Earth and Environmental Sciences

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Long-term evaluation of an organic-carbon permeable reactive barrier remediating mine-impacted groundwater and the potential of emulsified vegetable oil to increase treatment performance
(University of Waterloo, 2024-10-17) Miller, Austin
Degradation of water resources by acid mine drainage (AMD) and metal contaminants from the oxidation of mine wastes that are improperly managed is a global environmental concern. An established economical and passive method for managing the transport of oxidation products in groundwater is the installation of an organic-carbon permeable reactive barrier (PRB) to promote the growth of sulfate reducing bacteria (SRB) and dissimilatory sulfate reduction (DSR) in situ. A detailed biogeochemical evaluation was conducted on a PRB remediating AMD from an abandoned Ni-Cu mine after 26 years of treatment, providing the first long-term evaluation of this technology. Pore-water concentrations of Ni decreased from 97µg L⁻1 to < 25 µg L⁻¹ while Fe decreased by 402 mg L⁻¹ (77% of mean influent) through the PRB. Pore-water SO4 decreased by 1,243 mg L⁻¹ (70% of mean influent) coinciding with an increase in alkalinity and pore-water ẟ34Sₛₒ₄, suggesting DSR is actively occurring. There are distinctly different populations of putative SRB present within the sampled PRB material compared to the surrounding aquifer material. Low abundances of S and Fe oxidizing prokaryotes were detected, which may oxidize Fe-sulfide phases; re-mobilizing Fe and S or result in the formation of Fe(III) (oxy)hydroxide phases. A preponderance of S immobilized within the PRB is in the form of acid volatile sulfur with mineralogical investigations identifying FeS phases often replacing organic carbon in plant cellular material and framboidal pyrite. These results demonstrate that the PRB is still operating as designed with complex organic carbon compounds supporting a diverse microbial community that sustain rates of DSR to effectively precipitate Fe sulfides, decrease the acid potential of groundwater and immobilize contaminants. Column experiments were designed to evaluate the incorporation of emulsified vegetable oil (EVO) into solid-phase organic carbon through soaking and injection to promote and sustain treatment performance. Column effluent compositions demonstrate soaking organic-carbon in EVO resulted in high levels of Fe removal for the duration of observation (315 days). Moreover, an EVO injection re-established treatment after removal rates declined, providing a viable alternative to PRB replacement to maintain effective treatment system performance and extend PRB lifespan.
Graphical Analysis of Publicly Available Monitoring Well Databases to Evaluate and Categorize Groundwater Recovery Across Alberta, Canada
(University of Waterloo, 2024-09-09) Brunet, Melanie
A graphical analysis method is applied over the province of Alberta, Canada using publicly available water level data from standard monitoring wells to evaluate and categorize aquifer recovery. Agriculture in the province relies heavily upon surface water for irrigation, which is increasingly unreliable due to climate change and increasing climate variability. Due to an expected future reliance on groundwater, it is necessary to better understand groundwater flow and aquifer characteristics across Alberta to prevent over-allocation of groundwater resources. Water level data from provincial monitoring well hydrographs are examined and graphically analyzed to broadly characterize recovery in agriculturally significant regions of the province of Alberta, Canada. Through this analysis, the presence of a recharge boundary within a recovery curve can be ascertained. Of the 292 monitoring wells originally screened, recovery curve analysis is conducted on 49 monitoring wells. Using graphical analysis of recovery curves within monitoring well hydrographs, the presence or absence of recovery or aquifer replenishment in an area immediately surrounding monitoring well screens is determined. 785 recovery curves from the 49 monitoring wells are subsequently categorized as either “enhanced recovery”, “normal recovery”, or “inconclusive”, with continuing discussion and analysis focusing on results from 36 wells located in three significant aquifers within the province. These aquifers include the Paskapoo aquifer, aquifers within the irrigation districts of southern Alberta, and surficial aquifers within agriculturally rich regions of the province. Results demonstrate the presence of a potential recharge signal deviating from standard Theis recovery curve in 97.22% of the 36 monitoring wells studied. In individual wells, recovery curve classifications vary over time, with some recovery curves being classified as “normal recovery”, and some being classified as “enhanced recovery”, showing signs of a possible recharge boundary. This classification depends on the characterization of late-time recovery curve behavior, as pumping signals transition to regional aquifer signals over time. Analyzed hydrographs show the influence and effects of changes in groundwater pumping on surrounding water levels, including through change in water policy. This method provides information about the presence or absence of recharge over a large area, in contrast to traditional methods of determining recharge which cover smaller areas in comparison. However, a comprehensive database of monitoring well data are required to facilitate analysis, as 48.76% of recovery curves analyzed were classified as “inconclusive”. It is recommended that results from this method are paired with data such as climate indices or agricultural usage, to help determine possible correlations between results and climatic, geographic, or agricultural factors.
