Total Protein Determination by Recovery Fluorescence of Trinitrotoluene-Quenched Protein-Functionalized Gold Nanoclusters.

Determination of total protein content is very important for clinical, pharmaceutical and food chemistry, and the simplicity and rapidity of the existing total protein content assays should be improved. Here, a novel fluorescent sensor for total protein content measurement was described using near-infrared emitting fluorescent gold nanoclusters, which were prepared with egg whites. Trinitrotoluene served as highly efficient quencher to quench the fluorescence of gold nanoclusters. Interestingly, the trinitrotoluene-protein complex that formed by premixing of trinitrotoluene and protein-containing real samples maintained the fluorescence of gold nanoclusters. These new findings provided a novel mechanism to design a fluorescence sensor for determination of total protein levels in various real samples. With available and low-cost bovine serum albumin as reference, the obtained standard curve for total protein determination indicated a linear range of 0.1-3.5 g L- 1 with a detection limit of 0.06 g L- 1 (3σ rule) and a correlation efficiency (R2) of 0.9850. The applicability of the proposed sensor was validated by determination of total protein levels in real samples. Comparison with the existing spectrophotometric methods, the proposed sensor is advantageous of simplicity, rapidity, and cost-effectiveness.

Solid medium for the direct isolation of bacterial colonies growing with polycyclic aromatic hydrocarbons or 2,4,6-trinitrotoluene (TNT).

Isolation of hydrocarbon-degrading bacteria is a key step for the study of microbiological diversity, metabolic pathways, and bioremediation. However current strategies lack simplicity and versatility. We developed an easy method for the screening and isolation of bacterial colonies capable of degrading hydrocarbons, such as diesel or polycyclic aromatic hydrocarbons (PAHs), as well as the pollutant explosive, 2,4,6-trinitrotoluene (TNT). The method uses a two-layer solid medium, with a layer of M9 medium, and a second layer containing the carbon source deposited through the evaporation of ethanol. Using this medium we grew hydrocarbon-degrading strains, as well as TNT-degrading isolates. We were able to isolate PAHs-degrading bacterial colonies directly from diesel-polluted soils. As a proof of concept, we used this method to isolate a phenanthrene-degrading bacteria, identified as Acinetobacter sp. and determined its ability to biodegrade this hydrocarbon.

Critical Role of Monooxygenase in Biodegradation of 2,4,6-Trinitrotoluene by Buttiauxella sp. S19-1.

2,4,6-Trinitrotoluene (TNT) is an aromatic pollutant that is difficult to be degraded in the natural environment. The screening of efficient degrading bacteria for bioremediation of TNT has received much attention from scholars. In this paper, transcriptome analysis of the efficient degrading bacterium Buttiauxella sp. S19-1 revealed that the monooxygenase gene (BuMO) was significantly up-regulated during TNT degradation. S-ΔMO (absence of BuMO gene in S19-1 mutant) degraded TNT 1.66-fold less efficiently than strain S19-1 (from 71.2% to 42.9%), and E-MO mutant (Escherichia coli BuMO-expressing strain) increased the efficiency of TNT degradation 1.33-fold (from 52.1% to 69.5%) for 9 h at 180 rpm at 27 °C in LB medium with 1.4 µg·mL-1 TNT. We predicted the structure of BuMO and purified recombinant BuMO (rBuMO). Its specific activity was 1.81 µmol·min-1·mg-1 protein at pH 7.5 and 35 °C. The results of gas chromatography mass spectrometry (GC-MS) analysis indicated that 4-amino-2,6-dinitrotoluene (ADNT) is a metabolite of TNT biodegradation. We speculate that MO is involved in catalysis in the bacterial degradation pathway of TNT in TNT-polluted environment.

A novel method development and validation for determination of 2,4,6-Trinitrotoluene and its metabolites on LC-MS/MS.

