Experimental Evidence for a Lack of Thermodynamic Control on Hydrogen Concentrations during Anaerobic Degradation of Chlorinated Ethenes
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- 作者：Axel C. Heimann and Rasmus Jakobsen
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：June 1, 2006
- 年：2006
- 卷：40
- 期：11
- 页码：3501 - 3507
- 全文大小：430K
- 年卷期：v.40,no.11(June 1, 2006)
- ISSN：1520-5851
文摘
Hydrogen (H2) concentrations during reductive dechlorinationof cis-dichloroethene (cDCE) and vinyl chloride (VC)were investigated with respect to the influence of parametersentering the Gibbs free energy expression of the reactions.A series of laboratory experiments was conductedemploying a mixed, Dehalococcoides-containing enrichmentculture capable of complete dechlorination of chlorinatedethenes. The objective was to investigate whether aconstant energy gain controls H2 levels in dechlorinatingsystems, thereby evaluating the applicability of the partialequilibrium approach to microbial dechlorination atcontaminated sites. Variations in the temperature between10 and 30 
C did not affect the H2 concentration in afashion that suggested thermodynamic control through aconstant energy gain. In another set of experiments, H2 levelsat constant ionic strength were independent of thechloride concentration between 10 and 110 mmol chlorideper liter. These findings demonstrate that the partialequilibrium approach is not directly applicable to theinterpretation of reductive degradation of chlorinated ethenes.We also present recalculated thermodynamic propertiesof aqueous chlorinated ethene species that allow forcalculation of in-situ Gibbs free energy of dechlorinationreactions at different temperatures.
C did not affect the H2 concentration in afashion that suggested thermodynamic control through aconstant energy gain. In another set of experiments, H2 levelsat constant ionic strength were independent of thechloride concentration between 10 and 110 mmol chlorideper liter. These findings demonstrate that the partialequilibrium approach is not directly applicable to theinterpretation of reductive degradation of chlorinated ethenes.We also present recalculated thermodynamic propertiesof aqueous chlorinated ethene species that allow forcalculation of in-situ Gibbs free energy of dechlorinationreactions at different temperatures.