Energetic Residues From Live-Fire Detonations of 120-mm Mortar Rounds

Abstract : Only limited data are available on energetic residues resulting from the firing and detonation of rounds from 120-mm mortars. After a live-fire training exercise at Fort Richardson, Alaska, we sampled a firing point for propellant residues (NG) and the impact area for high-explosives residues (RDX, HMX, and TNT). The firing point was snow-covered soil, and the impact area was snow-covered ice. The total explosives residue mass averaged 19 mg per round at the impact plume, of which 74% was RDX, 9% was HMX, and the remainder was TNT. Approximately 6 10 4% of the explosive mass (2,990 g of Composition B per round) remained following high-order detonations. A plume sampled near a low-order detonation had near-gram quantities of explosives along its edge, 50 times the average of the other plumes, and over 300 g of HE were recovered there the following spring. At the firing point, relatively high concentrations of propellant residues were found, averaging 14 g NG. High-order detonations deposit very little explosive compounds and are not likely to be a threat to groundwater. Low-order detonations will be the major contributor of contamination on impact areas. Firing points need more study but are an area of concern.