Environmental science

This thesis determined the temporal dynamics of microplastics in the biosolid and final effluent of a WWTP for one year (October 2020–September 2021). The WWTP exported 354.1 ± 24.7 billion microplastic particles, or 296.7 ± 39.4 kg of microplastics; of this, 85.7% of counts and 86.6% of mass was exported via biosolids. As such, microplastic loads in biosolids need to be reduced before they are land applied. This thesis further examined the ability of settling treatments to liberate microplastics from biosolids under the effect of four variables (harvest method, stirring, settling time, and biosolid type). Across all treatments, average microplastic removal was 9.01 ± 5.82% in terms of count, and 6.91 ± 4.98% in terms of mass. Overall, this thesis contributed to our understanding of annual microplastic burden in a WWTP and set the foundation for the development of settling-based biosolids treatments to reduce microplastic emissions to the environment.

Author Keywords: Biosolid, Count Concentration, Final Effluent, Mass Concentration, Polymer, Treatment

Innovative strategies to manage copious waste streams by upcycling feedstocks to valorized products which are then used in environmental remediation applications is an attractive circular economy model. This thesis explores this approach using waste wood generated from the milling of Chlorocardium rodiei (greenheart), a tropical hardwood species abundant in Guyana. We evaluate the thermochemical conversion of this feedstock, using phosphoric acid as the activant, to super activated carbons with surface areas of more than 2200 m2/g. Owing to the presence of surface heteroatoms, these adsorbents are amenable to further surface modifications including base-treatment, O-functionalization and N-functionalization. Using a facile oxidation procedure and shrimp waste-based dopants, we increase oxygen and nitrogen content by 8-fold and 5-fold respectively. These increases are realized without catastrophic loss of surface area and porosity as generally occurs with many reported functionalization approaches. Functionalized materials demonstrated efficient removal of both metal ions and the chlorinated herbicides 2,4-dichlorophenoxy acetic acid and paraquat. Pristine and base-washed ACs removed more than 90% of iron, aluminum and manganese from natural pit-lake waters. O-functionalized adsorbents also showed excellent removal efficiencies for aluminum and lead but only removed moderate amounts of manganese. Nitrogen-enriched composites fabricated with the addition of commercial chitosan removed 67% 2,4-D and 89% paraquat from model solutions at environmentally relevant concentrations of 4 ppm and 40 ppm respectively. Their versatility is further demonstrated in their ability to remove both herbicides from binary mixtures albeit to different extents. Shrimp chitin-based composites were most effective at removing 2,4-D from model solutions with a maximum adsorption capacity of 101 mg/g. Both surface area and surface nitrogen had strong influences on the adsorption capacity of adsorbents. Mechanistically, physisorption interactions predominate the synergistic or antagonistic interaction between N-functionalized composites and herbicide species. These green adsorbent materials, fabricated from sustainable biopolymers, are promising candidates for diverse environmental remediation applications.

Author Keywords: adsorption, Environmental remediation, N-functionalization, O-functionalization, tropical hardwood waste, waste valorization

Forests play a critical role in the global carbon cycle, acting as carbon sinks that remove and store an estimated 0.4 to 4.1 Pg of atmospheric carbon annually. However, historical acid deposition and timber harvesting have disrupted nutrient cycles, leading to nutrient-deficient soils that hinder tree growth, particularly for sugar maple (Acer saccharum), a keystone species in Ontario sensitive to soil acidity and calcium (Ca) depletion. This study evaluates the effects of non-industrial wood ash (NIWA) applied at 0, 2, 4, 6, and 12 Mg ha-1 on soil chemistry, nutrient concentrations, microbial activity, CO2 fluxes, and sugar maple growth over two years. NIWA increased soil pH and exchangeable base cations, especially in the organic horizon, with some increase in forest floor metals, though foliar levels remained safe. Enzyme activity responses were minimal, and fine root biomass declined at higher doses. Soil CO₂ fluxes rose sharply at 12 Mg ha⁻¹, suggesting pH-driven effects. NIWA improves soil chemistry, but long-term impacts remain uncertain.

Author Keywords: carbon flux, extracellular soil enzyme, non-industrial wood ash, sugar maple

Calcium (Ca) limitation and sodium chloride (NaCl) toxicity tolerance are potential controllers of Daphnia populations. D. pulicaria neonates collected from 14 Kawartha Highland lakes were exposed to 6 Ca concentrations (0.5-5.0 mg Ca L-1) over 6 days. We did not find differences in maximum mass-specific growth rate or half-maximum thresholds between source lakes. Growth rates were reduced <1.5 mg Ca L-1, and there was a significant interaction between Ca and source lake lineage. We also compared log-logistic NaCl dosage models estimating 48-hour lethal concentration (LC)10, LC25, and LC50 by exposing 9 clones to 10 concentrations, 18-2700 mg Cl L-1. Survivorship decreased >1500 mg NaCl L-1, and there were differences between lake lineage LC50 estimations. This suggests our D. pulicaria genotypes may not have experienced extreme enough selection pressure from either stressor to develop local adaptation, but allele variability between lakes may explain differences in NaCl toxicity and Ca limitation responses.

