Foos, A., 2000, Sulfur Redox of Acidic Hot Springs and Mudpots, Yellowstone WY, USA, Geological Society of America Abstracts with Programs, v 32, No. 7,

ABSTRACT

The chemistry of 23 water samples from acidic hot springs and mudpots at Yellowstone National Park, Wyoming, USA was determined during July 1998. Samples were collected from the Mud Volcano, Rabbit Creek, Norris Geyser Basin and Artist Paint Pots areas. The temperature, pH and oxidation reduction potential (ORP) ranged from 23 to 92 C; 1.9 to 6.8; and -134 to 474 volts, respectively. There was a negative correlation between pH and ORP (R=71). H2S ranged from .01 to .85 mg/l and SO4= ranged from 45 to 2975 mg/l.
pe was calculated from the H2S/SO4= redox couple, pH and temperature and compared to pe determined from observed ORP and temperature. There was a very good agreement between observed pe, and thermodynamically calculated pe (R = .77). The data falls within the rhombic sulfur field on a pe-Ph diagram and sulfur was observed by X-ray diffraction in the associated sediments.
These results suggest that the redox of acidic hot springs and mudpots is controlled by the sulfur system. The waters are in thermodynamic equilibrium and it is unlikely that bacterially mediated reactions play a significant role in the redox of this system.