The Explosive 2,4,6-trinitrotoluene Research Articles

Biotransformation and partial mineralization of the explosive 2,4,6-trinitrotoluene (TNT) by rhizobia.

Three strains, T10, B5, and M8, each belonging to a different species of the family Rhizobiaceae and isolated from atrazine-contaminated soils, were tested for their ability to transform 2,4,6-trinitrotoluene (TNT) (50 microg x mL(-1)) in liquid cultures using glucose as the C-source. All three strains were able to transform TNT to hydroxylaminodinitrotoluenes (2-HADNT, 4-HADNT), aminodinitrotoluenes (2-ADNT, 4-ADNT), and diaminonitrotoluene (2,4-DANT). The transformation was significantly faster in the presence of glutamate. Furthermore, the major metabolites that accumulated in cultures were 2-ADNT with glucose, and 4-ADNT with glutamate plus glucose. Rhizobium trifolii T10 was also tested for its ability to transform high levels of TNT (approximately 350 microg x mL(-1)) in a soil slurry. Almost 60% of the TNT was transformed within 2 days in bioaugmented soil slurries, and up to 90% when cultures were supplemented with glucose and glutamate. However, mineralization was minimal in all cases, less than 2% in 78 days. This is the first report on the degradation of TNT by rhizobial strains, and our findings suggest that rhizobia have the potential to play an important role in the safe decontamination of soils and sites contaminated with TNT if bioaugmentation with rhizobia is shown to have no ecotoxicological consequence.

Biotransformation and partial mineralization of the explosive 2,4,6-trinitrotoluene (TNT) by rhizobia

Biotransformation and partial mineralization of the explosive 2,4,6-trinitrotoluene (TNT) by rhizobia

Characterization of a monoclonal TNT-antibody by measurement of the cross-reactivities of nitroaromatic compounds

The characterization of a commercially available monoclonal antibody directed against the explosive 2,4,6-trinitrotoluene (TNT) is reported. The cross-reactivities of various nitroaromatic compounds have been determined by competitive enzyme-linked immunosorbent assay (ELISA). Byproducts and metabolites of TNT were examined as well as the azo dye Disperse Blue 79 and its major metabolites (2-bromo-4,6-dinitroaniline and 2-chloro-4,6-dinitroaniline, respectively). By investigation of the cross-reactivities of different spacer derivatives of TNT it could be demonstrated that the bridge-recognition of the antibody is not very pronounced. N-(2,4,6-Trinitrophenyl)-methylamine shows the highest cross-reactivity (240%) of the examined compounds. Additionally, affinity constants of several nitroaromatic compounds have been determined. The affinity constant of TNT has been calculated to 1.3 × 109 L/mol from the minimal midpoint (IC50 value) of the standard curve. The detection limit achieved for TNT was 0.06 μg/L; the midpoint of the optimized assay was 0.34 μg/L.

Complete Reduction of TNT and Other (Poly)nitroaromatic Compounds under Iron-Reducing Subsurface Conditions

Contamination of soils and aquifers with (poly)nitroaromatic compounds ((P)NACs) is a widespread problem. This work demonstrates that (P)NACs such as the explosive 2,4,6-trinitrotoluene (TNT) can be completely reduced to the corresponding aromatic polyamines by Fe(II) present at the surface of Fe(III)(hydr)oxides or, less efficiently, by hydroquinone moieties of (natural) organic matter in the presence of H2S. The reduction kinetics of (P)NACs were investigated in sterile batch systems as well as in columns containing either FeOOH-coated sand and a pure culture of the iron-reducing bacterium Geobacter metallireducens or ferrogenic consortia in aquifer sediments. The relative reactivities as well as the competition behavior of (P)NACs in batch and column systems, respectively, correlated well with their one-electron reduction potentials, ‘, which we determined for TNT and its aminonitrotoluene transformation products. A similar reactivity pattern of (P)NACs was found irrespective of the processes that (re)generated the surface-bound Fe(II), i.e., adsorption of Fe(II) from aqueous solution or microbial reduction of Fe(III)(hydr)oxides. The apparent stability of the toxic arylamine products under ferrogenic conditions may compromise intrinsic attenuation as an acceptable remediation option for (P)NAC contaminated anoxic aquifers. Iron-reducing conditions would, however, be favorable as a first step in a two-stage anaerobic/aerobic treatment of PNAC contaminated sediments since aromatic polyamines are biodegradable and/or bind irreversibly to the solid matrix under oxic conditions.