Author Keywords: Calcium, Daphnia, Mass Specific Growth Rate, Sodium Chloride, Toxicity, Zooplankton

Agricultural and urban land uses have been linked to the recent resurgence of eutrophication and salinization issues in the lower Great Lakes. This thesis examined the relationship between watershed land use and stream nitrate-nitrogen (NO3-N), total phosphorus (TP), and chloride (Cl) concentrations across southern Ontario. Using a self-organizing map analysis, the watersheds were classified into eight distinct spatial clusters, representing four agricultural, two urban, and two natural clusters. Agricultural clusters under intensive row crop agriculture exhibited NO3-N and TP concentrations up to twelve and five times higher, respectively, than the most natural-dominated cluster. Urban clusters had Cl concentrations up to nine times greater than the natural-dominated clusters. Three agricultural land use practices, namely continuous corn-soybean rotation, synthetic fertilizer application, and tile drainage, were positively correlated with stream NO3-N concentrations, whereas Cl concentrations increased with urban area and human population density. This thesis also characterized sampling trends of the provincial stream water quality monitoring program and found that sampling frequency has declined since the mid-1990s, while current sites are monitored almost exclusively during the ice-free period. Sampling year-round is critical to capture seasonal variations in NO3-N and Cl, while sampling across a full range of flow conditions is important for describing TP. Exclusion of sampling sites in close proximity of downstream municipal wastewater treatment plants and greenhouses can help isolate and better understand water quality impacts of non-point sources. Although intensive agricultural watersheds in southwestern Ontario draining into Lake Erie remain a priority for research and management, regions experiencing row crop expansion such as along the northern shore of Lake Ontario as well as rapidly urbanizing areas require further attention as these land use shifts will likely increase stream NO3-N and Cl concentrations, placing further pressure on water resources in the lower Great Lakes.

Author Keywords: Chloride, Nitrogen, Phosphorus, Self-organizing map, Southern Ontario, Water quality

The Lesser Yellowlegs (Tringa flavipes) is a steeply declining shorebird that breeds across boreal North America. I studied nest survival in Anchorage, Alaska, USA and Churchill, Manitoba, Canada and nest site selection factors in Churchill. Nests were monitored at each site and daily nest survival rates (DSR) were calculated based on a maximum likelihood approach. Overall nest survival was ~63% for Anchorage (lcl–ucl = 0.450–0.773, n=49) and ~28% (lcl–ucl = 0.113–0.481, n=26) for Churchill. Earlier initiation dates, warmer mid-incubation temperatures and lower temperature variability during nesting were linked with higher DSR. I tested nest site selection at territorial and microhabitat scales using multiple logistic regression to compare nest sites with random points. Lesser Yellowlegs selected territories further from water and, at the microhabitat scale, taller shrubs. Projected climate-related shifts in weather and habitat will likely present both benefits and challenges to Lesser Yellowlegs.

Keywords: Lesser Yellowlegs, Tringa flavipes, shorebird, nest survival, nest success, nesting habitat, breeding habitat, boreal, sub-arctic, climate change, Anchorage, Alaska, Churchill, Manitoba

Author Keywords: boreal, breeding habitat, Lesser Yellowlegs, nest survival, shorebird, Tringa flavipes

In this study, twenty lake catchments surrounding Iqaluit, Baffin Island, were assessed for trace element concentrations (Al, As, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sb, Se, THg, V, Zn) in lake water, catchment soil, lake sediment, and moss (Hylocomium splendens). Additionally, the sources of each trace element were determined through the positive matrix factorization (PMF) model and enrichment factors (only in moss). Geogenic trace elements had the highest median concentrations (Fe>Al>Mn) throughout the study media and across the study catchments. Anthropogenic trace elements had the lowest median concentrations (Pb>As>Cd>THg) across the lake catchments, which were generally several orders of magnitude lower compared to geogenic elements. The PMF model identified trace elements associated with geogenic or anthropogenic sources, i.e., THg (47%), Cd (40%), Zn (34%), and Al (27%) were identified as originating from industrial emission sources deposited onto lakes because they accounted for a large proportion within the model.

