- Collections Home
- Alumni House Collection
- Arthur Virtual Archive
- Faculty Research Collection
- Journal GenObs
- Margaret Laurence Collection
- Stories of Resistance, Resurgence, and Resilience in Nogojiwanong / Peterborough
- Trent Community Research Centre Project Collection
- Trent University Academic Calendar Collection
- Trent University Archives
- Trent University Graduate Thesis Collection
- University Heritage Collection
Graduate Theses & Dissertations
Pages
-
- Relationships between Dissolved Organic Matter and Vanadium Speciation in the Churchill River, MB and the Mackenzie River Basin, NWT using diffusive gradients in thin films (DGT)
- This study examines the influence of dissolved organic matter (DOM) on dissolved vanadium (V) speciation in the Churchill River and Great Slave Lake using diffusive gradients in thin film (DGT). Vanadium is commonly found in natural environments such as rivers, lakes and oceans. It regulates normal cell growth, but in excessive amounts, it can have toxic effects on human and aquatic organisms. The use of in situ, time integrated DGT devices allows to better (1) monitor the most bioavailable fraction of V, the DGT-labile V, in Arctic Rivers and (2) assess the influence of DOM on dissolved V speciation. Higher DGT-labile V was found in the the central regions of the Mackenzie River (MR), with an average of 7.7 ± 2.3 nM, likely due to sediment leaching and permafrost thawing. The Churchill River and Great Slave Lake (GSL) showed lower DGT-labile V levels (2.2 ± 1.6 nM and 3.6 ± 2.7 nM, respectively), compared to central regions in MR. The CR DGT-labile V concentrations was positively correlated to protein-like DOM concentration and abundance (r = 0.3, p < 0.05). The data collected from this study will help in developing new strategies regarding environmental health and impact assessments of environmentally hazardous waste that consist of potentially high levels of toxic vanadium species. Developments in the use of DGT devices as a sampling method will also aid in future studies involved in analyzing environmental health and specifically dissolved V species in natural waters. Author Keywords: diffusive gradients in thin-films, dissolved organic matter, fluorescence, mass spectrometry, UV-Vis, vanadium
-
- Bioremoval of copper and nickel on living and non-living Eugelna gracilis
- This study assesses the ability of a unicellular protist, Euglena gracilis, to remove Cu and Ni from solution in mono- and bi-metallic systems. Living Euglena cells and non-living Euglena biomass were examined for their capacity to sorb metal ions. Adsorption isotherms were used in batch systems to describe the kinetic and equilibrium characteristics of metal removal. In living systems results indicate that the sorption reaction occurs quickly (<30 min) in both Cu (II) and Ni (II) mono-metallic systems and adsorption follows a pseudo-second order kinetics model for both metals. Sorption capacity and intensity was greater for Cu than Ni (p < 0.05) and were described by the Freundlich model. In bi-metallic systems sorption of both metals appears equivalent. In non-living systems sorption occurred quickly (10-30 min) and both Cu and Ni equilibrium uptake increased with a concurrent increase of initial metal concentrations. The pseudo-first-order model was applied to the kinetic data and the Langmuir and Freundlich models effectively described single-metal systems. The biosorption capacity of Cu (II) and) was 3x times greater than that of Ni (II). Sorption of one metal in the presence of relatively high concentrations of the other metal was supressed. Generally, it was found that living Euglena remove Cu and Ni more efficiently than non-living Euglena biomass in both mono- and bi-metallic systems. It is anticipated that this work should contribute to the identification of baseline uptake parameters and capacities for Cu and Ni by Euglena as well as to the increasing amount of research investigating sustainable bioremediation. Author Keywords: accumulation, biosorption, Cu, Euglena gracilis, kinetics, Ni
-
- Phosphorus deposition in forested watersheds
- Phosphorus (P) is an essential macronutrient. In south-central Ontario, foliar P concentrations are low and studies have suggested that P may be limiting forest productivity. Current catchment mass balance estimates however, indicate that P is being retained suggesting that P should not be limiting to tree growth. Phosphorus deposition is measured using bulk deposition collectors, which are continuously open and therefore are subject to contamination by pollen and other biotic material with high P and potassium (K) concentrations and may therefore overestimate net P inputs to forested catchments. Average annual TP and K deposition at three long-term (1984 – 2013) monitoring sites near Dorset, Ontario ranged from 15 to 20 mg·m-2y-1 and 63 to 85 mg·m-2y-1, respectively, and was higher at Paint Lake compared with Plastic Lake and Heney Lake. Phosphorus and K in bulk precipitation were strongly positively correlated, but deposition patterns varied spatially and temporally among the three sites. Total phosphorus and K deposition increased significantly at Plastic Lake and decreased significantly at Paint Lake, but there was no significant trend in TP or K deposition at Heney Lake over the 30 year period. All sites, but especially Paint Lake, exhibited considerable inter-annual variation in TP and K deposition. To quantify the contribution of pollen, which represents an internal source of atmospheric P deposition, Durham pollen collectors during the spring and summer of 2014 were used. The three sites, Paint Lake, Heney Lake, and Plastic Lake had pollen deposition amounts of 5202 grains·cm-2, 7415 grains·cm-2, and 12 250 grains·cm-2, respectively in 2014. Approximately 83% of pollen deposition can be attributed to white pine and red pine that has a concentration of 3 mg·g-1 of P. It was estimated that pollen alone could account for up to one-third of annual bulk P deposition. Extrapolating winter P deposition values to exclude all potential biotic influences (insects, bird feces, leaves), indicates that bulk deposition estimates may double actual net P to forests, which has implications for long-term P availability, especially in harvested sites. Author Keywords: Atmospheric Deposition, Phosphorus, Pine, Pollen, Potassium, South-Central Ontario
