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
An Investigation of Rare Earth Element Patterns and an Application of Using Zn and Cd Isotope Ratios in Oysters to Identify Contamination Sources in an Estuary in Southern China
Environmental monitoring and investigation of metal biogeochemical cycling has been carried out in the Pearl River Estuary (PRE), an important and complex system in Southern China. In this study, rare earth element (REE) patterns as well as isotope ratios (i.e., Zn and Cd) were evaluated as tools to identify contamination sources in environmental compartments (i.e., water and suspended particles (SP)) as well as in oysters collected from estuarine sites. Results show elevated concentrations (also called anomalies) of Pr, Nd, Dy and Ho, relative to other REE elements, in water samples, potentially from REE recycling and other industrialized activities in this area. Unlike water samples, no REE anomalies were found in SP or oysters, suggesting that the dominate REE uptake pathway in oysters is from particles. Secondly, site to site variations in Zn isotope ratios were found in water and SP, showing the complexity of the source inputs in this area. Also, in estuarine locations, larger spatially differences in Zn isotope ratios were found in water collected in wet season than those in dry season, which may due to mixing of different source inputs under the water circulations in different seasons. A series of laboratory experiments were conducted during which changes in Zn isotope ratios were measured during uptake under varying salinity and Zn concentrations and during depuration. Neither in vivo Zn transportation among the various tissues within the oysters nor water exposure conditions (i.e., different salinities or Zn concentrations) caused Zn isotopic fractionation in the oysters. Cd and Zn isotope ratios were also determined in oysters obtained from the PRE. Large variations in Cd and Zn isotope ratios suggest that oysters were receiving contaminants from different input sources within the PRE. A consistent difference (approximately 0.67‰) was observed for Zn isotope ratios in oysters collected from the east side of the PRE compared to those from sampling locations on the western side of the PRE, suggesting different Zn sources in these two areas. Ultimately, by combining biogeochemistry with physiology, this study represents a first attempt to assess pollution status, monitor contaminants using oysters and model/identify contamination sources using both REEs and metal isotope ratios. Author Keywords:
Assessing Measured and Perceived Risks to Drinking Water Sources
Microcontaminants originating from wastewater effluent and run-off from agricultural lands may be present in the sources of drinking water for rural and Indigenous communities in mixed-use watersheds. In this study, a convergent parallel mixed-methods design was applied to assess measured and perceived risks of contamination in the sources of drinking water for two communities; the Six Nations of the Grand River community in Ontario and the community of Soufriere in St. Lucia, West Indies. The overall goal of the project was to assess how measured and perceived risks of exposure to chemical and biological contaminants in drinking water sources could inform water management strategies for the communities. Quantitative data obtained from the analysis of water samples collected indicated that the highest levels and occurrence of fecal bacteria were found in the Soufriere watershed while the highest concentrations and occurrence of pesticides were found in the Grand River watershed. In the Grand River watershed, conventional treatment of water followed by activated carbon filtration and UV disinfection removed fecal bacteria and also removed many chemical microcontaminants with efficiencies as high as 98%. Data from both watersheds indicated that there was a strong positive correlation between the levels of caffeine and sucralose (i.e. indicators of wastewater contamination) in water samples and the levels of either Total Coliforms or fecal bacteria of human origin. Human health risk assessments of individual pesticides and pesticide mixtures performed by applying a hazard quotient (HQ) and hazard index (HI) model, respectively indicated that there were no apparent risks to human health from those microcontaminants. Qualitative data obtained from face-to-face interviews with water managers and health professionals working in the two communities, which were collected and analysed concurrently but independently, illustrated that there were cross-cultural similarities and differences in factors influencing the perceptions of risks associated with the sources of drinking water. These perceptions of risks were mainly influenced by factors such as heuristics or informal and informal reasoning, cognitive-affective factors, social-political institutions and cultural factors. These factors may have also influenced water managers and health professionals, as they often recommended more “soft” strategies for managing water resources in the communities. Key words: pesticides, fecal bacteria, microcontaminants, POCIS, measured risks, perceived risks, water management, First Nations, Grand River, Soufriere, St. Lucia Author Keywords: fecal bacteria, measured risks, microcontaminants, perceived risks, POCIS, water management