LC-MS/MS has recently emerged as the best practice for simultaneous analysis of 2, 4, 6 Trinitrotoluene (TNT) and its metabolites. We have developed and validated an LC-MS/MS method for simultaneous quantification of 2, 4, 6 Trinitrotoluene (TNT) and its metabolites 4-ADNT, 2-ADNT, 2,4-DNT, and 2,6-DNT in urine samples. These four metabolites were acid hydrolyzed using 1 mL of urine followed by extraction using n-Hexane and ethyl acetate as an extracting solvent. Separation was achieved by centrifugation, and the supernatant was dried under nitrogen, reconstituted with water and acetonitrile, and then filtered. Chromatographic separation was achieved on Agilent Poroshel 120 EC-C18 column (2.1 mm × 75 mm × 2.7 µm) utilizing two mobile phases 0.1% formic acid in water and 0.1% formic acid in acetonitrile in gradient flow. The validated AMR of TNT and its metabolites was 7.8-1000 ng/mL. The method showed an excellent correlation (>0.99) for TNT and its metabolites. Accuracy and within/between day precision of TNT and its metabolites were within ±15%. The integrity of diluted samples was maintained for each dilution factor. The method was found stable after storage and freeze-thaw cycle. The presented method can be used for TNT screening in occupationally exposed ordnance factory workers.

Sublimation and Diffusion Kinetics of 2,4,6-Trinitrotoluene (TNT) Single Crystals by Atomic Force Microscopy (AFM).

In this article, we report the in-situ nanoscale experimental measurement of sublimation rates, activation energy of sublimation, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals in air using atomic force microscopy (AFM). The crystals were prepared by slow evaporation at 5 °C using acetone-dissolved TNT. The mass loss was calculated by monitoring the shrinkage of the surface area of layered islands formed on the surface of the TNT crystals due to sublimation upon isothermal heating at temperatures below the melting point. The results suggest the sublimation process occurs via two-dimensional detachment of TNT molecules from the non-prominent facets on the crystal surface which imitates the nucleation and crystal growth process. Sublimation rates are one order of magnitude smaller than previously reported values. However, the calculated activation energy (112.15 ± 3.2 kJ/mol) and temperature-dependent sublimation rates agree well with the reported values for TNT thin films and microcrystals determined by UV-vis absorbance spectroscopy and quartz crystal microscopy (QCM) (90-141 kJ/mol). The average diffusion coefficient is (4.35 × 10-6 m2/s) which is within the range of the reported theoretical values with an average of 5.59 × 10-6 m2/s, and about 25% less than that determined using thermogravimetric analysis for powder TNT.

Recent advances in process engineering and upcoming applications of metal-organic frameworks.

Progress in metal-organic frameworks (MOFs) has advanced from fundamental chemistry to engineering processes and applications, resulting in new industrial opportunities. The unique features of MOFs, such as their permanent porosity, high surface area, and structural flexibility, continue to draw industrial interest outside the traditional MOF field, both to solve existing challenges and to create new businesses. In this context, diverse research has been directed toward commercializing MOFs, but such studies have been performed according to a variety of individual goals. Therefore, there have been limited opportunities to share the challenges, goals, and findings with most of the MOF field. In this review, we examine the issues and demands for MOF commercialization and investigate recent advances in MOF process engineering and applications. Specifically, we discuss the criteria for MOF commercialization from the views of stability, producibility, regulations, and production cost. This review covers progress in the mass production and formation of MOFs along with future applications that are not currently well known but have high potential for new areas of MOF commercialization.

A Simple Determination of Trinitrotoluene (TNT) Based on Fluorescence Quenching of Rhodamine 110 with FRET Mechanism.

