Electrodic voltages in the presence of dissolved sulfide: Implications for monitoring natural microbial activity

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Issue Date
2008-03Author
Slater, Lee
Ntarlagiannis, Dimitrios
Yee, Nathan
O'Brien, Michael P.
Zhang, Chi
Williams, Kenneth H.
Type
Article
Article Version
Scholarly/refereed, publisher version
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AbstractThere is growing interest in the development of new monitoring strategies for obtaining spatially extensive data diagnostic of microbial processes occurring in the earth. Open-circuit potentials arising from variable redox conditions in the fluid local-to-electrode surfaces (electrodic potentials) were recorded for a pair of silver-silver chloride electrodes in a column experiment, whereby a natural wetland soil containing a known community of sulfate reducers was continuously fed with a sulfate-rich nutrient medium. Measurements were made between five electrodes equally spaced along the column and a reference electrode placed on the column inflow. The presence of a sulfate reducing microbial population, coupled with observations of decreasing sulfate levels, formation of black precipitate (likely iron sulfide),elevated solid phase sulfide, and a characteristic sulfurous smell, suggest microbial-driven sulfate reduction (sulfide generation) in our column. Based on the known sensitivity of a silver electrode to dissolved sulfide concentration, we interpret the electrodic potentials approaching 700mV
recorded in this experiment as an indicator of the bisulfide (HS−) concentration gradients in the column. The measurement of the spatial and temporal variation in these electrodic potentials provides a simple and rapid method for monitoring patterns of relative HS− concentration that are indicative of the activity of sulfate-reducing bacteria. Our measurements have implications both for the autonomous monitoring of anaerobic microbial processes in the subsurface and the performance of self-potential electrodes, where it is critical to isolate, and perhaps quantify, electrochemical interfaces contributing to observed potentials.
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Slater, Lee, Dimitrios Ntarlagiannis, Nathan Yee, Michael O'Brien, Chi Zhang, and Kenneth H. Williams. "Electrodic Voltages in the Presence of Dissolved Sulfide: Implications for Monitoring Natural Microbial Activity." Geophysics 73.2 (2008): F65-70
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