-
- Executive Function as a Predictor of Emotional, Behavioural, and Social Competence Problems in Children with Epilepsy
- The study aimed to examine the association between different components of executive function (EF) and emotional, behavioural, and social competence problems (EBSP) in children with epilepsy. Although there is evidence of an association between EBSP and EF in typically developing children, little research has examined this relation in children with epilepsy. The sample comprised of 42 children with epilepsy, aged 6.0 to 18.1 years old. Results showed that EBSP were associated with EF in these children; however, different components of EF were related to different EBSP. Shifting was a significant predictor of emotional, behavioural, and social competence problems in children with epilepsy, whereas inhibition was a significant predictor of behavioural problems. This suggests that children with epilepsy, with different EF profiles may be at-risk for developing different types of problems. These results may aid researchers and clinicians with the development of new techniques to identify and treat children with EBSP. Author Keywords: behavioural problems, emotional problems, epilepsy, executive function, social competence
-
- Early Responses of Understory Vegetation to Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta
- Abstract Early Responses of Understory Vegetation After One Year of Above Canopy Nitrogen Additions in a Jack Pine Stand in Northern Alberta Nicole Melong Nitrogen (N) emissions are expected to increase in western Canada due to oil and gas extraction operations. An increase in N exposure could potentially impact the surrounding boreal forest, which has adapted and thrived under traditionally low N deposition. The majority of N addition studies on forest ecosystems apply N to the forest floor and often exclude the important interaction of the tree canopy. This research consisted of aerial NH4NO3 spray applications (5, 10, 15, 20, 25 kg N ha-1yr-1) by helicopter to a jack pine (Pinus banksiana Lamb.) stand in the Athabasca Oil Sands Region (AOSR) in northern Alberta, Canada. The main objective was to assess the impacts of elevated N after one year of treatment on the chemistry of understory vegetation, which included vascular plants, terricolous lichens, epiphytic lichens and a terricolous moss species. Changes in vegetation chemistry are expected to be early signs of stress and possible N saturation. Increased N availability is also thought to decrease plant secondary compound production because of a tradeoff that exists between growth and plant defense compounds when resources become available. Approximately 60% of applied N reached the ground vegetation in throughfall (TF) and stemflow (SF). Nitrate was the dominant form of N in TF in all treated plots and organic N (ON) was the dominant form of N in SF in all plots. The terricolous non-vascular species were the only understory vegetation that responded to the N treatments as N concentration increased with increased treatment. Foliar chemistry of the measured epiphytic lichens, vascular species, and jack pine was unaffected by the N treatments. Based on biomass measurements and N concentration increases, the non-vascular terricolous species appear to be assimilating the majority of TF N after one year. Vegetation from the high treatment plot (25 kg N ha-1yr-1) was compared to a jack pine forest receiving ambient high levels of N (21 kg N ha-1yr-1) due to its proximity to Syncrude mining activities. Nitrogen concentrations in plant tissues did not differ between the two sites; however, other elements and compounds differed significantly (Ca, Mg, Al, Fe). After one year of experimental N application, there were no environmental impacts consistent with the original N saturation hypothesis. Author Keywords: Athabasca Oil Sands Region, Canopy Interactions, Jack Pine, Nitrogen, Secondary Chemistry, Understory Vegetation
-
- 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
-
- Speciation of Aluminum and Zinc in Three Streams of a Forested Catchment of the Boreal Zone