Numerical Modelling of Structural Patterns in Tectonic Flow with Applications to the Neoarchean Crustal Dynamics
(University of Waterloo, 2024-09-03) Wu, Qihang
We formulate a numerical framework, in both 2d and 3d, to model the structural patterns emerging from viscous tectonic flow by coupling a level set description of the material interface with a finite element flow solver. Our formulation has the advantage of straightforward extensibility to encompass complex rheology and versatile mesh geometry, as well as improved computational efficiency. A distinct novelty of our formulation is the capability to offer a fully dynamical approach to modelling structural patterns resulting from an inhomogeneous and non-steady tectonic flow. The model output, in the form of lithological distribution and deformation patterns, can be directly compared with the results of based geological mapping and structural analysis, thus offering the opportunity to ground-truth the abstract numerical models with concrete field observations. As examples for the potential applications of our method, we apply our newly developed method to the modelling of the crustal dynamics of the Neoarchean granitoid-greenstone terranes in two case studies to shed light on the potential vertical- to horizontal-style tectonics. In the first case study, a field-based structural study is conducted in the Swayze greenstone belt in the Superior Craton and four generations (G1--G4) of ductile deformations are identified. Among them, G2 structures are associated with an oblique shearing kinematics with a granitoid-up/greenstone-down movement in the vertical direction and a dextral sense of shear in the horizontal direction, as well as an opposing plunge directions of L2 stretching lineation. The tectonic regime associated with G2 is interpreted to be the operation of vertical-style tectonism in the form of sagduction/diapirism under the backdrop of horizontal-style tectonism in the form of regional dextral simple shearing. To test this interpretation, an isothermal numerical model is constructed for the Swayze greenstone belt. The model replicates the observed lithological and deformation pattern, confirming the synchronous vertical and horizontal tectonism model as a viable regime to explain the observed structural patterns. To further explore whether the synchronous vertical and horizontal tectonism is applicable to the Neoarchean crustal dynamics in general, a thermomechanical model is constructed in the second case study with both thermal and rheological conditions appropriate for the Neoarchean granitoid-greenstone terranes. As in the first case study, many aspects of the crustal architecture and structural patterns are comparable to the observations in Neoarchean terranes worldwide. Due to the high competency of the cold upper crust, the density-induced sinking of the supracrustal assemblages into the granitoid domes operates by active diachronous pointwise ``dripping'' at triple junctions or by sheet-like sagduction with higher rate of horizontal shearing. Furthermore, the transitional process of the crustal dynamics towards the modern-day conditions from the hotter Archean Earth is further explored by systematically decreasing the Moho heat flux, which results in a delayed initiation and a slower rate of the vertical tectonic process. The increase in the horizontal strain rate results in the promotion of sheet-like sagduction pattern, the elongation of granitoid domes, the preferential alignment of the high strain zones and the reduction of the rate of greenstone sagduction. It is therefore postulated that through the secular cooling of the crustal thermal condition, the role of density-induced sagduction/diapirism is suppressed, thereby completing the transition of the Earth's crustal dynamics from a dominantly vertical style in the early Earth's history to a present-day dominantly horizontal style, with the Neoarchean being the interlude period where both processes coexisted. Furthermore, taking into account that the Neoarchean lithospheric dynamics of the southeastern Superior Craton is interpreted to be terrane accretion under a plate tectonics-like regime, we conclude that the synchronous horizontal and vertical crustal dynamics is not contradictory to a framework of plate tectonics on a lithospheric scale. In fact, the Neoarchean transition in crustal dynamics may mirror a similar transition in lithospheric dynamics from the early stagnant-lid tectonics to the modern day plate tectonics.
