Graduate Theses & Dissertations

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Nitrogen and phosphorus bioavailability in soil amended with alkaline stabilized biosolids
Agricultural land application of biosolids recycles nutrients and organic matter to the soil, however the effect of treatment process on nutrient availability requires further research for better nutrient management. This study examined the bioavailability of nitrogen (N) and phosphorus (P) in alkaline treated biosolids (TB) when amended into three different soils. Despite a 45% reduction in total N and P content during treatment, TB did not show reduced N or P availability compared with sewage sludge (SS). Results of a corn growth experiment and a soil incubation showed that TB amendment resulted in little mineralization and generally net immobilization of N, and 2% total P availability to corn from TB. Results suggest that TB are not a source of bioavailable N in the short-term, but can be used as a P amendment for corn. Nutrient management of agricultural land receiving these materials should focus on P added and liming properties. Author Keywords: Alkaline treated biosolids, Nitrogen, Phosphorus, Soil fertility
Non-Hippocampal Memory Systems Contributing to Reinstated Context Memory
Damage to the hippocampus (HPC) typically causes retrograde amnesia for contextual fear conditioning. Reinstating the conditioning over several sessions, however, can mitigate the retrograde amnesic effects. Reinstatements, thus, establish a sufficiently strong memory in non-HPC systems to no longer require the HPC for expression, meaning that it has become HPC independent. This thesis aimed to determine the structures comprising the non-HPC system supporting reinstated context fear memory. The contribution of the perirhinal cortex (PRH) and the anterior cingulate cortex (ACC) were examined because of their established role in context memory. Initially, it was demonstrated that HPC damage indeed causes retrograde amnesia for single session, but not reinstated, contextual fear conditioning. Then, it was demonstrated that combined HPC and PRH damage causes retrograde amnesia for reinstated contextual fear conditioning, whereas combined HPC and ACC damage had lesser effects. Therefore, the PRH is a key structure within the non-HPC memory system for reinstated context fear memory. Author Keywords: anterior cingulate cortex, contextual fear conditioning, hippocampus, memory, perirhinal cortex, retrograde amnesia
Novel Silica Sol-Gel Passive Sampler for Mercury Monitoring in Aqueous Systems
A novel passive sampler for mercury monitoring was prepared using organosilica sol-gel materials. It comprises a binding layer with thiol groups for mercury complexation and a porous diffusive layer through which mercury can diffuse and arrive at the binding layer. Our study demonstrated that this new sampler follows the principle of passive sampling. The mass of mercury accumulated in the binding layer depends linearly on the mercury concentration in solution, the sampling rate and the exposure time. A typical sol-gel sampler is characterized by a diffusive layer of 1.2 &mum, in which mercury ions diffuse with a coefficient of D = 0.09~10-6 cm2/s. The capacity for mercury uptake is approximately 0.64 &mug/cm2. Mercury diffusion and binding in the passive sampler are independent of the type of mercury-chloride complex. Its sampling rate increases with increasing water turbulence and decreases with increasing DOM amount. The field trial of sol-gel sampler in Miller Creek shows the concentration gained from the sol-gel passive sampler is slightly lower than that from the spot sampling. Author Keywords:
Nutritional stoichiometry and growth of filamentous green algae (Family Zygnemataceae) in response to variable nutrient supply
In this study, I investigate the effects of nitrogen (N) and phosphorus (P) on the nutritional stoichiometry and growth of filamentous green algae of the family Zygnemataceae in situ and ex situ. I found a mean of Carbon (C):N:P ratio of 1308:66:1 for populations growing in the Kawartha Lakes of southern Ontario during the summer of 2012. FGA stoichiometry was variable, with much of the variation in algal P related to sediment P (p < 0.005, R2 = 0.58). Despite large variability in their cellular nutrient stoichiometry, laboratory analysis revealed that Mougeotia growth rates remained relatively consistent around 0.28 day-1. In addition, Mougeotia was found to be weakly homeostatic with respect to TDN:TDP supply (1/HNP = 0.32). These results suggest that FGA stoichiometry and growth rates are affected by sediment and water N and P. However, they will likely continue to grow slowly throughout the summer despite variable nutrient supply. Author Keywords: Chlorophyll concentration, Filamentous algae, Growth rate, Homeostatic regulation, Nutritional stoichiometry
Observation-based assessment of atmospheric sulphur surrounding a major aluminum smelter in British Columbia, Canada
Recent developments at an aluminum (Al) smelter in Kitimat, BC resulted in a permitted increase of 27 to 42 tonnes of sulphur dioxide (SO2) emissions per day. Gaseous SO2 is a pollutant known to contribute to acidic deposition through processes of wet and dry deposition and can additionally react in-atmosphere to form particulate sulphate (pSO42-). Between June 2017 to October 2018, an extensive network consisting of ion exchange resin (IER) column, passive-diffusive, and active filter-pack samplers was established to provide an estimate of total annual S deposition and pSO42- variation throughout the Kitimat Valley. Filter-pack sampling determined the relative concentration of pSO42- increased downwind of the smelter. Comparison of observation-based and modelled total annual deposition suggested CALPUFF was accurate in representing the spatial viability of S deposition (R2 = > 0.85). However, the model appeared to overpredict near-field deposition suggesting the potential of underestimation further downwind of the smelter. Author Keywords: aluminum smelter, atmospheric deposition, filter-pack sampler, ion-exchange column sampler, pSO42-, SO2
