Graduate Theses & Dissertations


Trace Metal Geochemistry in Peatlands
Peatlands can be found widely across all latitudes and play a significant role in global cycles within the earth’s biosphere. The anoxic conditions in peatlands promotes the accumulation of organic matter through decreased rates of decomposition and the storage of certain elements, which have received contaminant loading over the course of human existence, with significant increases occurring during the period of industrialization. We assessed global patterns of metal enrichment in peatlands in 439 cores distributed across 5 continents and 21 countries and measured 35 elements by depth increments and by peatland type. Global patterns in enrichment factors (EF’s) were determined for all metals with the majority of metals being found to have a median EF < 2 indicating relatively minor enrichment. Principal component analysis indicated EF’s of 6 metals (Cd, Co, Cu, Ni, Pb, and Zn), 2 metalloids (As and Sb) and Se in the upper peat horizon had similar spatial patterns among peatlands and these elements had generally the highest EF’s with many cores exceeding EF >10 and some having EF values >100. Significant differences in EF’s were found for these 9 “pollution” elements by peatland type and to a greater extent by geographic region, with higher EF values typically occurring in Europe and North America. Enrichment factors for most elements exhibited weak but significant positive correlations with modelled [1850 – present] S deposition. Estimated pools for the “pollution metals” within the 0 - 40 cm depth varied considerably, with median global pools in peat ranging from 12.9 mg m-2 (Sb) to 439 mg m-2 (Zn) for these 9 metals. Climate changes presents a significant risk to global peatland geochemistry due to expected changes in hydrologic regimes, resulting in potentially increased metal mobility though drought-induced peatland acidification, with historic areas previously impacted by industrial activities presenting the greatest risk of metal release to downstream receiving environments. Using a case study, we examined the impact of simulated 30-day drought on pore water chemistry at six sites in a peatland complex in Elliot Lake Ontario that were historically impacted by uranium (U) mining activities. All sites responded similarly to simulated drought with pore water pH significantly declining. The decline in pore water pH was likely due to increasing sulphate (SO42-) concentrations, which accompanied large increases in Al, Ni, Cu, Pb, Zn, and U. Dissolved organic carbon (DOC) increased, which may further enhance Al, Cu, and U mobility as these metals are strongly complexed by organic acids. Metal partitioning (Kd) values could be significantly predicted by pH and DOC although the strength of the relationship varied considerably among sites. Multiple linear regression and the inclusion of SO4-2 improved predictions, indicating that declines in pH as a result of SO4-2 and H+ production primarily governs metals and U partitioning in peatland soils. The results from both studies show that metal enrichment in global peatlands is highly variable, with northern peatlands in industrialized areas presenting the greatest risk of metal release to downstream surface waters based on expected hydrologic impacts from climate change due to historical and on-going metal and S deposition. Author Keywords: Acidification, Climate Change, Drought, Enrichment Factors, Global, Peatlands
Unbridled Potential
Recently, equine assisted learning (EAL) has emerged as a novel approach to building resiliency competencies in at-risk youth. This mixed-methods study presents evaluation results for an 8-week community-based EAL program with 83 young women (age 13-18 years) with a history of interpersonal trauma. Analyses examined changes in self-reported mental health symptoms (posttraumatic, depression) and resiliency factors (sense of mastery, sense of relatedness, emotion regulation) from pre- to post-test and at 1-month and 6-month follow-ups. Changes in outcomes were also correlated with intervention processes (attendance, session ratings) to see if program experiences were associated with differential outcomes. Results showed that EAL has potential in improving resiliency outcomes, at least for those participants who derived greater satisfaction and value from the sessions. Many improvements were sustained over the long term. Participants’ qualitative feedback provided insight into their subjective experiences and highlighted the unique role that horses played in the EAL process. Author Keywords: Emotion Regulation, Equine Assisted Learning, Experiential Learning, Resilience, Sense of Mastery, Sense of Relatedness
