Graduate Theses & Dissertations

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Temporal Variability of Coloured Dissolved Organic Matter in the Canada Basin, Arctic Ocean (2007-2017)
This thesis investigated coloured and fluorescent dissolved organic matter in the Canada Basin, Arctic Ocean from 2007 to 2017. The first interannual time-series of its kind in the Canada Basin incorporated the use of EEM-PARAFAC to validate a seven-component model. Statistical temporal tests revealed (1) an increasing protein-like intensity in the upper polar mixed layer (UPML); (2) increasing intensities of humic-like components in the halocline due to increasing freshwater content; and (3) no change in DOM composition in deeper Atlantic waters (AW) congruent with the long residence time of the water mass (> 30 years). The significant decline in sea ice concentration was related to a decrease in humic-like FDOM due to enhanced photodegradation and an increase in protein-like FDOM, likely the results of increased biological activities in surface layers. This research provides evidence that the changes in physical and biological environment in the Arctic regions have already profound impacts on the composition and distribution of FDOM. Author Keywords: absorbance, Arctic Ocean, dissolved organic matter, fluorescence, parallel factor analysis, time-series
Monitoring and fate of selected tire-derived organic contaminants
Road runoff is a vector for the transport of potentially toxic chemicals into receiving waters. In this study, selected tire-derived chemicals were monitored in surface waters of rivers adjacent to two high traffic highways in the Greater Toronto Area in Ontario, Canada. Composite samples were collected from the Don River and Highland Creek in the GTA during 5 hydrological events that occurred in the period between early October 2019 and late March 2020, as well as an event in August 2020. Grab samples were collected from these rivers during a period of low flow in August 2020, as well as during a storm event in July of 2020. Analysis was performed using ultra-high pressure liquid chromatography with high resolution mass spectrometric detection (UHPLC-HRMS). Hexamethoxymethylmelamine (HMMM), a cross-linker of tire material, was detected at elevated concentrations (> 1 µg/L) during rain events in the fall and winter of 2019-20 and during a period of rapid snow melt in early March of 2020. These samples were also analyzed for the tire additive, 6PPD, and its oxidation by-product, 6PPD-quinone, as well as 1,3-diphenylguanidine (DPG). In many samples collected from the Don River and Highland Creek during storm events, the estimated concentrations of 6PPD-quinone exceeded the reported LC50 of 0.8 µg/L for Coho salmon exposed to this compound. Temporal samples collected at 3-hour intervals throughout rain event the October 2020 showed that there was a delay of several hours after the start of the event before these compounds reached their peak concentrations. In addition, 26 candidate transformation products and precursor compounds of HMMM were monitored; 15 of these compounds were detected in surface waters in the GTA. The maximum total concentration of this class of methoxymethylmelamine compounds in surface water samples was estimated to be 18 µg/L. There is limited knowledge about the properties of HMMM, its precursor contaminants, and its transformation compounds, as well as their fate in the environment. COSMO-RS solvation theory was used to estimate the physico-chemical properties of HMMM and its derivatives. Using the estimated values for these properties (e.g., solubility, vapour pressure, log Kow) as inputs to the Equilibrium Criterion (EQC) fugacity-based multimedia model, the compounds were predicted to readily partition into aqueous media, with mobility in water increasing with the extent of loss of methoxymethyl groups from HMMM. Overall, this study contributes to the growing literature indicating that potentially toxic tire-wear compounds are transported via road runoff into urban surface waters. In addition, this study provides insight into the environmental behaviour of HMMM and its transformation products. Author Keywords: 6PPD-quinone, COSMOtherm, Fugacity, Hexamethoxymethylmelamine, Road runoff, Tire wear
Extraction and Characterization of Hyaluronic Acid and Collagen from Eggshell Membrane Waste
Connecting academia to industry is one important way to advance towards meeting the United Nations (UN) Sustainability Goals (SDGs).1 Sustainability can be applied to all industrial sectors with the SDGs being implemented by 2030.2 This research contributes to the SDGs by investigating a way to remediate an industrial waste stream in the egg-breaking industry. If adopted, this would reduce the amount of eggshell membrane (ESM) waste placed in landfill where it does not decompose properly. The work described in this thesis specifically targets extraction of collagen and hyaluronic acid (HA), two components of the ESM that are of commercial value in the cosmetic, pharmaceutical, and biomedical industries3,4 . Deliverables from this research include economically viable extraction methods, developed based on green chemistry approaches, that can be transferred from lab bench to industrial scale. The extraction development process was guided by the 12 Principles of Green Chemistry5,6,7 and the 12 Principles of Green Engineering.8 HA was most successfully extracted using a sodium acetate solution on ground ESM. Filtrate was collected, exhaustively dialyzed and lyophilized. High molecular weight HA was recovered. Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy and proton nuclear magnetic resonance (NMR) spectroscopy compared extracted material to reference HA identifying successful extraction. Collagen was extracted using acetic acid or pepsin enzyme digestion. Hydrophilic interaction liquid chromatography (HILIC) coupled with mass spectrometry (MS) compared amino acid composition of extracted materials to reference collagen material. FTIR-ATR spectra also supported successful extraction of collagen. This work identifies that HA and collagen can be conveniently extracted from ESM using an economical approach that can be implemented into egg-breaking facilities. This work highlights the benefits of connecting academia to industry to advance green chemical approaches while implementing sustainable practices into existing industry. Author Keywords: collagen, eggshell membrane waste, extraction, green chemistry, hyaluronic acid, sustainability
