Suitable real-time monitoring of the aerobic biodegradation of toluene in contaminated sand by spectral induced polarizationmeasurements and CO2 analyses

International audienceHydrocarbons commonly contaminate aquifers and, in certain cases, can be successfully treated through biodegradation. Biodegradation is an effective technique for cleaning up pollution by enhancing pollutant-degrading bacteria in situ. However, in situ sampling for monitoring processes occurring into the ground during the treatment is expensive and invasive. In this article, an alternative method was tested. Spectral Induced Polarization (SIP) was combined with gas analyses, CO2 concentration and its carbon isotopic ratio, to monitor toluene aerobic biodegradation in laboratory columns. Microbial activity was characterized by an evolution of the SIP response in correlation with a CO2 production with the same carbon isotope signature as toluene. The spectral induced polarization response followed the variations of bacterial activity and displayed a phase shift up to 15 mrad. These results support the feasibility of using geophysical measurements, supported by CO2 analyses, to monitor in situ hydrocarbon biodegradation, and they are proving to be highly promising for real field scale monitoring