Till Stratigraphy and Sediment Provenance of the Dessert Lake Drumlin Field Area, West of Great Slave Lake, NT: Implications for Regional Glacial Dynamics Models
(University of Waterloo, 2024-08-30) Wenyao, Liang
The integration of till stratigraphic and sedimentologic studies with landform-based ice flow analysis has considerable potential for advancing our understanding of subglacial processes, particularly those related to subglacial sediment transport and the generation of subglacial landforms such as drumlins. Currently, few drumlin studies incorporate till provenance analysis, which limits our ability to establish relationships with subglacial sediment transport, drumlin forming processes, and the regional glacial history. Considerable effort has been made to reconstruct the last glaciation, with a particular focus on the geometry of the Laurentide Ice Sheet (LIS) ice margins and their retreat pattern and chronology. However, to comprehend the long-term evolution of the LIS during a glaciation, it is also essential to include the dynamics of ice streams, the positions of ice divides and their migration phases, and related shifts in ice flow. The history of glacial dynamics remains limited in many regions covered by the LIS. This research focuses on the Dessert Lake drumlin field, west of Great Slave Lake (GSL) within National Topographic System (NTS) map 85K. This area presents a significant opportunity to investigate tills and related sedimentary processes within a drumlin field due to road access and the presence of road cuts extending across several drumlins along Highway 3. Additionally, the bedrock geology consists of sufficiently contrasting bedrock units extending approximately perpendicular to the long axis of the drumlins, which is particularly useful for till provenance analysis. The glacial geology record of western GSL bears evidence for four distinct ice-flow phases of the LIS. These phases are preserved in various forms such as outcrop-scale erosional features, subglacial streamlined landforms, and in the orientation of clasts in different tills (a.k.a. till fabric) preserved within the drumlins, as well as in the composition of the till, which is useful to establish bedrock source regions (provenance). The sequence of ice flows indicates an initial southward (180 to 190 deg.) ice flow phase, followed by a clockwise shift towards westward (260 to 270 deg.) ice flow, then a slight deviation towards southwestward (215 to 245 deg.) flow. The counterclockwise shift is supported by the overprint relationship of southwesterly oriented landforms on westerly oriented landforms. The average direction of the drumlin’s long axis is 249 degrees, which is close to the top till fabric of drumlin section 1 (246 deg.). Finally, there is evidence along the shore of western GSL for a late northwestward (320 to 325 deg.) flow, which may have been limited in lateral extent. The till provenance analysis suggests some of the surficial till samples show a dominantly local provenance, but there is surficial till with a more distal signature such as more abundant Canadian Shield derived clasts. These changes in ice flow corresponded with the overall eastward retreat of the ice margin and the increasing influence of topography due to the diminishing thickness of the ice. In conclusion, glacial dynamics shifted in the area, and the evidence is well-preserved in both the erosional and depositional records. Till stratigraphy and related ice flow shifts are preserved within the drumlin cores. Since erosional processes are thought to play an important role in the formation of drumlins, it is likely, in the context of stratified drumlins, that the surficial till in the Dessert Lake drumlin field, and perhaps in other similar settings, consist of multiple till sheets deposited under different subglacial transport regimes and pathways and may thus have contrasting bedrock source regions. It is thus critical for applications like mineral exploration and environmental protection to determine if the till in lower stratigraphic positions occurs at the surface in the drumlin field.
