Computational Investigation on Interactions between Some Munition Compounds and Humic Substances

Area of Science:

• Environmental Chemistry
• Soil Science
• Computational Chemistry

Background:

• Insensitive munition compounds (MCs) and legacy explosives pose environmental risks.
• Humic substances (HAs) are major organic components in soils and sediments.
• Understanding HA-MC interactions is crucial for predicting environmental contaminant behavior.

Purpose of the Study:

• To investigate the binding interactions between humic acid model compounds and various munition compounds.
• To characterize the electronic properties (ionization potential, electron affinity) of HAs in relation to MCs.
• To elucidate the role of HAs in the environmental fate and degradation of munition compounds.

Main Methods:

• Molecular dynamics simulations.
• Thermodynamic integration.
• Density functional theory (DFT) calculations.

Main Results:

• Humic acids effectively bind most studied munition compounds.
• HAs function as both electron sinks and sources, influencing redox reactions.
• Ionization potentials indicate HAs are more prone to oxidation than the MCs.
• HA electron affinity is conformation-dependent and comparable to MCs.
• Complexation leads to HA radicalization, buffering MCs against degradation.

Conclusions:

• Humic acids play a significant role in the environmental retention and transformation of munition compounds.
• The electronic properties of HAs suggest they can mitigate the reactivity of explosives in soil environments.
• HA-MC interactions create a protective mechanism, altering the degradation pathways of energetic materials.