Graduate Theses & Dissertations

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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
Legacy Effects Associated with the World’s Largest Ongoing Liming and Forest Regeneration Program in Sudbury, Ontario, Canada
Soil and tree chemistry were measured across 15 limed sites that were established 14 to 37 years ago within the Sudbury barrens in Ontario, along with two unlimed pre-treatment condition reference sites and an unlimed remnant pine forest. Soil pH and base cation (calcium (Ca), magnesium (Mg), and potassium (K)) concentrations were elevated in surface organic [FH] horizons up to 37-years post limestone treatment. Limestone in the organic horizon was evident by higher Ca/Sr ratios (a good marker of dolomite) in younger sites. Base cation mass budgets were generally unable to account for the mass of added Ca and Mg. Sudbury is characterized by widespread metal contamination. Metal (copper (Cu), nickel (Ni), and lead (Pb)) concentrations were generally greatest within the FH horizon and unrelated to stand age. Copper and Ni concentrations in soil generally decreased with distance from the nearest smelter. Metal partitioning (Kd) in soil was most influenced by soil pH rather than organic matter suggesting that as liming effects fade over time metal availability may increase. Author Keywords: Afforestation, Degraded, Limestone, nutrient, Space-for-time, Sudbury
Influence of nitrogen and sulfur on cadmium tolerance in Euglena gracilis
Heavy metal pollution threatens human and ecosystem health. E. gracilis was investigated for its potential use in bioremediation due to its tolerance for heavy metals and ability to sequester them from the environment. E. gracilis can remove metals by producing metal binding compounds enriched in sulfur and nitrogen. In this thesis, E. gracilis cultures that were pretreated with elevated levels of sulfur or nitrogen had increased tolerance to CdCl2 compared to non-pretreated cultures. RNA-sequencing revealed that both pretreatments led to transcript level changes and that exposure to CdCl2 led to further transcript level changes. Gene ontology (GO) enrichment analysis reflected changes in nitrogen and sulfur metabolism as well as physiological processes related to metal binding. The data from this thesis revealed important transcription level changes that occur when E. gracilis is challenged with CdCl2 and helps us understand how organisms adapt to heavy metal pollution in the environment. Author Keywords: bioremediation, Cadmium, Euglena gracilis, GO-enrichment, metal-binding, RNA-Sequencing
Doing it Right
The cyanidation technique is currently a viable technique for gold recovery that can replace the present amalgamation technique in Guyana. To implement this technique effectively, laboratory scale experiments and at scale runs were conducted to determine the best particle size of the ore, cyanide concentration, and leaching time. In addition, the profitability of cyanidation was compared to the amalgamation technique so as to describe the economic value of cyanidation. Results indicated that up to 94% of gold can be recovered from the ore using an ore particle size of 150 (105 µm), meshes, a cyanide concentration of 0.05% and leaching for 24 h. An economic comparison of this technique with the amalgamation technique indicated that although initial costs are high for the cyanidation technique, profits as high as 83% can be achieved after initializing this method whereas profits would be capped at approximately 25% for the amalgamation technique. Keywords: gold recovery, cyanidation, mercury amalgamation, activated car Author Keywords: activated carbon, cyanidation, gold recovery, mercury amalgamation
Longitudinal trends of benthic invertebrates in regulated rivers
The Serial Discontinuity Concept describes the downstream recovery of key biophysical variables below an impoundment. With the proliferation of hydropower dams to meet increasing societal demands, further refinement and understanding of the Serial Discontinuity Concept is needed to accurately predict downstream impacts and ensure the proper management of rivers. In this study, I examine SDC predictions on physical, chemical and biological recovery in regulated rivers providing evidence from 1) a comprehensive literature review and 2) a formal test using two regulated rivers in Northern Ontario. I specifically address how these changes are reflected in benthic invertebrate abundance, diversity, and community composition. The literature review and case studies support the predicted recovery of temperature, periphyton, substrate, and drift. In addition, the study suggests that two recovery gradients exist in regulated rivers: 1) a longer, thermal gradient taking up to hundreds of kilometres downstream; and 2) a shorter, resource subsidy gradient recovering within 1-4 km downstream of an impoundment. Total benthic invertebrate abundance varies considerably and depends on the degree of flow alteration and resource subsidies from the upstream reservoir. In contrast, benthic diversity is reduced below dams irrespective of dam location and operation with little recovery observed downstream. Contrary to SDC predictions, the longitudinal gradient in regulated rivers is not a compaction of functional changes seen over several stream orders in natural rivers but a response to dam design and reservoir conditions. Stoneflies and dragonflies are particularly sensitive to regulation while filter feeding invertebrates are enhanced. Ward and Stanford's (1983) Serial Discontinuity Concept is still a useful framework for testing hypotheses. Future studies should further expand the SDC through empirical estimation within the context of the landscape to gain a better scientific understanding of regulated river ecology. Author Keywords: benthic invertebrates, dams, longitudinal, recovery, River Continuum Concept, Serial Discontinuity Concept
