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<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)

Accurate simulations of the global radiative impact of anthropogenic emissions must employ a tropospheric chemistry model that predicts realistic distributions of aerosols of all types. The need for a such a comprehensive yet computationally efficient tropospheric chemistry model is addressed in this research via systematic development of the various sub-models/mechanisms representing the gas-, aerosol-, and cloud-phase chemistries. The gas-phase model encompasses three tropospheric chemical regimes - background and urban, continental rural, and remote marine. The background and urban gas-phase mechanism is based on the paradigm of the Carbon Bond approach, modified for global-scale applications. The rural gas-phase chemistry includes highly condensed isoprene and a-pinene reactions. The isoprene photooxidation scheme is adapted for the present model from an available mechanism in the literature, while an a-pinene photooxidation mechanism, capable of predicting secondary organic aerosol formation, is developed for the first time from the available kinetic and product formation data. The remote marine gas- phase chemistry includes a highly condensed dimethylsulfide (DMS) photooxidation mechanism, based on a comprehensive scheme available in the literature. The proposed DMS mechanism can successfully explain the observed latitudinal variation in the ratios of methanesulfonic acid to non-sea-salt sulfate concentrations. A highly efficient dynamic aerosol growth model is developed for condensing inorganic gases. Algorithms are presented for calculating equilibrium surface concentrations over dry and wet multicomponent aerosols containing sulfate, nitrate, chloride, ammonium, and sodium. This alternative model is capable of predictions as accurate for completely dissolved aerosols, and more accurate for completely dry aerosols than some of the similar models available in the literature. For cloud processes, gas to liquid mass-transfer limitations to aqueous-phase reactions within cloud droplets are examined for all absorbing species by using the two-film model coupled with a comprehensive gas and aqueous-phase reaction mechanisms. Results indicate appreciable limitations only for the OH, HO₂, and NO₃ radicals. Subsequently, an accurate highly condensed aqueous-phase mechanism is derived for global-scale applications. / Ph. D.

Ammonium ionenes are macromolecules with quaternized nitrogen groups in the main chain. Ionenes are commonly referred to as x,y-ionene, where x and y represent the number of methylene groups between quaternized nitrogens. Synthesis of aliphatic ammonium ionenes has been studied since the early twentieth century; however, absolute molecular weight characterization has only been performed using extensive light scattering and viscosity experiments. Performing aqueous size exclusion chromatography (SEC) on ammonium ionenes provides absolute molecular weight determinations while eliminating the need for separate viscosity and light scattering experiments. We developed a mobile phase composition that provides reliable separation of aliphatic ammonium ionenes using aqueous SEC. For the first time, we report absolute molecular weights of aliphatic ammonium ionenes using this technique. We investigated the influence of charge density and structural symmetry on thermal and mechanical properties of ammonium 6,6-, 12,6- and 12,12-ionenes. Thermal properties were measured using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), and mechanical properties were measured using dynamic mechanical analysis (DMA) and an Instron. Incorporating low molecular weight polymer segments into the main chain of the ionene allows tailoring of polymer characteristics. Poly (tetramethylene oxide) segments decrease hydrophilicity and increase elastomeric character. Linear PTMO based ionenes have been synthesized previously, and we were interested in how branching affected thermal and mechanical properties. We synthesized bis(dimethylamino) poly(tetramethylene oxide) segments, and subsequently, synthesized linear and branched ionenes to study the effects of topology on thermal and mechanical properties. Polymers were analyzed using DMA, DSC, TGA, SAXS, and an Instron. / Master of Science