ROCK OUTCROPS IN THE CANADIAN SHIELD: AN INVESTIGATION OF CONTAMINANT TRANSPORT FROM SURFACE SOURCES IN FRACTURED ROCK AQUIFERS

Flow, recharge and transport dynamics in fractured rock aquifers with low lying rock outcrops is a largely unexplored area of study in hydrogeology. The purpose of this thesis is to examine these topics in an agricultural area in Eastern Ontario. The study consists of a regional scale groundwater quality study, an infiltration experiment that considers bacteria transport from the ground surface to a well, and a numerical modelling study that tests the parameters that affect surface infiltration of a tracer from a rock outcrop to a deeper horizontal fracture. In the water quality study, approximately 65% of the samples contained total coliform, 16% contained E. coli, and 1% contained nitrate-N at greater than 5 mg/L. Occurrence of E. coli increased when considering seasonality, where wells were drilled on rock outcrops, and for shallow well intervals. Nitrate-N did not occur above the Guidelines for Canadian Drinking Water Quality (Health Canada, 2012) of 10 mg/L. Rapid arrival times were observed in the infiltration study for both the microspheres (30 minutes) and a dye tracer (45 minutes) in a well approximately 6.0 m in horizontal and 2.8 m in vertical distance from the tracer source. Transport velocities were approximately 38.9 m/day for the dye tracer and 115.2 m/day for the colloidal tracer. Results of the model runs indicate that overburden can provide an effective protective layer to transport in fractures, that high groundwater velocities occur in larger fracture apertures and higher gradients dilute tracer concentrations, and that lower groundwater velocities occur with smaller fracture apertures and lower gradients result in elevated tracer concentrations. Lower rainfall rates, larger fracture apertures, early tracer time, larger gradients, and lower water levels maintained unsaturated conditions for longer time periods such that tracer transport was delayed until saturated conditions were attained. The overall heterogeneity of this aquifer environment creates a source water protection conundrum where the water quality is generally good, while transport can occur very quickly in proximity to rock outcrops and in areas with limited overburden.

The efficiency of excitation of a surface wave on a dielectric cylinder /

Vita.

Constraining storm-scale forecasts of deep convective initiation with surface weather observations

Thesis (Ph.D.)--University of Washington, 2016-06

A Geophysical Investigation of the Arctic Sea Ice Surface

Thesis (Ph.D.)--University of Washington, 2016-06

SCC initiation for X65 pipeline steel in the "high" pH carbonate/bicarbonate solution

The initiation of stress corrosion cracking (SCC) was studied using scanning electron microscope observations of linearly increasing stress test specimens. SCC initiation from the following surfaces was studied: (i) initiation from the commercial pipe surface covered by the Zn coating, (ii) initiation from a mechanically polished surface with a deformed layer, and (iii) initiation from an electro-polished surface. SCC initiation involved different features for these surfaces as follows. (i) For the Zn coated commercial pipe surface, a crack in the Zn coating led to the dissolution of the deformed layer and when the deformed layer was penetrated, intergranular SCC initiation became possible. (ii) For a mechanically polished surface with a deformed layer, cracks in the surface oxide concentrated the anodic dissolution to such an extent that there was transgranular SCC in the deformed layer. SCC was intergranular when the deformed layer had been penetrated. Transgranular stress corrosion cracks were stopped at ferrite grain boundaries (GBs) oriented perpendicular to the SCC propagation direction. (iii) For an electro-polished surface, the surface oxide film was cracked at many locations, but intergranular SCC only propagated into the steel when the oxide crack corresponded to a GB. An oxide crack away from a GB is expected to be healed. The observed SCC initiation mechanism was not associated with simple preferential chemical attack of the ferrite GBs. (C) 2003 Elsevier Ltd. All rights reserved.

Research on the BET surface area and packing of molecules on the activated carbon

Adsorption of different aromatic compounds (two of them are electrolytes) onto an untreated activated carbon (F100) is investigated. The experimental isotherms are fitted into Langmuir homogenous and heterogeneous Model. Theoretical maximum adsorption capacities that are based on the BET surface area of the adsorbent cannot be close to the real value. The affinity and the heterogeneity of the adsorption system observed to be related to the pK(a) of the solutes. The maximum adsorption capacity (Q(max)) of activated carbon for each solute dependent on the molecular area as well as the type of functional group attached on the aromatic compound and also pH of solution. The arrangement of the molecules on the carbon surface is not face down. Furthermore, it is illustrated that the packing arrangement is most likely edge to face (sorbate-sorbent) with various tilt angles. For characterization of the carbon, the N-2 and CO2 adsorption were used. X-ray Photoelectron Spectroscopy (XPS) measurement was used to surface elemental analysis of activated carbon.