Sensitive and selective detection of nitroaromatic explosives is an important issue in regard to human health, environment, public security and military issues. In this study, a simple and sensitive fluorescence quenching - based assay utilizing Rhodamine 110 as fluorophore probe was developed for the determination of trinitrotoluene (TNT). This sensitive fluorometric method could measure the decrease in fluorescence of Rhodamine 110 (λex = 490 nm, λem = 521 nm) owing to the primary amine groups of Rhodamine 110 (different from other rhodamines) capable of donor-acceptor interaction with TNT. The resulting TNT-amine complex can strongly quench the fluorescence emission of Rhodamine 110 by fluorescence resonance energy transfer (FRET) which occurs as the excited Rhodamine 110 fluorophore (donor) transfers its energy to TNT (acceptor) by non-radiative dipole-dipole interaction. Fluorescence quenching varied linearly with TNT concentration, with LOD and the LOQ of 0.71 and 2.38 mg L- 1 TNT, respectively. Similar explosives, common soil ions, and possible camouflage materials were found not to interfere with the proposed method, offering significant advantages with its easy methodology, low-cost, sensitivity, and rapidity of analysis. FRET mechanism based on dye donor-TNT acceptor interaction.

Phytoremediation of multiple persistent pollutants co-contaminated soil by HhSSB transformed plant.

The high toxicity of persistent pollutants limits the phytoremediation of pollutants-contaminated soil. In this study, heterologous expressing Halorhodospira halophila single-stranded DNA binding protein gene (HhSSB) improves tolerance to 2,4,6-trinitrotoluene (TNT), 2,4,6-trichlorophenol (2,4,6-TCP), and thiocyanate (SCN-) in A. thaliana and tall fescue (Festuca arundinacea). The HhSSB transformed Arabidopsis, and tall fescue also exhibited enhanced phytoremediation of TNT, 2,4,6-TCP, and SCN- separately contaminated soil and co-contaminated soil compared to control plants. TNT assay was selected to explore the mechanism of how HhSSB enhances the phytoremediation of persistent pollutants. Our result indicates that HhSSB enhances the phytoremediation of TNT by enhancing the transformation of TNT in Arabidopsis. Moreover, transcriptomics and comet analysis revealed that HhSSB improves TNT tolerance through three pathways: strengthening the defense system, enhancing the ROS scavenging system, and reducing DNA damage. These results presented here would be particularly useful for further studies in the remediation of soil contaminated by organic and inorganic pollutants.

Bacterial bioreporters for the detection of trace explosives: performance enhancement by DNA shuffling and random mutagenesis.

Landmines and other explosive remnants of war pose a global humanitarian problem that claims numerous casualties long after the conflict has ended. As there are no acceptable methodologies for the remote discovery of such devices, current detection practices still require the risky presence of personnel in the minefield. We have recently described bacterial sensor strains capable of reporting the existence of 2,4-dinitrotoluene (DNT) vapors in the soil above 2,4,6-trinitrotoluene (TNT)-based landmines, by generating a bioluminescent or a fluorescent signal. This may allow the identification of landmine location by remote imaging of an area over which the bacteria have been spread. In the study reported herein, we have improved the DNT-detection capabilities of these sensor strains by combining two DNT-responsive Escherichia coli gene promoters, yqjF and azoR, and subjecting them to three cycles of random mutagenesis by error-prone PCR, combined with segmentation and rearrangement ("DNA shuffling"). The activity of selected modified promoters was evaluated with the Aliivibrio fischeri and Photobacterium leiognathi luxCDABEG gene cassettes as the bioluminescent reporters, exhibiting a ten-fold background reduction that has led to a three-fold decrease in detection threshold. Signal intensity was further enhanced by modifying the ribosomal binding site of the yqjF gene promoter. The superior DNT detection capabilities on a solid matrix by the improved sensor strain were demonstrated. KEY POINTS: • Performance of microbial sensor strains for buried explosives was molecularly enhanced. • Manipulations included random mutagenesis, "DNA shuffling," and RBS reprogramming. • The re-engineered constructs exhibited superior detection of trace explosives.

Monodisperse amino-modified nanosized zero-valent iron for selective and recyclable removal of TNT: Synthesis, characterization, and removal mechanism.

