Dissipation of Thermal and Chemical Disequilibrium in Hot Springs

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SchoonenEAR-0073963Hot springs are environments characterized by thermal and chemical disequilibrium. The purpose of the proposed study is to determine the rates and mechanisms of abiotic processes by which the thermal and chemical disequilibrium is dissipated. The objective of this study is to obtain these rates through field studies of hot springs in Yellowstone National Park and possibly Lassen Volcanic National Park, complemented by a few laboratory experiments. As water flows away from the orifice or pool of hot spring, four types of interrelated abiotic processes take place. These are a) fluid flow b) cooling, c) gas transfer (e.g., O2 in gassing, H2, CO2 and H2S outgassing) , and d) chemical reactions in the water (e.g., travetine deposition, and hydrogen sulfide oxidation). A research strategy has been developed to obtain rates of these processes through detailed measurements of flow regimes (linear velocity and a measure of turbulence) in the drainages coupled with detailed temperature measurements to obtain cooling rates and chemical analyses to obtain the chemical evolution of the water as it flows away. The chemical analyses involve a determination of the concentration of dissolved gases (He, H2, Ar, O2, CO2, and H2S) and dissolved major ionic species. From the temperature profiles and concentration profiles the heat transfer coefficients and gas transfer coefficients can be derived. Because the determination of the gas transfer coefficients is crucial, a series of laboratory experiments is proposed in which the gas exchange coefficient of CO2 is derived by conducting a degassing experiment in a simple artificial channel with a flow regime similar to the drainages studied in Yellowstone. To keep these experiments simple they will be conducted at room temperature, but gas transfer theory is sufficiently well developed to allow extrapolation to higher temperature. The laboratory experiments will be conducted by undergraduate students.