Understanding Why RDX Persists in Soils and Developing Technologies to Prevent Transport of RDX and NTO from Testing and Training Ranges.

Timothy Cary | ERDC-CRREL

ER19-1247

Objective

In this project, studies will be conducted to establish why RDX persists in soil and surface run-off. In addition, it is important to develop a better understanding of the microbial detoxification pathways for NTO. These findings will be used to develop, and test, biotechnologies that can be deployed in the field to enhance RDX degradation in soils and reduce RDX in surface run-off. The specific objectives of this project are to:

  • Determine the fundamental reasons why RDX persists in soil and surface run-off.
  • Develop technologies to maximize biodegradation at the soil surface and minimize transport of RDX and 3-nitro-1,2,4-triazol-5-one (NTO) to the subsurface.
  • Establish biochemical detoxification pathways for NTO.

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Technical Approach

Experiments will determine the mechanism by which the co-contaminant, 2,4,6-trinitrotoluene (TNT), inhibits the RDX-degrading enzyme cytochrome P450-like protein (XplA). This information will be used to produce new TNT-insensitive XplA variants for future remediation technologies. Microcosm studies will be used to determine factors preventing the establishment and proliferation of XplAB-containing bacteria in RDX-contaminated range soils. The effect of practical amendments such as compost and manure will be investigated to assess whether these would be effective in-the-field. Phylogenetically, the xplAB gene system is currently limited to members of the order, Actinomycetales. Existing technologies will be further developed to facilitate the promiscuous, horizontal gene transfer of xplAB between diverse family of soil bacteria, particularly members of the Pseudomonadaceae which are known to populate RDX-contaminated soils. Following the experiments on soil bacteria, rhizospheric and endophytic bacteria will be isolated from plant species indigenous to, and growing on, military range soils. The xplAB genes will then be transferred to these rhizospheric and endophytic Pseudomonadaceae using the optimized horizontal gene transfer technologies. The transformed bacteria containing xplAB will be applied to soil microcosms to determine the ability of these species to remediate RDX.

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Benefits

The results from this project will significantly increase the understanding of RDX persistence in the environment and help to develop management strategies applicable to conventional and insensitive munitions. 

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Points of Contact

Principal Investigator

Mr. Timothy Cary

U.S. Army ERDC-CRREL

Phone: 603-646-4358

Fax: 603-646-4845

Program Manager

Environmental Restoration

SERDP and ESTCP

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