Transport of insensitive munitions constituents, NTO, DNAN, RDX, and HMX in runoff and sediment under simulated rainfall

Insensitive munition constituents derived from residues of low order detonations and deposited on military training grounds present environmental risks. A series of rainfall simulation experiments on small soil plots examined the effect of precipitation, soil properties, and particle size on transport of IMX-104 munition components: NTO (3-nitro-1,2,4-triazol-5-one), DNAN (2,4-dinitroanisole), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and HMX (octahydro-1,3,5,7- tertranitro-1,3,5,7-tetrazocine). The primary pathways for rainfall driven transport were subsurface infiltration, off-site transport in solution, and transport in solid form including re-adsorption onto soil particles. The transport was solubility dependent with NTO moving mostly in solution, which was dominated by either runoff or infiltration depending on soil. DNAN, RDX, and HMX, were transported primarily in particulate form. The fine energetic fraction (<2 mm) showed the highest mobility, while the coarsest fraction (>4.75 mm) remained in-situ after rainfall. A simple linear model relating energetics transport with sediment yield and energetics particle size and was proposed. These findings provide the first comprehensive mass balance of munition constituents as affected by overland flow under rainfall. They improve our understanding of environmental fate of munitions, can further be used for predictive modelling, developing mitigation strategies, and regulatory compliance.