Guiding future research to support water management decisions in the Canadian Prairies using an integrated hydrologic model
(University of Waterloo, 2024-08-22) Wilson, Hilary
Groundwater is the main source of water for most people in the Canadian Prairies. As the Canadian Prairies are prone to droughts, the need for additional water supplies is expected to increase as more changes to the climate in this region occur. With climate change, an increase in temperature and precipitation are anticipated. While an increase in precipitation should lead to an increase in infiltration of precipitation into the groundwater systems, this is not necessarily the case. As the temperature increases, it is expected that the already high rate of evapotranspiration will increase, limiting the chance for water to infiltrate the subsurface. This leads to the need for water management plans, which requires an understanding of the hydrologic flow system in the area. Hydrologic models are commonly used to help support water management decisions; however, they are often not developed until after most of the data collection and interpretation is completed. The utility of a preliminary hydrologic model to guide data collection efforts is not often employed, despite the opportunity for significant insight into key processes and data gaps. The goal of this research is to develop a preliminary integrated hydrologic model of an aquifer in the Canadian Prairies to identify research and data gaps that limit the creation of water management plans. The model, created using HydroGeoSphere, is based on the Dalmeny aquifer in Saskatchewan. A base model representing steady state historic conditions was developed, and then three climate change scenarios were simulated and compared to the results of this base model. These climate change scenarios were chosen based on their prevalent use by the Government of Canada using Representative Concentration Pathways. The three climate change scenarios are representative of (1) a significant reduction in global emissions of greenhouse gases, (2) there is no change to the current projected increase in global greenhouse gas emissions, and (3) a significant increase in global greenhouse gas emissions. The results of the base model indicate that groundwater flow is driven by topography, and yet updated, high-resolution topographical data is not readily available, indicating a data gap. The results of the climate scenarios indicate an overall decrease in hydraulic head in the aquifer due to increased estimated evapotranspiration. Evapotranspiration in this region is complex, as annual potential evapotranspiration is greater than precipitation, and so higher temporal resolution evapotranspiration data is necessary to capture infiltration. The direction of flow in some portions of the aquifer also change, leading to one of the boundaries, which is along the South Saskatchewan River, to change from a gaining river in the base scenario, to a losing river in the climate change scenarios. The uncertainty along the river boundaries, particularly related to their connectedness to the aquifer and their temporal and spatial variability, are key data gaps that should be addressed. In summary, this work shows that the preliminary integrated hydrologic model results indicate that , in order to support a more accurate simulation to support water management, additional data is necessary to improve: 1) the resolution of the topographical information of the study site, 2) the available methods of estimating temporally appropriate evapotranspiration and, 3) the understanding of groundwater-surface water interactions along the rivers, particularly South Saskatchewan River. With these alterations, a more robust water management plan can be developed, that will protect the availability of groundwater in the study area. By developing a preliminary model with limited information, improvements to the model development of the study area can be pursued.
Controls on Microplastics Accumulation in Stormwater Ponds
(University of Waterloo, 2024-07-04) Nguyen, Thu Hang
Microplastics (MPs), or plastic particles that are less than 5 mm in diameter, are an emerging threat to aquatic and terrestrial ecosystems because of their potential toxicity and their resistance to degradation. In urban watersheds, stormwater runoff is a major carrier of MPs to downstream water bodies, which often drains into green infrastructure such as stormwater ponds (SWPs). The existing evidence indicates that SWPs may be effective at reducing the export loads of MPs from urban areas. However, the effectiveness of SWPs in retaining MPs and the controls on their accumulation in SWP remain understudied. Hence, it is significant to investigate MP occurrence and factors controlling MP distribution in SWPs. In this thesis, I aimed to (1) assess the variability in MP types, sizes, and abundances within SWP sediment and water samples, (2) determine the influence of sediment properties (e.g., organic carbon concentration, particle size) on the types, shapes and sizes of MPs accumulating in sediments versus within and between SWPs, and (3) investigate the impact of SWP characteristics on MP accumulation, including land use and land cover (LULC). I addressed