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MONITORING POLYCHLORINATED BIPHENYLS (PCBS) BIODEGRADATION USING CONTINUOUS-FLOW ISOTOPE RATIO MASS SPECTROMETRY
Citation:
Mills**, M A. AND J R. Haines*. MONITORING POLYCHLORINATED BIPHENYLS (PCBS) BIODEGRADATION USING CONTINUOUS-FLOW ISOTOPE RATIO MASS SPECTROMETRY. Presented at The Second International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, CA, 05/22-25/2000.
Description:
Research has shown that polychlorinated biphenyls (PCBs) in some cases can be removed from the environment by biodegradation. Aerobic and anaerobic biological processes have been determined in previous research to be capable of degrading PCBs. During the aerobic and anaerobic degradation of PCBs, CO2 and CH4 are produced during biological respiration. Ratios of the stable carbon isotope (13C) to the most abundant carbon isotope (12C) can be used to differentiate the source of the respired carbon dioxide (CO2) and methane (CH4). Petrochemical-derived organic compounds have distinct 13C/12C ratios compared to recently deposited carbon. The respired gases from the biodegradation of a petrochemical contaminant should reflect the isotopic ratio of that contaminant.
A series of experiments were designed to verify the gases (CO2 and CH4) produced during the respiration of PCBs reflect that of the source materials. One set of experiments was conducted using PCB-contaminated sediments. The sediments were slurried to homogenize the material and dispensed into 60 ml vials. These vials were incubated with vials being sacrificed periodically for headspace analysis and chemical analysis. Preliminary results indicate the indigenous population has been producing methane during the degradation of organic materials within the sediment. The methane is highly depleted in its isotopic ratio (up to -600/00) as is expected during methanogenisis.
Results indicate that monitoring the gases produced during the biodegradation of organic contaminants may compliment existing monitoring methods. Additionally, this analysis technique may reduce the need to collect and analyze as many samples for the expensive and time-consuming traditional monitoring methods. Further research is being conducted to determine the compound specific isotopic ratios of the PCB contaminant and how that is reflected in the produced gases. Contributions of carbon from other carbon pools are also considered. Detailed analysis of natural soil organic carbon, plant debris, and non-PCB petrochemicals is essential for assigning the proportion of CO2 and/or CH4 produced during the biodegradation process.