Graduate Theses & Dissertations

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ASSESSING THE IMPACT OF ATMOSPHERIC DEPOSITION AND HARVEST INTENSITY ON SOIL ACIDITY AND NUTRIENT POOLS IN PLANTATION FORESTS
The objective of this thesis was to assess the influence of anthropogenic sulphur (S) and nitrogen (N) deposition, and harvesting on soil acidity and calcium (Ca2+), magnesium (Mg2+), potassium (K+) and N soil pools in plantation forest soils in Ireland. The response to reductions in anthropogenic S deposition was assessed using temporal trends in soil solution chemistry at two long-term monitoring plots--one on a blanket peat, the other on a peaty podzol. At the peat site, there was little evidence of a response to reductions in throughfall non marine sulphate (nmSO42-) and acidity; soil water acidity was determined by organic acids. In addition, temporal variation in soil water did not respond to that in throughfall. In the podzol, reductions in anthropogenic S and H+ deposition led to a significant improvement in soil water chemistry at 75 cm; pH increased and total aluminum (Altot) concentrations declined. The impact of harvest scenarios on exchangeable Ca2+, Mg2+ and K+ pools was assessed using input-output budgets at 40 sites (30 spruce, 10 pine). Harvest scenarios were stem-only harvest (SOH), stem plus branch harvest (SBH) and stem, branch and needle harvest (whole-tree harvesting; WTH). Average K+ and Mg2+ budgets were positive under these scenarios. However, exchangeable K+ pools were small and due to uncertainty in K+ budgets, could be depleted within one rotation. Average Ca2+ budgets for spruce were balanced under SOH, but negative under SBH and WTH. Nitrogen deposition was high, between 5 and 19 kg N ha-1 yr-1, but was balanced by N removal in SOH. However, N budgets were under SBH and WTH, indicating that these harvesting methods would lead to depletion of soil N over the long-term. Finally, monitoring of N cycling at a spruce plot indicated that N deposition was contributing to large NO3- leaching, and as such the site was N saturated. However, N cycling did not fit the criteria of the N saturation hypothesis; instead leaching was directly related to N deposition and supported the model of kinetic N saturation. Author Keywords: acidic deposition, base cations, input-output budgets, Ireland, nitrogen, whole-tree harvesting
Abject Utopianism and Psychic Space
This dissertation utilizes the psychoanalytic theories of French psychoanalyst Julia Kristeva as a lens through which to read the novels of American author Samuel R. Delany. I argue that concepts proper to Kristeva's work--namely abjection and/or the abject--can provide a way to think what it might mean to be utopian in the 21st century. Delany's novels are received historically, which is to say his work speaks from a certain historical and cultural viewpoint that is not that of today; however, I claim that his novels are exceptional for their attempts to portray other ways of being in the world. Delany's novels, though, contain bodies, psychologies, and sexualities that are considered abject with respect to contemporary morality. Nonetheless, this dissertation argues that such manifestations of abject lived experience provide the groundwork for the possibility of thinking utopianism differently today. Throughout, what I am working toward is a notion that I call Abject Utopianism: Rather than direct attention toward those sites that closely, yet imperfectly, approximate the ideal, one should commit one's attention to those sights that others avoid, abscond, or turn their nose up at in disgust, for those are the sites of hope for a better world today. Author Keywords: Abject, Delany, Kristeva, Literary Criticism, Psychoanalysis, Utopia
Absorbance and Fluorescence Characteristics of Dissolved Organic Matter in North Atlantic, Pacific and Arctic Oceans
This thesis was designed to quantify absorbance and fluorescence characteristics of dissolved organic matter (DOM) in North Atlantic, Pacific and Arctic Oceans. DOM was described in water masses of distinct sources and formation pathways as well as in regions where environmental forcings such as deep water upwelling, enhanced biological activity and receipt of freshwater discharge were prevalent. Influence of sea ice on DOM in Beaufort Sea mixed layer (0 to 30 m) seawater was investigated based on sea ice extent as well as freshwater fractions of meteoric (fmw) and sea ice melt water (fsim) calculated from oxygen isotope ratio (δ18O). The effect of DOM exposure to simulated solar radiation was also assessed to determine the resilience of fluorescent fractions of DOM to photodegradation. This research aims to further our ability to trace DOM in marine environments and better understand its transformation pathways and predict its fate as part of the oceanic carbon cycle in a changing climate. Author Keywords: Absorbance, Arctic Ocean, Dissolved organic matter, Fluorescence, Parallel Factor Analysis, Sea Ice
Abundance and Distribution of Microplastics in Lake Scugog Catchment, Ontario
Plastic pollution is a growing concern, owing to its durability, ubiquity, and potential health impacts. The overall objective of this study was to assess the abundance and distribution of microplastics within Lake Scugog catchment, Ontario. This was fulfilled through two tasks (i) the development of a microplastic particle budget for the lake catchment, and (ii) the determination of the dry deposition of atmospheric microplastics in Port Perry, Ontario. The total input of microplastics into Lake Scugog (atmospheric deposition and stream inflow) was 2491 x106 mp/day, while the output (lake outflow and sedimentation) was 1761 x106 mp/day, suggesting that 29% of inputs were retained in the lake. The dry deposition of microplastics in Port Perry was 1257 mp/m2/day, which was high when compared to bulk deposition (37 mp/m2/day) in the same area. By quantifying the major pathways of microplastics better management techniques can be implemented. Author Keywords: Catchment, Dry Deposition, Microplastics, Ontario, Particle Budget, Plastic pollution