Nitroaromatic explosives are major pollutants produced during wars that cause serious environmental and health problems. The removal of a typical nitroaromatic explosive, 2,4,6-trinitrotoluene (TNT), from aqueous solution, was conducted using a new recyclable magnetic nano-adsorbent (Fe@SiO2NH2). This adsorbent was prepared by grafting amino groups onto Fe@SiO2 particles with a well-defined core-shell structure and demonstrated monodispersity in solution. The removal performance of the nano-adsorbent towards TNT was found to be 2.57 and 4.92 times higher than that towards two analogous explosives, 2,4-dinitrotoluene (2,4-DNT) and 2-nitrotoluene (2-NT), respectively, under neutral conditions. The difference in the removal performance among the three compounds was further compared in terms of the effects of different conditions (pH value, ionic strength, humic acid concentration, adsorbent modification degree and dosage, etc.) and the electrostatic potential distributions of the three compounds. The most significant elevation is owing to modification of amino on Fe@SiO2 which made a 20.7% increase in adsorption efficiency of TNT. The experimental data were well fit by the pseudo-second-order kinetic model and the Freundlich adsorption isotherm model, indicating multilayer adsorption on a heterogeneous surface. The experimental results and theoretical considerations show that the interactions between Fe@SiO2NH2 NPs and TNT correspond to dipole-dipole and hydrophobic interactions. These interactions should be considered in the design of an adsorbent. Furthermore, the adaptability to aqueous environment and excellent regeneration capacity of Fe@SiO2NH2 NPs makes these remediation materials promising for applications.

Transformation of TNT, 2,4-DNT, and PETN by Raoultella planticola M30b and Rhizobium radiobacter M109 and exploration of the associated enzymes.

The nitrated compounds 2,4-dinitrotoluene (2,4-DNT), 2,4,6-trinitrotoluene (TNT), and pentaerythritol tetranitrate (PETN) are toxic xenobiotics widely used in various industries. They often coexist as environmental contaminants. The aims of this study were to evaluate the transformation of 100 mg L-1 of TNT, 2,4-DNT, and PETN by Raoultella planticola M30b and Rhizobium radiobacter M109c and identify enzymes that may participate in the transformation. These strains were selected from 34 TNT transforming bacteria. Cupriavidus metallidurans DNT was used as a reference strain for comparison purposes. Strains DNT, M30b and M109c transformed 2,4-DNT (100%), TNT (100, 94.7 and 63.6%, respectively), and PETN (72.7, 69.3 and 90.7%, respectively). However, the presence of TNT negatively affects 2,4-DNT and PETN transformation (inhibition > 40%) in strains DNT and M109c and fully inhibited (100% inhibition) 2,4-DNT transformation in R. planticola M30b.Genomes of R. planticola M30b and R. radiobacter M109c were sequenced to identify genes related with 2,4-DNT, TNT or PETN transformation. None of the tested strains presented DNT oxygenase, which has been previously reported in the transformation of 2,4-DNT. Thus, unidentified novel enzymes in these strains are involved in 2,4-DNT transformation. Genes encoding enzymes homologous to the previously reported TNT and PETN-transforming enzymes were identified in both genomes. R. planticola M30b have homologous genes of PETN reductase and xenobiotic reductase B, while R. radiobacter M109c have homologous genes to GTN reductase and PnrA nitroreductase. The ability of these strains to transform explosive mixtures has a potentially biotechnological application in the bioremediation of contaminated environments.

Chemically modified mesoporous wood: a versatile sensor for visual colorimetric detection of trinitrotoluene in water, air, and soil by smartphone camera.