Seasonal variation in nutrient and particulate inputs and outputs at an urban stormwater pond in Peterborough, Ontario
Stormwater ponds (SWPs) are a common feature in new urban developments where they are designed to minimize runoff peaks from impervious surfaces and retain particulate matter. As a consequence, SWPs can be efficient at retaining particle-bound nutrients, but may be less efficient at retaining nutrients that are present primarily in the dissolved form, like nitrogen (N). However, the forms of nutrients (e.g. particulate vs. dissolved) likely differ with hydrologic and seasonal conditions and few studies have examined year-round differences in nutrient forms and concentrations at urban SWPs. In order to contrast total suspended solids (TSS), phosphorus (P) and nitrogen (N) levels between low and high flow conditions, sampling was conducted at an urban SWP in Peterborough, ON between November 2012 and October 2013. Only an increase in TSS levels at the outflow between low and high flow conditions was observed, as well as a decrease in TSS levels at the outflow compared to Inflow 1 under low flow conditions. Nitrate-N (NO3-N) was the dominant form of N entering the pond under all flow conditions, whereas the fraction of total-P (TP) that was particulate increased under high flow conditions. Nevertheless, the dissolved fraction of TP was consistently high in these urban inlets. Only NO3-N was significantly greater in the inflows than outflow and only under low flow conditions. Increases in the proportions of organic-N and ammonium-N in the outlet suggest that biological processing is important for N retention. Author Keywords: nitrogen, Ontario, phosphorus, stormwater ponds, total suspended solids
Mixed methods approaches in marine mammal science
This thesis explored the contribution of mixed methods approaches to marine mammal science through the use of concurrent and sequential designs to study distribution and feeding ecology of bowhead whales (Balaena mysticetus) in the Arctic region of Nunavik, Quebec, Canada. The study combines Inuit knowledge (IK), collected through semi-directed interviews with Inuit harvesters, and analyses of stable isotopes and trace elements (SI/TE) in baleen plates. A systematic literature review found that mixed methods are increasingly used in marine mammal ecology studies in remote locations, yet are still relatively rare and face a number of challenges. Both IK and SI/TE, indicated that bowhead whales have a seasonal pattern in their distribution and feeding ecology. They are most commonly present in productive nearshore areas in summertime, feeding in areas of great prey diversity, and moving to offshore areas in winter to fast. Mixed methods approaches used in this case study enabled the collection of complementary knowledge about bowhead whale ecology important for local management in a changing climate. This study also shows the value of mixed methods approaches for future marine mammal studies in Nunavik and elsewhere. Author Keywords: Arctic, bowhead whale, distribution, feeding ecology, mixed methods, traditional ecological knowledge
Capital Ratios and Liquidity Creation
Using quarterly data from the six largest Canadian banks, we investigate the relationship between regulatory capital ratio and on-balance sheet liquidity created in the Canadian economy by “Big Six”. We find a significant positive relationship between Tier 1 capital ratio and on-balance sheet liquidity creation for Canadian big six banks, implying that large banks in Canada favor risks and rely on capital to fund illiquid assets. In contrast, for smaller banks, the relationship is significantly negative. Our results are robust to dynamic panel regression using 2-Step GMM, two exogenous shocks - COVID-19 crisis and the Global Financial Crisis (2007-2009), mergers & acquisitions activities in the banking industry, and core deposits financing. The COVID-19 pandemic and core deposits adversely impact the Tier 1 capital ratio’s relationship with on-balance-sheet liquidity creation, while the global financial crisis (2007-2009) effect on the association is insignificant. Author Keywords: Big Six, COVID -19, Deposits, Liquidity Creation, Tier 1 Capital Ratio,
Chemical characterization of dissolved organic matter in relation with hydrography in the Arctic Ocean