- This study presents a detailed assessment of the chemical speciation of aluminum and zinc in three streams of a small, acid-sensitive forested catchment on the southern edge of the Precambrian Shield. Speciation analysis was achieved using an in-situ analytical technique known as Diffusive Gradient in Thin film (DGT) which measures labile metals, and a predictive computer algorithm (WHAM VI) which calculates metal species concentrations. Three types of DGT with different metal scavenging capabilities were used and a total of 11 deployments performed across four seasons. WHAM VI predictions showed that the organic fraction of aluminum was the main contributor to the dissolved concentrations in the main inflow stream (PC1) (~ 80 %) and the lake's outflow (PCO) (~ 75%); in the upland stream (PC1-08) the inorganic fraction contributed ~ 75%. For zinc the free ion was the single most important contributor to the dissolved concentration (< 90%) in all three streams. A comparative study of the DGT and WHAM methods showed an agreement between their inorganic concentrations during the spring season. Both methods indicate the greatest environmental impact for Al takes place during snow melt period in PCO and PC1-08 and in the summer for PC1. The greatest environmental impact for Zn predicted with WHAM VI, occurs during the spring in all three streams. Author Keywords: Aluminum, DGT, Metal speciation, WHAM, Zinc
-
- Hydroclimatic and spatial controls on stream nutrient export from forested catchments
- Winter nutrient export from forested catchments is extremely variable from year-to-year and across the landscape of south-central Ontario. Understanding the controls on this variability is critical, as what happens during the winter sets up the timing and nature of the spring snowmelt, the major period of export for water and nutrients from seasonally snow-covered forests. Furthermore, winter processes are especially vulnerable to changes in climate, particularly to shifts in precipitation from snow to rain as air temperatures rise. The objective of this thesis was to assess climatic and topographic controls on variability in stream nutrient export from a series of forested catchments in south-central Ontario. The impacts of climate on the timing and magnitude of winter stream nutrient export, with particular focus on the impact of winter rain-on-snow (ROS) events was investigated through a) analysis of long-term hydrological, chemical and meteorological records and b) high frequency chemical and isotopic measurements of stream and snow samples over two winters. The relationship between topography and variability in stream chemistry among catchments was investigated through a) a series of field and laboratory incubations to measure rates and discern controls on nitrogen mineralization and nitrification and b) analysis of high resolution spatial data to assess relationships between topographic metrics and seasonal stream chemistry. Warmer winters with more ROS events were shown to shift the bulk of nitrate (NO3-N) export earlier in the winter at the expense of spring export; this pattern was not observed in other nutrients [i.e. dissolved organic carbon (DOC), total phosphorus (TP), sulphate (SO4), calcium (Ca)]. Hydrograph separation revealed the majority of ROS flow came from baseflow, but the NO3-N concentrations in rainfall and melting snow were so high that the majority of NO3-N export was due to these two sources. Other nutrient concentrations did not show such a great separation between sources, and thus event export of these nutrients was not as great. Proportionally, catchments with varying topography responded similarly to ROS events, but the absolute magnitude of export varied substantially, due to differences in baseflow NO3-N concentrations. Field and laboratory incubations revealed differences in rates of net NO3-N production between wetland soils and upland soils, suggesting that topographic differences amongst catchments may be responsible for differences in baseflow NO3-N. Spatial analysis of digital elevation models revealed strong relationships between wetland coverage and DOC and dissolved organic nitrogen (DON) concentrations in all seasons, but relationships between topography and NO3-N were often improved by considering only the area within 50 or 100m of the stream channel. This suggests nutrient cycling processes occurring near the stream channel may exert a stronger control over NO3-N stream outflow chemistry. Overall, topography and climate exert strong controls over spatial and temporal variability in stream chemistry at forested catchments; it is important to consider the interaction of these two factors when predicting the effects of future changes in climate or deposition. Author Keywords: biogeochemistry, forest, nitrate, south-central Ontario, stream chemistry, winter
-
- Near-road assessment of traffic related air pollutants along a major highway in Southern Ontario
- The spatial and temporal variation in atmospheric nitrogen dioxide (NO2), ammonia (NH3), and 17 elements (V, Cr, Fe, Ni, Cu, Zn, As, Cd, Pb, Mg, Al, Ca, Co, Se, Sb, Mn, and Na) were measured at 40 road side locations along a ~250 km traffic density gradient of 40,000–400,000 vehicles on the King’s Highway 401, in Ontario, Canada. Elemental concentrations were measured over a year, using moss bags as passive samplers, for four quarterly three-month exposure periods (October 2015 – October 2016). Gaseous NO2 and NH3 concentrations were measured using Willem’s badge passive diffusive samplers for twelve one-week exposure periods (one per month: October 2015–October 2016). Dry deposition of nitrogen was estimated using the inferential method. There were significant linear relationships between NO2 and NH3 and average annual daily traffic (AADT) volumes across the study area; higher concentrations corresponded to higher volume traffic sites. Average NO2 concentrations at sites ranged from 23.5 to 73 μg/m3, with an annual average of 43.7 μg/m3. Ammonia ranged from 2.56 to 13.55 μg/m3, with an annual average of 6.44 μg/m3. There were significant quarterly variations in NO2, with concentrations peaking during the winter months. In contrast, NH3 showed no significant quarterly