Graduate Theses & Dissertations

Pages

Potential for Greenhouse Gas Emissions from Sediments of Agricultural Streams and Lake Erie
This thesis examines how dissolved organic matter quantity and quality and nutrients influence the flux potential of greenhouse gases (GHG) from sediments collected from streams across southern Ontario as well as Lake Erie. Sediments were collected and incubated in a laboratory setting where headspace gases and interstitial waters were analyzed. Results demonstrated that nutrients (dissolved organic carbon (DOC), total dissolved phosphorous (TDP) and total dissolved nitrogen (TDN)) were commonly significant predictors of CO2, CH4, and N2O fluxes, but spatial discrepancies were observed for the significance of DOM quality and sedimentary characteristics. Land use was not found to be directly related to gas flux potential. Different relationships were observed between the streams and lake, and between the basins of Lake Erie. Overall, results from this study suggest that sediments from freshwater systems have the potential to be sources of GHG, the degree of which depends on nutrient concentrations and DOM structure from watershed inputs. Author Keywords: dissolved organic matter, greenhouse gases, Lake Erie, nutrients, sediment, streams
Disease ecology of ophidiomycosis in free-ranging snakes
Ophidiomycosis (snake fungal disease) is caused by the pathogen Ophidiomyces ophiodiicola. Infected snakes exhibit dermal lesions, occasional systemic infections, and, in some cases, mortality. We studied snakes at Rondeau Provincial Park, Ontario, Canada, to explore whether ophidiomycosis develops during brumation or year-round. Throughout their active season, we quantified the prevalence of clinical signs of the disease on snakes and conducted qPCR of skin swabs to determine the prevalence of O. ophiodiicola on snakes. Prevalence of O. ophiodiicola and disease symptoms were highest on eastern foxsnakes (Pantherophis vulpinus) and very rare on other snake species. In P. vulpinus, pathogen and clinical sign prevalence was highest, directly after emergence from overwintering, with the majority of P. vulpinus being able to resolve clinical signs of ophidiomycosis by the return of winter. When we analyzed the survivorship of P. vulpinus we determined that the likelihood of a snake dying with ophidiomycosis is similar to a snake dying without ophidiomycosis. Given that P. vulpinus were the most affected species at our study site, ophidiomycosis does not appear to pose an imminent threat to our study population of P. vulpinus under current conditions. Author Keywords: Eastern Foxsnake, Fitness, Ophidiomycosis, Pantherophis vulpinus, Seasonal trends, Snake fungal disease
Effects of wood ash addition on soil chemical properties and sugar maple (Acer saccharum, Marsh.) seedling growth in two northern hardwood forest sites in central Ontario
One possible solution to acidification and losses of base cations in central Ontario forest soils may be the application of wood ash. Wood ash is generally high in pH and contains large amounts of calcium (Ca) and other nutrients essential for ecosystem health, however it also contains trace metals. Understanding the chemistry of soils following ash application to forests is crucial for future policy recommendations and remediation efforts. In this study, soil and soil water chemistry was measured at two acidic forest sites in central Ontario. Sugar maple (Acer saccharum, Marsh.) seedling growth and chemistry, as well as understory vegetation composition, were also measured. At site one, plots (2 m x 2 m) were established with sugar maple, white pine (Pinus strobus L.) and yellow birch (Betula alleghaniensis Britt.) residential wood ash treatments and applied at rates of 0 and 6 Mg ha-1. The effects of residential wood ash on soil and understory vegetation were measured three- and 12-months following ash addition. At site two, plots (5 m x 5 m) were established with both fly and bottom industrial grade bark ash treatments of 0, 4 and 8 Mg ha-1 (n=4), and tension lysimeters were positioned in each plot at 30, 50, and 100 cm depths. The effects of industrial grade wood ash on soil, soil water and understory vegetation were measured four years following ash addition. Metal concentrations in the ashes were generally low but were higher in the fly ash and yellow birch ash types. At site one, significant increase in soil pH, and Ca and magnesium (Mg) concentrations were observed after three months, however changes varied by treatment. Some metal concentrations increased in the upper organic horizons, but metals were likely immobilized in the soil due to increases in soil pH, electrical conductivity (EC) and high organic matter content of the soil. After one year, changes to metal concentrations in soils could be seen in mineral horizons, and a few metals (aluminum (Al), zinc (Zn), copper (Cu), chromium (Cr), strontium (Sr)) increased in treatment plots. At site two, the effects of industrial-grade bark