275-6 Understanding and addressing arsenic mobilization in Chilean geothermal systems

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

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Despite the vast potential of geothermal resources in Chile for energy production (e.g., the 83 MW Cerro Pabellón geothermal power plant operating since 2017 in the Antofagasta Region) and direct use applications with several pilot projects of space heating in both the northern and southern parts of the country, arsenic (As) mobilization in Chilean geothermal systems presents a significant environmental and health challenge. This necessitates comprehensive understanding and mitigation strategies, as the geological conditions that favor geothermal activity also facilitate As mobilization into geothermal fluids, and subsequently to the near-surface environment. The high temperatures and the presence of As-bearing minerals in geothermal reservoirs contribute to the dissolution and release of As into geothermal fluids. This mobilization poses risks to both environmental and human health, as As can contaminate water sources used for drinking, irrigation, and industrial processes. Consequently, understanding the mechanisms of As release and transport is critical for developing effective management and mitigation measures.

While the solubility of As in geothermal fluids is influenced by several factors, including pH, temperature, redox potential, and the presence of other chemical species, the interplay between these factors determines As speciation and mobility, complicating efforts to predict its behavior and impact accurately. Furthermore, the interaction of geothermal fluids with subsurface materials, such as rocks, soils, and sediments, can alter the geochemical conditions, enhancing or reducing As mobility. To address these challenges, a multidisciplinary approach is essential, including detailed geochemical modeling to predict As behavior under different conditions, in situ monitoring of As concentrations in geothermal fluids, and developing treatment technologies to remove As from geothermal fluids before their use or discharge. Integrating environmental impact assessments with community health studies can help devise policies and practices that safeguard public health and preserve ecosystems.

In conclusion, while Chile’s geothermal resources offer significant opportunities for sustainable energy development, the challenge of As mobilization must be addressed through comprehensive research, monitoring, and mitigation strategies.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10452

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