The Fate of the Cyclic Nitramine Explosive RDX in Natural Soil

Abstract

The sorption-desorption behavior and long-term fate of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was examined in sterilized and nonsterilized topsoil. Results of this study indicate that although RDX is not extensively sorbed by the topsoil (Ks(d) of 0.83 L/kg), sorption is nearly irreversible. Furthermore, there was no difference in the sorption behavior for sterile and nonsterile topsoil. However, over the longterm, RDX completely disappeared within 5 weeks in nonsterile topsoil, and hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) metabolites formed in the aqueous phase. Over the same period, recovery of RDX from sterile topsoil was high (55-99%), and the nitroso metabolites were not detected. Only traces of RDX were mineralized to CO2 and N2O by the indigenous microorganisms in nonsterile topsoil. Of the RDX that was mineralized to N2O, one N originated from the ring and the other from the nitro group substituent, as determined using N15 ring-labeled RDX. However, N2O from RDX represented only 3% of the total N2O that formed from the process of nitrification/denitrification.

Functional Characterization of pGKT2, a 182-Kilobase Plasmid Containing the xplAB Genes, Which Are Involved in the Degradation of Hexahydro-1,3,5-Trinitro-1,3,5-Triazine by Gordonia sp. Strain KTR9

“…5). Moreover, a binding site for FadR-like proteins (48), such as XplR, occurs 5 bp from the Ϫ35 promoter region of cyp151C (Fig. 2).…”

“…Of the nitroaromatic and nitramine explosives that exist on these sites, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has a low sorption capacity (48) and can migrate through soil into surface water and groundwater (15). RDX-contaminated groundwater also has been found at sites affected by manufacturing, storage, or disposal facilities (19).…”

Microbially Mediated Biodegradation of Hexahydro-1,3,5-Trinitro-1,3,5- Triazine by Extracellular Electron Shuttling Compounds

“…TNX, the trinitroso metabolite, is less stable and may degrade via several putative pathways in situ (29). However, several reports have demonstrated that TNX may accumulate during RDX biodegradation (41,44,50), which suggests that the ultimate fate of the nitroso metabolites depends on the site conditions. Initial experiments with MNX and DNX suggested reduction in less than 2 h (Fig.…”

Dynamic and equilibrium studies of the RDX removal from soil using CMC-coated zerovalent iron nanoparticles

“…Indeed, the soil sorption coefficient values for RDX range from 63.1 to 270 indicating a medium to high mobility (Swann et al, 1983). RDX can thus be expected to easily leach into groundwater creating a major environmental problem (Sheremata et al, 2001). The toxicity of RDX has been well documented since many people involved with military activities suffered from generalized convulsions, muscular twitching, hyperactive reflexes, headaches, severe nausea and vomiting, hematuria, and loss of memory within several hours of ingesting 25-180 g C-4 explosive (containing 91% of RDX) (Stone et al, 1969).…”