30 Apr 2024

Bioaugmentation for Enhanced Mitigation of Explosives in Surface Soil

Abstract: Residual munition constituents (MCs) generated from live-fire training exercises persist in soil and can migrate to groundwater, surface waters, and off-range locations. Techniques to mitigate this potential migration are needed. Since the MC hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) can be biodegraded, soil inoculation with RDX-degrading bacteria (i.e., bioaugmentation) was investigated as a means to reduce the migration potential of RDX. Metagenomic studies using contaminated soils have suggested that a greater diversity of bacteria are capable of RDX biodegradation. However, these bacteria remain uncultivated and are potentially a source of novel enzymes and pathways for RDX biodegradation. In situ soil cultivation of a novel soil array was used to isolate the uncultivated bacteria that had been inferred to degrade RDX. Approximately 10.5% of the bacteria isolated from the soil arrays degraded RDX by the aerobic denitration pathway. Of these, 26.5% were possibly novel species of RDX-degrading bacteria, based on 16S rRNA sequence similarity. Both cell encapsulation in hydrogels and coating cells onto granules of polymeric carbon sources were investigated as carrier/delivery approaches for soil inoculation. However, neither of these approaches could confirm that the observed RDX degradation was by the inoculated bacteria.

30 Aug 2022

Live-Fire Validation of Command-Detonation Residues Testing Using a 60 mm IMX-104 Munition

Abstract: Command detonation (i.e., static firing) provides a method of testing munitions for their postdetonation residues early in the acquisition process. However, necessary modifications to the firing train and cartridge orientation raise uncertainty whether command detonation accurately represents residue deposition as it occurs during live-fire training. This study collected postdetonation residues from live-fired 60 mm IMX-104 mortar cartridges and then compared estimated energetic-compound deposition rates between live fire and prior command detonations of the same munition. Average live-fire deposition rates of IMX-104 compounds deter-mined from 11 detonations were 3800 mg NTO (3-nitro-1,2,4-triazol-5-one), 34 mg DNAN (2,4-dinitroanisole), 12 mg RDX (1,3,5-Trinitroperhydro-1,3,5-Triazine), and 1.9 mg HMX (1,3,5,7-Tetranitro-1,3,5,7-Tetrazocane) per cartridge. Total live-fire residue deposition (mean ± standard deviation: 3800 ± 900 mg/cartridge) was not significantly different from command detonation using a representative fuze simulator (3800 ± 900 mg/cartridge, n = 7, p = 0.76) but was significantly different from command detonation using a simplified fuze simulator (2200 ± 500 mg/cartridge, n = 7, p < 0.01). While the dominant residue compound NTO was broadly similar between live fire and command detonation, the minor residue compounds RDX and DNAN were underestimated during command detonation by a factor of approximately three to seven.