HC-Biiodegradation monitoring by geo-electrical measurements and CO2 analyses : field implementation

Abstract : Hydrocarbon contaminated aquifers can be successfully treated through biodegradation. However, in situ monitoring of the treatment is expensive, invasive and can be insufficient as the information provided is restricted to vertical profiles at discrete locations. An alternative method was tested in order to improve the robustness of the monitoring. Geophysical methods, Electrical Resistivity (ER) and Induced Polarization (IP), was combined with gas analyses, CO2 concentration and its carbon isotopic ratio, to propose a non-destructive method for monitoring in situ biodegradation of hydrocarbons. It was tested at a BTEX-polluted site under aerobic bio-treatment. Geophysical monitoring show a more conductive and chargeable area which corresponds to the contaminated zone. Moreover, in this area, CO2 emissions have been measured with an isotopic signature typical of biodegradation. Combining geophysics with gas analyses is thus promising to provide a new methodology for in situ monitoring.