Automated Separation and Preconcentration of Ultra-Trace Levels of Radionuclides in Complex Matrices by Online Ion Exchange Chromatography Coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Radionuclides occur in the environment both naturally and artificially. Along with weapons testing and nuclear reactor operations, activities such as mining, fuel fabrication and fuel reprocessing are also major contributors to nuclear waste in the environment. In terms of nuclear safety, the concentration of radionuclides in nuclear waste must be monitored and reported before storage and/or discharge. Similarly, radionuclide waste from mining activities also contains radionuclides that need to be monitored. In addition, a knowledge of ongoing radionuclide concentrations is often required under certain ‘special’ conditions, for example in the area surrounding nuclear and mining operations, or when nuclear and other accidents occur. Thus, there is a huge demand for new methods that are suitable for continuously monitoring and rapidly analyzing radionuclide levels, especially in emergency situations. In this study, new automated analytical methods were successfully developed to measure ultra trace levels of single or multiple radionuclides in various environmental samples with the goal of faster analysis times and less analyst involvement while achieving detection limits suitable for typical environmental concentrations. Author Keywords: automation, ICP-MS, ion exchange, radionuclide
Electrochemical Biosensors for Neurodegenerative Disease Biomarkers
The onset of neurodegenerative diseases such as Alzheimer’s disease (AD) and amyotrophic lateral sclerosis (ALS) are typically characterised by the aggregation of protein biomarkers into cytotoxic fibrils. Novel means of analysing these biomarkers are needed to expand the literature toward earlier diagnosis of these conditions. Electrochemical sensors could offer the sensitivity and selectivity needed for specialised analysis, including potential point-of-care applications. The AD biomarker Tau, and ALS biomarker TDP-43 proteins are explored here by using a label-free electrochemical sensors. Tau protein was covalently bound to gold electrode surface to study the in vitro mechanisms of aggregation for this protein. An immunosensor to TDP-43 was developed by covalently binding primary TDP-43 antibodies (Abs) on gold electrode surface. A novel direct ELISA sensor for TDP-43 with visual detection and electrochemical quantification was also developed. The results validated the experimental designs toward specialised and selective analysis of these biomarkers and their aggregation mechanisms. Author Keywords: ALS, Alzheimer's, Biosensors, Electrochemistry, Tau, TDP-43
Electrochemical versus Chemical Oxidation of Bulky Phenols
Phenolic compounds are used in industry, such as agriculture and biotechnology, and inevitably end up in our environment. These compounds may serve as a phenolic precursor to produce raw materials for a wide range of applications. Chemical oxidation has been the common synthetic pathway to oxidize phenols and related compounds. However, traditional chemical approaches suffer from use of harsh chemicals, waste generation, and lack of reaction selectivity. Electrochemical synthesis has emerged as an alternative method to mitigate common challenges associated with organic synthesis. Herein, electrochemical oxidation of 2,6-diphenylphenol (DPP) and 2,2-dihydroxybiphenol (DHBP) was carried out and compared to traditional chemical oxidation. Contrasted with chemical oxidation, cyclic voltammetry of DPP resulted in a range of products based on the specific potential ranges used, whereas chemical oxidation of DHBP yield a dark-coloured polymeric product. The electrooxidation and chemical oxidation of DPP and DHBP resulted in a solution colour change, indicative of the formation of new, but different products monitored by UV-vis, and characterized by nuclear magnetic spectroscopy (NMR), X-ray single crystal diffraction, IR spectroscopy, transmission electron microscopy (TEM), and gas chromatography-mass spectrometry (GC-MS). The data indicate that the synthetic outcomes are dependent on the synthetic methodology employed, and that electrooxidation and chemical oxidation can form products unique to the pathway utilized. Author Keywords: chemoselectivity, electrochemistry, phenols, radical, synthesis
Molecular Architectures for Improved Biomaterials Derived from Vegetable Oils – Application to Energy Storage and Lubricants
The replacement of petroleum with renewable feedstock for energy and materials has become a priority because of concerns over the environment and finite nature of petroleum. The structures of the available natural biomass feedstocks fall short in delivering key functionality required in materials such as lubricants and phase change energy storage materials (PCMs). The approach taken in this thesis was to combine select functional groups with vegetable oil derivatives to create novel PCMs and lubricantswhich deliver desired functionality. One series of diester PCMs were prepared with terephthalic acid and fatty alcohols to address known shortcomings of esters. The second class of PCMs are sulfones prepared from oxidation of fatty sulfides to improve thermal energy storage. Overall, the new PCMs presented narrow phase change temperature ranges, high transition temperature (between 67 to 110℃), high transition enthalpy (210 to 266J/g), minimal supercooling and congruent phase transitions unaffected by cooling rates. They also demonstrated higher thermal degradation stability with onset of degradation from 290 to 310℃. The series of lubricants studied consists of sulfide and sulfonyl functional groups attached to the unsaturation sites of oleyl oleate as pendant groups to improve the thermal and flow properties. The new lubricants present subzero crystallization temperatures, very low crystallization enthalpy and dynamic viscosity as high as 180mPas. Furthermore, they also presented high onset of degradation (up to 322℃) and oxidation (up to 298℃). The PCMs and lubricants of the present thesis demonstrate that select functional groups can be used with common structural elements of vegetable oil such as fatty acids, ester groups and unsaturation sites to make a variety of molecular structures capable of delivering desired properties Author Keywords: Crystal Structure, Lubricant, Phase Change Material, Renewable, Structure-Property Relationships, Vegetable Oil

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Format: 2023/01/28