Lithium levels in irrigation water, cabbages and potatoes from farms surrounding the C-57 mine (Gonçalo, Portugal)

Introduction: Lithium (Li) is a Critical Raw Material used in modern technology, including green energy storage technology. Its growing uses led to an increased exploration of Li's sources. Li levels in soils, waters, and foods vary depending on environmental factors and soil characteristics. This fact becomes more evident near mines with Li mineral resources. Portugal has active and prospective Li mining concessions. Aims: This study investigates the potential effects of Li pegmatite exploitation at the C-57 mine (Gonçalo region, Portugal) on the crops grown in nearby subsistence farms (cabbages and potatoes) and irrigation water. The sampling locations were selected based on their proximity to the mine, with some located within 1.5 km (L1) and others ranging between 2 to 8.5 km (L2) from the mine. Methodology: The sampling plan involved selecting nine subsistence farms from two locations (L1 and L2). Three cabbages and three potatoes were collected from each farm (n=54) and analyzed as laboratory pools (n=18). Irrigation water samples were also collected in each location. The analytical procedures followed the ISO/IEC 17025:2017 standard, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine Li concentration in samples. Results were expressed as the average of three replicates in µg/kg fresh weight for cabbages leaves and peeled potatoes and µg/L for water samples. Results and Conclusions: This preliminary study revealed higher Li concentration in most samples collected in L1 compared to L2. Additionally, it was observed that, in both locals, the concentration of Li in cabbages (L1: 44 – 1022 µg/kg; L2: 41 – 509 µg/kg) is higher than in potatoes (L1: 4-17 µg/kg; L2: 3-6 µg/kg), and low Li variability in irrigation waters (L1: 6-24 µg/L; L2: 2-17 µg/L). These findings demonstrate the impact of the proximity and exploitation of a hard-rock quartz-feldspath- lithium mineral resource.