Non-Ligninolytic TNT Mineralization in Contaminated Soil by Phanerochaete chrysosporium

The explosive 2,4,6-trinitrotoluene (TNT) is widely used and results in widespread soil contamination. The white-rot fungus Phanerochaete chrysosporium has been shown to degrade TNT, using the peroxidase enzyme. In this study, we report peroxidase-independent degradation of TNT by non-ligninolytic P. chrysosporium. Significant disappearance of TNT from highly contaminated soil using P. chrysosporium has been observed. Soil highly contaminated with TNT (2270 ppm [10 mM]) was diluted to 100 ppm (0.44 mM) with malt extract medium. Pregrown (48 hours) mycelial pellets of P. chrysosporium were added in 100 mL malt extract medium and incubated in Gledhill flasks. Analysis by high-performance liquid chromatography (HPLC) was conducted on soil extracts at specific time points to estimate the disappearance of TNT from contaminated soil incubated with P. chrysosporium. When the pregrown mycelial pellets were added, TNT disappeared within 48 hours. The dissolved concentration of 2-amino-4,6-dinitrotoluene (2Am-DNT) increased up to the third day, then declined before its final disappearance by day 10. Results show that the pregrown mycelial pellets of P. chrysosporium mineralized up to 17.3±6.3% [14C]-TNT within 30 days.

Biological Treatment of TNT-Contaminated Soil. 1. Anaerobic Cometabolic Reduction and Interaction of TNT and Metabolites with Soil Components

The explosive 2,4,6-trinitrotoluene (TNT), found as a major contaminant at armament plants from the two world wars, is reduced by a variety of microorganisms when electron donors such as glucose are added. This study shows that the cometabolic reduction of TNT to 2,4,6-triaminotoluene by an undefined anaerobic consortium increased considerably with increasing TNT concentrations and decreased with decreasing concentrations and feeding rates of glucose. The interactions of TNT and its reduction products with montmorillonitic clay and humic acids were investigated in abiotic adsorption experiments and during the microbial reduction of TNT. The results indicate that reduction products of TNT particularly hydroxylaminodinitrotoluenes and 2,4,6-triaminotoluene bind irreversibly to soil components, which would prevent or prolong mineralization of the contaminants. Irreversible binding also hinders a further spread of the contaminants through soil or leaching into the groundwater.

Decreased transpiration in poplar trees exposed to 2,4,6‐trinitrotoluene

AbstractThis article discusses the effects of various concentrations of the explosive 2,4,6‐trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations ≥5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot‐scale experiment showed good scale‐up potential.

Remote electrochemical sensor for monitoring TNT in natural waters

An electrochemical sensor for remote continuous monitoring of the explosive 2,4,6-trinitrotoluene (TNT) is described. The probe relies on rapid and sensitive square-wave voltammetry at a submersible carbon-fiber working-electrode assembly, connected to a 50ft-long shielded cable. Operational conditions have been optimized to meet the specific requirements of remote operations. Tests with untreated river water, groundwater, and drinking water samples, spiked with TNT, displayed results similar to those obtained with synthetic buffer solutions. Due to the low detection potential of TNT, coexisting sample constituents do not contribute to the response. The use of ultrafast square-wave voltammetric scanning, without a regeneration step, leads to a rapid detection of dynamic concentration changes, low ppb detection limits, and high stability. Prospects for using the electrochemical probe for real-time monitoring of TNT are discussed.

DECREASED TRANSPIRATION IN POPLAR TREES EXPOSED TO 2,4,6-TRINITROTOLUENE

This article discusses the effects of various concentrations of the explosive 2,4,6-trinitrotoluene (TNT) on the transpiration of hybrid poplar trees growing in hydroponic media. Transpiration was measured daily by gravimetric means. The rapid removal of TNT from hydroponic solutions was a result of plant uptake and required a daily dosage of TNT to ensure a relatively constant exposure over time. Transpiration decreased with increasing TNT concentrations ≥5 mg/L. Decreases in transpiration were accompanied by leaf chlorosis and abscission. A comparison between a laboratory study and a pilot-scale experiment showed good scale-up potential.