Assessing effects and fate of environmental contaminants in invasive, native, and endangered macrophytes
Macrophytes play an important role in aquatic ecosystems, and thus are integral to ecological risk assessments of environmental contaminants. In this dissertation, I address gaps in the assessments of contaminant fate and effects in macrophytes, with focus on glyphosate herbicide use for invasive plant control. First, I evaluated the suitability of Typha as future standard test species to represent emergent macrophytes in risk assessments. I concluded that Typha is ecologically relevant, straight-forward to grow, and its sensitivity can be assessed with various morphological and physiological endpoints. Second, I assessed effects from glyphosate (Roundup WeatherMAX® formulation) spray drift exposure on emergent non-target macrophytes. I performed toxicity tests with five taxa, Phragmites australis, Typha × glauca, Typha latifolia, Ammannia robusta, and Sida hermaphrodita, which in Canada collectively represent invasive, native, and endangered species. I found significant differences in glyphosate sensitivity among genera, and all species’ growth was adversely affected at concentrations as low as 0.1% (0.54 g/L), much below the currently used rate (5%, 27 g/L). Third, I assessed the potential for glyphosate accumulation in and release from treated plant tissues. I found that P. australis and T. × glauca accumulate glyphosate following spray treatment, and that accumulated glyphosate can leach out of treated plant tissues upon their submergence in water. Finally, I assessed effects of released glyphosate on non-target macrophytes. I found that P. australis and T. × glauca leachate containing glyphosate residues can stimulate the germination and seedling growth of T. latifolia, but can exert an inhibiting effect on A. robusta, although leachate without glyphosate caused similar responses in both plants. Additionally, I found no negative effects in A. robusta when exposed to glyphosate residues in surface water, or when grown with rhizosphere contact to an invasive plant that was wicked (touched) with glyphosate. My results show that non-target macrophytes can be at risk from glyphosate spray for invasive plant control, but risks can be mitigated through informed ecosystem management activities, such as targeted wick-applications or removing plant litter. Integrating contaminant fate and effect assessments with emergent macrophytes into ecological risk assessments can support the protection of diverse macrophyte communities. Author Keywords: Ecosystem management, Ecotoxicology, Glyphosate, Herbicide, Invasive plant, Species at risk
Assessing the Potential for Contamination of Lakes from Upwelling of Arsenic-Laden Groundwater Through Sediments
A bedrock fracture hosting arsenic (As) contaminated groundwater was suspected to be transported to Ramsey Lake, a drinking water resource for more than 50,000 residents of Sudbury, Ontario. A high resolution, spatial, water quality mapping technique using an underwater towed vehicle (UTV) was used to identify sources of upwelling groundwater into lake water and localize the upwelling As contaminated groundwater vent site. The top 7 cm of lake sediments (in-situ) at this vent site were observed to adsorb 93 % of the dissolved As, thus inhibiting lake water quality degradation from this contaminant source. Sediment samples from this location were used in laboratory experiments to assess the potential for this system to become a source of As contamination to Ramsey Lake water quality and elucidate As(III) fractionation, transformation and redistribution rates and processes during aging. Arsenic speciation is important because As(III) has been shown to be more toxic than As(V). To accomplish this a sequential extraction procedure (SEP) that maintains As(III) and As(V) speciation in (sub)oxic sediments and soils was validated for the operationally defined fractions: easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and the residual fraction for total As because the characteristics of the reagents required to extract the final fraction do not maintain As species. Batch reaction experiments using sediment spiked with As(III) or As(V) and aged for up to 32 d were sequentially extracted and analysed for As(III) and As(V). Consecutive reaction models illustrate As(III) is first adsorbed to the sediment then oxidized to As(V). Fractionation analyses show As(III) most rapidly adsorbs to the easily exchangeable fraction where it is oxidized and redistributes to the strongly sorbed and amorphous Fe oxide bound fractions. Oxidation of As(III) adsorbed to the amorphous and crystalline Fe oxide bound fractions is less efficient and possibly inhibited. Select samples amended with goethite provide evidence supporting Mn(II) oxidation is catalyzed by the goethite surface, thus increasing As(III) oxidation by Mn(III/IV) complexed with the strongly sorbed fraction. Although As immobilization through groundwater sediment interactions may be inhibited by increased ion activity, particularly phosphate or lake eutrophication, this threat in Ramsey Lake is likely low. Author Keywords: arsenic, fractionation, modelling, redistribution, speciation, water quality mapping
