Water Quality Impacts of Hard-Rock Lithium Mining in North Carolina

By Dr. Noopur JainReviewed by Laura ThomsonNov 29 2024

In a recent article published in the journal Science of The Total Environment, researchers highlighted the environmental impacts of lithium mining, particularly examining the water quality surrounding a legacy pegmatite mine in North Carolina, USA.

The research aims to assess the concentrations of various elements in surface and groundwater, evaluate the leaching behavior of mining materials, and understand the implications of these findings for environmental management and public health.

Background

The increasing demand for lithium, primarily driven by its essential role in rechargeable batteries for electric vehicles and renewable energy storage, has led to a surge in hard-rock lithium mining activities.

Lithium is a critical component in modern technology, and its extraction from hard-rock sources has become a focal point for mining operations.

The legacy pegmatite mine in North Carolina, which has been inactive for several decades, presents a unique opportunity to study the long-term environmental effects of lithium mining.

Previous studies have indicated that mining activities can release contaminants into surrounding water bodies, potentially affecting aquatic ecosystems and human health.

This research builds on existing knowledge by comprehensively analyzing water quality near the mine, focusing on the concentrations of regulated and unregulated contaminants, including lithium, rubidium, and cesium.

The Current Study

The study systematically collected and analyzed water samples from surface and groundwater sources around the mine site. Following the protocols established by the U.S. Geological Survey (USGS), water samples were immediately filtered and preserved in high-density polyethylene (HDPE) bottles to prevent contamination. For trace element analyses, samples were acidified to a pH of less than 2 using nitric acid (HNO₃).

Solid samples from the mining site were homogenized, dried, and crushed before being digested using a combination of hydrofluoric acid (HF) and nitric acid (HNO3). This method was designed to ensure the accurate extraction of trace elements, and the accuracy and precision of the digestion were assessed against reference concentrations from established standards.

Leaching tests were performed following the U.S. Environmental Protection Agency (EPA) Leaching Environmental Assessment Framework (LEAF) method 1313. This method assesses the distribution of constituents between solid and liquid phases over a broad pH spectrum.

The experiments involved mixing pre-weighed solid samples with extraction fluids at various pH levels, followed by a 24-hour shaking period. The leachate solutions were then filtered and analyzed for trace and major elements using inductively coupled plasma mass spectrometry (ICP-MS). Major anions in the water samples were measured through ion chromatography, while total alkalinity and bicarbonate levels were determined via titration.

Results and Discussion

The results of the water quality analysis revealed that surface and groundwater samples from the mining area exhibited low concentrations of regulated contaminants, suggesting that the immediate impacts of mining activities on water quality may be limited. However, elevated lithium, rubidium, and cesium levels were detected, raising concerns about the potential long-term effects on aquatic ecosystems and human health. The presence of these elements is particularly noteworthy, as they are not typically monitored under standard water quality regulations.

The leaching experiments provided further insights into the behavior of mining materials in contact with water. The findings indicated that certain minerals, such as spodumene and phosphate minerals, can significantly influence the leachability of trace elements. The leaching behavior varied across different pH levels, highlighting the importance of understanding the geochemical conditions governing contaminants' release from mining materials.

The study also discussed the implications of these findings in the context of environmental management. The elevated lithium concentrations and other trace elements in natural waters could adversely affect aquatic life, particularly in sensitive ecosystems. Furthermore, the potential for these contaminants to enter the human water supply raises public health concerns, necessitating ongoing monitoring and assessment of water quality in mining-affected areas.

Conclusion

This study provides valuable insights into the water quality impacts of hard-rock lithium mining, particularly in the context of a legacy pegmatite mine in North Carolina.

While the immediate concentrations of regulated contaminants in surface and groundwater were found to be low, the elevated levels of lithium, rubidium, and cesium warrant further investigation.

The leaching experiments underscored the complex interactions between mining materials and water, emphasizing the need for a comprehensive understanding of the geochemical processes.

This research highlights the importance of monitoring water quality in mining regions and developing strategies to mitigate potential impacts on aquatic ecosystems and human health. Future studies should focus on long-term monitoring and the development of best practices for sustainable lithium extraction, ensuring that the benefits of this critical resource do not come at the expense of environmental integrity.