The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater

Adsorption of a basic dye, methylene blue, from aqueous solutions onto as-received activated carbons and acid-treated carbons was investigated. The physical and surface chemical properties of the activated carbons were characterized using BET-N-2 adsorption, X-ray photoelectron spectroscopy (XPS), and mass titration. It was found that acid treatment had little effect on carbon textural characteristics but significantly changed the surface chemical properties, resulting in an adverse effect on dye adsorption. The physical properties of activated carbon, such as surface area and pore volume, have little effect on dye adsorption, while the pore size distribution and the surface chemical characteristics play important roles in dye adsorption. The pH value of the solution also influences the adsorption capacity significantly. For methylene blue, a higher pH of solution favors the adsorption capacity. The kinetic adsorption of methylene blue on all carbons follows a pseudo-second-order equation. (c) 2004 Elsevier Inc. All rights reserved.

The role of histidine residues in low-pH-mediated viral membrane fusion

A central event in the invasion of a host cell by an enveloped virus is the fusion of viral and cell membranes. For many viruses, membrane fusion is driven by specific viral surface proteins that undergo large-scale conformational rearrangements, triggered by exposure to low pH in the endosome upon internalization. Here, we present evidence suggesting that in both class I (helical hairpin proteins) and class 11 (beta-structure-rich proteins) pH-dependent fusion proteins the protonation of specific histidine residues triggers fusion via an analogous molecular mechanism. These histidines are located in the vicinity of positively charged residues in the prefusion conformation, and they subsequently form salt bridges with negatively charged residues in the postfusion conformation. The molecular surfaces involved in the corresponding structural rearrangements leading to fusion are highly conserved and thus might provide a suitable common target for the design of antivirals, which could be active against a diverse range of pathogenic viruses.

Sulphide ore minerals:surface chemical properties

The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.

Hydrophobicity and surface electrostatic charge of conidia of the mycoparasite Coniothyrium minitans

The effect of increasing culture age on cell surface hydrophobicity (CSH) and cell surface electrostatic charge (measured as zeta potential) of conidia from five isolates of Coniothyrium minitans representing three different morphological types was examined. Conidial CSH of three isolates (A2 960/1, CH1 and CH2) decreased with culture age, whereas CSH of two others (B 1300/2 and IMI 134523) remained high for the whole 42 day experimental period. In contrast, cell surface electrostatic charge decreased uniformly in conidia of all five isolates for the first 34 d and then rose slightly at 42 d. The variation in cell surface electrostatic charge (spectrum width) of the sampled conidia decreased with age for all five isolates. In all five isolates cell surface electrostatic charge of conidia became increasingly negative as the pH of the buffer used to suspend conidia was increased from pH 3.0 to 9.0. No relationship between colony morphology of C. minitans and conidial CSH and cell surface electrostatic charge was found.

Effect of the Hofmeister anions upon the swelling of a self-assembled pH-responsive hydrogel

We report the effect of a range of monovalent sodium salts on the molecular equilibrium swelling of a simple synthetic microphase separated poly(methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)-block-poly(methyl methacrylate) (PMMA88-b-PDEA223-b-PMMA88) pH-responsive hydrogel. Sodium acetate, sodium chloride, sodium bromide, sodium iodide, sodium nitrate and sodium thiocyanate were selected for study at controlled ionic strength and pH; all salts are taken from the Hofmeister series (HS). The influence of the anions on the expansion of the hydrogel was found to follow the reverse order of the classical HS. The expansion ratio of the gel measured in solutions containing the simple sodium halide salts (NaCl, NaBr, and NaI) was found to be strongly related to parameters which describe the interaction of the ion with water; surface charge density, viscosity coefficient, and entropy of hydration. A global study which also included nonspherical ions (NaAce, NaNO3 and NaSCN) showed the strongest correlation with the viscosity coefficient. Our results are interpreted in terms of the Collins model,(1) where larger ions have more mobile water in the first hydration cage immediately surrounding the gel, therefore making them more adhesive to the surface of the stationary phase of the gel and ultimately reducing the level of expansion.