Automated Separation and Preconcentration of Ultra-Trace Levels of Radionuclides in Complex Matrices by Online Ion Exchange Chromatography Coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS)
Radionuclides occur in the environment both naturally and artificially. Along with weapons testing and nuclear reactor operations, activities such as mining, fuel fabrication and fuel reprocessing are also major contributors to nuclear waste in the environment. In terms of nuclear safety, the concentration of radionuclides in nuclear waste must be monitored and reported before storage and/or discharge. Similarly, radionuclide waste from mining activities also contains radionuclides that need to be monitored. In addition, a knowledge of ongoing radionuclide concentrations is often required under certain ‘special’ conditions, for example in the area surrounding nuclear and mining operations, or when nuclear and other accidents occur. Thus, there is a huge demand for new methods that are suitable for continuously monitoring and rapidly analyzing radionuclide levels, especially in emergency situations. In this study, new automated analytical methods were successfully developed to measure ultra trace levels of single or multiple radionuclides in various environmental samples with the goal of faster analysis times and less analyst involvement while achieving detection limits suitable for typical environmental concentrations. Author Keywords: automation, ICP-MS, ion exchange, radionuclide
Carbon Exchange along a Natural Gradient of Deciduous Shrub Coverage in the Low-Arctic
Arctic terrestrial ecosystems have experienced substantial structural and compositional changes in response to warming climate in recent decades, especially the expansion of shrub species in Arctic tundra. Climatic and vegetation changes could feedback to the global climate by changing the carbon balance of Arctic tundra. The objective of this thesis was to investigate the influence of increased shrub coverage on carbon exchange processes between atmosphere and the Arctic tundra ecosystem. In this study a space-for-time substitution was used, referred to as a shrub expansion “chronosequence”, with three sites along a natural gradient of deciduous shrub coverage in the Canadian low Arctic. Leaf-level photosynthetic capacity (Amax) of dominating birch shrub Betula glandulosa (Michx.) was significantly higher (P<0.05) at the site where shrubs were more abundant and taller than at the other sites. For all sites, mean Amax in 2014 was significantly lower than in 2013, in part potentially due to differences in precipitation distribution. Bulk soil respiration (RS) rate was significantly higher (P<0.05) at the site with more shrubs compared with the other sites. The differences in RS across sites appeared to be driven by differences in soil physiochemical properties, such as soil nitrogen and soil bulk density rather than soil microclimate factors (e.g. soil temperature, moisture). The three sites were either annual CO2 sources (NEP<0) to the atmosphere or CO2 neutral, with strongest annual CO2 sources (-44.1±7.0 g C m-2) at the site with most shrubs. Overall this study suggests that shrubs tundra carbon balance will change with shrub expansion and that shrub ecosystems in the Arctic currently act as annual carbon sources or neutral to the atmospheric CO2 and further shrub expansion might strengthen the CO2 emissions, causing a positive feedback to the warming climate. Author Keywords: arctic tundra, carbon exchange, climate change, photosynthetic capacity, shrub expansion, soil respiration
Characterization of Synthetic and Natural Se8 and Related SenSm Compounds by Gas Chromatography-Mass Spectrometry
Elemental selenium has been extensively quantitatively measured in sediments; however, its physical composition is largely unknown, despite it being the dominant selenium species in some reducing environments. Here, for the first time, it is shown that small, cyclic selenium compounds can account for a quantitatively-relevant fraction of the total elemental selenium present. A new method was developed to analyze for cyclooctaselenium (Se8) in both synthetic samples and selenium-impacted sediments. Despite some analytical limitations, this gas chromatography-mass spectrometry (GC-MS) method is the first GC-MS method developed to identify and quantify Se8 in sediments. Once this method was established, it was then applied to more complex systems: first, the identification of compounds in mixed selenium-sulfur melt solutions, and then the determination of SenSm in selenium-impacted sediments. Despite complications arising from pronounced fragmentation in the ion source, assignment of definitive molecular formulae to chromatographically-resolved peaks was possible for five compounds. Developing a fully quantitative method to obtain elemental ratio information can aid in the assignment of molecular formulae to chromatographically-resolved SeS-containing chromatographic peaks. Coupling the existing gas chromatography method to an inductively coupled plasma-mass spectrometer (ICP-MS) system should accomplish this. However, due to a number of complications, this was not completed successfully during the duration of this thesis project. High detection limits for sulfur, retention time discrepancies, and inconsistent injection results between the GC-MS and GC-ICP-MS system led to difficulties in comparing results between both analytical methods. Despite these limitations, GC-ICP-MS remains the most promising method for the identification and quantification of SenSm compounds in synthetic melt mixtures and selenium impacted sediments. Author Keywords: gas chromatography-mass spectrometry, sediments, selenium
