A satellite comparison of the Hobet-21 Mine in 1987 and 2002 (Courtesy of NASA).

A satellite comparison of the Hobet-21 Mine in 1987 (below) and 2002 (Courtesy of NASA).

By Ashley Mooney

While mining the Appalachian mountains provides fuel to many areas of the East coast, Mariah Arnold, Fulbright scholar and Duke doctoral candidate, found that current mining practices may release toxic substances that devastate local ecosystems.

Arnold said about 450 mountains across the country have been destroyed by mountaintop mining. She focuses her research on the Hobet-21 mine in southeastern West Virginia—the largest surface mine in the state.

“The problem with mountaintop mining is that the impacts are so long term,” said Richard Di Giulio, professor of environmental toxicology and Arnold’s advisor. “We’ve blown away mountains and they will never come back.”

Most mountaintop mining in West Virginia occurs in remote, sparsely populated areas, Di Giulio said. Although one can drive relatively close to the sites themselves, the true effects are hard to see from the ground.

During mountaintop mining, miners extract coal by removing the land above the coal seams, then use a process called valley filling to repurpose the excess land, Arnold said. The process releases selenium, a sometimes toxic naturally occurring element found in the earth.


Arnold and Research Analyst Ty Lindberg collecting samples in the Mud River. Courtesy of Mariah Arnold and Ty Lindberg.

“Selenium is released into the environment when you blast off that mountain and you have all that excess rock, which has been in that mountain for a very long time,” Arnold said. “When you expose it to the air and rain and weathering events, that rock is broken down, and in that rock is selenium. Selenium is then washed down into aquatic habitats.”

Not all forms of selenium are toxic, and some are actually required in human diets to survive. According to the U.S. Environmental Protection Agency website, there is a limit on “the highest concentration of [selenium] in surface water to which an aquatic community can be exposed indefinitely without resulting in an unacceptable effect.”

Arnold found that samples taken from the Mud River, which flows through the mining site, contain significantly more selenium than the legal limit. The excess selenium has killed off several fish species and caused reproductive failure and jaw deformities in the remaining fish, she said. Species from a fork of the river that does not flow through the mining site do not exhibit the same problems.

A key to Arnold’s findings is biofilm, which refers to a group of microorganisms that stick to each other on surfaces in the river. The biofilm in the Mud River converts the selenium released from mining from an inorganic, harmless form to a dangerous organic form of the compound. Some animals, including fish and insects, eat the biofilm and therefore ingest the now-harmful substance.

“A third of [the selenium in the river] was in green algae,” Arnold said. “The first thing these fish eat is that green algae, so that’s really the dose the fish are getting…. These biofilms are controlling the movement of selenium.”

The long-term impact of selenium exposure in many species, including humans, is still unknown, said Di Giulio. Future studies will include selenium’s effect on human health and further understanding the role of biofilm.

While some species can evolve and adapt to the rising selenium concentrations, Di Giulio said the mountains themselves could never recover, because they require hundreds of years to adapt to the changing ecology.

“You have forever essentially destroyed this landscape,” Di Giulio said. “You go there, its like, ‘oh we need flat space here for shopping centers and hospitals and schools,’ but yet the population density really is [low]. Do you need this much?”