ashes on soil pH could still be seen after four years and soil water metal concentrations were not elevated relative to controls. Changes to understory vegetation composition following ash application were observed, but ash addition had no significant effect on sugar maple seedling growth (root:shoot ratio) and did not lead to significant increases in foliar metal concentrations. There were significant differences in root chemistry, suggesting metal translocation and uptake could be restricted. Mass balance estimates indicate that the organic horizon is a sink for all metals and simulated drought in this horizon led to a decrease in soil pH and increase in soil water metal concentration, but this occurred in all treatments including control. These results suggest that application of industrial and residential wood ash in moderate doses with trace metal concentrations below or near regulatory limits will increase soil pH and base cation concentrations, as well as increase seedling tissue nutrient concentrations in northern hardwood forest soils. However, depending on the parent material of the ash, increased metal availability can also occur. Author Keywords: Acer saccharum, calcium decline, forest soil amendment, Haliburton Forest and Wildlife Reserve, heavy metal, wood ash
Assessing basin storage
Water storage is a fundamental component of drainage basins, controlling the synchronization between precipitation input and streamflow output. The ability of a drainage basin to store water and regulate streamflow may mediate sensitivity to climate and land cover change. There is currently no agreement on the best way to quantify basin storage. This study compares results of a combined hydrometric and isotopic approach for characterizing inter-basin differences in storage across the Oak Ridges Moraine (ORM) in southern Ontario. The ratio of the standard deviation of the stable isotope signature of streamflow relative to that of precipitation has been shown to be inversely proportional to mean water transit times, with smaller ratios indicating longer water transit times and implying greater storage. Stable isotope standard deviation ratios were inversely related to baseflow index values. Basins demonstrating longer transit times were associated with hydrological characteristics that promote infiltration and recharge of storage. Author Keywords: baseflow, basin storage, climate change, mean transit time, Oak Ridges Moraine, stable isotopes
Shorebird Stopover Ecology and Environmental Change at James Bay, Ontario, Canada
I examined how shorebirds respond to environmental change at a key subarctic migratory bird stopover site, the southwestern coast of James Bay, Ontario, Canada. First, I investigated if the morphology of sandpipers using James Bay during southbound migration has changed compared to 40 years prior. I found shorter, more convex and maneuverable wings for sandpipers in the present-day compared to the historical monitoring period, which supports the hypothesis that wing length change is driven by increases in predation risk. Secondly, I assessed the relationship between migration distance, body condition, and shorebird stopover and migratory decisions. Species that travelled farther distances from James Bay to wintering areas migrated with more characteristics of a time-minimizing migration strategy whereas species that travelled shorter distances migrated with energy minimizing strategies. Body condition impacted length of stay, wind selectivity at departure, groundspeeds, and probability of stopover and detection in North America after departing James Bay. Thirdly, I examined annual variation in dry/wet conditions at James Bay and found that shorebirds had lower body mass in years with moderate drought. In the present-day, drought resulted in lower invertebrate abundance and refuelling rates of shorebirds during stopover, which led to shorter stopover duration for juveniles and a higher probability of stopover outside of James Bay for all groups except white-rumped sandpiper. Finally, I estimated the relative importance of intertidal salt marsh and flat habitats to the diets of small shorebirds and found that semipalmated and white-rumped sandpiper (Calidris pusilla and C. fuscicollis) and semipalmated plover (Charadrius semipalmatus) diets consist of ~ 40 – 75% prey from intertidal marsh habitats, the highest documented in the Western Hemisphere for each species. My research shows that James Bay is of high importance to white-rumped sandpipers, which are unlikely to stop in North America after departing James Bay en route to southern South America. Additionally, intertidal salt marsh habitats (and Diptera larvae) appear particularly important for small shorebirds in the region. My thesis shows that changing environmental conditions, such as droughts, can affect shorebird refuelling and stopover strategies. Author Keywords: body condition, diet, environmental change, migration, ornithology, stopover ecology
