Trinitrotoluene Concentration Research Articles

Use of Microcantilevers for the Monitoring of Molecular Binding to Self-Assembled Monolayers

We measured the adsorption of water vapor and trinitrotoluene (TNT) on a silicon cantilever that was coated with a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid on one surface. Even though hydrogen bonding is responsible for adsorption in both cases, the adsorption characteristics were quite different for the two species. In the case of water vapor, the mass loading and bending both increased with relative humidity in a linear fashion. For TNT in the dry nitrogen carrier, the mass loading and bending initially increased rapidly and then leveled off around one monolayer of coverage irrespective of the TNT concentration. This study shows that microcantilevers provide a convenient and versatile platform for the monitoring of molecular binding to SAMs.

The use of box lysimeters with freshly contaminated soils to study the phytoremediation of recalcitrant organic contaminants.

The potential for phytoremediation of soil contaminated by trinitrotoluene (TNT) and 2,2',5,5'-tetrabromobiphenyl (PBB was used as a surrogate for PCBs) was examined in a 2-year study using box lysimeters under field conditions. The treatments were a warm season grass, Johnson grass, and a cool season grass, Canadian wildrye, and a rotation of Johnson grass and wildrye plus a fallow condition. The experiment was conducted using 12 large (1.50 m x 1.50 m x 0.75 m), in-ground, box lysimeters filled with a Weswood silt-loam soil freshly spiked with the TNT and PBB compounds to a concentration of 10 mg kg(-1) for each chemical. The lysimeters were sheltered to permit controlled applications of water. A total of five sampling rounds were conducted where soil, herbage, and leachate samples were collected for laboratory analysis. TNT and PBB concentrations were determined using the U.S. EPA approved immunoassay test procedures. In the soil, TNT concentrations dropped below the detection limit of 0.25 mg kg(-1) by day 92 and PBB concentrations dropped below the detection limit of 0.50 mg kg(-1) by day 184. There were no significant differences in chemical concentrations among any of the vegetated or fallow treatments at a significance level of alpha < 0.05. However, PBB soil concentrations rebounded above the 0.50 mg kg(-1) level by day 720 for all treatments. No detectable concentrations of TNT or PBB were found in any of the herbage samples or in the leachate.

Immunotoxicity of explosives-contaminated soil before and after bioremediation.

Soils from the Yorktown Naval Base contaminated with trinitrotoluene (TNT) and other explosives were used to prepare eluates before and after bioremediation using microbial growth amendments in the presence (P1 eluates) or absence (P2 eluates) of exogenous white rot fungus. Effectiveness of bioremediation was examined by several immunotoxicity assays-viability/growth of lymphocytes, cytokine production, and expression of the interleukin-2 (IL-2) receptor-using human peripheral blood mononuclear cells exposed to the eluates. Although TNT concentrations decreased in both P1 and P2 eluates relative to untreated baseline soil (BL) eluates, a recovery in lymphocyte growth/viability and IL-2 secretion was seen with P2 but not P1 eluates relative to BL eluates. IL-2 receptor levels were higher in cells exposed to BL and P2 eluates than when exposed to P1 eluates. Interferon-gamma, tumor necrosis factor-beta, and IL-10 levels were highest in BL and P2 eluates and lowest in P1 eluates. Taken together, these results suggest that treatment of the soil with microbial growth amendments in the absence but not the presence of exogenous white rot fungi lead to partial bioremediation as assessed by lymphocyte functions.

Dip-and-read test strips for the determination of trinitrotoluene (TNT) in drinking water

A test strip to quantify trinitrotoluene (TNT) in water has been developed using a homogenous apoenzyme reactivation immunoassay system (ARIS). In comparison with other test kits for the detection of TNT, the novel test strip is much simpler in application. The test strip has only to be dipped into the aqueous sample. A blue color develops on the reagent strips proportional to the TNT concentration. The concentration of TNT is determined either by visual comparison with a color card, or more precisely using a reflectometer. A measuring range of about 1–10,000 μg l −1 TNT in water was demonstrated. The reagent strips were prepared by sequential impregnation of a cellulose pad with two solutions, one based on acetone and the other based on aqueous buffer. All necessary components are included in the reagent strip in dry form.

Cametabolic biotransformation of trinitrotoluene (tnt) supported by aromatic and non-aromatic cosubstrates

A microbial consortia was isolated from trinitrotoluene (TNT) contaminated soil and cultured in media supplemented with structurally similar (aromatic) or non-aromatic cosubstrates and TNT to examine their impact on cometabolic TNT biotransformation. A microbial inoculum with 10 5 CFU/ml with TNT concentrations of 5, 10, 30 and 50 ppm in separate triplicate cultures revealed maximum TNT biotransformations of 23, 21, 9 and 3%, respectively, after 9 days. A larger inoculum (l0 7CFU/ml) resulted in transformation of TNT concentrations of 8, 15, 22 and 30 ppm by 71, 54, 50 and 38%, respectively. Cultures supplemented with benzene, nitrobenzene or toluene revealed no enhancement of TNT biotransformation rates or extents over those in culture with TNT as sole carbon source. With glucose and citric acid at 30 mg/l, TNT biotransformations of 56 and 51%, respectively, were obtained. With glucose or citric acid at 3000 mg/l, 100% transformation of 30ppm TNT was realized in 24 hours and of 100ppm TNT in 72hrs. Metabolites identified included 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,6-diamino-4-nitrotoluene, and 2,4-dinitrotoluene; analysis also demonstrated that TNT disappearance paralleled glucose utilization and cell growth.

