Reviewed by Lexie CornerFeb 11 2025
The researchers from Duke University Nicholas School of the Environment have been examining the potential environmental and human health impacts of lithium mining both domestically and internationally. Their study was published in Environmental Science & Technology Letters.
From left: Avner Vengosh and Gordon Williams collected lithium-brine samples from the Salar de Uyuni for chemical analysis. Image Credit: Avner Vengosh
The world's largest known lithium deposit is located in the Salar de Uyuni, an expansive salt pan spanning thousands of square miles atop a high, arid Andean plateau in Bolivia. For most of the year, the landscape is covered by salt crystals, while during the rainy season, pooled rainwater reflects the sky and surrounding mountains.
The Salar is a magical place for travelers from all over the world who come to see the colors, the reflections, in this endless white landscape.
Avner Vengosh, Nicholas Chair, Environmental Quality, Duke University Nicholas School of the Environment
Most tourists are unaware of the vast lithium reserves dissolved in the highly saline brine beneath the surface of the Salar de Uyuni. This resource, found in sediments and salts extending from a few feet to over 160 feet deep, could play a critical role in the renewable energy industry.
Gordon Williams, a Ph.D. candidate, and Avner Vengosh, chair of the Nicholas School's Division of Earth and Climate Sciences, conducted the first comprehensive chemical analysis of wastewater associated with lithium brine mining at the Salar de Uyuni. Their research aims to inform more sustainable management strategies for mining operations while protecting the delicate salar ecosystem.
Lithium extraction involves pumping brine from underground into a series of shallow evaporation ponds. As water evaporates, unwanted salts precipitate out in successive ponds, increasing the lithium concentration in the remaining brine. The concentrated lithium is then processed into lithium carbonate, a key component in rechargeable batteries.
Lithium extraction at the Salar de Uyuni remains in its early stages. However, studies in other salt pans, such as Chile's Salar de Atacama, indicate that long-term lithium brine mining can lower groundwater levels and contribute to land subsidence. Similar impacts could affect future lithium mining in the Salar de Uyuni.
Williams and Vengosh analyzed the chemical composition of lithium brine and waste materials from a pilot mining operation at the site, focusing on acidity and trace elements such as arsenic, a toxic metal harmful to both humans and wildlife. They collected samples from eight evaporation ponds, wastewater from the lithium processing plant, and naturally occurring brine pumped from underground.
The results showed that naturally occurring brine samples had relatively neutral acidity and arsenic levels ranging from 1 to 9 parts per million. However, as brine became more concentrated in the evaporation ponds, acidity increased significantly.
Arsenic levels also rose sharply from pond to pond. In the final evaporation pond, arsenic concentrations reached nearly 50 parts per million—1,400 times higher than the U.S. Environmental Protection Agency’s ecological safety threshold.
“This arsenic level is extremely high. My group has worked all over the world — in Africa, Europe, Vietnam, India — and I don’t think we ever measured that level of arsenic,” remarked Vengosh.
The authors note that wildlife may be affected if brine leaks or is intentionally discharged from evaporation ponds into the surrounding salt pan.
“There’s a risk for bioaccumulation,” said Williams.
Williams highlighted the potential for chemical accumulation in organisms, which could have adverse effects. For example, local brine shrimp, a key food source for flamingos, are vulnerable to arsenic concentrations exceeding 8 parts per million.
The researchers also found that boron levels increased progressively across the evaporation ponds, raising concerns about potential health impacts depending on the type of exposure. However, wastewater from the lithium processing plant contained relatively low arsenic and boron levels, often comparable to or lower than those found in natural brines.
Williams and Vengosh also examined the potential consequences of injecting either lithium processing wastewater or spent brine—the residual brine left after lithium extraction—back into the lithium deposit. Some in the lithium mining industry suggest these methods could mitigate land subsidence.
The study found that both approaches could have unintended consequences. Spent brine is unlikely to mix well with natural brine, potentially disrupting subsurface flow and causing operational challenges during pumping. Conversely, injecting wastewater back into the deposit could dilute the lithium concentration, reducing resource quality.
The authors suggested that carefully blending spent brine with wastewater to match the chemical composition of natural brine may help mitigate land subsidence. However, they emphasized the need for further research to evaluate the environmental implications of this approach.
Williams and Vengosh continue to focus on the Salar de Uyuni as a key lithium source in their ongoing research.
We’re building a geochemical model to understand why lithium is enriched in those brines. What’s the source? And what’s the mechanism causing this concentration?
Gordon Williams, Ph.D. Candidate, Duke University Nicholas School of the Environment
Williams, Vengosh, and Ph.D. student Hannah Wudke are also collaborating with another Nicholas School team, led by Erika Weinthal and Distinguished Professor John O. Blackburn, to assess the potential health and well-being impacts of lithium-brine mining at the Salar de Uyuni on nearby Indigenous communities.
“We see lithium as the future for energy security, so we’re trying to analyze it from different angles to ensure sustainable development and supplies,” said Vengosh.
The study was supported by the Duke University Graduate School Dissertation Research Travel Award, the Duke University Josiah Charles Trent Memorial Foundation Endowment Fund, and the Duke University Climate Research Innovation Seed Program (CRISP).
Journal Reference:
Williams, D, Z, G., et al. (2025) Quality of Wastewater from Lithium-Brine Mining. Environmental Science & Technology Letters. doi.org/10.1021/acs.estlett.4c01124