Academic Efficiency
Universities produce a significant and increasing share of basic research that is later commercialized by firms. We argue that the university's prominence as a producer of basic research is the result of a differential efficiency in research production that cannot be replicated by firms or individual agents - teaching. By using research accomplishments to signal knowledge and attract tuition-paying students, universities are uniquely positioned to undertake certain types of research projects. However, in a market for innovation without patent rights, a significant and increasing number of basic research projects, that are social welfare improving, cannot be initiated by firms or universities. The extension of patent rights to university-generated research elegantly redresses this issue and leaves us to ponder important questions about the future of our innovation-driven economies. Author Keywords: Innovation, Intellectual Property Rights, Research, Science Technology and Innovation Policy
Achieving Equity in Mathematics Education
Little thought is given to how equitable mathematics would better the lives of those marginalized, or how the increased inclusion of marginalized voices improves the practice of mathematics. The purpose of this narrative research is to explore students’ voices and analyze aspects of math identity: the reported beliefs and practices of a group of elementary urban students who identify as Black/Brown. Understanding voice through counter-narrative is a methodology for the equitable practice of teaching/learning mathematics. CRRP describes participants engaged in the metacognitive task of writing untold stories as it relates to their beliefs, practices, and experiences in mathematics learning. The findings offer meaningful and appropriate insights to math educators about student competency, belongingness, and agency. Keywords: Black and Brown, marginalized students, student engagement, math identity, mathematical competence, sense of belonging to mathematics, mathematical agency, gateway, gatekeeper, fixed mindset, growth mindset, STEM pipeline, counter narrative. Author Keywords: Black and Brown, marginalized students, mathematical competence, math identity, sense of belonging to mathematics, student engagement
Acidification of lakes in northern Saskatchewan
The emission of acid precursors by large point sources in Western Canada (such as the Athabasca Oil Sands Region) has prompted studies into the possible impact to downwind aquatic and terrestrial ecosystems. Sensitivity of catchments to acidic deposition was estimated for the total lake population of northern Saskatchewan (n=89,947) using regression kriging. Under the Steady State Water Chemistry model, a range of 12-15% of the total catchment population was predicted to be in exceedance of critical loads under 2006 deposition levels and 6% of catchments were estimated to be very sensitive (pH below 6 and acid neutralizing capacity, alkalinity, calcium below 50 eqL-1). Temporal changes in soil and water chemistry estimated for 18 Alberta and Saskatchewan catchments using the Very Simple Dynamic and PROFILE models showed that changes in soil base saturation and lake acid neutralizing capacity between 1850 and 2100 were slight, declining 0.8% and 0.9% by 2012, respectively. Author Keywords: acidification, critical loads, exceedance, PROFILE, regression kriging, VSD
Active layer thermal regime in subarctic wetlands at the southern edge of continuous permafrost in Canada
The fine-scale controls of active layer dynamics in the subarctic at the southern edge of continuous permafrost are currently poorly understood. The goal of this thesis was to understand how environmental conditions associated with upland tundra heath, open graminoid fen, and palsas/peat plateaus affected active layer thermal regime in a subarctic peatland in northern Canada. Indices of active layer thermal regime were derived from in-situ measurements of ground temperature and related to local measurements of air temperature, snow depth, and surface soil moisture. Active layer thaw patterns differed among landforms, with palsas and tundra heath having the least and greatest amount of thaw, respectively. Tundra heath thaw patterns were influenced by the presence of gravel and sandy soils, which had higher thermal conductivity than the mineral and organic soils of fens and palsas. Vegetation also influenced thaw patterns; the lichen cover of palsas better protected the landform from incoming solar radiation than the moss, lichen, and low-lying shrub cover of upland tundra heath, thus allowing for cooler ground temperatures. Air temperature was the most significant predictor of active layer thermal regime. Surface soil moisture varied among landforms and greater surface soil moisture reduced the amount of active layer thaw. These findings improved understanding of how landform and climate can interact to affect the active layer. Author Keywords: Active layer thermal regime, Active layer thickness, Climate change, Peatland, Permafrost, Subarctic
Adaptive Genetic Markers Reveal the Biological Significance and Evolutionary History of Woodland Caribou (Rangifer tarandus caribou) Ecotypes
