Stability of Immobilized TNT Derivatives in Soil as a Function of Nitro Group Reduction

Abstract

The stability of soil bound metabolites of 2,4,6-trinitrotoluene (TNT) was investigated. Highly TNT-contaminated soil from a former production site was spiked with [ring-UL-14C]TNT. An anaerobic short-term treatment (8 days) was carried out and compared with a previously described long-term anaerobic (51 day) treatment. In the short-term experiment the anaerobic treatment was stopped to examine the early-stage effects of the reduction process on the stability of TNT derivatives in soil at the time of the maximum accumulation of aminodinitrotoluenes, whereas the long-term anaerobic treatment was continued until the formation of triaminotoluene. In contrast to the soil from long-term anaerobic treatment, no significant reduction of aminodinitrotoluenes to diaminonitrotoluenes was observed after short-term anaerobic treatment, and the binding of reduced metabolites to the soil was incomplete. In both experiments the anaerobic phase was followed by an aerobic treatment. After the short-term anaerobic/aerobic treatment only 40% of the initial radioactivity was bound to the soil compared to 98% after the extended anaerobic incubation. A significant amount of this bound radioactivity could be released into organic solvents by silylation. The silylation extracts were analyzed by thin-layer chromatography and radiocounting. The released radioactivity from silylation after the long-term treatment was attributed to polar compounds cross-linked with humic material. For the silylated extracts after short-term anaerobic treatment conditions, a significant amount of released radioactivity (28%) found in fractions was attributed to TNT and aminodinitrotoluenes. This study indicates that with a shorter duration of the anaerobic phase in the overall treatment, physically entrapped (sequestered) metabolites remain in the soil. To eliminate physical entrapment, TNT derivatives should be completely reduced by a sufficiently extended anaerobic treatment.

Fate and metabolism of [15N]2,4,6‐trinitrotoluene in soil

“…The metabolites 2-amino-4,6-dinitrotoluene and 4-amino-2,6dinitrotoluene that generally are observed in similar soil experiments were detected only transiently in amounts Յ3% of the applied TNT. During anaerobic treatments of TNT-contaminated soils, ADNT and DANT initially were detected in amounts one order of magnitude higher than after aerobic treatments [6,7]. Formylated or acetylated metabolites known from fungal metabolism of TNT [5], as well as HADNT, were not detected in the present experiments.…”

Mineralization of 2,4,6-Trinitrotoleune (TNT) in Coastal Waters and Sediments

“…With smectite clays, the binding of the nitro groups of TNT essentially replace the calcium in the clay matrix, thus integrating the energetic ). Under anoxic conditions in water, the nitro groups of TNT can be reduced to amines (Barrows et al 1996) which also affects its reactivity (Achtnich et al 2000). The presence of reduced colloidal or particulate iron (ZVI) can also reduce these nitro groups and enhance both the reactivity and mineralization of TNT in aqueous environments (Agrawal and Tratnyek 1996, Devlin et al 1998, Brannon et al 2002 though transformation rates based on laboratory experiments may overestimate the expected rates in the field (Bandstra et al 2005).…”

Adsorption of 2,4-Dinitrotoluene on Dickite: The Role of H-Bonding

“…Intercalation of nitroanilines into kaolinite was studied in the work of Takenawa et al [31]. The results of several experimental investigations of interactions of soils with explosives, especially with nitroaromatic explosives, using several physicochemical methods, were recently published [33][34][35][36][37][38][39][40][41]. Townsend and Myers [33] found that the major factor affecting the fate and transport of TNT in the subsurface were transformation, sorption, and irreversible soil binding.…”