Interaction of Microbial and Abiotic Processes in Soil Leading to the (Bio)Conversion and Ultimate Attenuation of New Insensitive Munitions Compounds

ER-2221

Objective

Relatively little is known about the environmental behavior of two new insensitive munitions compounds (IMCs), 3-nitro-1,2,4-triazole-5-one (NTO) and 2,4-dinitroanisol (DNAN). Bacteria are known that can degrade and biotransform nitroaromatic compounds, and biotransformations catalyzing the reduction of nitro-groups or demethylation of methoxy groups create reactive intermediates that are subject to oxidative coupling and formation of bound residue. In order to better understand the environmental fate of the new IMCs, the objective of this project is to study the interaction of biological and abiotic processes in the soil that collectively contribute to their conversion and attenuation under a range of soil conditions. The project will provide a thorough understanding of the potential risk for the accumulation of toxic intermediates, the potential for soil to attenuate the risk, as well as provide a scientific basis to predict the long-term fate of the IMCs to either mineralized products, bound residue in humus, or tightly adsorbed species based on soil composition and biogeochemical conditions.

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Technical Approach

Researchers will first evaluate the environmental fate of IMCs as a function of soil type collected from five sites. The fates to be monitored include IMC sorption onto soil and (bio)transformation yielding intermediate compounds, mineralized products, and humus-bound residue. Based on the fates observed, soils will be selected for further study to elucidate the main mechanisms of biodegradation and sorption/abiotic transformation. This information will be combined to test whether small structural modifications catalyzed by abiotic and biotic reactions will impact the ultimate fate of IMCs. The consequences of the findings will be assessed by evaluating the microbial and ecological toxicity of IMC-contaminated soils, IMCs, and their (bio)transformation products. An understanding of which mechanisms lead to the conversion of IMCs to safe end products can be used to predict which soil conditions are suitable for attenuating IMCs and to apply measures for improving attenuation.

The conversion processes will be monitored with isotope labeled IMCs using 13C- and 15N-nuclear magnetic resonance (NMR) spectroscopy as well as liquid chromatography-tandem mass spectrometry (LC-MSMS) and gas chromatography-mass spectometry (GC-MS) techniques. The microbial diversity of IMC-degrading organisms will be characterized by combining DNA-stable isotope probing (SIP) with clone libraries. Selected pure cultures that benefit from IMC degradation will be isolated in order to identify putative genes involved in biodegradation. The reaction of IMCs and intermediates with reactive soil particles will be studied using batch and column experiments to gauge the importance of abiotic processes in IMC attenuation.

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Benefits

Land management and bioremediation will be aided by the knowledge of soil conditions conducive to attenuation of IMCs. The identity of intermediates can be used to design environmental monitoring protocols. The identification of dominant microorganisms and genes involved in biodegradation can be translated into PCR reactions to monitor IMC sites for biodegradation potential. The elucidation of important secondary minerals involved in the abiotic conversion of IMCs can translate in practice to monitoring key constituents in soil that predict abiotic conversion. (Anticipated Project Completion - 2015)

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Points of Contact

Principal Investigator

Dr. James A. Field

University of Arizona

Phone: 520-301-8011

Program Manager

Environmental Restoration

SERDP and ESTCP

Document Types

  • Fact Sheet - Brief project summary with links to related documents and points of contact.
  • Final Report - Comprehensive report for every completed SERDP and ESTCP project that contains all technical results.
  • Cost & Performance Report - Overview of ESTCP demonstration activities, results, and conclusions, standardized to facilitate implementation decisions.
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  • Workshop Report - Summary of workshop discussion and findings.
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