A NEW METHOD FOR RAPID SOURCE ZONE DELINEATION AND DETERMINATION OF VADOSE ZONE CONTAMINANT BIODEGRADATATION RATES USING SURFICIAL GAS EFFLUXES
One approach to achieve these objectives is to measure the carbon effluxes (CO2 and CH4) at the ground surface above the contaminated region. This method is suitable for identifying regions of active biodegradation and for quantifying depth and terminal electron acceptor-integrated biodegradation rates. In ecosystem sciences a common technology for this kind of measurement is a dynamic closed chamber system; however, this technique has not previously been applied at contaminated sites. Preliminary work in a crude oil-contaminated aquifer near Bemidji, MN demonstrated that measurements of surficial CO2 effluxes using the chamber methods are useful to delineate petroleum hydrocarbon containing source zones and to provide estimates of depth-integrated vadose zone hydrocarbon degradation rates.
In order to further test the capabilities of the method under different hydrogeologic conditions and to determine its sensitivity to a variety of contaminant classes, follow-up studies were conducted at several field sites, including a pipeline leak, former refinery sites, and biofuel releases. Results of these trials indicate that the method provides a robust tool for evaluating vadose zone biodegradation rates under a wide range of environmental conditions.