Thesis (Ph.D.)--Ohio University, November, 2004. / Includes bibliographical references (p. 94-101)

Thesis (Ph.D.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 94-101)

Thesis (Ph. D.)--Mississippi State University. Department of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Dr. Joseph B. Hughes; Committee Member: Dr. Jian Luo; Committee Member: Dr. Jim C. Spain; Committee Member: Dr. Patricia Sobecky; Committee Member: Dr. Spyros G. Pavlostathis

TNT (2,4,6-trinitrotoluene) is a persistent contaminant at many military installations and poses a threat to aquatic ecosystems. Data from environmental fate and toxicity studies with TNT revealed that sediment toxicity test procedures required modification to accurately assess sediment TNT toxicity. Key modifications included aging TNT-spiked sediments 8-14 d, basing lethal dose on measured sediment concentrations of the molar sum of TNT and its main nitroaromatic (NA) transformation products (SNA), basing sublethal dose on average sediment SNA concentrations obtained from integration of sediment SNA transformation models, avoiding overlying water exchanges, and minimizing toxicity test durations. Solid phase microextraction fibers (SPMEs) were investigated as a biomimetic chemical measure of toxicity and bioavailability. Both organism and SPME concentrations provided measures of lethal dose independent of exposure scenario (TNT-spiked sediment or TNT-spiked water) for Tubifex tubifex. Among all benthic organisms tested (Chironomus tentans, Ceriodaphnia dubia, T. tubifex) and matrixes, median lethal dose (LC50) estimates based on SPME and organism concentrations ranged from 12.6 to 55.3 mmol SNA/ml polyacrylate and 83.4 to 172.3 nmol SNA/g tissue, ww, respectively. For Tubifex, LC50s (95% CI) based on SNA concentrations in sediment and SPMEs were 223 (209-238) nmol SNA/g, dw and 27.8 (26.0-29.8) mmol SNA/ml, respectively. Reproductive effects occurred at slightly lower exposures. Median effective dose (EC50) estimates (95% CI) for Tubifex cocoon production, based on sediment and SPME concentrations, were 118 (114-122) nmol SNA/g, dw and 21.8 (21.2-22.4) mmol SNA/ml, respectively. Bioconcentration experiments with Tubifex revealed that compound hydrophobicity predicted the toxicokinetics and bioconcentration of these compounds from water, however, there was a large discrepancy between the toxicokinetics of absorbed versus metabolically-generated aminodinitrotoluenes. A large portion of bioconcentrated, radiolabeled TNT transformation products could not be identified. In addition to their ability to provide matrix-independent measures of dose, SPME concentrations were more accurate indicators of bioavailable NAs than were sediment concentrations.

Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 m) and IR wavelengths (9.38 and 8.1 m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is demonstrated for the two IR wavelengths, as supported by appearance of fine mode structure in the laser spectrum. The 8.1 m wavelength exhibits a dramatic change in the output spectrum caused by the weak intracavity absorption of acetone. Numerical solution of the laser rate equations yields a sensitivity estimation of acetone partial pressure of 165 mTorr corresponding to ~ 200 ppm. The system is also found sensitive to the humidity in the laboratory air with an absorption coefficient of just 3 x 10-7 cm -1 indicating a sensitivity of 111 ppm. Reported also is the design of a compact integrated data acquisition and control system. Potential applications include military and commercial sensing for threat compounds such as explosives, chemical gases, biological aerosols, drugs, banned or invasive organisms, bio-medical breath analysis, and terrestrial or planetary atmospheric science.

Contamination of soils and groundwater with nitroaromatic compounds such as 2,4,6-trinitrotoluene (TNT) and dinitrotoluenes (DNTs) has drawn considerable attention due to widely distributed contamination sites and substantial efforts for cleanup. Two isomers of DNT, specifically 2,6-dinitrotoluene (2,6-DNT) and 2,4-dinitrotoluene (2,4-DNT), occur as soil and groundwater contaminants at former TNT production sites. The discovery of bacteria that use DNT isomers as electron donors has encouraged bioremediation at contaminated sites. Current work is extending the existing engineered bioremediation to naturally occurring in situ biodegradation and focuses on the application of natural attenuation (NA) as a remediation strategy for residual DNT at contaminated sites. More specifically this research evaluated factors influencing in situ bioremediation of DNTs and TNT in surface soils, vadose zones, and saturated medium. Applications involving surface soils and vadose zones investigated the potential of water infiltration to promote in situ bioremediation. Studies in saturated media were more applicable to NA. Factors that were also considered in studies conduced included: 1) the presence and distribution of degrading microbes in field soils (Barksdale, WI); 2) the dissolution and bioavailability of contaminants in historically contaminated soils; and 3) the effect of mixtures of contaminants (i.e., DNTs and TNT) on biodegradation processes. This research provided information useful for practitioners considering an in situ bioremediation NA as a remedial solution for contaminated sites. Under the condition simulating downflow of surface waters or rainwater, the rapid rate of DNT degradation could be facilitated by the availability of oxygen in the soil gas without concern of toxicity (i.e., nitrite evolution and pH drop) and addition of nutrients. As a result, in situ bioremediation or NA should be strongly considered as a remedial option for Barksdale soils and similar sites where relatively low concentrations of DNT isomers are present as contaminants. At TNT contaminated sites TNT was not mineralized by indigenous microorganisms despite oxidative biotransformation, and mixed culture capable of growth on DNT also could not develop the mineralization of TNT during DNT degradation. This suggests that the mixtures of contamination did not improve the potential for in situ TNT bioremediation.

