Thermal water chemistry of Yellowstone National Park after 24 years of research

Abstract

The collection, analysis, and interpretation of 24 years of thermal water chemistry data from Yellowstone National Park have led to substantial insights into the water-rock interactions here and implications for other geothermal areas. New sampling and analytical methods have been developed and tested for trace elements. Quantitative measurements were obtained for changes in redox species of S, Fe, As, Sb, and Hg during outflow of thermal waters in which biotic and abiotic reactions play important roles. Fluoride speciation calculations were confirmed with ion-selective electrode measurements. The fate of contaminants, especially As and F, from thermal features in major rivers revealed no significant attenuation during downstream transport. Continuous monitoring for heat flux using year-round conductivity measurements was established. Testing of the “Multiple Equilibria Geothermometer” was achieved with high-quality, long-term data from Ojo Caliente, a continuously flowing hot spring. Yellowstone continues to be an outstanding field laboratory for expanding our knowledge of thermal water-rock interactions.