In this thesis, water mass distribution of dissolved organic matter (DOM) characteristics (i.e. molecular weight, fluorescent components, thiols and humic substances concentration) was observed in the Arctic Ocean. For the first time, DOM molecular weight (MW) in Beaufort Sea was assessed using asymmetrical flow field-flow fractionation, as well as the first monitoring of thiols and humic substances (HS) using cathodic stripping voltammetry (CSV) in the Arctic Ocean. Based on fluorescence property, DOM characterization was carried out using parallel factor analysis – excitation-emission matrices. Pacific winter waters in the Canada Basin showed higher MW DOM associated with higher fluorescence intensity. High HS was associated with the Arctic outflow waters in top 300 m of the Canadian Arctic Archipelago. Interestingly, maximum thiol concentration was associated with the subsurface chlorophyll-a maximum at most sites, but not universal along the study area. Comparable distributions of CSV-based HS and humic-like fluorescent components suggest similar sources/ processes in the Arctic Ocean. The findings in this thesis suggested DOM characteristics could be used as fingerprints in tracing water masses in the Arctic Ocean. Author Keywords: Asymmetrical flow field-flow fractionation, Cathodic stripping voltammetry, DOM, Metal-binding ligands, Molecular weight, PARAFAC-EEMs
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
Fate of Silver Nanoparticles in Lake Mesocosms
The fate of silver nanoparticles (AgNPs) in surface waters determines the ecological risk of this emerging contaminant. In this research, the fate of AgNPs in lake mesocosms was studied using both a continuous (i.e. drip) and one-time (i.e. plug) dosing regime. AgNPs were persistent in the tested lake environment as there was accumulation in the water column over time in drip mesocosms and slow dissipation from the water column (half life of 20 days) in plug mesocosms. In drip mesocosms, AgNPs were found to accumulate in the water column, periphtyon, and sediment according to loading rate; and, AgNP coating (PVP vs. CT) had no effect on agglomeration and dissolution based on filtration analysis. In plug mesocosms, cloud point extraction (CPE), single-particle-inductively coupled mass spectroscopy (spICP-MS), and asymmetrical flow field-flow fractionation (AF4-ICP-MS) confirmed the temporal dissolution of AgNPs into Ag+ over time; however, complexation is expected to reduce the toxicity of Ag+ in natural waters. Author Keywords: AF4-ICP-MS, cloud point extraction, fate, mesocosms, silver nanoparticles, SP-ICP-MS
Effects of Local, Landscape, and Temporal Variables on Bobolink Nest Survival in Southern Ontario
Populations of grassland birds, including the Bobolink (Dolichonyx oryzivorus), are experiencing steep declines due to losses of breeding habitat, land use changes, and agricultural practices. Understanding the variables affecting reproductive success can aid conservation of grassland species. I investigated 1) whether artificial nest experiments accurately estimate the impacts of cattle on the daily survival rate of Bobolink nests and 2) which local, landscape, and temporal variables affect daily survival rate of Bobolink nests in Southern Ontario. I replicated an artificial nest experiment performed in 2012 and 2015 to compare the daily survival rate of artificial and natural nests at multiple stocking rates (number of cattle × days × ha-1). I also monitored Bobolink nests and modeled daily survival rate using local variables (e.g., stocking rate, field use, patch area), landscape variables (e.g., percent forest within 2, 5, and 10 km), and temporal variables (e.g., year, date of season). Results indicate that artificial nest experiments using clay shooting targets overestimated the impacts of stocking rate on the daily survival rate of Bobolink nests. With natural nests, region (confounded by year and field use), stocking rate, and date of season were the strongest predictors of daily survival rate; with stocking rate and date of season both having a negative effect. Management should focus on conserving pastures with low stocking rates (< 40 cattle × days × ha-1), late-cut hayfields, fallow fields, and other grasslands to protect breeding grounds for the Bobolink and other declining grassland bird species. Author Keywords: Bobolink, Daily survival rate, landscape variables, local variables, Nest survival, temporal variables
Impaired contextual fear discrimination learning after long-term amygdala kindling
