Historic Lithium Mining: Assessing Water Quality in the Carolina Tin-Spodumene Belt

A recent study investigated the potential water quality impacts of historic lithium mining and processing operations in the Carolina Tin-Spodumene Belt, a region in North Carolina located south of Charlotte. This area contains one of the country's largest lithium deposits, primarily occurring within pegmatite rocks rich in spodumene.

The research, conducted by a team from Duke University and published in Environmental Science & Technology, focused on two legacy mine sites (in Kings Mountain and near Bessemer City) as well as an active lithium processing site.

The primary aim of the study was to assess whether past mining and processing activities had altered the chemical composition of ground and surface water in the area.

Over a three-year period, the team collected 93 groundwater samples, mainly from domestic wells, and 99 stream samples from within and around the Tin-Spodumene Belt. These samples were subsequently analyzed to identify specific chemical patterns.

Key Findings on Lithium and Other Metals

Groundwater (Domestic Wells)

The study found no direct evidence of impacts from historic lithium mining or processing on domestic well water. Instead, the natural geology of the area was determined to be the primary factor affecting groundwater chemistry.

Natural Occurrences

Groundwater samples consistently exhibited elevated levels of lithium, rubidium, and cesium compared to average North Carolina groundwater. These naturally higher concentrations are attributed to natural chemical interactions between groundwater and the underlying pegmatite rock.

Surface Water

In contrast, streams near legacy mining and processing sites showed relatively high levels of lithium and rubidium. These elevated concentrations likely resulted from interactions between water and gypsum, a material found in lithium processing waste. Significantly, these impacts diminished due to dilution as streams flowed further from the sites.

Arsenic Hotspot Discovery

Separately, the study also tested groundwater for arsenic. While most samples were below the federal drinking water standard, a notable cluster of wells in Gaston and Lincoln counties registered levels exceeding the standard.

This arsenic hotspot is attributed to specific geological conditions where pegmatite rocks coexist with mica schist, which naturally contains arsenic.

Interactions with pegmatite are believed to enhance arsenic leaching from mica schist into local groundwater.

Implications for Future Mining

Residents with wells affected by the arsenic hotspot are reportedly transitioning to municipal water supplies.

The study suggests that future lithium mine siting decisions should include thorough geological investigations to assess the potential for water quality impacts. This is particularly crucial regarding the co-occurrence of pegmatite and mica schist.

It was also noted that the U.S. Environmental Protection Agency (EPA) has not established limits for lithium, rubidium, or cesium in drinking water.