these research objectives by collecting sediment and water samples from five SWPs with different LULC (industrial, residential, and commercial) in the City of Kitchener, Ontario, Canada, extracting MPs from environmental samples, and characterizing MP particles using laser direct infrared (LDIR) imaging spectroscopy. In Chapter 2, I extracted MPs from sediment cores in triplicates and determined MP counts and morphologies using the LDIR. I also analyzed sediment for grain size, mineralogy, and organic carbon (OC) content. The results revealed that the MPs accumulated in the sediments were predominantly fragments, with concentrations approximately 50 times higher than fibers, implying an important role of particle shape in controlling the accumulation of MP particles in SWP sediments. The highest fragment concentrations (2.3×108 particles kg dw-1) were found in the commercial SWP, while the highest fiber concentrations (4.5×106 particles kg dw-1) were found in the industrial SWP. Surface area-normalized MP accumulation rates in the forebays were generally 2-5 times higher than in the main basins. Sediment grain size and catchment impervious cover were significantly correlated with MP accumulation rates, with increasing MP concentrations observed with finer sediment grain size and higher catchment imperviousness. Polyamide and polyethylene were the two most abundant polymers found in the pond sediment, along with an overwhelming dominance of MP particles less than 50 µm. MP polymer composition and size distribution thus reflected the contribution of urban activities to MP pollution in a watershed. These findings indicate the important role of catchments’ land cover in the build-up and wash-off of sediments and MPs to downstream areas such as SWPs. In Chapter 3, I quantified and characterized MP shapes, types, and sizes in stormwater samples collected bi-monthly from 5 SWPs. In a one-year water sample collections, MPs appeared to fluctuate with significant seasonal variation throughout the year with the highest concentration recorded in a residential pond (up to 20,166 fragment L-1 and 559 fiber L-1). Polyamide and polyethylene accounted for approximately 80% of total MP in the pond water, while small-sized MPs make up 85% of the particles, highlighting the impact of catchment land use on MP occurrence in SWP. Precipitation, wind speed, and pond hydraulic loading were found to wash away surface MPs and dilute MP concentration in the water column. These findings demonstrate the diversity in MP profiles associated with climate factors, implying a need for long-term monitoring to address those spatial and temporal variability. The results from Chapters 2 and 3 overall provided an insight into MPs' preferential partitioning between two different environmental matrices, which can be applied in future research to assess the sources, transport, and fate of MPs in the freshwater ecosystem. Data from this research can be applied to generate MP accumulation rates across the Grand River watershed and eventually the Great Lakes. The outcomes from this study, moreover, actors influencing MP accumulation in urban catchments, and therefore, can support further studies on characterizing MP mass balance and budget for urban watersheds. Since SWPs are an effective indicator of local sources of MP pollution, understanding the MP from urban catchment can inform policymakers in a larger aquatic ecosystem to tailor management strategies accordingly. The research study presented in this thesis therefore contributes to the development of local policies and regulations, which not only address specific sources of MP pollution but also serve as models for larger-scale regulations aimed at protecting the freshwater environment.
Assessing the biodegradability of dissolved organic carbon in freshwater systems
(University of Waterloo, 2024-06-18) Green, Danielle
Dissolved organic carbon (DOC) is an important contributor to both carbon (C) cycling and other biogeochemical processes in aquatic ecosystems as it is the most mobile fraction of organic matter. The biodegradable fraction of DOC can be microbially degraded over time, producing carbon dioxide (CO2), a greenhouse gas (GHG) that is subsequently released to the atmosphere. In addition, microbial degradation-resistant DOC can accumulate in water bodies, causing chemical and physical changes to aquatic systems, resulting in decreased primary productivity, formation of anoxic zones, and negative implications on the aquatic food cycle. Although biodegradable DOC (BDOC) is widely studied, there is no agreed-upon standard method for assessing DOC biodegradability. Given its important control on CO2 production and natural functioning of aquatic ecosystems, it is essential to develop an accurate and reproducible method for quantifying BDOC in aqueous samples. In Chapter 2, I developed and evaluated a new method for determining BDOC in freshwater samples. The method includes filtering water samples to below 0.22 µm, to remove existing microbial cells, prior to inoculating the samples with a concentrated microbial inoculum produced by stepwise isolation of microbial cells from a peat sample. Additionally, I added solutions containing nitrogen (N) and phosphorus (P) (in