Explosives & the Environment

Secondary explosives (TNT, HMX, and RDX) have historically been discussed within the realm of safety related issues versus an HTRW waste classification perspective.

Explosives-contaminated process waste waters can be subdivided into two categories: red water from the manufacture of TNT and pink water which includes any washwater associated with load, assemble, and pack operations or with the demilitarization of munitions involving contact with finished explosive. Despite their names, red and pink water cannot be identified by color. Both are clear when they emerge from their respective processes and subsequently turn pink, light red, dark red, or black when exposed to light. The chemical composition of pink water varies depending on the process and explosive operation from which it is derived; red water has a more defined chemical composition.

Pinkwater is a wastewater generated in the production and handling of high explosive munitions. The principal contaminants in pinkwater are trinitrotoluene (TNT) and cyclo trimethylene trinitramine (RDX); they are transferred to water in washdown operations, and washout and steamout of old munitions. TNT and RDX are persistent contaminants that are regulated in discharges from Army Ammunition Plants. Chemical compounds such as TNT and RDX are resistant to aerobic attack because the nitro compounds act as electron-withdrawing substituents. Other substituents that cause the same effect are halogens, such as chlorine, which is often found in synthetic organic compounds persistent in the natural environment.

Under ambient environmental conditions, explosives are highly persistent in soils and groundwater, exhibiting a resistance to naturally occurring volatilization, bio-degradation, and hydrolysis. Where biodegradation of TNT occurs, 2-AmDNT and 4-AmDNT are the most commonly identified transformation products. Photochemical decomposition of TNT to TNB occurs in the presence of sunlight and water, with TNB being generally resistant to further photodegradation. TNB is subject to biotransformation to 3,5-dinitroaniline, which has been recommended as an additional target analyte in EPA Method 8330. Picrate is a hydrolysis transformation product of tetryl, and is expected in environmental samples contaminated with tetryl. Site investigations indicate that TNT is the least mobile of the explosives and most frequently occurring soil contamination problem. RDX and HMX are the most mobile explosives and present the largest groundwater contamination problem. TNB, DNTs, and tetryl are of intermediate mobility and frequently occur as co-contaminants in soil and groundwater. Metals are co-contaminants at facilities where munitions compounds were handled, particularly at OB/OD sites.

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