Laboratory weathering studies to evaluate the water quality impact of a lithium mining in Portugal

Abstract

In recent decades, the increasing demand for energy and raw materials in modern societies has led to a significant increase in mining exploration. However, this has also sparked the emergence of movements against mining exploration all over the world, particularly in Europe. During the operation of open pit mines, materials are deposited on the surface and subjected to weathering processes. These processes can create an environmental impact by causing the migration of chemical elements from soils to waters. Given the importance of the theme of water and soil contamination nowadays, it is important to verify the potential environmental impact resulting from open pit mine exploration. Laboratory tests were used to simulate weather conditions due to leaching of soils in a lithiniferous feldspar mine located in the centre of Portugal. Soil samples, resulting from the activity of the C57 mine (Guarda, Portugal) were collected and determined its granulometry. Water samples (surface and underground) were also collected in the area to allow a characterization of the existing waters upstream and downstream of the mining operation. To simulate the soil leaching process, the Soxhlet extractor method was utilized, and spectroscopic methods were used to determine the alkali and alkaline earth metals, as well as the transition and post-transition metals. Upon comparison with the results obtained for surface and groundwater, the findings suggest that there are notable concentrations of certain elements in the weathering solution, throughout the 3,000-hour duration of the laboratory test. This indicates that, for certain chemical elements, particularly aluminium and chromium, there may be some adverse effects on water quality.