Salar de Uyuni, home to the world’s largest lithium reserve, faces environmental threats from mining activities. A study conducted by researchers from Duke University reveals that lithium-brine evaporation ponds significantly elevate arsenic levels, which pose risks to local wildlife and groundwater. The researchers also examined reinjection methods to mitigate land subsidence, although these could interfere with lithium extraction processes.
Located in Bolivia, Salar de Uyuni is an expansive salt flat that spans thousands of square miles atop a high, arid Andean plateau. For much of the year, the surface sparkles with salt crystals resembling confectioner’s sugar, while the wet season transforms the area into a shimmering mirror reflecting the surrounding mountains and sky.
“The Salar is a magical place for travelers from all over the world who come to witness its colorful reflections in the endless white landscape,” said Avner Vengosh, Nicholas Chair of Environmental Quality at Duke University’s Nicholas School of the Environment.
Beneath the surface lies a vast reserve of lithium dissolved in highly saline brine, trapped within sediments and salts ranging from a few feet to over 160 feet deep. This untapped resource could play a vital role in the renewable energy sector.
Williams and Vengosh are focusing on the origin of lithium at Salar de Uyuni. “We’re developing a geochemical model to understand why lithium is concentrated in these brines,” Williams explained. “What is the source, and what mechanisms are involved in this concentration?”
Additionally, Williams, Vengosh, and Ph.D. student Hannah Wudke are collaborating with another Nicholas School team, led by John O. Blackburn Distinguished Professor Erika Weinthal, to assess how lithium-brine mining at Salar de Uyuni could impact the health and well-being of nearby Indigenous communities.
“We view lithium as crucial for future energy security, so we are analyzing it from multiple perspectives to ensure sustainable development and supply,” Vengosh noted.
Reference: “Quality of Wastewater from Lithium-Brine Mining” by Gordon D. Z. Williams and Avner Vengosh, January 17, 2025, Environmental Science & Technology Letters. DOI: 10.1021/acs.estlett.4c01124
Funding: This study received support from the Duke University Climate Research Innovation Seed Program (CRISP), the Duke University Josiah Charles Trent Memorial Foundation Endowment Fund, and the Duke University Graduate School Dissertation Research Travel Award.
For the past few years, Vengosh, who also chairs the Division of Earth and Climate Sciences at the Nicholas School, along with Ph.D. student Gordon Williams, has been investigating the potential environmental health implications of lithium mining both domestically and internationally.
The First Comprehensive Study on Lithium Brine Wastewater
In a report published in Environmental Science & Technology Letters in January 2025, Williams and Vengosh conducted the first detailed chemical analysis of wastewater linked to lithium brine mining at Salar de Uyuni. Their findings could guide strategies for more sustainable mining practices and the protection of the fragile salar environment.
Currently, lithium-brine mining involves a multi-step process: brine is pumped from underground into a series of shallow evaporation ponds. As the liquid evaporates, unwanted salts precipitate, concentrating lithium in the brine at each stage. The concentrated lithium is eventually transported to a nearby facility for processing into lithium carbonate, the primary material used in rechargeable batteries.
Although lithium extraction at Salar de Uyuni is still in the preliminary stages, research indicates that prolonged mining of lithium brines in other salt flats, such as the Salar de Atacama in Chile, can lead to declining groundwater levels and land subsidence. These impacts could pose challenges for future lithium mining efforts at Salar de Uyuni, according to Vengosh.
In their study, Williams and Vengosh analyzed the chemistry of lithium brine and waste products associated with a pilot mining operation at Salar de Uyuni. They focused on assessing the acidity and presence of trace elements, particularly arsenic, a toxic metal associated with various health risks for exposed individuals and wildlife. The samples included natural brine, brine from eight evaporation ponds, and wastewater from the lithium processing facility.
The team found arsenic levels ranging from 1 to 9 parts per million in natural brine samples, which also exhibited relatively neutral acidity. In contrast, evaporation pond brine became increasingly acidic as it concentrated.
Williams and Vengosh continue to investigate the origins of lithium at Salar de Uyuni, aiming to build a comprehensive understanding of the geochemical processes at play.
Reference: “Quality of Wastewater from Lithium-Brine Mining” by Gordon D. Z. Williams and Avner Vengosh, January 17, 2025, Environmental Science & Technology Letters.
Funding: This study was supported by the Duke University Climate Research Innovation Seed Program (CRISP), the Duke University Josiah Charles Trent Memorial Foundation Endowment Fund, and the Duke University Graduate School Dissertation Research Travel Award.