Composition and Transformation of Dissolved Organic Matter in Hudson Bay, Canada
The Hudson Bay region is a sensitive environment, where anthropogenic (e.g., dams, diversions, and/or reservoirs) impacts have increased in recent decades, potentially influencing the functioning of the ecosystem. Dissolved organic matter (DOM) entering Hudson Bay comes from both terrestrial (allochthonous) and aquatic (autochthonous) sources. The chemical composition of DOM is important, as it controls carbon biogeochemistry, nutrient cycling, and heat exchange. In rivers, estuaries, and oceans, photochemical processes and microbial degradation play a significant role in the chemical composition of DOM. Yet, our knowledge is scarce into how photochemical and microbial processes effect DOM composition specifically in Arctic aquatic systems making it difficult to predict how the carbon cycle will respond to a changing environment. This Ph.D. thesis addresses: (1) the composition of photochemically altered autochthonous and allochthonous DOM; (2) the photochemical transformations of DOM in surface waters of Hudson Bay; and (3) the microbial transformations of DOM in Hudson Bay surface waters. Using multiple analytical techniques, this work demonstrated that photochemical and microbial effects were different for light absorbing DOM compounds and ionisable DOM analyzed by Fourier transform-ion cyclotron-resonance-mass spectrometry (FT-ICR-MS). Based on FT-ICR-MS analysis, microbial processes had a greater impact on the molecular composition of allochthonous DOM originating from riverine sources and estuary whereas photochemical processes were the dominant mechanism for degradation of autochthonous DOM in Hudson Bay. Photochemical processes significantly decreased colored dissolved organic matter (CDOM) and fluorescence dissolved organic matter (FDOM) loss whereas microbial degradation was minimal in Hudson Bay river, estuary, and coastal waters. The results of this thesis highlight the importance of photochemical and microbial alteration of DOM in Arctic regions, two processes that are expected to be enhanced under climate change conditions. Author Keywords: Carbon cycle, Field flow fractionation, Microbial transformation, Optical properties, Photochemical degradation
Dynamics and Mechanisms of Community Assembly in a Mined Carolinian Peatland
Theoretical work on community recovery, development, stability, and resistance to species invasions has outpaced experimental field research. There is also a need for better integration between ecological theory and the practice of ecological restoration. This thesis investigates the dynamics of community assembly following peat mining and subsequent restoration efforts at Canada's most southerly raised bog. It examines mechanisms underlying plant community changes and tests predictions arising from the Dynamic Environmental Filter Model (DEFM) and the Fluctuating Resource Hypothesis (FRH). Abiotic, biotic and dispersal filters were modified to test a conceptual model of assembly for Wainfleet Bog. Hydrology was manipulated at the plot scale across multiple nutrient gradients, and at the whole bog scale using peat dams. Trends in time series of hydrological variables were related to restoration actions and uncontrolled variables including precipitation, evapotranspiration and arrival of beaver. Impacts of a changing hydrology on the developing plant community were compared with those from cutting the invasive Betula pendula. Transplanting experiments were used to examine species interactions within primary and secondary successional communities. Seedlings of B. pendula and the native Betula papyrifera were planted together across a peat volumetric water content (VWC) gradient. Impacts of beaver dams were greater than those of peat dams and their relative importance was greatest during periods of drought. Cutting of B.pendula had little effect on the secondary successional plant community developing parallel to blocked drains. Phosphorus was the main limiting nutrient with optimum levels varying substantially between species. Primary colonisers formed a highly stable, novel plant community. Stability was due to direct and indirect facilitative interactions between all species. Reduction in frost heaving was the major mechanism behind this facilitation. Interactions within the secondary successional community were mostly competitive, driven by light and space availability. However, restricted dispersal rather than competition limited further species recruitment. Predictions based on the DEFM were partially correct. A splitting of this model's biotic filter into competition and facilitation components is proposed. There was little support for the FRH based on nutrient levels and VWC. B. pendula had higher germination and growth rates, tolerance to a wider range of peat VWCs and a greater resistance to deer browsing than native birch. Peat mining, combined with restoration actions and the arrival of beaver has moved much of the bog back to an earlier successional stage circa 350+ years BP. Evidence points to B. pendula being a "back-seat driver" in the ecosystem recovery process. Indirect facilitation of a native by an exotic congener, mediated through herbivory, has not been described previously. Shifts in relative contributions of facilitation, competition and dispersal limitations to community assembly may be useful process-oriented measures for gauging progress in restoration. Author Keywords: Betula pendula, community assembly, competition, facilitation, peatland, restoration