Simultaneous Biodegradation of 2,4-Dinitrotoluene and 2,6-Dinitrotoluene in an Aerobic Fluidized-Bed Biofilm Reactor

Mixtures of 2,4- and 2,6-dinitrotoluene are produced in large quantities as precursors of polyurethane foams and the explosive 2,4,6-trinitrotoluene (TNT). The two isomers are widely distributed in contaminated groundwater and soil. Bacteria capable of growing with the individual isomers as the sole source of carbon, nitrogen, and energy have been isolated previously. However, attempts to degrade 2,4- and 2,6-DNT simultaneously have failed. We tested the hypothesis that a mixed culture could degrade an isomeric DNT mixture if the bacteria were grown in an aerobic biofilm at low substrate concentrations. Such conditions were achieved with a fluidized-bed biofilm reactor (FBBR). The reactor was fed aqueous solutions containing 2,4- (40 mg L-1) and 2,6-DNT (10 mg L-1). The feed flow rate was gradually increased to yield surface loading rates of 36−600 mg of DNT m-2 d-1. Removal efficiencies higher than 98% for 2,4-DNT and 94% for 2,6-DNT were achieved at all loading rates. The nitrogen released from DNT was ...

A Displacement Flow Immunosensor for Explosive Detection Using Microcapillaries

In this paper, we report on the characterization of a capillary-based displacement flow immunosensor for the explosive, 2,4,6-trinitrotoluene (TNT). Anti-TNT antibody is immobilized onto the silanized inner walls of a fused-silica capillary using a heterobifunctional cross-linker followed by saturating the capillary with fluorophore-labeled antigen. To perform the assay, an aliquot of target analyte solution is injected into the capillary column. The target analyte competes for the binding pocket of the fluorophore-labeled antigen, which is detected downstream. We have demonstrated that the sensitivity of the capillary-based immunosensor is improved by at least 3 orders of magnitude compared to packed-column or membrane-based displacement flow immunosensors. We have investigated the effect of flow rate and length of the capillary on the performance of the capillary immunosensor. We have demonstrated that, by the appropriate choice of an antibody, one can prepare a capillary immunosensor for the specific d...

Mutagenicity of tetranitroazoxytoluenes: a preliminary screening in Salmonella typhimurium strains TA100 and TA100NR

Tetranitroazoxytoluenes are polynitroaromatic compounds that can be produced during the microbial reduction of the explosive, 2,4,6-trinitrotoluene (TNT). The three major tetranitroazoxytoluenes were synthesized and tested in Salmonella typhimurium strains TA100 and TA100NR. All compounds were mutagenic in TA100 but not in TA100NR, indicating the need for nitroreductase activity to induce mutagenicity. The most active chemical was 4,4′,6,6′-tetranitro-2,2′-azoxytoluene (2735 rev/μmol) followed by 2′,4,6,6′-tetranitro-2′,4-tetranitro-2′,4-azoxytoluene (929 rev/μmol) and 2,2′,6,6′-tetranitro-4,4′- azoxytoluene (320 rev/μmol). These chemicals were more active than the aminodinitrotoluenes (298 rev/μmol for 2-amino-4,6-dinitrotoluene and 115 rev/μmol for 4-amino-2,6-dinitrotoluene) and only 4,4′,6,6′-tetranitro-2,2′-azoxytouene was more active than the parent compound, TNT (1022 rev/μmol).

Pjhototoxicology.: 1. Light Enhanced Toxicity of TNT and Some Related Compounds to Daphnia magna and Lytechinus variagatus Embryos

Many environmental pollutants interact with solar near-ultraviolet (nuv) light in a manner which greatly increases their toxic effects. The phenomenon of light-mediated toxicity (phototoxicity) is only now becoming generally recognized to any significant degree. Manufacture of, and loading munitions with, the explosive 2,4,6-trinitrotoluene (TNT) in past decades caused contamination of soils and sediments at levels exceeding 1000 ppm and of waters at levels near saturation (100 ppm). Manufacture of TNT produces numerous nitrated by-products, and most of these compounds, including TNT, can be metabolized by many species, including bacteria, fungi, plants, and mammals. This study investigated the phototoxicity of TNT, and 2,3-, 2,4-, 2,6-, and 3,4-dinitrotoluene (DNT) and -diaminotoluene (DAT), and the major metabolites 2-amino-4,6-dinitrotoluene (2A) and 4-amino-2,6-dinitrotoluene (4A), to Daphnia magna (acute toxicity) and Lytechinus variagatus (sea urchin) embryos (subacute, developmental toxicity). Most of the compounds were weakly toxic or nontoxic in the dark. All were phototoxic to sea urchins. In D. magna, 2,3- and 3,4-DNT/DAT and 4A were not toxic but were phototoxic, and 2A was toxic and phototoxic; the other isomers were not toxic or phototoxic to this species.