Five of North Carolina’s lakes—some recreational sites and vistas for homeowners—contain large quantities of coal ash sediment, as found in a study published by scientists at Duke University and Appalachian State University today.

The hazardous byproduct of coal-burning power plants contains the five metals—mercury, lead, chromium, cadmium, and arsenic—most commonly linked to human poisoning. 

Using age-dating methods the scientists reconstructed the sedimentary history of the lakes thereby identifying the accumulation of the coal ash material in the base of the lakes. The lakes tested were Hyco Lake and Mayo Lake, located north of Durham in Person County; Belews Lake, located northwest of Greensboro in Rockingham, Forsyth, and Stokes counties; Mountain Island Lake, located northwest of Charlotte in Mecklenburg County; and Lake Sutton, located northwest of Wilmington in Brunswick County.

But the coal ash is not only stored in these sediments. Chemical analyses of pore water, or water held between gaps in soil or rock, revealed that the metals have breached the buried layers and can enter the aquatic food chain, said Avner Vengosh, a professor of environmental quality at Duke University’s Nicholas School of the Environment. 

The microscopic analysis of the coal ash revealed the shift in deposits over time, said the study’s co-author, Ellen Cowan, a professor of geology at Appalachian State University. Initially, unfiltered coal ash was directly deposited into the lakes. Then, new smokestack scrubbers introduced under the Clean Air Act refined the pollution, creating deposits of smaller particles. Yet, alarmingly, these smaller particles actually contain the highest concentration of toxic components. 

These findings highlight the limits of engineered coal ash ponds, long used as repositories for the harmful byproducts, and reveal the alarming quantity of deposits of coal ash into environmental spaces.

“We thought that the majority of the coal ash is restricted to coal ash ponds and landfills. Now we see it’s already in the open environment,” Vengosh said. 

The study authors say that these findings are likely replicable across the country. 

“The phenomenon that we discovered probably applies to many other sites across the U.S. and all of them are going to be vulnerable to more extreme weather events and flooding that we know is coming from global warming,” Vengosh said. 

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