Homogeneous immunoassay for the detection of trinitrotoluene (TNT) based on the reactivation of apoglucose oxidase using a novel FAD-trinitrotoluene conjugate

A flavin adenine dinucleotide-trinitrotoluene derivative (FAD-TNT) was synthesized by coupling N6-(2-aminoethyl)-FAD covalently to the N-hydroxysuccinimidyl ester of trinitrophenyl-γ-aminobutyric acid and characterized by negative-ion electrospray-ionization mass spectrometry (ESI-MS) after purification by reversed-phase HPLC. Free FAD-TNT can be detected at very low levels by recombination with apoglucose oxidase, since the FAD-TNT-glucose oxidase complex is enzymatically active. On the contrary, if FAD-TNT has been bound by an anti-TNT antibody, the conjugate cannot recombine with apoglucose oxidase any more. Based on these two phenomena, a homogeneous apoenzyme reactivation immunoassay system (ARIS) was developed for the detection of TNT. No separation step is needed in this assay. Proportionality between the TNT concentration and enzyme activity was demonstrated with a detection limit of 5 μg/L TNT.

Phytoremediation: Modeling removal of TNT and its breakdown products

AbstractContamination of soil and groundwater by trinitrotoluene (TNT) is a widespread problem confronting military bases and ammunition manufacturing facilities throughout the United States. Phytoremediation provides a promising treatment of TNT‐contaminated groundwater and wastewater because many plants contain the necessary enzymes to degrade explosives such as TNT. Two phytoremediation methods are proposed in this article: controlled reactors and constructed wetlands. Controlled reactors provide greater control of operating parameters, a reduced possibility of contaminant migration, control of animals feeding on the plants, and minimization of competition from other plant species. Constructed wetlands have relatively low capital costs, and the wetland becomes a desirable ecological resource. Because cost, as opposed to reactor size, appears to be the most significant factor for military base cleanup, this project focused on the constructed wetland approach.To estimate the disappearance of TNT and its breakdown products from a constructed wetland, a first‐order, nonreversible reaction, plug‐flow, finite‐difference model was developed. Batch scale experiments were conducted to define disappearance kinetics for individual chemical species. The results of the model suggest that reasonably sized wetlands may be used to treat a wastestream with an influent TNT concentration of 2.25 ppm at flow rates ranging from 10 to 5,000 gpm. Economic comparisons to other published costs for competing technologies are promising.

Detection of TNT in Water Using an Evanescent Wave Fiber-Optic Biosensor

A general health hazard from explosive toxicity exists due to poor storage facilities for explosives and from contamination of soil and water with byproducts of explosive manufacture. To provide an effective method for monitoring water contamination, the Naval Research Laboratory's fiber-optic biosensor was adapted for the detection of small molecules such as explosives. A competitive immunoassay was developed for the detection of the most widely used explosive, trinitrotoluene (TNT). Trinitrobenzenesulfonic acid (TNB), an analog of TNT, was labeled with a fluorophore and used as the analyte competitor. A solution containing 7.5 ng/mL sulfoindocyanine 5-ethyl-enediamine-labeled TNB (Cy5-EDA-TNB) was exposed to an antibody-coated optical fiber, generating a specific signal above background that corresponds to the 100% or reference signal. Inhibition of the 100% signal was proportional to the TNT concentration in the sample. Detection sensitivities of 10 ng/mL TNT (8 ppb) in buffer were achieved. Tests on river, harbor, and bilge water samples spiked with TNT showed results similar to tests on laboratory (buffer matrix) samples. To determine possible interferences, several structural analogs ofTNT were tested.

A sensitive bioluminescent immunoassay for dinitrophenol and trinitrotoluene

A bioluminescent immunoassay for measuring dinitrophenol and trinitrotoluene (TNT) has been developed. The DNP and TNT were covalently linked to firefly luciferase, resulting in a conjugate containing 1 mol of DNP or trinitrophenyl (TNP) per mole of luciferase. The conjugate retained 90% of its original catalytic activity. When the conjugate was incubated with immobillzed anti-TNT or anti-DNP and varying concentrations of free TNT or DNP-leucine, the amount of conjugate bound was inversely proportional to the concentration of the free compound. Using this procedure it is possible to detect 2.5 pmol of DNP-leucine and 1.0 pmol of TNT. If the TNP or DNP is linked to glucose-6-phosphate dehydrogenase instead of luciferase, much lower quantities of antigen can be detected. This is due to the fact that this enzyme has a large turnover number so that amplification is possible. The NADH produced is measured using immobilized bacterial NADH:FMN oxidoreductase and luciferase. With this procedure, 10 amol (10 −17 mol) of antigen can be measured. These procedures should be suitable for measuring any antigen.