Organic Matter and Total Mercury in Acid-Sensitive Lakes in Ireland
The following study measured dissolved organic carbon (DOC) and total mercury (THg) concentrations in acid sensitive lakes in the Republic of Ireland. Sixty-eight upland lakes and 48 lowland lakes were sampled for DOC; the upland lakes were additionally sampled for THg. Spatial variability of DOC was explained by regional precipitation and soil organic matter. A subset of lakes was tested for long-term trends and in contrast to reports of rising DOC in European surface waters, changes in DOC were minor. Spatial variability in THg was explained by DOC and organic matter aromaticity. Long-term THg concentrations increased, likely caused by inputs of terrestrial THg. A subset of lakes was sampled for sediment and soil and the results suggested soils drove THg variation in lake water and sediment. Lake water and sediment THg was low and consistent with background regions, while soil THg was relatively high due to high organic content. Author Keywords: Dissolved Organic Carbon, Lakes, Organic Matter, Soil, Total Mercury, Water
Particulate Matter Component Analyses in Relation to Public Health in Canada
This thesis explores the shot-term relationship between exposure to ambient air pollution and human health through metrics such as mortality and hospitalization in Canada. We begin by detailing the organization and interpolation of air pollution data from its partially quality-controlled source form. Analyses of seasonal, regional and temporal trends of all major components of PM2.5, was performed, showing a seasonal variation across most regions and validating the dataset. A one-pollutant statistical Generalized Additive Model was applied to the data, estimating the health risk associated with exposure to thirteen different components of PM2.5. The selected components were based on those that compromised the majority of the mass and included: sulphate, nitrate, zinc, silicon, iron, nickel, vanadium, potassium, organic carbon, organic matter, elemental carbon, total carbon. Trends based on annual estimates of the association for PM2.5, and its constituents,were compared, showing that carbonaceous compounds, sulphate and nitrate had similar estimates of association. Many estimates, as is common in population ecologic epidemiology, had association estimates statistically indistinguishable from zero, but with clear features of interest, including evident differences between cold and warm season associations in Canada's temperate climate. A method to model two correlated pollutants (in this case, PM2.5 and O3) was developed using thin plate splines. In this approach, the location of the response surface (after accounting for the temperature, a smooth function of time and day of week) that corresponds to the average pollutant concentration and the average plus one unit was used as the estimate of the joint contribution of pollutants due to a unit increase. The estimates from the thin plate spline (TPS) approach were compared to the single pollutant models, with large increases and decreases in PM2.5 and O3 being captured in the TPS estimates. However, this approach indicated significantly larger error in the estimates than would be expected, indicating a possible future area for refinement. Author Keywords: Air pollution, Environmental Epidemiology, Generalized Additive Models, Human Health, Multivariate Models, Thin Plate Splines
Passage population size, demography, and timing of migration of Red Knots (Calidris canutus rufa) staging in southwestern James Bay
Many shorebirds rely on small numbers of staging sites during long annual migrations. Numerous species are declining and understanding the importance of staging sites is critical to successful conservation. We surveyed endangered rufa Red Knots staging in James Bay, Ontario during southbound migration from 2009 to 2018. We used an integrated population model to estimate passage population size in 2017 and 2018 and found that up to 27% of the total rufa population staged in James Bay. We also extended the model to incorporate age composition of the passage population. In future applications, this method could improve our understanding of the role of breeding success in population declines. We then estimated annual apparent survival from 2009 to 2018. Survival remained near constant, though lower than estimated elsewhere in the Red Knot range, which may reflect higher permanent emigration rates rather than truly lower survival. This work demonstrates that this northern region is a key staging site for endangered Red Knots and should be included in conservation planning. Author Keywords: integrated population model, mark-recapture, migratory stopover, shorebirds, species at risk, survival
Passive sampling of indoor and outdoor atmospheric nitrogen dioxide in the greater Toronto area
The reliability and performance of four passive sampler membrane coatings specific to nitrogen dioxide (NO2) were evaluated through co-exposure at multiple Ontario Ministry of Environment and Climate Change (OMOECC) active monitoring stations. All four coatings performed relatively similar under a wide range of meteorological conditions, notably showing exposure-specific atmospheric uptake rates. Further, indoor and outdoor atmospheric concentrations of NO2 (a marker of traffic-related air pollution) were evaluated at multiple elementary schools in a high-density traffic region of Toronto, Ontario, using a Triethanolamine based passive sampler membrane coating. Samplers were also co-exposed at OMOECC active monitoring stations to facilitate calibration of exposure-specific atmospheric uptake rates. Indoor NO2 atmospheric concentrations were 40 to 50% lower than outdoor concentrations during the spring−summer and autumn−winter periods, respectively. In large cities such as Toronto (Population 2,700,000), the influence of a single major road on outdoor and indoor NO2 concentrations is predominantly masked by spatially-extensive high-density traffic. Author Keywords: active sampler, membrane coating type, nitrogen dioxide, passive sampler, Toronto, traffic density
