Investigation into the environmental fate of the combined Insensitive High Explosive constituents 2,4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and nitrotriazolone (NTO) in soil

Abstract

Contamination of military ranges by the use of explosives can lead to irreversible environmental damage, specifically to soil and groundwater. The fate and effects of traditional explosive residues are well understood, while less is known about the impact of Insensitive High Explosives (IHEs) that are currently being brought into military service. Current research has focussed on the investigation of individual constituents of IHE formulations, which may not be representative of real-world scenarios when explosive residues will be deposited together. Therefore, this study investigated the fate and transport of the combined IHE constituents 2,4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO) in two UK soil types. Static experiments ran for 9weeks to determine the fate of the combined explosive constituents in soil by monitoring the rate of degradation. Transport was examined by running soil column experiments for 5weeks, with a watering regime equivalent to the average yearly UK rainfall. Both static and soil column experiments confirmed that DNAN and NTO started to degrade within twenty-four hours in soil with high organic content, and were both completely degraded within sixty days. NQ was more stable, with 80% of the original material recovered after sixty days. The major degradation product of DNAN in the test soils was 2-amino-4-nitroanisole (2-ANAN), with trace amounts of 4-amino-2-nitroanisole. NTO was rapidly degraded in soil with high organic content, although no degradation products were identified. Results supported work from literature on the individual constituents DNAN, NQ and NTO suggesting that the three explosives in combination did not interact with each other when in soil. This study should provide a useful insight into the behaviour of three combined Insensitive High Explosive constituents for the predication of soil and water contamination during military training.

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

“…However, from soils with higher organic content the percentage of NTO extracted was lower: 50% ± 43% (PEN) and 37 ± 2% ESK) ( Table 4) ( Figure 5). Although NTO degrades in soils with high TOC, the IHE constituents were only exposed to soil for a maximum of 24 hours, which makes it unlikely to account for the 60% unrecovered material [29]. In addition, SBN soil with the highest TOC (6.5%) did not fit the trend of decreasing recovery with increasing TOC, and good extraction efficiency was achieved (87% ± 5%).…”

“…The ASE method used the same operating parameters as previously published [29]: 100°C oven temperature, 1500 psi pressure with a ten minute static time, 60% rinse volume and 200 second purge, taking approximately twenty minutes in total. An appropriate solvent was identified by evaluating the efficiency of extractions of IHE from an artificially contaminated inert matrix (quartz sand).…”

“…Therefore, guidance to do this was taken and adapted from the application note for the extraction of TNT and its degradation products from soil and a previous publication [15,29].…”

“…Satisfactory one-step extraction of all available IHE constituents has not been reported in the literature [29], which may underestimate the extent of contamination and therefore the risk.…”

“…Research conducted previously by the authors used an ACN/water (1:3) solvent system for the extraction of DNAN, NQ and NTO from soil using a modified ASE method for the extraction of conventional explosives [14,29]. DNAN and NQ were both efficiently extracted (~100%) from the two soil types (sandy and loamy), however only approximately 60% of NTO could be recovered therefore results were corrected for the missing mass with a recommendation for further development of the method [29].…”