Understanding biogeobatteries: Where geophysics meets microbiology

Abstract

[1] Although recent research suggests that contaminant plumes behave as geobatteries that produce an electrical current in the ground, no associated model exists that honors both geophysical and biogeochemical constraints. Here, we develop such a model to explain the two main electrochemical contributions to self-potential signals in contaminated areas. Both contributions are associated with the gradient of the activity of two types of charge carriers, ions and electrons. In the case of electrons, bacteria act as catalysts for reducing the activation energy needed to exchange the electrons between electron donors and electron acceptors. Possible mechanisms that facilitate electron migration include iron oxides, clays, and conductive biological materials, such as bacterial conductive pili or other conductive extracellular polymeric substances. Because we explicitly consider the role of biotic processes in the geobattery model, we coined the term ''biogeobattery.'' After theoretical development of the biogeobattery model, we compare model predictions with self-potential responses associated with laboratory and field scale investigations conducted in contaminated environments. We demonstrate that the amplitude and polarity of large (>100 mV) self-potential signatures requires the presence of an electronic conductor to serve as a bridge between electron donors and acceptors. Small self-potential anomalies imply that electron donors and electron acceptors are not directly interconnected, but instead result simply from the gradient of the activity of the ionic species that are present in the system.

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

“…For instance, bacteria can be very efficient catalysts for redox reactions and in the presence of a biofilm. The relationship between the current density and the gradient of the redox potential is found to be linear (Revil et al 2010a). The effects should not be confused with electrodic voltages associated with changes in the surface chemistry of the electrodes which are not self-potential signals Williams et al 2010).…”

“…The difference between the abiotic and biotic models of geobatteries is that in the biotic model, there are no potential losses because the bacterial biofilms play the role of catalysts in the transfer of electrons between electron donors and electron acceptors (Revil et al 2010a). These concepts of geobatteries were also tested and confirmed in the laboratory (Timm and Möller 2001;Naudet and Revil 2005;Castermant et al 2008).…”

Microbial ecology and geoelectric responses across a groundwater plume

“…Previous models position the electrical field and SP dipoles vertically with a cathode in the aerobic vadose zone directly above the anaerobic anode which usually lies below the water table (Timm and Möller 2001;Revil et al 2010;Sato and Mooney 1960;Naudet et al 2004). In this particular case there is lateral dipole across a redox gradient / plume boundary (Figures 1b & 5).…”

Quadrature conductivity: A quantitative indicator of bacterial abundance in porous media

“…In the last decade, the remote detection of processes associated with bacterial activity in porous media has been demonstrated using various active and passive geophysical methods including electric and seismic techniques (e.g., Naudet and Revil, 2005;Ntarlagiannis et al, 2005b;Williams et al, 2005;Davis et al, 2006;Linde and Revil, 2007;Personna et al, 2008;Zhang et al, 2010). Under some circumstances, bacterial activity can also be detected passively using the self-potential method (Naudet et al, 2003(Naudet et al, , 2004Revil et al, 2010;Risgaard-Petersen et al, 2012. This passive technique is used to detect remotely the occurrence of electric current associated with the displacement of electrons through biotic electronic conductors.…”