Indiana University-Purdue University Indianapolis (IUPUI) / Canines are regularly utilized by law enforcement agencies to detect explosives. However, the mechanism by which canines respond to explosive vapors is not well understood, leading to difficulties in canine training and testing. It is known that the amount of vapor generated from explosive compounds is dependent upon several factors including sample amount, vapor pressure, and the degree of confinement. Underlying these factors is the basic process of evaporation of an unconfined explosive, which is rucial to understanding how explosive vapors behave in other, more confined, systems. In Stage One of this study, evaporation rates were determined for several explosive liquids using an analytical balance. These rates were compared to one another as well as to theoretical models for the evaporation of liquids. In general and as expected, mass decreased linearly with time and evaporation rates decreased logarithmically as boiling point increased. Several examples of solvent “pinning” on a metal surface were also observed. While an empirical model for the evaporation of unconfined explosive liquids was developed, a comprehensive model for the escape of explosive vapors from sealed containers (i.e., a suitcase, knapsack, or IED container itself) is needed. The second part of Stage One of this study was to determine that the flow rate of explosive vapors escaping from relatively large orifices does not conform to Fick’s Law of Diffusion. Fick’s model states that the flow rate is linearly dependent upon the cross sectional area of the orifice and the material’s diffusion coefficient. Instead, the flow rate was found to be linearly dependent upon the diameter of the orifice due to the tendency of the flow to diffuse outwards from its circular edge. A clear relationship between flow rate and diffusion coefficient was seen, however. Additional uncertainty arises concerning the complexity of the odor generated from explosive compounds. Because explosive vapors are often complex (they consist of multiple chemical compounds), confusion exists regarding the cause of canine alert; that is the “odor compound” that allows for canine detection of various explosives. Although 2, 4- dinitrotoluene (DNT) has been explored as a potential odor compound, the possibility of a nitrated explosive inherently producing nitrated gas upon decomposition has not. Stage Two of this study focused on evaluating nitrate as a potential cause of canine alerts. An LC/MS method for the detection of nitrate ions in Composition C-4 and flake trinitrotoluene (TNT) was developed and tested. Instrumental analysis was not successful in detecting nitrate ions in any of the explosives tested. The lack of nitrate was confirmed using a diphenylamine color test for nitrates, thus eliminating nitrate as an odor compound and cause of canine alert to nitroaromatic compounds. 2, 4-DNT has been introduced as a potential odor compound of TNT, however, the mechanisms behind its vapor emission have not been thoroughly explored. More specifically, due to the “sticky” nature of the 2, 4-DNT isomer, the effects of surface adhesion to container walls are of concern. In particular, whether the amount of material lost to surface adhesion is significant enough to effect canine detection of TNT. A second focus of Stage Two explored this concern. A GC/MS method for the detection and separation of TNT and DNT isomers in liquid extracts was developed and the amount of 2, 4-DNT residues adhering to container walls was quantified. These values, compared to the amount 2,4-DNT expected to saturate each container (determined by the Ideal Gas Law), showed a significant preference of 2,4-DNT in the solid phase as opposed to in the gas phase. The amount of residue adhering to the walls of a gallon can differed from expected values by nearly 70%. The amount of material extracted from a quart can exceeded expected values by 137%. The apparent sticky nature of 2, 4-DNT resulted in a significant loss of material needed to fully saturate a container and thus canine detection success may be affected. In the final stage of this study, theories regarding odor compounds and odor availability of nitromethane, TNT, and Composition C-4 were tested using certified explosives-detecting canines. These trials included thirty-three canine-handler teams from eight government agencies. The odor availability of nitromethane was tested by placing varying volumes of nitromethane in containers with differing degrees of confinement and studying the effects on canine detection success. The odor availability trial showed no significant effect of sample amount or degree of confinement on canine detection so long as the sample volume was sufficient to saturate its container. In this study that volume was determined to be < 1 mL. Detection of 2, 4-DNT, TNT-NESST (Non-Hazardous Explosives for Security Training and Testing), and flake TNT were also studied using certified canines. The purpose of this was to identify the odorant responsible for canine alert to the explosive TNT. These trials showed a significant response to 2, 4-DNT compared to TNT and its training aid; this suggests that 2, 4-DNT is the primary cause of canine alerts to TNT. Additionally, Composition C-4 and RDX-NESTT were tested along with potential odor compounds that included the manufacturing solvent, cyclohexanone, the energetic “taggant” 2, 3-dimethyl-2.3-dinitrobutane (DMNB), the plasticizer dioctyladipate (DOA) and its degradation product 2-ethyl-1-hexanol. While some response to DMNB and cyclohexanone was seen, the most significant response was to the actual Composition C-4. This suggests that the cause of canine alert to Composition C-4 is the explosive mixture as a whole and not a single chemical component of the mixture