235 Advancing the Understanding and Management of Groundwater Pollution with Arsenic and Other Geogenic Contaminants Using Geospatial Tools, Machine Learning, and Data Science, Part I

The growing trend of data aggregation and analysis, along with emerging technologies like machine learning, has significantly improved our understanding of groundwater basins, enabling better assessments of water quality for direct consumption and treatment in groundwater supply management.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 210AB

Geogenic Arsenic, Boron, and Lithium as Key Determinants of Groundwater Quality in the Lithium-Rich Coipasa Salt Basin, Bolivian Altiplano

Paper number: 235-3
Program: Technical Sessions
Time: 8:35 AM – 8:50 AM

Authors

Abstract

With the growing global demand for lithium, a critical component in batteries and emerging technologies, the exploitation of lithium-rich brines in the Altiplano Lithium Triangle has raised increasing concern, particularly due to its potential impact on regional groundwater quality. The Coipasa Basin (CB), a salt basin located in the Bolivian Altiplano and home to the third-largest salt flat in South America, has gained strategic importance due to its potential for future lithium extraction. In this study, we investigate the occurrence of natural arsenic (As), boron (B), and lithium (Li) in groundwater. Geostatistical (GIS) and geochemical modeling (PHREEQC) were used to analyze groundwater geochemistry and assess the Groundwater Quality Index (GWQi). A total of 107 groundwater samples used for drinking and domestic purposes were analyzed for field and laboratory parameters. Major ions and trace elements were measured using ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS). Results reveal remarkably high concentrations of As, B, and Li in drinking water sources with As ranged from 2 to 1100 μg/L, B from 77 to 14003 μg/L, and Li from 1 to 3468 μg/L. Groundwater pH ranged from 6.1 to 9.8, while electrical conductivity (EC) varied from 74 to 10610 μS/cm, with the highest EC values observed near the Coipasa salt flat. Predominant water types included Na-Cl, Na-Cl-HCO₃, and Ca-Mg-Cl-SO4-HCO₃ water facies signifying the dominance of carbonate and silicate dissolution. Furthermore, rock-water interaction and evaporation-precipitation are the dominant processes controlling groundwater geochemistry. Potential GWQi anomalies caused by unacceptable concentrations of major ions and trace elements were assessed by comparing the measured values with World Health Organization  drinking water guidelines. Calculated GWQi values ranged from 4 to 765. The lowest values were found in samples collected from the headwaters of the basin, while the highest values were recorded in the lower reaches of the basin and areas mainly influenced by hot springs. The spatial distribution of calculated GWQi values closely mirrored the concentrations of Li, B, and As. These hydrogeochemical trends are characteristic of arid volcanic regions with evaporitic reservoirs, and geothermal fluid influence. Establishing a comprehensive baseline of groundwater quality and understanding the natural hydrogeochemical processes across the CB is critical for protecting public health, preserving ecosystems, and supporting sustainable development in the region.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412005

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