There is great interest in detection of the level of 2,4,6-trinitrotoluene (TNT) explosive due to its importance in public security and environmental protection fields. The conventional chemical sensors do not simultaneously realize simple, rapid, sensitive, selective, and direct detection of TNT in different medium without sample pretreatment. Here we present a modified wood-based chemical sensor for visual colorimetric detection of TNT in water, air, and soil. The natural wood undergoes a delignified process, which is further functionalized by 3-aminopropyltriethoxysilane (APTES). When TNT solutions are introduced, the wood-based sensor shows a colorimetric transition from light yellow to brown for naked-eye readout because of the generation of Meisenheimer complex between APTES and TNT. The photographs are collected by smartphone camera, and the RGB components are extracted to calculate the adjusted intensity for qualitative detection of TNT. This visual colorimetric sensor for TNT solution displays a linearity in the range of 0.01-5 mM with a limit of detection of 3 µM. In addition, by taking advantage of its inherent mesostructure, the wood-based sensor can be employed for visual detection of TNT vapor as well. Furthermore, it is also able to directly detect TNT in wet soil samples based on capillary action, in which TNT carried by water transports upward along the wood microchannel, triggering the generation of Meisenheimer complex. Graphical Abstract.

Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms.

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn⁻Wall, and Kissinger models were 105.9 ± 1.4 kJ mol-1, 102.1 ± 2.7 kJ mol-1, and 105.8 ± 1.6 kJ mol-1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

Batch Adsorption and Column Transport Studies of 2,4,6-Trinitrotoluene in Chinese Loess.

In present study, batch and column tests were conducted to investigate the kinetic and thermodynamic characteristics of the adsorption and transport of 2,4,6-trinitrotoluene (TNT) in Chinese loess with specific focus on the role of inherent colloid particles. Batch tests showed that a lot of TNT was absorbed in suspended colloid particles, and its adsorption reached equilibrium after about 10 h, the adsorption process can be best-fit by the pseudo-second order kinetic and Freundlich model. The adsorption was spontaneous, endothermic process, implying the adsorbed TNT is likely to release from soil matrix. These portend that the adsorbed TNT has a potential to co-transport with inherent colloid particles in loess. The column tests identified the potential, and showed TNT transport had obvious retardation effect, which may be ascribed to the release and transport of inherent colloidal particles as a key carrier. These findings are helpful to evaluate the loess interception and antifouling performance.

A High Aspect Ratio Bifurcated 128-Microchannel Microfluidic Device for Environmental Monitoring of Explosives.

Design and evolution of explosives monitoring and detection platforms to address the challenges of trace level chemical identification have led investigations into the use of intricately designed microfluidic devices. Microfluidic devices are unique tools that possess distinct characteristics that, when designed properly and configured with optical and fluidic components, can produce detection platforms with unmatched performance levels. Herein, we report the design, fabrication and integration of a bifurcated high aspect ratio microfluidic device containing 128 microchannels (40 mm × 40 µm × 250 µm; L × W × H) for explosives detection at trace levels. Aspect ratios measuring >6:1 support improved receptor-target molecule interactions, higher throughput and extremely low limits of detection (LOD). In addition to superior assay sensitivity, the bifurcated microfluidic device provides greater durability and versatility for substrate modification. Using the explosive 2,4,6-trinitrotoluene (TNT) as the model compound in a fluorescence-based displacement immunoassay, we report LODs for TNT at 10 parts-per-trillion (pptr) using a neutravidin-coated biotinylated anti-TNT microfluidic device. Solution to wall interactions were also simulated in COMSOL Multiphysics to understand fluid flow characteristics. Reynolds numbers were calculated to be 0.27⁻2.45 with a maximum pressure of 1.2 × 10-2 psi.

Expression of a Drosophila glutathione transferase in Arabidopsis confers the ability to detoxify the environmental pollutant, and explosive, 2,4,6-trinitrotoluene.