Migratory and sedentary ecotypes are phenotypic distinctions of woodland caribou. I explored whether I could distinguish between these ecotypes in Manitoba and Ontario using genetic signatures of adaptive differentiation. I anticipated that signatures of selection would indicate genetic structure and permit ecotype assignment of individuals. Cytochrome-b, a functional portion of the mitochondrial genome, was tested for evidence of adaptation using Tajima’s D and by comparing variations in protein physiology. Woodland caribou ecotypes were compared for evidence of contemporary adaptive differentiation in relation to mitochondrial lineages. Trinucleotide repeats were also tested for differential selection between ecotypes and used to assign individuals to genetic clusters. Evidence of adaptive variation in the mitochondrial genome suggests woodland caribou ecotypes of Manitoba and Ontario corresponded with an abundance of functional variation. Woodland caribou ecotypes coincide with genetic clusters, and there is evidence of adaptive differentiation between migratory caribou and certain sedentary populations. Previous studies have not described adaptive variation in caribou using the methods applied in this study. Adaptive differences between caribou ecotypes suggest selection may contribute to the persistence of ecotypes and provides new genetic tools for population assessment. Author Keywords: Adaptation, Cytochrome-B, Ecotype, RANGIFER TARANDUS CARIBOU, Selection, TRINUCLEOTIDE REPEAT
Adoption of a Finite Element Model of Material Deformation Relevant to Studying Corneal Biomechanics
The human cornea is required to exhibit specific material properties to maintain its regular shape under typical intraocular pressures which then allow for its correct optical functionality. In this thesis, the basis of continuum solid mechanics and the finite element method are introduced. We use finite element modelling to simulate the extension of an effective-1d, linear-elastic bar, a cornea-like body governed by Poisson’s equation, and the deformation of a loaded, linear-elastic, cube. Preliminary results for the deformation of a simulated, linear-elastic, cornea have also been achieved using the finite element approach. Author Keywords: continuum solid mechanics, corneal biomechanics, finite element method, intraocular pressure
Advanced broadband CARS microscopy based on a supercontinuum-generating photonic crystal fiber
I have developed and improved a coherent anti-Stokes Raman scattering (CARS) microscope based on the spectral focusing (SF) technique. The CARS microscope uses an 800 nm oscillator and a photonic crystal fibre module to generate the supercontinuum Stokes. The photonic crystal fibre was originally designed to generate light beyond 945 nm which is useful for CARS microscopy in the CH/OH frequencies but essentially prevents access to the important fingerprint region at lower frequencies. With expert and nontraditional approaches to generating supercontinuum with sufficient power at wavelengths below 945 nm, I substantially extend the usefulness of the module for SF-CARS microscopy deep into the fingerprint region. Moreover, with the invention of a dynamic supercontinuum generation scheme we call "spectral surfing," I improve both the brightness of the CARS signal and extend the accessible CARS frequency range to frequencies as low as 350 cm$^{-1}$ and as high as 3500 cm$^{-1}$---all in a single scan-window. I demonstrate the capabilities of our broadband SF-CARS system through CARS and four-wave mixing hyperspectroscopy on samples such as astaxanthin, lily pollen and glass; liquid chemicals such as benzonitrile, nitrobenzene and dimethyl sulfoxide; and on pharmaceutical samples such as acetaminophen, ibuprofen, and cetirizine. Furthermore, In search of more useful Stokes supercontinuum sources, I compare the performance of two commercial photonic crystal fibre modules for use in SF-CARS applications, ultimately finding that one module provides better spectral characteristics for static supercontinuum use, while the other provides improved characteristics when spectral surfing is implemented. Author Keywords: coherent anti-Stokes Raman scattering, nonlinear microscopy, scanning microscopy, spectroscopy, supercontinuum generation, vibrational spectroscopy
Aeolian Impact Ripples in Sand Beds of Varied Texture
A wind tunnel study was conducted to investigate aeolian impact ripples in sand beds of varied texture from coarsely skewed to bimodal. Experimental data is lacking for aeolian megaripples, particularly in considering the influence of wind speed on ripple morphometrics. Additionally, the modelling community requires experimental data for model validation and calibration. Eighteen combinations of wind speed and proportion of coarse mode particles by mass were analysed for both morphometrics and optical indices of spatial segregation. Wind tunnel conditions emulated those found at aeolian megaripple field sites, specifically a unimodal wind regime and particle transport mode segregation. Remote sensing style image classification was applied to investigate the spatial segregation of the two differently coloured size populations. Ripple morphometrics show strong dependency on wind speed. Conversely, morphometric indices are inversely correlated to the proportion of the distribution that was comprised of coarse mode particles. Spatial segregation is highly correlated to wind speed in a positive manner and negatively correlated to the proportion of the distribution that was comprised of coarse mode particles. Results reveal that the degree of spatial segregation within an impact ripple bedform can be higher than previously reported in the literature. Author Keywords: Aeolian, Impact Ripples, Megaripple, Self-organization, Wind Tunnel

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Graduate student theses produced at Trent University. You may also browse theses and dissertations by year, program, or author.

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