Pathogen vs. Predator
Stressors are often an inescapable part of an organism’s life. While the effects of many stressors have been well studied individually, potential interactions between stressors exist that may result in greater than additive negative effects. Stressors may be linked by conflicting demands on energy budgets, interfering with important physiological pathways, or necessitating incompatible adaptive responses. Using Ranavirus (FV3) and larval dragonfly predators (Anax spp.) in a 2x2 factorial experiment on green frog (Lithobates clamitans) tadpoles, I investigate the interactions in behaviour, morphology, and metabolism when both stressors were applied in concert. I demonstrate that activity and feeding are reduced additively by both stressors, and tadpoles increase distance between conspecifics in FV3-exposed tanks, but only in the absence of predators. I also note decreases in mass, and a non-significant marginal increase in metabolic rate of tadpoles exposed to FV3. Interestingly, I provide evidence that FV3 can compromise morphometric responses through antagonistic interactions with perceived predation risk exposure, which may result in significantly elevated mortality even when either stressor is present in sub-lethal quantities. Thus, I conclude that sub-lethal exposure to stressors can nonetheless have substantial impacts on organisms and a more integrative approach to examining the impacts of stressors on individual physiology and fitness is necessary. Author Keywords: Behaviour, Interaction, Morphology, Predation Risk, Ranavirus, Tadpoles
Pathways to Innovation
Research and development activities conducted at universities and firms fuel economic growth and play a key role in the process of innovation. Specifically, prior research has investigated the widespread university-to-firm research development path and concluded that universities are better suited for early stage of research while firms are better positioned for later stages. This thesis aims to present a novel explanation for the pervasive university-to-firm research development path. The model developed uses game theory to visualize and analyze interactions between a firm and university under different strategies. The results reveal that as academic research signals knowledge it helps attract tuition paying students. Generating these tuition revenues is facilitated by university research discoveries, which, once published, a firm can build upon to make new innovative products. In an environment of weak intellectual property rights, moreover, the university-to-firm research development path enables firms to bypass the hefty costs that are involved in basic research activities. The model also provides a range of solution scenarios where a university and firm may find it viable to initiate a research line. Author Keywords: Game theory, Intellectual property rights, Nash equilibrium, Research and development, University to-firm research path
Patterns of Vegetation Succession on Nickel-Copper Mine Tailings near Sudbury, Ontario
Natural establishment of vegetation on mine tailings is generally limited. Understanding the processes leading to vegetation germination and the survival mechanisms that vegetation species employ in these harsh environments is critical to future remediation efforts. As metalliferous mine tailings are generally nutrient-poor, high in harmful metals, and acidic, vegetation species require distinct mechanisms to germinate and survive in such harsh environments. In this study, edaphic and biotic factors linked to vegetation establishment and diversity were studied at two nickel-copper (Ni-Cu) tailings sites near Sudbury, Ontario. One site had experienced minimal treatment, and the second site was split into partial (hand-distribution of lime) and full (lime, fertilizer, seeding) treatment areas. Tailings were generally acidic, low in organic matter and “available” nutrients, and high in metals such as Al, Cu, Fe, and Ni, but these physical and chemical properties were extremely spatially variable. At both sites, vegetation was distributed in sparse patches, with the greatest diversity in treated areas. There was no clear link between metals and vegetation establishment/diversity at the sites. The primary limiting nutrients on the tailings were phosphorous (P) and potassium (K), and while there were areas of increased soil fertility at the sites, they were not clearly associated with increased vegetation diversity. Both traditional ecological succession and nucleation succession patterns were observed on the site, and the chief species associated with nucleation were primary colonizing trees such as B. papyrifera and P. tremuloides. The relationship between B. papyrifera nutrient retranslocation and tailings restoration was assessed and while B. papyrifera at the sites were deficient in P and K, the trees efficiently retranslocated both P and K during senescence. This research can provide insight into possibilities for future revegetation of similar tailings, enabling industry to make educated decisions when choosing where and how to revegetate, mimicking natural succession patterns. Author Keywords: Acid-mine drainage, Betula papyrifera, ecosystem health, metals, Sudbury, tailings

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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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1973 - 2033
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