Ecosystem Response to Above Canopy Nitrogen Addition in a Jack Pine (Pinus banksiana) Forest in the Athabasca Bituminous Sands Region of Northeastern Alberta, Canada
In this study we seek to better understand the potential effects of short-term (5-year) N fertilization on jack pine forest biogeochemistry, vascular plant community composition and to project a temporal endpoint of nitrogen leaching below the major rooting zone. Aqueous ammonium nitrate (NH4NO3) was applied above the forest canopy across five treatment plots (20 x 80 m) four times annually. The experimental deposition gradient followed those known for localized areas around the major open pit operations at 0, 5, 10, 15, 20 and 25 kg N ha-1 yr-1 over a five-year period (2011 – 2015). Nitrate recovery in throughfall was significantly higher than NH4+ (p < 0.05), indicating canopy NH4+ immobilization. There was a strong treatment effect (p < 0.05) of N on the epiphytic lichen thalli concentrations of Hypogymnia physodes and Evernia mesomorpha after five years. The canopy appeared to approach saturation at the highest deposition load (25 kg N ha-1 yr-1) during the fifth year of N additions as most N added above the canopy was accounted for in throughfall and stemflow. The non-vascular (lichen and moss) vegetation pool above the forest floor was the largest receptor of N as cryptogam foliar and thalli N concentrations showed a significant treatment effect (p < 0.05). Nitrogen in decomposing litter (25 kg N ha-1 yr-1) remained immobilized after five years, while treatments ≤ 20 kg N ha-1 yr-1 started to mobilize. Understory vascular plant cover expansion was muted when deposition was ≥ 10 kg N ha-1 yr-1. Finally, modeling suggests the forest may not leach N below the rooting zone until around 50 years after chronic addition begin (25 kg N ha-1 yr-1). The modeling results are consistent with empirical data from a high exposure (~20 - 25 kg N ha-1 yr-1) jack pine site approximately 12 km west of the experimental site that has not yet experienced N leaching. Author Keywords: Biogeochemistry, Canopy, Deposition, Jack Pine, Nitrogen, Understory
Effect Assessment of Binary Metal Mixtures of Ni, Cu, Zn, and Cd to Daphnia magna
Mixtures of metals occur in surface waters, toxicity of which has drawn world-wide attention due to their crucial role in both ecotoxicology and regulations. The present research was undertaken to study the acute toxicity of binary mixtures of Ni, Cu, Zn, and Cd to the freshwater organism, Daphnia magna. The experimental approach included single and binary metal toxicity tests based on the 48h acute toxicity bioassay of Environment Canada. The acute toxicity of single metals followed the order of Cd > Cu > Zn > Ni. Based on the calculated 48h EC50 value of single metals, a toxic unit (TU) approach was used to combine two metals in a binary mixture, in which 1TU was equal to the 48h EC50 value of a metal in single exposure. The toxicity of binary metal mixtures to D. magna followed the order of Cu-Cd > Cu-Zn > Zn-Cd > Cu-Ni > Zn-Ni > Cd-Ni, which demonstrated three types of toxicity (i.e., less than additive, additive, and greater additive). Predictions from additivity models (including concentration addition (CA) and independent action (IA) models), a generalized linear model (GLM), and a biotic-ligand-like model (BLM-like) were compared to the bioassay results. The CA and the RA models also predicted three types of toxicity of the binary metal mixtures (i.e., less than additive, additive, and greater than additive). However, the CA model mostly overestimated the toxicity of binary mixtures. Predictions from the GLM supported the inclusion of the interaction between two metals in a mixture to predict the toxicity of binary metal mixtures. The binary metal toxicity was also predicted using a BLM-like model based on the calculated concentrations of free ionic forms of the metals, affinity constants, and toxic potency of each metal. In this model, it was hypothesized that the toxicity of metal mixture is the result of competition of metals with Ca2+ at biotic ligands, which can lead to whole-body deficiency of Ca2+ in D. magna. The BLM-like model provided the toxic potency of single metals with the following order, Cu > Cd > Zn > Ni. Although the prediction of the BLM-like model was not in good agreement with the observed toxicity of binary metal mixtures, an overestimation of risk of mixture toxicity was obtained using this model, which could be promising for use in environmental risk assessment. Author Keywords: biotic ligand model, concentration addition, Daphnia magna, independent action, metal toxicity, modeling

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