Hydrochemistry and critical loads of acidity for lakes and ponds in the Canadian Arctic
Threats such as climate change and increased anthropogenic activity such as shipping, are expected to negatively affect the Arctic. Lack of data on Arctic systems restricts our current understanding of these sensitive systems and limits our ability to predict future impacts. Lakes and ponds are a major feature of the Arctic landscape and are recognized as ‘sentinels of change’, as they integrate processes at a landscape scale. A total of 1300 aquatic sites were assessed for common chemical and physical characteristics. Geology type was found to be the greatest driver of water chemistry for Arctic lakes and ponds. Acid-sensitivity was assessed using the Steady State Water Chemistry model and a subset of 1138 sites from across the Canadian Arctic. A large portion of sites (40.0%, n = 455) were classified as highly sensitive to acidic deposition, which resulted in a median value of 35.8 meq·m―2·yr―1 for the Canadian Arctic. Under modelled sulphur deposition scenarios for the year 2010, exceedances associated with shipping is 12.5% (n = 142) and 12.0% (n = 136) for without shipping, suggesting that impacts of shipping are relatively small. Author Keywords: Acidic deposition, Arctic lakes, Critical loads, Shipping emissions, Steady-State Water Chemistry Model, Water chemistry
Land Cover Effects on Hydrologic Regime within Mixed Land Use Watersheds of East-Central Ontario
Land cover change has the potential to alter the hydrologic regime from its natural state. Southern Ontario contains the largest and fastest growing urban population in Canada as well as the majority of prime (Class I) agricultural land. Expansions in urban cover at the expense of agricultural land and resultant ‘agricultural intensification’, including expansion of tile drainage, have unknown effects on watershed hydrology. To investigate this, several streams with a range of landcovers and physiographic characteristics were monitored for two years to compare differences of flashiness and variability of streamflow using several hydrologic metrics. Urban watersheds were usually the flashiest while agriculture had moderate flashiness and natural watersheds were the least flashy across all seasons, signifying that landcover effects were consistent across seasons. Tile drainage increased stream flashiness during wet periods, but minimized the stream response to an extreme rain event in the summer, perhaps due to increases in soil moisture storage. A sixty-year flow analysis showed that flashiness and streamflow increased (p < 0.05) above a development threshold of ~10% of watershed area. Flashiness was also greater in wetter years suggesting that climate shifts may enhance stream variability in developed watersheds. Author Keywords: Agriculture, Flashiness, Hydrologic Metrics, Hydrologic Regime, Landcover Change, Urban
Population Genetics and Scarification Requirements of Gymnocladus dioicus
The Kentucky coffee tree (Gymnocladus dioicus) is an endangered tree species native to the American Midwest and Southwestern Ontario. Significant habitat loss and fragmentation due to agricultural, industrial and urban development has caused gradual decline across its native range. The aims of this study were to investigate: (1) patterns of genetic diversity and, (2) genetic differentiation (3) relative levels of sexual vs. clonal reproduction, and (4) potential for reduced genetic diversity at range edge for wild G. dioicus populations. An analysis of variation at nine microsatellite loci from populations in the core of the species distribution in the U.S.A. and 4 regions of Southwestern Ontario indicated that G. dioicus has remarkably high genetic similarity across its range (average pairwise FST= 0.05). Germination trials revealed that the seed coats require highly invasive treatments (e.g. 17.93 mol/L H2SO4) to facilitate imbibition, with negligible germination observed in treatments meant to emulate prevailing conditions in natural populations. Low levels of sexual reproduction, high genetic similarity, and habitat degradation are issues that exist across the entire native range of G. dioicus. Author Keywords:
Phosphorus delivery in the Rainy-River Lake of the Woods Watershed
Lake of the Woods (LOW) is a large international waterbody which suffers from frequent and widespread algae blooms. Previous studies have highlighted the importance of the lake's largest tributary, the Rainy River (RR) and its significance in total phosphorus (TP) delivery to the LOW. Unfortunately, little is known about TP contributions from the RR and its tributaries within the Canadian portion of the watershed. This thesis examines patterns and sources of TP from four tributaries on the Canadian side of the lower RR region, two of which are predominantly natural, and two that are predominantly agricultural. Relationships between water quality parameters, land use and geologic characteristics were observed over a complete hydrologic year (Oct 1, 2018 - Sept 31, 2019), and through an intensive sampling campaign using a nested watershed approach during the spring high flow and summer low flow periods. Results revealed that TP and total suspended sediment (TSS) concentrations (>100 µg/L and >20 mg/L respectively), and