Investigating the regional variation in frequencies of the invasive hybrid cattail, Typha × glauca
Interspecific hybridization rates can vary depending on genomic compatibilities between progenitors, while subsequent hybrid spread can vary depending on hybrid performance and habitat availability for hybrid establishment and persistence. As a result, hybridization rates and hybrid frequencies can vary across regions of parental sympatry. In areas around the Laurentian Great Lakes, Typha × glauca is an invasive plant hybrid of native Typha latifolia and introduced Typha angustifolia. In areas of parental sympatry in Atlantic Canada and outside of North America, T. × glauca has been reported as either rare or non-existent. I investigated whether the low frequencies of hybrids documented in Nova Scotia, Atlantic Canada, are influenced by reproductive barriers that prevent hybrid formation or environmental factors (salinity) that reduce hybrid performance. I identified an abundance of hybrids in the Annapolis Valley (inland) and a scarcity of hybrids in coastal wetlands through preliminary site surveys throughout Nova Scotia. In Annapolis Valley populations, flowering times of progenitor species overlapped, indicating that asynchronous flowering times do not limit hybrid formation in this region. Viable progeny were created from interspecific crosses of T. latifolia and T. angustifolia from Nova Scotia, indicating that there are no genomic barriers to fertilization and germination of hybrid seeds. Typha × glauca germination in high salinity was significantly lower than that of T. latifolia, but there was no difference at lower salinities. Therefore, while germination of hybrid seeds may be impeded in the coastal wetlands where salinity is high, inland sites have lower salinity and thus an environment conducive to hybrid germination. However, I found that once established as seedlings, hybrids appear to have greater performance over T. latifolia across all salinities through higher ramet production. Moreover, I found that T. latifolia sourced from Ontario had reduced germination and lower survivorship in high salinities compared to T. latifolia sourced from Nova Scotia, which could indicate local adaptation by T. latifolia to increased salinity. These findings underline that interactions between environment and local progenitor lineages can influence the viability and the consequent distribution and abundance of hybrids. This, in turn, can help explain why hybrids demonstrate invasiveness in some areas of parental sympatry but remain largely absent from other areas. Author Keywords: flowering phenology, Hybridization, invasive species, physiology, pollen compatibility, salinity tolerance
Study of Aerosols for use in Water Remediation of Pharmaceutical Pollutants
In this thesis, aerosolization was studied as a possible means of water remediation for several environmentally relevant pharmaceutical pollutants, known for their persistence in wastewater effluent and potable water sources. Seven different pharmaceutical compounds and a well-known plasticizer were all shown to decrease considerably in concentration in aerosol that was produced and subsequently collected within a short time span. Strong evidence is presented that an enhanced rate of partitioning into the gas phase at the air-water interface of water droplets exists for every compound tested relative to that occurring in bulk solution. UV photolysis in aerosols was also explored and shown for sulfamethoxazole to be at least an order of magnitude faster in aerosols then in bulk solution. The implications towards both the environmental fate, and removal of these compounds from water sources is discussed. Author Keywords: Aerosols, Air-water partitioning, Pharmaceuticals, Photolysis, Sulfamethoxazole
Anthropogenic microfibres in background natural environments in Ireland
Microfibres, which are threadlike particles < 5 mm, are the most common type of microplastic reported in the environment. However, few studies have focused on their abundance in background natural environments. This study assessed the abundance of microfibres in rainfall samples (from four precipitation monitoring stations) and across three headwater lake catchments that were in remote, undeveloped areas, away from anthropogenic disturbance and anthropogenic emission sources (i.e., sites were background natural environments). Anthropogenic microfibres were observed in all samples using visual identification methods, with Raman spectroscopy confirming the presence of polyester film and synthetic pigments, e.g., indigo and hostasol green. The estimated annual average atmospheric deposition of microfibres was ~28,800 mf m-2. Meteorological variables, e.g., rain, wind direction, and relative humidity were correlated with the abundance of microfibres. The average abundance of microfibres in headwater lake catchments was 24 mf g-1 in moss, 0.70 mf m-3 in surface trawl, 9,690 mf m-3 in subsurface, 910 mf kg-1 in lake sediment and 576 mf kg-1 in lakeshore sediment. Author Keywords: Atmospheric Deposition, Background Environments, Headwater Lake Catchments, Microfibres, Microplastics, Rainfall