The explosive 2,4,6-trinitrotoluene (TNT) is a significant, global environmental pollutant that is both toxic and recalcitrant to degradation. Given the sheer scale and inaccessible nature of contaminated areas, phytoremediation may be a viable clean-up approach. Here, we have characterized a Drosophila melanogaster glutathione transferase (DmGSTE6) which has activity towards TNT. Recombinantly expressed, purified DmGSTE6 produces predominantly 2-glutathionyl-4,6-dinitrotoluene, and has a 2.5-fold higher Maximal Velocity (Vmax ), and five-fold lower Michaelis Constant (Km ) than previously characterized TNT-active Arabidopsis thaliana (Arabidopsis) GSTs. Expression of DmGSTE6 in Arabidopsis conferred enhanced resistance to TNT, and increased the ability to remove TNT from contaminated soil relative to wild-type plants. Arabidopsis lines overexpressing TNT-active GSTs AtGST-U24 and AtGST-U25 were compromised in biomass production when grown in the absence of TNT. This yield drag was not observed in the DmGSTE6-expressing Arabidopsis lines. We hypothesize that increased levels of endogenous TNT-active GSTs catalyse excessive glutathionylation of endogenous substrates, depleting glutathione pools, an activity that DmGST may lack. In conclusion, DmGSTE6 has activity towards TNT, producing a compound with potential for further biodegradation. Selecting or manipulating plants to confer DmGSTE6-like activity could contribute towards development of phytoremediation strategies to clean up TNT from polluted military sites.

Graphene oxide/Fe3O4 as sorbent for magnetic solid-phase extraction coupled with liquid chromatography to determine 2,4,6-trinitrotoluene in water samples.

A fast, simple, economical, and environmentally friendly magnetic solid-phase extraction (MSPE) procedure has been developed to preconcentrate 2,4,6-trinitrotoluene (TNT) from water samples prior to determination by liquid chromatography-UV-Vis employing graphene oxide/Fe3O4 nanocomposite as sorbent. The nanocomposite synthesis was investigated, and the MSPE was optimized by a multivariate approach. The optimum MSPE conditions were 40 mg of nanocomposite, 10 min of vortex extraction, 1 mL of acetonitrile as eluent, and 6 min of desorption in an ultrasonic bath. Under the optimized experimental conditions, the method was evaluated to obtain a preconcentration factor of 153. The linearity of the method was studied from 1 to 100 µg L-1 (N = 5), obtaining a correlation coefficient of 0.994. The relative standard deviation and limit of detection were found to be 12% (n = 6, 10 µg L-1) and 0.3 µg L-1, respectively. The applicability of the method was investigated, analyzing three types of water samples (i.e., reservoir and drinking water and effluent wastewater) and recovery values ranged between 87 and 120% (50 µg L-1 spiking level), showing that the matrix had a negligible effect upon extraction. Finally, the semiquantitative Eco-Scale metrics confirmed the greenness of the developed method.

Enhancement of microbial 2,4,6-trinitrotoluene transformation with increased toxicity by exogenous nutrient amendment.

In this study, the bacterial strain Citrobacter youngae strain E4 was isolated from 2,4,6-trinitrotoluene (TNT)-contaminated soil and used to assess the capacity of TNT transformation with/without exogenous nutrient amendments. C. youngae E4 poorly degraded TNT without an exogenous amino nitrogen source, whereas the addition of an amino nitrogen source considerably increased the efficacy of TNT transformation in a dose-dependent manner. The enhanced TNT transformation of C. youngae E4 was mediated by increased cell growth and up-regulation of TNT nitroreductases, including NemA, NfsA and NfsB. This result indicates that the increase in TNT transformation by C. youngae E4 via nitrogen nutrient stimulation is a cometabolism process. Consistently, TNT transformation was effectively enhanced when C. youngae E4 was subjected to a TNT-contaminated soil slurry in the presence of an exogenous amino nitrogen amendment. Thus, effective enhancement of TNT transformation via the coordinated inoculation of the nutrient-responsive C. youngae E4 and an exogenous nitrogen amendment might be applicable for the remediation of TNT-contaminated soil. Although the TNT transformation was significantly enhanced by C. youngae E4 in concert with biostimulation, the 96-h LC50 value of the TNT transformation product mixture on the aquatic invertebrate Tigriopus japonicas was higher than the LC50 value of TNT alone. Our results suggest that exogenous nutrient amendment can enhance microbial TNT transformation; however, additional detoxification processes may be needed due to the increased toxicity after reduced TNT transformation.

