Dissolution and transport of insensitive munitions formulations IMX-101 and IMX-104 in saturated soil columns

Abstract

Military training exercises can result in deposition of energetic residues on range soils, which ultimately can contaminate groundwater with munitions constituents. Column experiments followed by HYDRUS-1D modeling were conducted to evaluate dissolution and transport of energetic constituents from the new insensitive munitions (IM) formulations IMX-101, a mixture of 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), and 2, 4-dinitroanisole (DNAN), and IMX-104, a mixture of NTO, 1,3,5-hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and DNAN. NTO and DNAN are emerging contaminants associated with the development of insensitive munitions as replacements for traditional munitions. Flow interruption experiments were performed to investigate dissolution kinetics and sorption non-equilibrium between soil and solution phases. The results indicated that insensitive munitions compounds dissolved in order of their aqueous solubility, consistent with prior dissolution studies conducted in the absence of soil. Initial elution of the high concentration pulse of highly soluble NTO and NQ was followed by lower concentrations, while DNAN had generally lower and more constant concentrations in leachate. The sorption of NTO and NQ was low, while RDX, 1,3,5,7-octahydro-1,3,5,7-tetranitrotetrazocine (HMX, an impurity in technical grade RDX), and DNAN all exhibited appreciable sorption. DNAN transformation was observed, with formation of amino-reduction products 2-ANAN (2-amino-4-nitroanisole) and 4-ANAN (4-amino-2-nitroanisole). HYDRUS-1D model, incorporating one-dimensional advective-dispersive transport with particle dissolution and first-order solute transformation was used to simulate the measured breakthrough curves. Optimized dissolution parameters varied widely but were correlated between compounds in the same formulation. Determined adsorption coefficients generally agreed with values determined from batch and column studies conducted with pure NTO and DNAN, while mass-loss rate coefficients were in better agreement with ones from batch than column studies possibly due to suppression of microbial transformation during elution of high concentrations of explosives. Even in the low organic matter soils selected in this study DNAN experienced significant retardation and transformation, indicating potential for its natural attenuation.

The effect of soil type on the extraction of insensitive high explosive constituents using four conventional methods

“…However, NTO proved more difficult to fully extract by sonication and shaking with only 41% and 64% NTO recovered by sonication and shaking respectively ( Figure 2). This was most likely due to the lower solubility of NTO in ACN, confirming findings from the literature (Figure 2) [26,27]. Figure 2: Extraction of RDX, DNAN, NQ and NTO from an inert matrix by EPA8330B method.…”

“…Therefore, extracting with only organic solvent as per the EPA8330B standard may not be suitable. Despite concerns of the efficacy of EPA8330B for the extraction of IHE, the method has continued to be used by agitating (stir, shake or vortex) with only ACN, which may explain the low reported recoveries of NTO [26,27]. Therefore, new and adapted EPA8330B methods have been developed such as a two-step procedure for the extraction of RDX, DNAN and NTO from soil that used sonication with a 3:7 mixture of ACN and acidified water (0.1 % trifluoroacetic acid), followed by 18 hours sonication in ACN [23].…”

Abiotic reduction of 3-nitro-1,2,4-triazol-5-one (NTO) and other munitions constituents by wood-derived biochar through its rechargeable electron storage capacity

“…Munitions constituents (MCs) used in explosive formulations have caused contamination of soil and groundwater at/near military sites across the U.S. 1 3-Nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), and 2,4-dinitroanisole (DNAN) are the major constituents in the insensitive formulation IMX-101, and NTO, DNAN, and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are the main constituents in the formulation IMX-104. 2,3 While insensitive MCs are less prone to accidental detonation than legacy MCs such as 2,4,6-trinitrotoluene (TNT), they are more water-soluble. 4–6 For example, the solubility of NTO is 16 642 mg L −1 at 25 °C, 7 two orders of magnitude higher than that of TNT (100–128 mg L −1 at 25 °C).…”

Evaluation of small-scale combustion of an insensitive high explosive formulation containing 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX)

“…NTO has typically been found to show very little toxicity towards humans, however it is highly soluble and rapidly degrades in the environment most likely to 5-amino-1,2,4-triazol-3-one (ATO) and other degradation products. In addition, NTO is acidic (pKa 3.7-3.76) and may cause leaching of other contaminants such as heavy metals from soils, which is a particular concern at training ranges and demolition areas due where heavy metal contamination is common (Arthur et al 2018;Clausen and Korte 2009). The environmental impact of NTO continues to be investigated, and the environmental impacts are not yet fully understood (Lent et al 2012;Reddy et al 2011;Jalal Hawari 2014).…”