Cognitive impairments, such as memory loss, are a frequent and devastating co-morbidity associated with epilepsy. The neurobiological mechanisms through which recurrent seizures induce cognitive impairments are not well understood. New neurons born after seizures develop abnormal morphological and functional characteristics that promote network hyperexcitability and hippocampal dysfunction. Previously, we found that kindling dramatically increases the rate of neurogenesis at early stages of seizure development, followed by a long-term suppression at later stages. These changes in the rate of cell proliferation coincides with aberrant modifications in the migration, excitability, and functional integration of these new neurons. It has been suggested that the long-term consequences of seizure-induced neurogenesis contributes to the development of cognitive impairment seen in chronic epilepsy. However, direct experimental evidence has been limited. The present series of experiments sough to determine if blocking aberrant seizure-induced neurogenesis can reduce cognitive deficits associated with chronic epilepsy. Our findings suggest that chronic seizures impair the ability of rats to differentiate between similar contexts. In addition, blocking aberrant seizure-induced neurogenesis through treatment with the cytotoxic agent temozolomide was capable of preventing some of the deficits in context discrimination learning when neurogenesis levels were reduced to non-epileptic control levels. This research provides further support of targeting aberrant neurogenesis as a novel treatment to restore cognitive functioning in individuals living with epilepsy. Author Keywords: Amygdala kindling, Dentate gyrus, Hippocampus, Neurogenesis, Pattern separation, Seizures
Exploring reproduction in wild blue lupine (Lupinus perennis) in comparison to L. polyphyllus and L. albus
Wild lupine (Lupinus perennis) restoration efforts seek to increase and connect populations, using seeds, to facilitate the recovery of endangered butterflys in Ontario. This study observed plant growth and phytohormone levels of L. albus, L. polyphyllus, and L. perennis through stages of seed development, each with varying strategies in growth and reproductive investment. L. polyphyllus is similar to L. perennis in morphology, acting as similar comparable with L. albus, a well-studied annual, as an outgroup comparator. Wild lupines showed a lack of sexual reproductive effort as they did not put as much effort into above ground growth, and few in the population reproduces. They also showed cis-zeatin, a weaker cytokinin, throughout development and had higher amounts of abscisic acid at the end of seed maturity, impacting their ability to develop and germinate. These factors contribute to why wild lupines are difficult to restore using seeds, limiting expansion and challenging restoration. Author Keywords: L. albus, L. perennis, L. polyphyllus, plant physiology, seed development, Wild blue lupine
Exploring Characteristics of those Utilizing Different Modalities of Treatment for Substance Use Disorders
Substance use disorder (SUD) is a pervasive psychological disorder detrimentally impacting both individuals and society on a psychological, economic, and social level. The best protocol for treating SUD as well as what defines success in treatment is often debated in the research. However, researchers agree that different psychosocial factors can influence outcomes. The literature suggests that mood, dark personality traits (narcissism and psychopathy), social supports, and state of change may be associated with treatment for SUD. The current study explored whether these factors predicted the type of treatment (abstinence-based or harm reduction) individuals with SUD were in. The sample consisted of 37 participants in a 12-step abstinence-based program and 65 in a harm reduction program at a local hospital. Results indicated that those in abstinence-based groups reported significantly fewer symptoms of anxiety and depression, lower levels of narcissism and psychopathy, more social supports, and advanced stage of change in comparison to those attending a harm reduction program. In addition, depression, narcissism, and perceived social support were significant predictors of treatment group membership. These findings suggest that those involved in abstinence-based groups appear to experience overall more wellness than those in harm reduction. Although further research is needed to specify the relations among factors, this study is a step towards understanding the difference between people who utilize one program versus another. Author Keywords: Abstinence, Addiction, Harm Reduction, Personality, Treatment


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Format: 2024/02/22