DURHAM, N.C., Nov. 29 (UPI) -- As the U.S. government considers defining coal ash as a hazardous waste material, researchers say they've developed new ways of measuring its ecological impact.
Researchers from Duke University studied contaminant levels in aquatic ecosystems over an 18-month period following a massive coal sludge spill in 2008 at a Tennessee Valley Authority power plant in Kingston, Tenn., a university release said.
The Duke scientists found that high concentrations of arsenic from the TVA coal ash remained in river-bottom sediment long after contaminant levels in surface waters had dropped back below safe thresholds.
"The take-away lesson is we need to change how and where we look for coal ash contaminants," Avner Vengosh, professor of geochemistry and water quality, says. "Risks to water quality and aquatic life don't end with surface water contamination, but much of our current monitoring does."
Samples extracted from 4-18 inches below the surface of sediment in rivers contained arsenic levels of up to 2,000 parts per billion, well above the Environmental Protection Agency's thresholds of 10 parts per billion for safe drinking water and 150 parts per billion for protection of aquatic life.
"It's like cleaning your house," Vengosh says. "Everything may look clean, but if you look under the rugs, that's where you find the dirt."
The impacts of this contamination extend far beyond the river bottom, he says, because "this is where the biological food chain begins, so any bioaccumulation of toxins will start here."
The study comes as the EPA mulls whether to define ash from coal-burning power plants as hazardous waste; a final ruling is expected in coming months.
Vengosh says the decision will be "a defining moment."
"As long as coal ash isn't regulated as hazardous waste, there is no way to prevent discharges of contaminants from these facilities and protect the environment."