The effect of water content and soil-water hysteresis on transport of unreactive water-tracers and volatile organic compounds (VOCs) in porous media is investigated under steady-state water-flow conditions. Specifically, this research addresses the effect on dispersive and mass transfer processes affecting the movement of NaC1 and trichloroethene (ICE) and how these processes influence the approach to Fickian flux conditions. Transport experiments were conducted in a 25-cm column packed with silica sand. Based on the results, it is concluded that water content (0), pore-water velocity, and flow history affect the average movement and spread of water-tracers and VOCs. It is suggested that non-volatile solutes in unsaturated media travel longer distances or times to achieve a Fickian state. Consequently, a greater number of averaged heterogeneities are encountered and solute flux is characterized by a greater dispersion coefficient (D). A power (n) law relationship (D(m) = η(v(m)/ θ(m))ⁿ), found between mobile dispersion coefficients (D(m_), pore-water velocity (v(m)), and water content (θ(m)) for different porous media, indicates that dispersivity (η) is not only a function of the media, but also of θ(w). TCE transport is controlled by advection processes for Ow greater than 50% saturation. Lower θ(w) result in greater TCE dispersion, retardation, mass-transfer resistance, vapor diffusion, and spreading. Consequently, VOCs reach the Fickian regime at shorter distances than unreactive solutes in water. Although VOC transport is influenced by multiple rate-limited mass transfer, the mechanisms controlling the overall mass-transfer resistance vary as a function of θ(w). The hysteretic behavior of solute transport parameters is attributed to a greater degree of irregular flow paths and entrapped air, higher air-water interfacial areas, and thicker water-films for wetting than draining scenarios. Consequently, wetting conditions result in slower mixing (up to 98% lower mass-transfer coefficients) of dissolved solutes. Since TCE transport at low water contents and wetting conditions is dominated by diffusion and dispersion mechanisms, the TCE velocity distribution in the liquid phase is normalized by velocity distributions in the gas-phase and becomes closer to Fickian conditions.

Oscillatory boundary layer flow is found under waves in the near shore region. This region is responsible for large volumes of sediment transport and whilst a large number of studies have investigated the broader problem only a handful of studies have investigated the boundary layer flow in detail. Most of these studies have also only considered boundary layer flow over rough impermeable beds and therefore do not take into account the potential effect of the flow interaction with a permeable bed. Similar studies in other felds of environmental fluid mechanics have concluded that the presence of a permeable bed can lead to significant diff erence in the boundary layer hydrodynamics when compared to the equivalent flow over an impermeable bed. This thesis presents a series of laboratory experiments that have been conducted over an impermeable gravel bed and a permeable gravel bed to identify the differences in the boundary layer hydrodynamics with a particular reference to the differences in the horizontal velocity profile, the shear stress, turbulence and the bed friction factor. The results indicate that a difference exists in the near-bed flow between the two bed cases. The results also demonstrate that the magnitude of the differences vary with flow Reynolds number, so the more energetic the wave the larger the impact of the permeable bed. The bed shear stress and resulting friction factor was found to be 40% greater for the flows over the permeable bed for the most energetic test case whilst the friction factor for the two bed cases for the least energetic test case are similar. The results also indicate that the permeable bed introduces an unexpected asymmetry in the flow cycle. This is attributed to the high vertical velocities that have been observed. A second series of experiments have been conducted to shed light on the interaction between the flow above the bed and within the bed to help explain the results from the initial gravel-bed experiments. The second series of experiments have been conducted over a regular permeable bed that allows for velocity measurements within the pores. The results indicate that the horizontal velocity, shear stress and turbulence all display signs of being effected by the exchange of flow, or ventilation, that naturally occurs.

No description available.

Although extensive literature exists on NMR of water in MCM-41, the origin of a number of NMR spectral features in this material had not been understood. Specifically, the OH proton resonance observed in the dry material disappears completely as it is hydrated to 0.2 mono-layer hydration level. The purpose of this study was to gain insight into the physical basics for these spectral features and in the process broaden our understanding of behaviour/interactions of water molecules in porous material. First, measurements of MAS spectra as a function of temperature and hydration, at very low hydrations, made possible a definitive spectral peak assignment. Second, using 1D and 2D selective inversion recovery and magnetization exchange experiments, as well as MAS and non-MAS techniques, magnetization exchange between the water protons and surface OH group protons was quantified. The present results lead to the conclusion that chemical exchange is not responsible for producing the observed changes in proton spectra in MCM-41 as this material is hydrated up to the 0.2 mono-layer hydration level. This represents an important result as it is at odds with what is assumed in the literature in this connection and means that previous conclusions about hydration dynamics in this material need to be revisited. A dynamics model of water interaction with the surface OH hydration sites was introduced to explain the observed proton spectra. The model can successfully predict the observed chemical shifts and temperature dependent changes of proton spectra in the very low hydration MCM-41.

No description available.

Thesis (Ph. D - Hydrology and Water Resources) / Includes bibliographical references (leaves 208-221).

Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 208-221).

Thesis (Ph.D. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references (leaves 241-249).

Thesis (M. App. Sc.) -- University of Adelaide, Department of Chemical, Engineering, 1966.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Yan Jin, Dept. of Plant & Soil Sciences. Includes bibliographical references.