Anaerobic Oxidation of Vinyl Chloride Under Humic-Acid Reducing Conditions

Prompted by the growing recognition that naturally occurring humic acids compounds can serve as terminal electron acceptors for microbial metabolism, an investigation was initiated to assess the potential contribution of this process to the observed oxidation of vinyl chloride (VC) under methanogenic conditions. The fact that addition of 2-bromoethane sulfonic acid (BES) completely inhibited methanogenesis but had no effect on VC oxidation indicated that VC oxidation in this study was not coupled to methanogenesis. Subsequently, 2,6-anthraquinone disulfonate (AQDS, a model humic acids compound) was used to demonstrate that VC oxidation was coupled to microbial humic acids reduction. Microbial oxidation of dichloroethene (DCE) under humic acids reducing conditions was also demonstrated. These results indicated that, in the presence of humic acids, efficient mineralization of VC and DCE without accumulation of reduced intermediates can occur even under methanogenic conditions. Because humic acids are abundant in both environments, this study indicates that chloroethene oxidation under humic acids reducing conditions may be important in aquatic sediments and shallow ground-water systems.

Reference

• Bradley, P.M., Chapelle, F.H., and Lovley, D.R., 1998,
  Humic acids as electron acceptors for anaerobic microbial oxidation of vinyl chloride and dichloroethene: Applied and Environmental Microbiology, v. 64, no. 8, p. 3102-3105.

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