the forms of ammonium nitrate (NH4NO3) and potassium phosphate (K2HPO4), respectively) to ensure that the microbes were not nutrient-limited. The samples were then capped with foam stoppers and incubated in the dark at 25⁰C on a shaker for 28 days to allow constant aeration during BDOC degradation. When applied to five freshwater samples collected from rivers, stormwater ponds, and a lake, and a glucose control, I observed that the amount of BDOC in the natural samples ranged from 15% to 53% and was 90% in the glucose control. Rates of BDOC degradation were calculated from DOC measurements at six sampling time points between days 0 and 28. I found that the DOC trends with time were best explained by two successive phases for BDOC degradation in all of the samples: an initial, fast, phase of BDOC degradation followed by a second, slower, phase of BDOC degradation where the rate constant for the second phase was between 5.57 and 565 times slower than for the initial phase. Changes in chemical characteristics of DOC measured using absorbance and fluorescence parameters including specific ultraviolet absorbance at 254 nm (SUVA254), humification index (HIX), and parallel factor analysis (PARAFAC) at each sampling time revealed that the initial, fast, phase of BDOC degradation often represents the utilization of small, non-aromatic compounds while the later, slower, phase of BDOC degradation often represents the utilization of more complex, aromatic compounds. The developed method provides a new approach to measure and characterize BDOC degradability and degradation kinetics that can be applied to future studies on biogeochemical processes in aquatic ecosystems. In Chapter 3, I examined the potential for CO2, a greenhouse gas, to be produced from two stormwater ponds (SWPs) in the City of Kitchener, Ontario, Canada by quantifying the biodegradability of DOC entering the ponds through the inlet sewers during rain events. Further, BDOC, the fraction of DOC that can be mineralized by microbes during respiration to produce CO2, was related to the optical properties of water entering each of the SWPs to determine if any statistically significant relationships exist between BDOC and the optical properties of water. In the two studied SWPs, one with industrial land use and one with residential land use in the catchment area, we found significant negative linear correlations between BDOC and SUVA254, HIX, biologic index (BIX), and humic-like and tryptophan-like PARAFAC components. Additionally, there were significant positive linear correlations between BDOC and DOC concentration, benzoic acid, and tyrosine-like PARAFAC components. These optical properties are influenced by characteristics of the SWP catchment areas including imperviousness and land use. Overall, these findings indicate that increased urbanization results in changes in optical properties of DOC entering SWPs, increasing the amount of BDOC and, in turn, the potential for increased CO2 emissions.
Evaluation of the Potential Impacts of Submerging the Oxidized Tailings and Adding a Cover Layer at Mine Principale
(University of Waterloo, 2024-04-24) Agau, Majak
Oxidation of sulfide minerals generates acid and forms various secondary phases including Fe(III) (oxy)hydroxide phases, jarosite, and gypsum, which can attenuate hazardous metal(loid)s by precipitation, co-precipitation, and adsorption reactions within tailings. The abandoned Cu-Ag mine at Mine Principale, Chibougamau, Québec, has three tailings impoundments (Parcs, A, B, and C) that have oxidized for more than 50 years. This project focused on Parc B, where tailings are stored to an average depth of 8.0 meters below the ground surface (mbgs). The study involved mineralogical, chemical, and microbiological analyses to evaluate the potential impacts of the proposed elevated water table (EWT) technique on the partially oxidized tailings. The EWT involves raising the water table and maintaining it above reactive tailings. Increasing the water content limits sulfide-mineral oxidation by minimizing O2 ingress into the tailings, owing to its low diffusivity in saturated media. However, the EWT can cause direct dissolution of soluble secondary phases, and also can potentially induce reducing conditions that promote microbially catalyzed reductive dissolution of Fe(III) (oxy)hydroxide phases fueled by organic C compounds. In this study, mineralogical and selective chemical extraction techniques indicate the presence of various secondary phases including Fe(III) (oxy)hydroxides that are associated with significant amounts of hazardous metal(loid)s including Cu, Ni, Co, Zn, As and Pb in the oxidized zone, which is limited to a depth of about 1.5 mbgs in Parc B. Results of amplicon sequencing of 16S rRNA genes show significant abundances of Fe- and S-oxidizing bacteria and S-reducing bacteria but no presence of Fe-reducing bacteria. Solid-phase analyses indicate a low amount of total C in the oxidized tailings. These findings suggest that EWT technique can be an effective reclamation method for Mine Principale tailings if use in conjunction with another suitable method to address potential low-quality drainage resulting from the inducement of reducing conditions post EWT application.
