Abstract

Yellowstone National Park is well known among microbiologists for its unique microbial ecology, where microorganisms adapt to extreme environments (temperature and pH) associated with geothermal features including hot springs, geysers, and fumaroles. Recently, we developed a portable, battery-operated potentiostat to control the potential of electrodes in in Heart Lake Geyser Basin. The goal of this work is to compare the electrochemical activity in polarized and non-polarized electrodes deployed in alkaline hot springs. We used carbon fabric electrodes (3 inch x 3 inch) working electrode, graphite felt (5 inch x 5 inch x 0.25 inch) counter electrode, and Ag/AgCl reference electrode. A carbon fabric electrode (3 inch x 3 inch) was used as a non-polarized control. These electrodes were immersed in four hot springs with temperature ranging between 45οC and 91οC, and pH between 8 and 8.8. In total, eight polarized electrodes and controls were deployed; one anode and one cathode in each hot spring. The cathodes were deployed approximately 1 foot below the surface of the water, and polarized at -0.6 VAg/AgCl. The anodes were deployed near the bottom of each hot spring at depth 3-10 feet, and polarized at +0.4 VAg/AgCl. All electrodes were deployed for a period of 30 days, and then harvested for electrochemical analysis. Cyclic voltammetry reveals the presence of multiple anodic and cathodic peaks in both polarized and control electrodes. Increased temperature seems to activate redox couples, with anodic (positive current) peaks at -0.2 and 0.35 VAg/AgCl, and two corresponding cathodic (negative current) peaks at -0.4 and 0.25 VAg/AgCl. Temperature-controlled experiments shows that the peak height increases with temperature, which alludes to the presence of thermally-activated electrochemical reactions.

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