Biodegradation

, Volume 19, Issue 5, pp 705–715

Biotransformation products and mineralization potential for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in abiotic versus biological degradation pathways with anthraquinone-2,6-disulfonate (AQDS) and Geobacter metallireducens

Original Paper

DOI: 10.1007/s10532-008-9175-5

Cite this article as:
Kwon, M.J. & Finneran, K.T. Biodegradation (2008) 19: 705. doi:10.1007/s10532-008-9175-5

Abstract

This study investigated extracellular electron shuttle-mediated RDX biodegradation and the distribution of ring cleavage metabolites generated by biological degradation (cells) versus the products formed by abiotic degradation (reduced electron shuttles), and when the two pathways were acting simultaneously. All pathways were influenced by pH. Buffered suspensions (pH 6.8/7.9/9.2) were performed with cell-free anthrahydroquinone-2,6-disulfonate as the sole electron donor, cells (Geobacter metallireducens) + acetate, or cells/acetate + anthraquinone-2,6-disulfonate as an electron shuttle. The metabolites identified included methylenedinitramine, formaldehyde, nitrous oxide, nitrite, ammonium and carbon dioxide. As pH increased, the rates of RDX reduction by AH2QDS also increased. Cells alone reduced RDX faster at the lower pH values. However, at all pH the rates of the electron shuttle-mediated pathways were consistently the fastest, and the proportion of carbon present as formaldehyde, which is a precursor to mineralization, was highest in the presence of electron shuttles. Formaldehyde accounted for 45/51/54% of the carbon in electron shuttle amended cell suspensions as opposed to 13/42/45% of carbon without shuttles at the pH 6.8/7.9/9.2, respectively. Approximately 7–20% of RDX was mineralized to CO2 in the presence of cells at all pH tested; AQDS increased the extent of 14CO2 produced. Nitrous oxide and nitrite were end products in the strictly abiotic pathway, but nitrite was depleted in the presence of cells to form ammonium. Understanding the different products formed in the abiotic versus biological pathways and the influence of pH is critical to developing mixed biotic–abiotic remediation strategies for RDX.

Keywords

Bioremediation RDX Electron shuttling Fe(III)-reducing microorganisms 

Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  1. 1.Environmental Engineering and Sciences, Department of Civil and Environmental EngineeringUniversity of Illinois at Urbana-ChampaignUrbanaUSA
  2. 2.3221 Newmark Civil Engineering Laboratory MC-250UrbanaUSA

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