<p> Matrix diffusion from planar fractures was studied both mathematically and through physical model experiments. A conceptual model was developed based on previous work by Parker (1994) and Crank (1956). Mathematical models were developed to simulate diffusion from 2D and 3D instantaneous disk sources and a 3 D continuous disk source. The models were based on analytical solutions previously developed by Carslaw and Jaeger (1959). Analytical solution is not available for the total mass diffused into the porous matrix for a 3D continuous disk source, and it was therefore calculated through the summation of the iso-concentration lines, which were assumed to be a semi-spherical shape.</p> <p> The mathematical simulations indicated that the 2D scenario produces significantly different results from the 3D scenario, the time for mass disappearance is significantly larger for continuous sources than for instantaneous sources, the normalized concentration generally decreased over time for instantaneous sources while it increased over time for continuous sources, diffusion rates decrease significantly over time and space, and the normalized mass loss from the source zone never reaches 1 for continuous sources due to the semi-infinite integral. The simulations also showed that disappearance times increase exponentially with increasing source radii and matrix porosity, and decrease with increasing aqueous-phase NAPL solubilities.</p> <p> The observations from the physical model experiments were very close to the simulated data at z = 0, validating the 3D mathematical models for this elevation. A plot of the observed vs simulated data did not reveal any trends, indicating that the majority of the differences can be attributed to experimental error. The experimental concentrations were below the method detection limit at depths of 3 and 6 cm however, indicating that either the experiments should have been conducted over a longer time period or a more sensitive analytical method should have been employed, to enable model validation at these depths.</p> / Thesis / Master of Applied Science (MASc)

<p> Although successful in laboratory studies, field applications of in situ remediation of chlorinated solvents in groundwater have met with limited success. This is most often attributed to the inability to deliver the amendment evenly throughout the target zone, especially in low permeability and heterogeneous materials. The goal of this research was to employ a prototype of a novel delivery system to evenly deliver amendment across the depth and breadth of the subsurface in a cost-effective method. The research was conducted at 42 Voyager Court, Toronto, ON where concentrations of vinyl chloride in groundwater were in excess of Ontario Ministry of the Environment guidelines (O.Reg.153/04). The subsurface consisted of sandy and clayey silt fill underlain by sandy silt till.</p> <p> The delivery system comprised 29, 1/4" diameter, delivery points with small perforations along the length, installed in a fence perpendicular to groundwater flow, approximately 0.5 m upgradient of the area of concern. The delivery system used low flow rates (approximately 13 to 23% of total groundwater flow) and discrete delivery holes to deliver a potassium permanganate solution (approximately 40 g/L) amended with sodium bromide (approximately 0.8 g/L) across the depth of the subsurface. Fourteen multi-level monitoring wells, each with five sampling ports were installed to monitor the effectiveness.</p> <p> After six months of delivery, sample results indicated that oxidant demand hindered the ability of potassium permanganate to reach and degrade the vinyl chloride. However, elevated bromide concentrations were detected at all downgradient sampling ports within a 1.5 m distance. Thus, the delivery system was successful at delivering the amendment across the depth and breadth of the target area and achieving even delivery.</p> <p> Problems, typically leaks, were encountered with the delivery system design. Additional engineering would be required to improve the header system prior to commercializing this process. This would be a beneficial endeavor, as results of this work indicate that this passive delivery fence technique meets a real need in the remediation industry, which is the even distribution of amendment to target zones in the saturated subsurface, including zones of low permeability.</p> / Thesis / Master of Applied Science (MASc)

No / Mechanochemistry provides a method to reduce or eliminate the use of solvents by carrying out reactions through the grinding of neat reagents. Until recently a significant drawback of this form of synthesis has been the limited ability to scale up. However, it has been shown that twin screw extrusion (TSE) may overcome this problem as demonstrated in the continuous synthesis of co-crystals, Metal Organic Frameworks (MOFs) and Deep Eutectic Solvents (DES), in multi kg h−1 quantities. TSE has provided a means to carry out mechanochemical synthesis in a continuous, large scale and efficient fashion, which is adaptable to a manufacturing process. Herein, we highlight the potential of this technique for organic synthesis by reporting four condensation reactions, the Knoevenagel condensation, imine formation, aldol reaction and the Michael addition, to produce analytically pure products, most of which did not require any post synthetic purification or isolation. Each reaction was carried out in the absence of solvents and the water byproduct was conveniently removed as water vapour during the extrusion process due to the elevated temperatures used. Furthermore, the Knoevenagel condensation has been studied in detail to gain insight into the mechanism by which these mechanochemical reactions proceed. The results point to effective wetting of one reactant by another as being critical for these reactions to occur under these reaction conditions. / EPSRC EP/L019655/1

