Predicting the Fate and Transport of Insensitive High Explosives in Soils
posterposted on 07.01.2020, 16:30 by Encina Gutierrez Carazo
A great deal of studies on the environmental fate and transport of legacy explosives such as cyclotrimethylenetrinitramine (RDX), 2,4,6-trinitrotoluene (TNT) and 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX) has been conducted. However, less is known about the behaviour of Insensitive High Explosive (IHE) constituents being brought into military service such as 2,4-dinitroanisole (DNAN) and 5-nitro-1,2,4-triazol-3-one (NTO) in soil and water environmental compartments. Typically fate and transport of explosives are often performed under controlled laboratory conditions. However, experimental data are often limited to a particular soil type under specific climatic conditions (i.e. pH, soil saturation, temperature), which are not always representative of genuine environments. For example, several studies have addressed the dissolution mechanisms of energetic compounds on soil surfaces; many, however, have addressed dissolution of individual IHE without considering formulations with multiple constituents. Such results may have limited applicability for dissolution of residues on soils at impact zones or firing ranges because IHE often contain mixtures of energetic materials e.g. DNAN, RDX, and NTO, as well as small quantities of other chemicals such as stabilisers, which may alter physico-chemical properties compared to the pure compound. Therefore, computational modelling software is increasingly being used as an additional tool to simulate real scenarios. However, models are limited by the quality of the empirical data used to predict the temporal and spatial behaviour e.g. rate of transport of IHE to an aquifer. This is a particular problem for the prediction of the behaviour of IHE in the environment where key experimental data has not been obtained for a wide variety of soils and environments, and whose compounds are frequently investigated in isolation even though they are used in combination in IHE formulations.
Therefore, the aim of this study is to review and assess two predictive models including GoldSim Simulation Software and Hydrus-1D for a representative range of soil-IHE combinations, and to develop a standardised method for the prediction of the behaviour of IHE in the environment. To date the GoldSim simulations have been compared to soil columns under controlled laboratory conditions to estimate the accuracy of the model developed. GoldSim was initially chosen due to its flexibility, which enabled the use of experimentally determined empirical data for specific soil types and IHE constituents. Initial comparisons were undertaken with DNAN and a simple quartz sand medium to determine which empirical data gave the most accurate predictions e.g. soil adsorption coefficient, degradation rates and solubility. The comparisons will be extended to include mixtures of IHE constituents in a variety of soil types e.g. sandy, loamy, and silty under various climatic conditions.