ARSENIC AND OTHER GEOGENIC CONTAMINANTS IN THE HYDROLOGIC AND HYDROGEOLOGICAL SYSTEM OF THE BOLIVIAN ALTIPLANO

Arsenic (As) contamination of water is a global concern affecting millions of people; the Bolivian altiplano (BA) is no exception. Since the colonial times, mining has been responsible for water contamination and environmental degradation. The first reports of elevated concentrations of As and other contaminants in water bodies were always related to mining activities, but few information is available on the presence of Geogenic Contaminants (GCs). This study shows the natural presence of high concentrations of As and other GCs in different water bodies as a prevailing phenomenon throughout the BA, which provides an opportunity to better understand the hydrogeochemical conditions for As and other GCs mobilization using an integrated approach with mapping (GIS), geostatistics, and geochemistry. The results indicate that the predominant water type within the BA is Na-Cl-HCO3, with high concentrations of As, B, Li, and other GCs. In rivers, the concentration of As varies from 5 to 2,617 μg/L, B varies between 1 and 9,573 μg/L, and Li varies between 10 and 2,980 μg/L, whereas in springs, As varies from 1 to 1,400 μg/L, B varies between 52 and 11,364 μg/L, and Li varies between 1 and 2,700 μg/L. In groundwater, As concentration levels vary between 1 and 3,497 μg/L, B vary between 93 to 68,891 μg/L and Li vary between 2 to 31,570 μg/L ; in hot springs, As concentrations vary between 2 and 8,100 μg/L, B vary between 4,021 to 50,352 μg/L and Li vary between 315 to 25,000 μg/L, and in lagoons, the values of As vary between 10 and 76,000 μg/L, B vary between 341 to 730,875 μg/L and Li vary between 1000 to 165,000 μg/L. Laguna Colorada presented the highest and most extreme concentration of measured As. The high concentrations of As and other GCs are consistent with the geological characteristics of the area, including volcanic rocks, sedimentary deposits, and geothermal fluids. As and other GCs are released into the environment through multiple hydrogeochemical processes between water and rock. Contaminated water bodies are often used for irrigation, consumption, and recreation, putting the health of the exposed population at risk.

Key words: Bolivian Altiplano, Geochemistry, Geogenic arsenic, Health effects, Hydrochemistry.