Microcosms were constructed from aquifer sediment samples taken from an actively degrading chlorinated solvent contaminated site located in Virginia Beach, Virginia. The objective of this study was to determine if and how the addition of cyclodextrin (CD) affects reductive dechlorination of chlorinated ethenes. After chlorinated solvent degradation rates were established in anaerobic and aerobic microcosms, 100 mg/L of CD solution was added for a period of 21 days. CD was then removed after 26 days to simulate the degradation response of the aquifer in a post CD injection environment. Degradation rates were determined by analyzing PCE, TCE, and cis-DCE concentration data over the various phases of the experiment. Results from this study indicated that chlorinated solvent degradation could be either impaired or facilitated by the addition of CD. CD appeared to stimulate one anaerobic microcosm (IY-2c) where daughter production had not previously occurred. The activity of this microcosm was greatly enhanced by the addition of CD (0 uM/day to 13.89 uM/day). However, biotransformation of PCE in another anaerobic microcosm in which reductive dechlorination was occurring, ceased after the addition of CD (IY-1a). In a third group of microcosms the rate and extent of reductive dechlorination was greatly enhanced by the addition of CD. The effect of adding CD was also found to be highly dependent on the redox conditions in the microcosm, specifically if the conditions were strongly reducing. The most active microcosms, found in the Aerobic Group, also had the lowest ferrous iron concentrations (3.57 mg/L for BY-1a, 2.25 mg/L for BY-1b, and 0.41 mg/L for BY-1c). The microcosm (IY-2b) that showed no daughter production had the highest level of ferrous iron (44.22 mg/L). This study presents a qualitative approach to the affect of CD on MNA. / Master of Science

Laboratory microcosm experiments were conducted to assess the potential for biostimulation and bioaugmentation as source reduction measures in support of a monitored natural attenuation remedial strategy at Naval Amphibious Base (NAB) Little Creek. Previous work with laboratory microcosms conducted under simulated natural (unamended) conditions has demonstrated that indigenous dehalorespirators were capable of partial dechlorination of tetrachloroethene (PCE) to cis-dichloroethene (cis-DCE). This study attempts to achieve complete reductive dechlorination with amendments to static microcosms to test the hypotheses that nutrient-limited or microorganism-limited conditions exist in aquifer sediments obtained from the site. The enhanced bioremediation experiments were comprised of nutrient-amended microcosms receiving additions of electron donors, mineral medium, or anaerobic digester supernatant, and dechlorinating culture-amended microcosms were inoculated with a culture capable of transforming PCE to ethene. Reductive dechlorination in the nutrient-amended microcosms proceeded to cis-DCE over a 260-day study period, at slightly higher rates than in experiments conducted with aquifer sediments from the same location under natural conditions. Inoculation of aquifer sediments with a small amount of dechlorinating culture initiated rapid transformation of PCE to vinyl chloride (VC) by day 18 of the study. Zero-order rates of PCE dechlorination in unamended, propionate-, formate-, mineral medium-, digester supernatant-, and dechlorinating culture-amended microcosms were 0.24, 0.750, 1.30, 0.339, 0.177, and 1.75 µM/day, respectively. The results of this study suggest that an engineered biostimulation approach alone may not be as beneficial for PCE source reduction at NAB Little Creek, than bioaugmentation with competent dehalorespirators, along with the inclusion of supplemental nutrients which would be available to stimulate dechlorination activity of both indigenous and introduced microorganisms. / Master of Science

Sodium borohydride reduces alkyl halides and their related tosylate derivatives in the order primary > secondary > tertiary, while the relative order of leaving-group ability is Ts⁻ ≥ I⁻ > Br⁻ > > Cl⁻. The yields obtained ranged from 90-100% for most simple, primary and secondary iodides, bromides, and tosylates, to 1-2% for the tertiary compounds. As in the case of the more reactive lithium aluminum hydride, the. reduction is believed to occur by an S_N2 displacement on carbon. The reduction of a series of para-substituted benzyl chlorides revealed that the electronic effects of groups ranging from p-methoxy to p-nitro had a rather small effect on the rate of reduction. Aryl halides arc reduced by sodium borohydride in yields dependent upon the particular halogen involved, the presence of other ortho and para electron-withdrawing substituents, and the reaction temperature, among other factors. The same relative order of dehalogenation displayed by the alkyl halides was found. Polyhalomethanes such as carbon tetrachloride react with sodium borohydride to give the monohydro and dihydro compounds as the major products, the former predominating. The exact mechanism of the reduction is as yet undetermined, as water apparently catalyzes the reaction in some unknown manner. / Master of Science

The expanding role of electronic nose instrumentation, as a quality-monitoring tool for food-packaging materials, is examined and reviewed. The food industry is interested in determining the applicability of using an electronic nose for odor analysis of retained printing solvent levels in packaging. Three electronic nose systems were optimized for this application and their performance assessed. These include the FOX 3000, the Cyranose 320, and the QMB6. Response surface methodology was used to generate 2nd order models of sensor response as a function of system and experimental parameters for the three electronic nose systems. Forty-seven of 50 sensor models generated were found to be significant at an a-level of 0.05. Optimum settings, that allowed adequate signals to be obtained for the full range of examined retained solvents levels, were selected for the remaining work using these models. Performance analyses of these systems, which use three leading sensor technologies, showed that the conducting polymer sensor technology demonstrated the most discriminatory power. All three technologies proved able to discriminate among different levels of retained solvents. Each complete electronic nose system was also able to discriminate between assorted packaging having either conforming or non-conforming levels of retained solvents. Each system correctly identified 100% of unknown samples. Sensor technology had a greater effect on performance than the number of sensors used. Based on discriminatory power and practical features, the FOX 3000 and the Cyranose 320 were superior. The results indicate that electronic nose instrumentation can be used as a complimentary discriminatory tool in quality control. / Master of Science