variation, but a slight peak occurred during the summer. Gaseous NO2 and NH3 were highly positively correlated (r = 0.63), suggesting a common emission source from traffic. Concentrations in exposed moss were determined by subtracting the total concentration of each metal in the exposed sample from the background concentration present in the moss. Relative accumulation factors (RAF) and contamination factors were also calculated to determine the anthropogenic influence on tissue concentrations in exposed moss. All metals showed elevated levels versus background concentrations, with all metals except Ni and Co showing considerable enrichment. The highest levels of contamination were from V, Cr, Fe, Zn, Cd, Sb, Pb and Na. Principal component analysis indicated 5 clear clusters of related elements, with PC1 accounting for 36.2% and PC2 accounting for 25.6% of the variance. Average annual daily traffic was significantly related to Cr, Fe, Cu, Sb, Mn, Al, and Na. Road side monitoring shows consistently higher concentrations than active monitoring sites located further from the edge of the road, indicating a need for increased road side monitoring in Ontario, Canada. Author Keywords:
-
- Equilibria and distribution models of ionizing organic chemical contaminants in environmental systems
- Ionizing organic chemicals are recognized as constituting a large fraction of the organic chemicals of commerce. Many governments internationally are engaged in the time-consuming and expensive task of chemical risk assessment for the protection of human and environmental health. There are standard models that are consistently used to supplement experimental and monitoring data in such assessments of non-ionizing organics by both government regulators and industry stakeholders. No such standard models exist for ionizing organics. Equilibrium distribution models, the foundational equations within multimedia environmental fate models for non-ionizing organics, were developed for the standard series of biphasic systems: air-water, particle-water, air-particle and organic-aqueous phases within living tissue. Multiple chemical species due to the ionization reaction were considered for each system. It was confirmed that, under select conditions, the properties of the neutral parent are sufficient to predict the overall distribution of the organic chemical. Complications due to biotransformation and paucity of identifiable equilibrium distribution data for ionizing organics limited the development of the model for living tissues. However, the equilibrium distributions of ionizing organics within this biotic system were shown to correlate with the abiotic sediment-water system. This suggests that the model developed for particle-water systems should be adaptable to the biotic system as model input and test data become available. Observational data for soil- and sediment- water systems, i.e., particle-water systems, allowed the development of a primarily non-empirical distribution equation for mono-protic acids; this model was almost entirely theoretically derived. The theoretical approach to model development allowed a quantitative assessment of the role of the neutral ion pair, resulting from the complexation of the organic anion with metal cations. To demonstrate the model's potential usefulness in governmental screening risk assessments, it was applied to a broad range of mono-protic organics including drugs and pesticides using standard property estimation software and generic inputs. The order-of-magnitude agreement between prediction and observation typical of the existing models of non-ionizing organics was generally achieved for the chemicals tested. The model was sensitive to the octanol-water partition coefficient of the most populous species. No calibration set was used in the development of any of the models presented. Author Keywords: bioconcentration, chemical equilibrium, environmental modelling, ionizing organic, sorption
-
- Factors affecting road mortality of reptiles and amphibians on the Bruce Peninsula
- Road mortality is one of the leading causes of global population declines in reptiles and amphibians. Stemming losses from reptile and amphibian road mortality is a conservation priority and mitigation is a key recovery measure. I developed a model of road mortalities relative to non-‐mortalities, based on predictors varying across space (road surface type, traffic volume, speed limit, distance to wetland) and time (weather conditions, traffic volume). Herpetofauna road mortalities were recorded during daily bicycle and vehicle surveys to investigate the impact of roads on reptiles and amphibians within the Bruce Peninsula, Ontario in 2012 and 2013. A total of 2541 observations of herpetofauna on roads were recorded, 79% of which were dead. The major factor influencing turtle road mortality was proximity to the nearest wetland and dates early in the season (spring). For the Massasauga, high daily temperatures and low daily precipitation were associated with road mortality. The major factors driving colubrid snake mortality were also high daily temperature, low daily precipitation, as well as low speeds and paved roads. Frog and toad mortality was driven by proximity to wetland and late summer dates. These models will increase our understanding of factors affecting road losses of herpetofauna and serve as a basis for planned, experimental mitigation within the Bruce Peninsula. Author Keywords: amphibians, hotspot, mitigation, reptiles, road ecology, road mortality
-
- 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