Chlorophyll-a Mapping in a Large Lake Using Remote Sensing Imagery: A Case Study of Western Lake Ontario
(University of Waterloo, 2024-04-23) Shahvaran, Ali Reza
Western Lake Ontario (WLO) and Hamilton Harbour (HH) experience significant eutrophication challenges. Despite an overall decrease in the limiting nutrient phosphorus (P) inputs, recurrent nuisance (Cladophora) and cyanobacterial harmful algal blooms (cHABS) are observed in nearshore hotspots of WLO and HH, respectively. These events hint at a complex interplay of contributing factors including not only of P availability but nutrient enrichment in general, as well as invasive mussel species altering ecosystem dynamics, climate change, and other anthropogenic influences. As a result, continued and consistent monitoring is of paramount importance. Eutrophication in WLO and HH is also linked to the expanding urbanization within the Golden Horseshoe, which includes the Greater Toronto Area (GTA), along with nutrient point and nonpoint load sources from stormwater management systems and agricultural watersheds. Of importance are also the nutrient inputs flowing from Lake Erie through the Niagara River creating local productivity zones at the river mouth. Traditional field-based monitoring methods face limitations, including high costs, labour intensity, limited temporal resolution and inadequate spatial coverage. In that respect, remote sensing (RS) may offer an alternative approach, leveraging the water colour (optical properties) to detect optically active constituents (OACs) like Chlorophyll-a (Chl-a) that can provide proxies for phytoplankton abundance in algae. The distinct spectral signatures of Chl-a make multi-spectral imagery a valuable tool for water quality assessment that can complement ongoing in-situ monitoring. This thesis presents a comprehensive analysis aimed at enhancing the capacity for monitoring nearshore algal blooms in the oligo-mesotrophic WLO and eutrophic HH through publicly available high-spatial-resolution (< 100 m) RS satellites data, specifically Landsat 5, 7, 8, 9, and Sentinel-2. The research explores the optimal combinations of atmospheric correction methods and reflectance indexes to develop semi-empirical based Chl-a retrieval models specific to the (sub)regions considered. As an additional application, the satellite based Chl-a data are used to assess the spatial-temporal variability and trends of algal productivity over the past decade, identifying productivity hotspots and anomalies. The thesis is structured in five chapters, beginning with a general introduction in Chapter 1, followed by Chapter 2, which offers the necessary background for understanding the research presented in the thesis. Chapters 3 and 4 delve into comparative evaluations of Chl-a retrieval methods and time-series analysis of algal bloom dynamics, respectively. The thesis ends with Chapter 5, which synthesizes the main findings and offers conclusions and future research directions. Chapter 3 presents a comprehensive comparative evaluation of atmospheric correction processors and reflectance indexes, assessing their performance in Chl-a concentration retrieval from a multi-platform collection of satellite data. By analyzing satellite scenes from different platforms alongside in-situ measured Chl-a data, the chapter develops predictive linear regression models. The results highlight the superior performance of certain combinations, particularly ACOLITE-corrected Landsat 8 and Sentinel-2 imagery utilizing two band ratio indexes, that is blue-to-green or blue-to-red, in capturing Chl-a concentration with acceptable accuracy. Delving into the Chl-a dynamics, Chapter 4 presents a time-series analysis using Landsat 8 and 9 imagery from 2013 to 2023, to reconstruct the spatial-temporal patterns and hotspots in WLO and HH. After preprocessing a collection of Level-1 images with the optimal combination of atmospheric correction method and retrieval index, as identified in Chapter 3, a time-series collection of estimated Chl-a concentration maps are produced. By applying three algal growth indicators, namely bloom intensity, extent, and severity, along with averaging annual and monthly estimated Chl-a concertation maps and conducting a Mann-Kendall trend analysis, we are able to examine algal bloom dynamics, seasonality, and delineate areas of concern. The results should help in planning monitoring and design eutrophication management strategies for the region. The findings from this thesis underscore the potential of space-borne RS in advancing water quality monitoring that can inform management practices. By identifying the most effective methods for Chl-a concentration retrieval and providing a nuanced understanding of algal growth dynamics, the research in this thesis contributes to both fields of aquatic RS and water quality monitoring. The comparative analyses, model developments, and spatial-temporal investigations not only offer practical tools for water quality assessment but also set the stage for future studies leveraging machine learning and existing satellite datasets. The work demonstrates the critical role of tailored RS applications in addressing eutrophication issues, advocating for integrated monitoring approaches to sustain aquatic ecosystems in the face of changing environmental conditions.
