Predicting the Future Fate and Transport of New Munition Compounds

The readiness of our military forces depends on their ability to develop and test improved weapons systems and to train troops under realistic operational and wartime scenarios. SERDP and ESTCP fund a variety of efforts to ensure the sustainability of our testing and training ranges, including mitigation of the release of munition compounds. One aspect of these mitigation efforts is the prediction of the potential fate and transport of new munition compounds under development.

Numerous methods exist to predict the chemical properties and fate of new chemical materials. Standards and regulations for the development and production of new chemicals can be found through both the Toxic Substances Control Act (TSCA) as well as the Organisation for Economic Co-operation and Development (OECD); however, these regulations and standards apply to high-production chemicals only, and are not applicable to most munition compounds. There is no other standard or regulation that specifically applies to munition compounds. Fate, transport, and toxicity can be estimated from Quantitative Structural Activity or Property Relationships (QSARs/QPARs), but these have a strong dependence on data from existing, similar chemicals. Without this, estimates of fate, transport, and toxicity cannot be considered definitive. Materials developed for military use are unique in both their structure and their use; current methods for prediction of chemical properties and fate may not adequately address these unique conditions.

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Computer modeling simulation of one possible pathway for breakdown of TNT in water.

New munition compounds typically undergo thorough toxicity evaluation to ensure safety through occupational exposure. However, environmental exposure is often evaluated only to a limited extent, even though adverse environmental impacts from a new munition compound have the potential to seriously limit its development and use. Incorporating predictive techniques to assess potential environmental health risks early in the development of new munition compounds will ultimately help to reduce life cycle costs associated with any new weapon system. In 2010, SERDP released a solicitation to develop new predictive techniques specifically for munition compounds. Three projects were funded, all of which are nearing completion and are described below.

Dr. Paul Tratnyek from the Oregon Health & Science University has been developing a novel, fully in silico approach to QSAR development in his SERDP project, where all of the calibration data are calculated from molecular structure theory. Rates of the most likely breakdown pathways are calculated with the highest level of theoretical accuracy, and these data will be correlated to molecular properties that are obtained with computational methods that are more available and feasible for most chemists. Once QSARs have been obtained by this approach, researchers will attempt to validate them by predicting data for safe and available model compounds and comparing them to measured experimental values. Possible breakdown pathways for various chemicals have been simulated, as shown in the accompanying video.

Under a SERDP project led by Dr. Dominic Di Toro from the University of Delaware, the research team are developing models for predicting physical and chemical properties such as aqueous solubility, octanol-water partition coefficient, and Henry’s Law constant, as well as the potential bioaccumulation and metabolism of new munition compounds partitioning into soil organisms and plants. This requires a new generation of models that rely on quantum chemical methods to estimate the physical chemical properties and the necessary model partition coefficients and metabolism parameters.

Dr. Eric Weber from the U.S. EPA Ecosystems Research Laboratory with team members from the Pacific Northwest National Lab are working on a SERDP project in which they are developing a tool titled Framework for Risk Analysis of Multimedia Environmental Systems (FRAMES)-based Environmental Fate Simulator (EFS). This tool will provide managers of DoD training and testing ranges estimates of the vulnerability of aquifers and surface waters to new and proposed energetic materials as well as the potential transformation products.

Researchers from these three teams have been working closely with each other and members of the DoD to develop the most useful and accurate prediction tools possible to ultimately reduce lifecycle costs associated with the development of new munition compounds and support sustainability of testing and training ranges. Results from these efforts are expected later in 2014.

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