Cytokinins in nematodes
To investigate cytokinins (CKs) in nematodes, CK profiles of a free-living Caenorhabditis elegans and a plant parasitic Heterodera glycines (soybean cyst nematode, SCN) were determined at the egg and larval stages. SCN had higher total CK level than C. elegans; however, CKs in SCN were mostly inactive precursors, whereas C. elegans had more bioactive forms. This is the first study to show that methylthiols are present in nematodes and may affect plant infection. In infectious SCN larvae, methylthiol levels were much higher than in eggs or C. elegans larvae. Furthermore, The CK profiles of SCN-susceptible and resistant Glycine max cultivars at three developmental stages revealed that, regardless of the resistance level, SCN infection caused an increase in root CKs. One resistant cultivar, Pion 93Y05, showed significantly high levels of bioactive N6-isopentenyladenine (iP) in the non-infected roots which indicated a potential role of CKs in soybean resistance to SCN. Author Keywords: Cytokinins, HPLC-MS/MS, Nematode, SCN resistance, Soybean
Ligand Binding Properties of Giardia Flavohemoglobin
The parasitic protist Giardia intestinalis possesses flavohemoglobin (gFlHb), an enzyme that detoxifies nitric oxide to the less harmful nitrate, and is a potential target for antigiardial drugs that act as ligands to the iron of its heme cofactor. In this work, the binding constants KD of gFlHb, three active-site variants (Q54L, L58A, Y30F) and the E. coli flavohemoglobin (Hmp) towards cyanide, azide and several substituted imidazoles were measured by optical titration. Certain cases such as gFlHb and Hmp were studied further by isothermal titration calorimetry. Binding constants for cyanide and the imidazoles ranged from 2 to 100 M, with the highest affinities observed with for miconazole, a bulky substituted imidazole. Azide was a poor ligand, with binding constants between 0.48 and 26 mM. Among gFlHb and its mutants, L58A tended to have the highest ligand affinities, as mutation of the distal leucine to a less bulky distal alanine residue facilitates the access of the exogenous ligand to the heme iron. In contrast, the Q54L and Y30F variants had binding affinities that in most cases were similar to wild type, which suggests that the inability of their side chains to form hydrogen bonds to these ligands is not a significant factor in binding of imidazole ligands to the enzyme. Comparative results for Hmp and gFlHb ligand binding affinities revealed slight differences which might be explained by the presence of different residues in their active sites apart from their conserved residues. Author Keywords: Flavohemoglobin, Giardia intestinalis, Imidazole binding, Ligand binding, Nitrosative stress
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
Investigation of Air Recirculation and Thermal Efficiency within a Climate Controlled Passage
Historically, entrances have been used for passage between two separate temperature environments, such as moving from inside to outside of a building. Energy loss through entrances is a cause for concern, as it has been known to increase energy consumption to replace the lost energy; and with the exchange of air masses and cold air entering the building, human discomfort may occur. In this research, thermal efficiency and air circulation within a Conventional Entrance (CE) and Climate Controlled Passage (CCP) are compared. A small scale model of the CE and CCP was constructed to examine forty-eight energy exchange conditions, emulating those found through an entrance between a temperature controlled lab and the model. Instruments such as a power meter, a flow explorer laser Doppler anemometer, and thermocouples were used to measure and compare the energy consumption, velocity vectors, and temperature energy within the entrance. Results indicate that the CCP did retain thermal energy compared to the CE. The CE developed sloped isotherm lines and air flow that enabled and maintained thermal exhaust. Conversely, the CCP developed horizontal isotherm lines and a two-layer density current to recirculate and retain thermal energy. The research demonstrates that it is possible to increase energy efficiency of entrances in many applications. Author Keywords: Air Recirculation, Building, Entrance, Oven, Thermal Energy Efficiency, Two-layer Density Current

Pages

Description

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

In collections

Search Our Digital Collections

Query

Enabled Filters

  • (-) ≠ Master of Education
  • (-) ≠ Nocera
  • (-) = Environmental and Life Sciences
  • (-) ≠ Balch, Jordan
  • (-) ≠ Farell, Jana
  • (-) ≠ Alshamlih, Mohammed M.
  • (-) ≠ Chemistry

Filter Results

Date

2004 - 2024
(decades)
Specify date range: Show
Format: 2024/05/24

Collection

Author Name

Show more

Name (Any)

Show more

Degree

Subject (Topic)

Show more