Water associated with abandoned lithium mines contains low levels of common pollutants but high levels of other elements

Lithium ore and mine waste from a historic lithium mine west of Charlotte, North Carolina, are unlikely to contaminate surrounding waters with common pollutants such as arsenic and lead, according to a new study.

However, high levels of other metals are present in mining-related waters, namely lithium, rubidium, and cesium.

The study is published in the journal Science of The Total Environment.

A new discovery by a team that includes corresponding author Abner Vengosh, Distinguished Professor of Environmental Quality at Duke University’s Nicholas School of the Environment, sheds light on the potential impact of heritage or historic lithium mines on water quality. They will also provide baseline data for future studies investigating how the reopening of lithium mines in the North Carolina Piedmont may affect water quality in nearby drinking water resources.

“The world is increasing its reliance on lithium in the transition to green energy, but previous studies on the environmental impact of hard-rock lithium mining have shown mixed results,” Vengosh said. . “This study provides important new data to clarify potential environmental impacts.

The area where the Kings Mountain mine is located was once the world’s largest lithium producing region. The mine, located in a mountainous countryside, was opened in the 1950s and abandoned in the 1980s when more accessible lithium deposits attracted prospectors to South America. The lithium at Kings Mountain is primarily found in granite-like rocks called pegmatites, combined with a greenish mineral called spodumene.

The researchers collected samples of pegmatite and waste rock from in and around the mine, as well as samples of tailings (crushed rock left over from historic spodumene mining) for their study. They also sampled the mine’s groundwater and the surface water of Kings Creek, which flows from the mine. Samples from various rivers in Piedmont provided baseline data on water quality.

The researchers crushed rock samples and mixed them into a solution designed to test how different pollutants enter the surrounding environment. These laboratory experiments simulate how contaminants in rocks leach out under natural conditions. The researchers then analyzed the solution and surface and groundwater samples for a variety of metals commonly used to assess water quality.

The leaching experiments and water samples analyzed in this study showed common regulated contaminants such as arsenic, lead, copper, and nickel at levels below drinking water and ecological standards set by the U.S. Environmental Protection Agency. It was shown that

“The fact that these toxic contaminants were not identified is in some ways reassuring, as it suggests that future lithium exploration in North Carolina will not cause significant adverse water quality effects with respect to these elements.” Vengosh said.

However, the research team found high concentrations of other metals at the mine site compared to concentrations in Piedmont’s water resources.

“We found high concentrations of lithium, as expected, but we also found levels of rubidium and cesium, which are not normally found in natural waters and are not federally regulated,” said lead author Dr. Gordon Williams. students in Vengosh’s lab and the Department of Earth and Climate Sciences. “Therefore, an open question is how these elements affect human and environmental health.”

Evidence from leaching experiments and water samples also showed that conventional lithium mines do not contribute to the environmentally harmful acid runoff commonly associated with other mining operations such as coal mining. Rather, the interaction of ore and waste rock samples with water resulted in temporary alkaline or basic conditions.

The authors stressed that the study did not address the impact of active lithium mining and processing on water quality.

“Drilling and crushing ore is only one aspect of lithium mining. Processes that require chemical processing to separate lithium and spodumene involve additional chemicals that can impact water quality. It’s possible,” Williams said. “If lithium mining increases again in the region, its processing could have impacts on local water resources that we do not measure,” he warned.

The researchers are now expanding their study by assessing drinking water quality across a swath of Piedmont’s lithium-rich landscape. Sampling private wells and surface water will help us better understand the potential impacts of lithium mining on water quality in North Carolina.