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Natural Organic Matter as Reductant for Chlorinated Aliphatic Pollutants

Kappler, Andreas and Haderlein, Stefan B. (2003) Natural Organic Matter as Reductant for Chlorinated Aliphatic Pollutants. Environmental Science and Technology, 37 (12). pp. 2714-2719. ISSN 0013-936X. doi:10.1021/es0201808.

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Humic acids (HA) are ubiquitous redox-active compounds of natural aquatic and soil systems. Here we studied the potential of HA as reductants for chlorinated aliphatic pollutants. To avoid artifacts potentially involved when studying chemically reduced HA, we prepared electrochemi cally reduced soil, aquatic and synthetic HA, and anthrahydroquinone-2,6-disulfonic acid (AHQDS), a model compound for hydroquinone moieties in HA. Both reduced HA and AHQDS reduced hexachloroethane (HCE) at appreciable rates. Some reduction of HCE by HA, however, occurred even before electrochemical reduction of the humic acids. This indicates that a small fraction of reduced moieties in HA persists at oxic conditions for some time. The initial reaction followed pseudo-first-order reaction kinetics, and tetrachloroethylene was the only halogenated product. The relatively small variations in carbon-normalized rate constants, kDOC, found indicate that despite inherent variations in concentration, accessibility, and reactivity of redox-active groups in HA of various origins their overall dechlorination activity is fairly constant. However, HCE transformation rate constants and reducing capacities of different HA did not correlate. Rate constants normalized to both carbon content and reducing capacity of HA clearly indicate that reduced functional groups in different HA exhibit different reactivities. Our results together with the fact that reduced HA can be formed by a variety of microbiological and chemical processes suggest that HA could play a significant role as reductants in the reductive transformation of subsurface contaminants and that such a process could potentially be enhanced at contaminated sites by addition of reducible natural organic matter.

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Additional Information:© 2003 American Chemical Society. Received 30 August 2002. Date accepted 4 April 2003. Published online 10 May 2003. Published in print 1 June 2003. We gratefully acknowledge M. Elsner, Dr. T. Hofstetter, Prof. R. Schwarzenbach, and L. Zwank for critically reviewing the manuscript. This work was part of the European Union project “Protection of Groundwater Resources at Industrially Contaminated Sites (PURE)” and was supported by the Swiss Federal Office for Education and Science (grant no. BBW 99.0396).
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Swiss Federal Office for Education and ScienceBBW 99.0396
Issue or Number:12
Record Number:CaltechAUTHORS:20170316-085457626
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Official Citation:Natural Organic Matter as Reductant for Chlorinated Aliphatic Pollutants Andreas Kappler and Stefan B. Haderlein Environmental Science & Technology 2003 37 (12), 2714-2719 DOI: 10.1021/es0201808
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75176
Deposited By: Ruth Sustaita
Deposited On:16 Mar 2017 16:20
Last Modified:15 Nov 2021 16:31

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