Time-lapse self-potential signals from microbial processes: A laboratory perspective

Microorganisms play a critical role in hydrocarbon degradation, contaminant sequestration, and pollution monitoring. However, the complex relationships between microbial processes and geological media's physical and chemical properties remain ambiguous. The self-potential (SP) is an efficient, low-cost, and nonintrusive passive geophysical technique suitable for monitoring dynamic activities. Herein, we conducted the 3D monitoring experiments to obtain time-lapse SP signals generated from cultivating typical microorganisms (Shewanella oneidensis MR-1) under laboratory-controlled conditions. The 3D multi-channel SP experimental devices enable dynamic monitoring and measurement of weak signals. At the beginning of the experiment, we observed a rapid increase in SP signals that consist mainly of the streaming potential and the redox potential. The peak values of negative anomalies monitored in the two experiments were − 75.9 mV and − 59.5 mV, respectively. During subsequent monitoring, the abnormal potential signal gradually decreased. After a sufficient period, the amplitude of the SP generated solely by the Shewanella oneidensis MR-1 activities ranged from −45 to −35 mV. Our laboratory research paves the way for developing dynamic model data to link the self-potential response with microbial processes. Then, we inverted the measured SP data to obtain the current source density distribution. The consistency of current density results and anomalous potentials shows that SP data collected by pre-buried non-polarizable electrodes can be utilized as a direct indicator signal for spatiotemporal monitoring of microbial activities. The SP method shows promise in environmental bioremediation and biodegradation.