A sandbox experiment to investigate bacteria-mediated redox processes on self-potential signals

Abstract

We investigated the influence of microbial processes on self-potential signals in a Plexiglas tank filled with a water-saturated quartz sand. A small region of the tank was treated with sulfato-reducer bacteria and organic nutrients. Redox potential measurements were performed both in the treated portion containing the bacteria and in the non-treated portion of the tank. Self-potential signals were recorded at the upper (free-air) surface of the tank to monitor biodegradation. We observed a linear correlation between the temporal variation of these self-potential signals and the redox potential difference between the treated and the non-treated portion of the tank. Self-potential signals can therefore be used as a non-intrusive redox sensor. In addition, we propose a geobattery concept in which biofilms and the possible precipitation of metallic particles (biominerals) at the redox front allow electron transfer (therefore a net driving current density) between the reduced and oxidized parts of the system. In turn, this current is responsible for an electrical field in the Maxwell equations. Copyright 2005 by the American Geophysical Union.