NTO s degradation under environmentally relevant conditions: DFT study
Abstract
The modeling of degradation processes for chemicals in the environment is increasing in importance as it is an effective tool for understanding safety of chemical compounds for living organisms in case of their release into the environment. Quantum-chemical methods could play an important role in such studies. Calculations predict the most relevant pathways for chemicalsÕ transformation, their mechanisms, products, and rates. Soil and water contamination by explosives is present in training areas where armament testing occurs and industrial sites where explosives are developed and manufactured for military and commercial use. NTO (3-nitro-1,2,4-triazol-5-one) is one of the new explosive compounds used in insensitive munitions and developed to replace traditional explosives, TNT (2,4,6-trinitrotoluene) and RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), but its fate and transport in the environment have been poorly described. When munitions do not completely detonate, a significant mass of the explosive compounds originally present in a round can be deposited on the ground. Upon entering the subsurface, NTO will experience reactive transport through the soil. As a chemical compound migrates through the soil profile, it can undergo irreversible and reversible adsorption by different mineral and organic phases in the soil. It may also experience transformation, volatilization, and bio-uptake. When a compound dissolves, it may move to the groundwater. Data on NTOÕs fate and transport are needed to determine its environmental behavior and potential for groundwater contamination. In the present project, we have proposed to examine the adsorption and possible degradation pathways of NTO that may occur in soil and water using density functional theory (DFT) techniques. The first part of the project relates to NTOÕs interaction with soil. The structural and energetic characteristics of adsorbed complexes that NTO may form with soil components have been proposed to be analyzed using Atom in Molecule (AIM) approach to determine the strength and type of bonding. The most essential pathways for chemicalsÕ degradation in the environment are oxidation and reduction processes. Redox reactions have been proposed to be analyzed on the adsorbed forms of NTO to understand the feasibility of NTOÕs decomposition mediated by soil mineral components. Another important way for NTOÕs disappearing in soil is biodegradation. We have proposed to model NTOÕs decomposition by microbial enzymes to predict its mechanism. The second part of the project proposes a detailed analysis of NTOÕs decomposition in water. We have included hydrolysis and photolysis in the project to understand the effect of UV-irradiation on NTOÕs degradation. The experiments in these directions contain limited data. The interesting feature of this project is that we are able to generate the reaction mechanism with known structures of all intermediates and products. The computational approach we developed to predict the rates of decay and appearance in multistep chemical and biological reactions allows one to predict the concentration of any reagent, product, and intermediate at any period of time. An important aspect of this project is that the computationally modeled NTO behavior under environmentally relevant conditions will enrich the available experimental data by understanding the reaction mechanism of the decomposition processes to get the complete picture for NTOÕs degradation in the environment.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 09, 2020
- Source ID
- W911NF2010116
Entities
People
- Jerzy Leszczynski
Organizations
- Army Contracting Command
- Jackson State University
- United States Army