Author Keywords: Arctic lake catchments, Biomonitoring, Enrichment factors, Positive matrix factorization model, Trace elements, Water chemistry

Chromophoric dissolved organic matter (CDOM), a chemically diverse family of organic compounds defined by their ability to absorb ultraviolet and visible light, is a critical constituent of numerous environmental systems, including freshwater lakes. Industrial operations in the Athabasca Oil Sands Region (AOSR, Alberta, Canada) are major sources of acidic inorganic gases and organic contaminants to the atmosphere, the subsequent deposition of which posed the potential to alter the composition of natural CDOM within surrounding lake surface-waters. The objective of this thesis was to determine if OS sources measurably impacted CDOM quality within 50 regionally monitored acid sensitive lakes by means of a) altered acid-base chemical processes or b) industrial atmospheric CDOM inputs. Ultraviolet-visible light spectroscopy and excitation emission matrix (EEM) fluorescence spectroscopy were applied to characterize CDOM within regional lake surface-waters to identify the primary sources (e.g., natural, anthropogenic) and process (e.g., acid-base chemistry) influencing chromophoric organic matter quality. These spectroscopic techniques were further used to evaluate industrial CDOM within atmospheric aerosols and deposition to assist with the identification of industrial CDOM within lake waters. Spectroscopic analysis of regional lake surface-water found weak associations between CDOM and acid-base variables, suggesting that acid inputs from OS sources would have limited influence over surface-water chromophoric organic matter. A distinct fluorescent component (i.e., fluorophore) measured within the lake samples (C3) displayed decreasing emission intensity as a function of distance from OS sources and positive correlations with surface-water polycyclic aromatic compounds, implying industrial influence. Spectral similarity between C3 and industrial fluorophores observed from regional aerosol and atmospheric deposition samples further confirmed the lake fluorophore was linked to OS sources. This research suggests that EEM fluorescence spectroscopy could be used as a cost-effective technique to detect industrial pollution within lake surface-waters throughout the AOSR.

Author Keywords: atmospheric brown carbon, atmospheric deposition, atmospheric pollution, dissolved organic matter, fluorescence spectroscopy, lake chemistry

Decades of sulphur and nitrogen deposition acidified forest ecosystems across northeastern North America causing declines in pH and exchangeable base cation concentrations, negatively affecting biota. To assist natural recovery, researchers are investigating using alkaline soil amendments such as wood ash. However, much remains unknown about its use. This thesis evaluated the effects of non-industrial wood ash application (between 0 – 12 Mg ha-1) on soil chemistry, understory vascular plant communities and sugar maple (Acer saccharum Marsh.) regeneration in central Ontario. Wood ash increased soil pH and concentrations of calcium, magnesium and several metals. Vascular plant species abundance, richness, and diversity exhibited no consistent treatment effect. Sugar maple seedling survivorship was adversely affected by wood ash applications > 4 Mg ha-1, while growth was unaffected. These results support related research regarding the ability for wood ash to increase soil pH and base cation status but raises uncertainty regarding consequences for vascular plants.

Author Keywords: Acer saccharum, Acid deposition, Ecosystem regeneration, Soil amendment, Understory vegetation, Wood ash

Measuring biodiversity has become increasingly complex as biologists and ecologists have gradually learned more about how biotic systems are structured and interact. Given the wide range of tools, techniques and approaches now in use to quantify biological diversity, it is useful to consider different "dimensions of diversity" to classify these measurements and provide context for their interpretation. Even within the genetic dimension of diversity alone, recent improvements in theory, technology, and statistics has generated several approaches which can provide distinct insights into natural systems. In this thesis, I use multiple "axes of diversity" to subdivide the dimension of genetic diversity to better understand a complex ecological system - the unisexual Ambystoma complex on Pelee Island, Ontario. By focusing on the genomotype axis, I found that the composition of local unisexual Ambystoma assemblages generally reflects the current relative abundance of the local sexual host populations. This suggests that sexual hosts can be thought of as a keystone species for the complex not only because they are required for unisexual Ambystoma to reproduce, but also because their relative abundance governs the composition of entire unisexual Ambystoma assemblages. Comparatively, when assessing the lineage axis of genetic diversity, unisexual Ambystoma assemblage diversity patterns primarily reflected historic landscape structure, and spatial patterns of increased lineage richness were linked to areas where both potential hosts were locally available (currently or historically). Thus, while both of the investigated axes of diversity are forms of genetic diversity, each revealed distinct factors that have shaped contemporary diversity patterns across the landscape operating at different spatial and temporal scales. Critically, our understanding of complex ecological systems is likely to be broadened by including additional axes of diversity (e.g., allelic, loci, or chromosomal structure axes), and such investigations are not limited to clonal hybrid systems. Overall, this work illustrates the importance of combining insights from distinct conceptual and analytical toolkits to generate a comprehensive understanding of the factors which have shaped the patterns of diversity we observe today.

Author Keywords: Biological diversity, Dimensions of diversity, Ecological genetics, Metacommunity ecology, Unisexual Ambystoma