Breakdown products, environmental persistence

A relatively broad variety of aquatic toxicity studies exists for nitro-substituted phenol, toluene, and benzene explosives and related compounds, but very little toxicological information is available for tetryl, cyclic nitramines, and the other energetic compounds discussed in this chapter. Several explosives, such as tetryl, are no longer manufactured and are, therefore, of diminishing environmental concern, although their persistence and the nature, stability, and toxicity of their breakdown products is not understood in sufficient detail and should be further investigated. A variety of other energetic compounds, for example, perchlorates, are used in military operations, and due to environmental concerns with their release, additional studies on their fate and effects in aquatic systems are recommended. 

Trinitrotoluene (TNT) is the most commonly used energetic compound and found in the soils at U.S. Army installations [16,17], Military grades of TNT contain up to 8% DNTs (2,4-dinitrotoluene and 2,6-dinitrotoluene) as manufacturing impurities, and TNT is often degraded to DNT in hydric soils (i.e., wet anaerobic environments) [18,19], Other compounds are also generated when TNT is degraded (e.g., 2-amino-4,6-dinitrotoluene [2-ADNT], 4-amino-2,6-dinitrotoluene [4-ADNT], 1,3,5-trinitrobenzene [TNB], and others). Contamination from TNT, DNTs, and their environmental breakdown products is known to persist in soil for years [20],... 

In the environmental compartments, PCBs are degraded mainly hy microorganisms. Mono-, di-, and trichlorobiphenyls are broken down relatively quickly, whereas the more highly chlorinated PCBs are much more persistent. Highly chlorinated PCBs are reductively dechlorinated anaerobically with replacement of Cl by H, and the less-chlorinated products are subject to aerobic breakdown processes. The formation of ortho-dioh is thought to involve arene epoxides (Figure 11). 

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