Multivariate soil fertility relationships for predicting the environmental persistence of 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-tricyclohexane (RDX) among taxonomically distinct soils.

After nearly a century of use in numerous munition platforms, TNT and RDX contamination has turned up largely in the environment due to ammunition manufacturing or as part of releases from low-order detonations during training activities. Although the basic knowledge governing the environmental fate of TNT and RDX are known, accurate predictions of TNT and RDX persistence in soil remain elusive, particularly given the universal heterogeneity of pedomorphic soil types. In this work, we proposed overcoming this problem by considering the environmental persistence of these munition constituents (MC) as multivariate mathematical functions over a variety of taxonomically distinct soil types, instead of a single constant or parameter of a specific absolute value. To test this idea, we conducted experiments where the disappearance kinetics of TNT and RDX were measured over a >300 h period in taxonomically distinct soils. Classical fertility-based soil measurements were log-transformed, statistically decomposed, and correlated to TNT and RDX disappearance rates (k-TNTand k-RDX) using multivariate dimension-reduction and correlation techniques. From these efforts, we generated multivariate linear functions for k parameters across different soil types based on a statistically reduced set of their chemical and physical properties: Calculations showed that the soil properties exhibited strong covariance, with a prominent latent structure emerging as the basis for relative comparisons of the samples in reduced space. Loadings describing TNT degradation were largely driven by properties associated with alkaline/calcareous soil characteristics, while the degradation of RDX was attributed to the soil organic matter content - reflective of an important soil fertility characteristic. In spite of the differing responses to the munitions, batch data suggested that the overall nutrient dynamics were consistent for each soil type, as well as readily distinguishable from the other soil types used in this study. Thus, we hypothesized that the latent structure arising from the strong covariance of full multivariate geochemical matrix describing taxonomically distinguished "soil types" may provide the means for potentially predicting complex phenomena in soils.

Use of dilute ammonia gas for treatment of 1,2,3-trichloropropane and explosives-contaminated soils.

Laboratory studies were performed to test a novel reactive gas process for in-situ treatment of soils containing halogenated propanes or explosives. A soil column study, using a 5% ammonia-in-air mixture, established that the treatment process can increase soil pH from 7.5 to 10.2. Batch reactor experiments were performed to demonstrate contaminant destruction in sealed jars exposed to ammonia. Comparison of results from batch reactors that were, and were not, exposed to ammonia demonstrated reductions in concentrations of 1,2,3-trichloropropane (TCP), 1,3-dichloropropane (1,3-DCP), 1,2-dicholoropropane (1,2-DCP) and dibromochloropropane (DBCP) that ranged from 34 to 94%. Decreases in TCP concentrations at 23° C ranged from 37 to 65%, versus 89-94% at 62° C. A spiked soil column study was also performed using the same set of contaminants. The study showed a pH penetration distance of 30 cm in a 2.5 cm diameter soil column (with a pH increase from 8 to > 10), due to treatment via 5% ammonia gas at 1 standard cubic centimeter per minute (sccm) for 7 days. Batch reactor tests using explosives contaminated soils exhibited a 97% decrease in 2,4,6-trinitrotoluene (TNT), an 83% decrease in nitrobenzene, and a 6% decrease in hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). A biotransformation study was also performed to investigate whether growth of ammonia-oxidizing microorganisms could be stimulated via prolonged exposure of soil to ammonia. Over the course of the 283 day study, only a very small amount of nitrite generation was observed; indicating very limited ammonia monooxygenase activity. Overall, the data indicate that ammonia gas addition can be a viable approach for treating halogenated propanes and some types of explosives in soils.