Hydrochemical baseline and lithium occurrence in the Pastos Grandes basin, Bolivian Altiplano : A field study of spatial variability, hydrochemical processes, and implications for future lithium extraction

Sammanfattning

This study was conducted as a bachelor’s thesis at KTH Royal Institute of Technology in collaboration with Universidad Mayor de San Andrés (UMSA) in La Paz, Bolivia. It is motivated by the globally increasing demand for lithium, as the salt flats of the Bolivian Altiplano host some of the world’s largest lithium reserves. In this context, and considering the potential impacts of lithium extraction, the study aims to map the hydrochemical conditions of the Pastos Grandes basin and establish a preliminary hydrochemical baseline for an area of interest for future lithium extraction. A total of 22 samples were collected during a three-day field trip in May 2025. Sampling was conducted in lagoons, wetlands, rivers, springs, thermal springs and evolved waters. Analyses were carried out through field measurements of physicochemical parameters and laboratory analyses, including ICP-MS and ion chromatography. Data processing included statistical methods such as Pearson correlations, box- and whisker plots, as well as visualisation using Piper and Gibbs diagrams.The results show that lithium is present in all samples, but concentrations vary between water sources and sampling sites. The highest lithium concentrations were observed in thermal springs, evolved waters and lagoons, suggesting that geothermal inputs, evaporative concentration and water–rock interaction are likely contributors to lithium enrichment in the basin. The main conclusion is that the sampled waters in the Pastos Grandes basin exhibit substantial hydrochemical variability, both between different water sources and over short distances. This has important implications for future resource management related to potential lithium extraction, as it complicates generalisation and requires a site-specific understanding of the area. Overall, the study provides valuable data from this remote area, where similar information has previously been limited. It can therefore serve as a reference for future research and environmental monitoring, while also providing comparative data for similar saline environments.