Quantifying the mineralization of contaminants using stable carbon isotoperatios

Current techniques used to monitor in situ degradation of organic contamina nts require time intervals of days to months to measure significant changes in concentration. In addition, these methods are unable to monitor mineral ization or measure absolute degradation of complex mixed wastes. The abilit y to continuously and definitively monitor mineralization (conversion to CO 2 and H2O) would greatly enhance the ability to study the fate of contamina nts. The objectives of this study were to show that in environments with ap propriate background delta(13)C signatures, simultaneous measurement of CO2 production and delta(13)C signatures of the produced CO2 will allow both t he quantification and qualification of contaminant mineralization. In labor atory microcosm studies the mineralization of hexadecane was monitored by b oth traditional C-14 radiorespirometry techniques and by measuring the delt a(13)C ratio and total amount of produced CO2. The total mass of hexadecane mineralized determined by each technique was statistically the same. More importantly, the first order rate constants calculated from the respective mineralization curves were virtually identical. These results indicate that stable carbon isotope ratios are an appropriate means of monitoring aerobi c mineralization of contaminants in environments in which differences in de lta(13)C ratios exist between contaminant and natural organic matter. (C) 1 999 Elsevier Science Ltd. All rights reserved.