Monitored natural attenuation (MNA) has been widely used as a remedial strategy, acknowledged by the EPA as the most appropriate technology for cost effective remediation under certain site conditions. Despite the widespread use of MNA, empirical methods are lacking to evaluate the sustainability of MNA at a site. The objective of this thesis is to investigate the natural attenuation capacity (NAC) as a quantitative metric for evaluating the sustainability of MNA for contaminants in groundwater systems. Five DoD sites were selected for this study, where the common thread between the sites is the existence of a mature chlorinated ethene groundwater plume and the use of MNA as the long-term remediation strategy. Constituent specific NAC values were quantified and statistically examined to determine past performance of MNA at the sites. A conceptual decision model was developed to be a framework of the statistical tools demonstrated in this thesis. Analyzing MNA sustainability at a site can be separated into two components; past performance of natural attenuation and evaluation of current MNA parameters. The former is the focus of this thesis where NAC is the screening metric and the temporal trend in the rate of natural attenuation being evaluated. Within the conceptual decision model, the use of NAC as a screening tool in combination with a specific analysis of MNA parameters allows engineers, regulators, and decision makers to clearly determine whether MNA at a site is sustainable and whether site specific remediation goals will be met. / Master of Science

Hydrocarbon solvents are widely used in the production of paints, adhesives, dyes, polymers, plastics, textiles, printing inks, agricultural products and pharmaceuticals. While the neuropathic potential of aliphatic solvents was shown in the 1970s, little is known about the neuropathic potential of aromatic solvents. The present study examines such solvents, 1,2-diethylbenzene (DEB) and its metabolite 1,2-diacetylbenzene (DAB), to determine (a) the neuropathological evidence for peripheral neuropathy in rodents treated with 1,2-DAB, (b) the neurochemical basis for the neurotoxic properties of this compound, and (c) the structural requirements for nerve fiber damage. The properties of 1,2-DAB and 2,5- hexanedione (HD) are also compared. A key finding of this thesis is that 1,2-DAB induces a 2,5-HD-like pattern of nerve damage of motor and sensory axons with focal swellings containing neurofilaments. Whereas nerve damage begins distally in 2,5-HD intoxication, with 1,2-DAB treatment axonal swellings begin intraspinally and in the proximal ventral roots of motor nerve fibers. A second key finding is the reactivity of 1,2-DAB with amino acids, notably lysine, a property that is shared with 2,5-HD. 1,2-DAB and 2,5-HD react with amino acids and proteins to form blue and yellow chromophores, respectively. Relative to 2,5-HD, 1,2-DAB is three orders of magnitude more reactive in forming high-molecular-weight species. 1,2-DAB treatment of spinal cord slices in vitro and intact sciatic nerve in vivo showed that neurofilament proteins react more readily than beta-tubulin. The heavy and medium subunits of neurofilament protein were more reactive than the light subunit. The reactivity of these four axonal proteins was in proportion to their lysine content. These data are consistent with selective accumulation of neurofilaments in giant axonal swellings. In summary, these studies have shown a relationship between the chromogenic and neuropathic properties of two gamma-diketones, one aliphatic (2,5-HD) the other aromatic (1,2-DAB). These studies are relevant to occupational and public health for at least two reasons. First, urinary chromogens generated by neuropathic aliphatic and aromatic hydrocarbons could serve as biological markers of exposure to solvents with neuropathic potential, and second, other chromogenic solvents (such as tetralin) should be considered for neuropathic potential. / Graduation date: 2002

This work seeks to develop new solvents for environmentally benign chemical synthesis. Switchable solvents are a new class of compounds that change properties upon the application of some stimulus such as heat, UV light, or pH. We have developed the use of a new solvent, thiirane oxide, that has chemical properties similar to DMSO. Thiirane oxide, however, undergoes facile decomposition to two gases at temperatures above 100 C, which is much lower than the temperature required for removing DMSO. Thus we have a solvent with excellent solvation properties, but with a built-in switch for easier removal. However, thiirane oxide leaves behind sulfurous products which make the reverse reaction to reform the solvent unfeasible. We are also developing the use of another solvent, piperylene sulfone, which is expected to have good solvent properties, yet with decomposition products that can be reacted to reform the solvent. This thesis also details the work to date on piperylene sulfone. Gas-expanded liquids (GXLs) also show promise as a new reaction medium. In order to design solvent systems that take full advantage of this medium, we desire to understand the microstructure of these fluids. To that end, we are using cage reactions to probe solute-solvent and solvent-solvent interactions at the molecular level. This thesis discusses the current research on using cage reactions to probe the structure of GXLs.