and salinity could be explained by the amount of upstream surface mining."
The Upper Mud flows through sparsely populated sections of Boone and Lincoln counties in southern West Virginia to the Mud River reservoir 15 miles downstream. For about six miles, the river passes through the Hobet 21 surface mining complex, which has been active since the 1970s and is among the largest in the Appalachian coalfields region.
The Duke team selected the Upper Mud watershed because water-quality impacts from other potential sources are largely absent, according to the media release. Historically, surface rather than underground mining has been the dominant form of coal extraction and few people now live within the Hobet mine's permitted boundary, minimizing other factors that might account for changes in water quality.
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