Utilization of Stable Carbon Isotope Analysis in the Verification of Bioremediation of Chlorinated Hydrocarbons

In Situ bioremediation systems, such as bioventing, have been applied at numerous sites to remediate petroleum hydrocarbons and other common organic contaminants. Monitoring the progress of biodegradation for in situ systems has been problematic. One monitoring method examined at a limited number of sites utilizes stable carbon isotope analysis. Through the use of stable carbon isotopes, the relative amount of carbon dioxide contributed from the biodegradation of organic contaminants can be determined. This source determination for carbon dioxide can be used to verify biological degradation at active bioremediation and bio-attenuation sites. The benefits of the stable isotope method include: lower costs per sample, lower time required per sample and fewer samples require per site. The goal of this proposal is to further the development of the stable carbon isotope monitoring method. Currently, the major impediment to application of the method is the limited amount of data available regarding fractionation of carbon isotopes by biological systems during the aerobic degradation of xenobiotic compounds. For the method to be effectively applied fractionation of the carbon isotopes must be determined for a variety of compounds undergoing biodegradation, with varying microbial inoculum responsible for the carbon dioxide production. The effects of various bacterial oxygenase systems will also be assessed, as well as the effects of fractionation on the carbon isotope composition of end products (i.e. carbon dioxide) resulting from the biodegradation of mixtures of compounds.