Oxidation of aminonitrotoluenes by 2,4-DNT dioxygenase ofBurkholderia sp. strain DNT

Ionization behaviors of nitrotoluenes and dinitrotoluenes by reactions with acetone-related reactant ion

Dinitrotoluenes (DNTs) and nitrotoluenes (NTs) are found in the environment as metabolites of trinitrotoluene (TNT). When acetone is used as the solvent/eluent in atmospheric pressure chemical ionization-mass spectrometry (APCI-MS), the reactant ion is [2Acetone + O2 ]•- for the negative ion mode. The reactant ion reacts with an analyte to produce M•- and/or [M - H]- under atmospheric pressure. In this study, ionization behaviors of NT (2-, 3-, and 4-NTs) and DNT isomers (2,3-, 2,4-, and 2,6-DNTs) by reactions with [2Acetone + O2 ]•- were investigated. The energy-minimized structures of the product ions and their energies were calculated to explain the differences in the ionization behaviors. Typical NT- and DNT-related ions were produced by reactions with [2Acetone + O2 ]•- ; NT•- , [NT - H]- , DNT•- , [DNT - H]- , and [DNT - NO]- ions. The ionization efficiencies of NT- and DNT-related ions increased by increasing the source fragmentor voltage, and those of DNT-related ions were higher than those of the NT-related ions owing to the presence of an additional nitro group. The ionization efficiency of 3-NT•- was higher than that of [NT - H]- , while that of [DNT - H]- was higher than those of DNT•- and [DNT - NO]- . The ionization efficiency order of NT•- was 3-NT > 4-NT > 2-NT, while that of [DNT - H]- was 2,4-DNT > 2,6-DNT > 2,3-DNT. The [NT - H]- and [DNT - H]- ions were stabilized by resonance structures containing nitro groups. The [DNT - NO]- ions were formed through the transition state.

Characteristics of ionization behaviors of aminonitrotoluene isomers produced by atmospheric pressure chemical ionization

RATIONALE

Six of the isomers of aminonitrotoluene (ANT) are 2-amino-3-nitrotoluene (2A3NT), 2A4NT, 2A5NT, 2A6NT, 4A2NT, and 4A3NT. Some of them can be identified by chromatography and spectroscopy. Biochemical transformation of 2,4,6-trinitrotoluene (TNT) and dinitrotoluenes (DNTs) is very complex and ANTs are decomposition products of TNT and DNTs.

METHODS

Each isomer in acetone was ionized using atmospheric pressure chemical ionization in positive and negative ion modes, and kinds and abundances of the product ions were analyzed. Energy-minimized structures of the product ions and their energies were calculated to explain the analysis results.

RESULTS

The [M + H]⁺ , [M + H + Acetone - H₂ O]⁺ , and [M + H + Acetone]⁺ ions as positive product ions were detected, while [M - H]^- , M^•- , and [M + O₂ ]^•- ions as negative ones were observed. The order of the ionization efficiencies for the positive product ions was 4A3NT > 4A2NT > 2A4NT > 2A6NT > 2A5NT > 2A3NT, while that of the negative ones was 2A5NT > 2A3NT > 4A3NT > 2A4NT > 2A6NT > 4A2NT. Ion abundance ratios for 2A3NT and 2A5NT showed very similar trends, while those of 2A6NT and 4A2NT also showed similar trends. Differences in the ionization behaviors were explained using the heats of reaction.

CONCLUSIONS

The product ions were produced by ion-molecule reactions with the reactant ions of [2Acetone + H]⁺ and [Acetone + O₂ ]^•- . The [M + H + Acetone]⁺ ion was fragmented to produce [M + H]⁺ and [M + H + Acetone - H₂ O]⁺ , while the [M + O₂ ]^•- ion was fragmented to generate the [M - H]^- and M^•- ions. Differences in the ionization behaviors of the ANTs can be used for their differentiation.

Biodegradation of 2,4-dinitrotoluene with Rhodococcus pyridinivorans NT2: characteristics, kinetic modeling, physiological responses and metabolic pathway

Physiological responses ofRhodococcus pyridinivoransNT2 and elucidation of metabolic intermediates formed during biodegradation of 2,4-DNT.

Investigating the fate of nitroaromatic (TNT) and nitramine (RDX and HMX) explosives in fractured and pristine soils

Explosives compounds, known toxins, are loaded to soils on military training ranges predominantly during explosives detonation events that likely fracture soil particles. This study was conducted to investigate the fate of explosives compounds in aqueous slurries containing fractured and pristine soil particles. Three soils were crushed with a piston to emulate detonation-induced fracturing. X-ray diffraction, energy-dispersive X-ray spectrometry, gas adsorption surface area measurements, and scanning electron microscopy were used to quantify and image pristine and fractured soil particles. Aqueous batches were prepared by spiking soils with solutions containing 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2,4-dinitrotoluene (2,4-DNT). Samples were collected over 92 d and the concentrations of the spiked explosives compounds and TNT transformation products 2-amino-4,6-dinitrotoluene (2ADNT) and 4-amino-2,6-dinitrotoluene (4ADNT) were measured. Our results suggest soil mineralogical and geochemical compositions were not changed during piston-induced fracturing but morphological differences were evident with fractured soils exhibiting more angular surfaces, more fine grained particles, and some microfracturing that is not visible in the pristine samples. TNT, 2,4-DNT, RDX, and HMX exhibited greater analyte loss over time in batch solutions containing fractured soil particles compared to their pristine counterparts. 2ADNT and 4ADNT exhibited greater concentrations in slurries containing pristine soils than in slurries containing fractured soils. Explosives compound transformation is greater in the presence of fractured soil particles than in the presence of pristine soil particles. Our results imply fractured soil particles promote explosive compound transformation and/or explosives compounds have a greater affinity for adsorption to fractured soil particle surfaces.

A time series investigation of the stability of nitramine and nitroaromatic explosives in surface water samples at ambient temperature

We investigated the fate of nitramine and nitroaromatic explosives compounds in surface water to determine how surface water biogeochemistry affects the stability of explosives compounds. Five river water samples and 18.2 MOmega deionized water were spiked with 10 explosives compounds and the samples were held at ambient temperatures (20 degrees C) for 85 d. Surface water represented three rivers with a range of total organic carbon concentrations and two rivers draining glacial watersheds with minimal organic carbon but high suspended solids. 18.2 MOmega deionized water exhibited no explosives transformation. Nitroaromatic compound loss from solution was generally: tetryl>1,3,5-TNB>TNT>1,3-DNB>2,4-DNT. The HMX, RDX, 2,6-DNT, 2ADNT, and 4ADNT concentrations remained somewhat stable over time. The surface water with the highest total organic carbon concentration exhibited the most dramatic nitroaromatic loss from solution with tetryl, 1,3,5-TNB and TNT concentrations decreasing to below detection within 10d. The two water samples with high suspended solid loads exhibited substantial nitroaromatic explosives loss which could be attributable to adsorption onto fresh mineral surfaces and/or enhanced microbiologic biotransformation on mineral surfaces. An identical set of six water samples was spiked with explosives and acidified with sodium bisulfate to a pH of 2. Acidification maintained stable explosives concentrations in most of the water samples for the entire 85 d. Our results suggest sampling campaigns for explosives in surface water must account for biogeochemical characteristics. Acidification of samples with sodium bisulfate immediately following collection is a robust way to preserve nitroaromatic compound concentrations even at ambient temperature for up to three months.