loads (>20 kg/km2 and >3500 kg/km2, respectively), were greater at agricultural sites compared with natural sites (<65 µg/L TP and <15 mg/L TSS concentration, and <20 kg/km2 TP and <4000 kg/km2 TSS export). Total P, TSS, Fe, and Al were significantly positively correlated (R2= 0.26-0.59; p<0.05) and intensive sampling revealed that these relationships were strongest during the spring and at the agricultural sites (R2= 0.73-0.98; p<0.05). In contrast, the summer intensive sampling revealed that TP and redox sensitive Fe were significantly correlated (R2= 0.72; p<0.005), whereas redox insensitive Al and TSS were not, suggesting TP may be sourced via redox processes in the summer due to favourable hydrologic conditions. This was observed not only at sites with high wetland influence, but also at sites with more agricultural presence suggesting that redox sourced TP may also originate from mineral stream bed sediment during low flow periods. This research suggested two primary TP sources in the lower RR region: erosion in the spring, and redox processes (internal release) in the summer. It is recommended that intensive monitoring continue in Canada, and further research be conducted to fully understand the significance of internal P release in the tributaries. Author Keywords: erosion, land use, nutrients, particulates, redox, water quality
Evaluating Environmental DNA (eDNA) Detection of Invasive Water Soldier (Stratiotes Aloides)
In 2008, the first North American water soldier (Stratiotes aloides) population was discovered in the Trent River, Ontario. Water soldier is an invasive aquatic plant with sharp, serrated leaves that has the potential to spread rapidly through dispersed vegetative fragments. Although it is too late to prevent water soldier establishment in the Trent River, its local distribution remains limited. In this study, environmental DNA (eDNA) was explored as a potential tool for early detection of water soldier. Species-specific markers were designed from chloroplast DNA regions matK and rbcL, and a qPCR assay with rbcL primers yielded the most sensitive detection of water soldier eDNA. Positive detections were obtained from six of 40 sampling locations, of which five were collected in Seymour Lake, an area with large patches of water soldier. As water soldier plants were known to be present at these sites, high eDNA concentrations were expected. The sixth positive detection from Trent Lock 5 (50 km downstream of Lake Seymour) was unexpected as it was obtained at a site with no water soldier sightings. This is one of the first studies to demonstrate the effectiveness of eDNA detection from aquatic plants. Author Keywords: aquatic plant, eDNA, environmental DNA, invasive species, Stratiotes aloides, water soldier
An Evaluation of Wastewater Treatment by Ozonation for Reductions in Micropollutant Toxicity to Fish
Micropollutants are discharged into the aquatic environment with industrial and domestic wastewater and these compounds may cause toxic effects in aquatic organisms. In this study, the toxic effects to fish of micropollutants extracted from ozonated and nonozonated municipal wastewater effluent (MWWE) were measured in order to assess the effectiveness of ozonation in reducing toxicity. Juvenile rainbow trout (Oncorhynchus mykiss) injected with extracts prepared from ozonated MWWE had significantly reduced induction of plasma vitellogenin (VTG), significantly reduced hepatic total glutathione (tGSH) levels and an elevated oxidized-to-total glutathione (GSSG-to-tGSH) ratio. Exposure of Japanese medaka (Oryzias latipes) embryos to extracts prepared from both ozonated and non-ozonated MWWE resulted in elevated developmental toxicity in both treatment groups. These results indicate that wastewater treatment by ozonation reduces the estrogenicity of wastewater, but treatment may induce oxidative stress and embryonic developmental toxicity due to the production of toxic by-products. Author Keywords: Estrogenicity, Micropollutants, Oxidative stress, Ozonation, Toxic by-products, Wastewater
Tracking Mercury and Mercury Stable Isotopes Throughout the Wabigoon/English River System
In the Wabigoon/English River system, mercury concentrations downstream from Dryden, ON, where there was a former chlor-alkali plant, remain elevated in sediments and biota. Understanding the current extent and severity of mercury contamination downstream from the former chlor-alkali plant is of great interest in furthering the clean-up of mercury within the traditional territory of Asubpeeschoseewagong Netum (Grassy Narrows) First Nation. The objective of this study was to evaluate the current level and extent of mercury contamination within sediments, crayfish, Hexagenia mayflies, yellow perch, spottail shiner and walleye in the Wabigoon/English River system. An additional objective was to use mercury stable isotope analysis to distinguish between legacy mercury from the former chlor-alkali plant and mercury from geogenic sources. Mercury contamination within surface sediments and biota at locations as far as 178 kms downstream of the historical source of mercury contamination are elevated relative to the reference lake, Wabigoon Lake. Isotope ratios in young of the year fish and sediments collected from within the system were distinct from fish from the reference lake, Wabigoon Lake, indicating that anthropogenic mercury contamination is distinguishable from geogenic mercury. Author Keywords:

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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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