Glacial Dispersion at the Canadian Malartic Gold Deposit
(University of Waterloo, 2024-04-19) Taylor, Caroline Emily
A novel drift prospecting approach detected components from previously established bedrock footprints at the world-class Canadian Malartic gold deposit within the site’s surrounding Quaternary sediments. The measured glacial dispersion of footprint components is significantly more extensive than the largest bedrock footprint. This new method could apply to similar high-tonnage disseminated gold deposits and other deposits with similar features. Drift prospecting methods included ice flow indicator mapping, surficial sediment sampling and characterization, particle size distribution analyses, till matrix geochemistry (major oxide, minor, and trace elements), glacial clast lithology, gold grain counts, and petrography. Our novel approach combined hyperspectral imaging analyses with petrographic analyses targeting glacial granules and pebbles. Within the study area, the direction of past ice flow phases evolves from ~210º to ~150º; it dominates towards ~170º. Multivariate analysis of till matrix major oxide geochemistry links clusters of samples to bedrock geology and postglacial processes. Till clast lithologies link to bedrock type. The spatial distribution of till matrix minor and trace element geochemical values reveals glacial dispersal trains for Au, Ag, Rb, W, and potentially Ba; however, glacial dispersal trains for Cs, Mo, Pb, and Sr are unclear (all listed elements have been previously reported as footprint components). Multivariate analyses of till matrix minor and trace element geochemistry link clusters of samples to footprint components (Mo has the highest first principal component positive loading in the relevant cluster), bedrock geology background values, and postglacial processes. Sand-sized gold grain counts from till and their morphology link to the phengitic white mica bedrock footprint associated with the deposit. Hyperspectral imaging analysis of bulk glacial clasts reveals dispersal extents that are significantly larger than the extent of the phengitic white mica footprint in bedrock (i.e, the most extensive bedrock footprint at the Canadian Malartic gold deposit). 4-8 mm tracer till clasts produce a dispersal extent 7.0-13.5 times larger while 2-4 mm tracer till clasts produce a dispersal extent 4.5-8.4 times larger than the bedrock footprint. Further, petrographic analyses of 42 highly phengitic 4-8 mm clasts classify 14 clasts as showing mineralogy and rock texture similar to the host quartz-monzodioritic, granodioritic, and meta-sedimentary rocks at the deposit. One of these clasts is mineralized with gold like the mineralization at the Canadian Malartic deposit, and this is the first reported instance of finding a mineralized clast using this novel technique. The Quaternary dispersion relative to the previously established bedrock footprints at the Canadian Malartic gold deposit is significant. Ongoing hyperspectral imaging and petrographic analyses of similar clasts may demonstrate numerous practical applications to exploration campaigns seeking other Canadian Malartic-type gold deposits or other deposits with similar characteristics.
Evolution of the Laurentide Ice Sheet in north-central Ontario from subglacial sediments
(University of Waterloo, 2024-03-12) Taves, Robin
Till stratigraphic analysis of 10 sediment bluffs near Ogoki Post in the Hudson and James Bay Lowlands.
Proterozoic zircon dates from auriferous zones at the Island Gold deposit: implications for late gold remobilization in the Superior Province
(University of Waterloo, 2024-02-13) Gagnon, Sophie Marie
The Island Gold deposit is a high-grade Archean orogenic gold deposit within the Michipicoten greenstone belt of the Superior Province. Hosted within the ~2750 Ma felsic to intermediate Wawa metavolcanic assemblage, gold mineralization has been constrained to between ~2680 and 2673 Ma. However, anomalous Proterozoic ages have been discovered within auriferous alteration zones, suggesting that late hydrothermal activity may have affected the deposit and potentially remobilized gold. Mineralization is hosted within quartz (± carbonate) veins, with minimal mineralization within the surrounding altered host rock. To investigate the occurrence and spatial distribution of these anomalous young ages within the deposit, samples along an alteration gradient (weakly to strongly altered) adjacent to auriferous quartz ± carbonate veins, and from differing depths within the ore zone were examined. U–Pb LA-ICP-MS analyses of zircon from strongly altered auriferous zones yielded Archean protolith dates as well as Mesoproterozoic and early Paleozoic to late Mesozoic dates. Compared to Archean zircons in the host metavolcanic rocks, the younger zircons have generally higher concentrations of heavy rare earth elements and moderate enrichment in Y, Ta, U, and Th. We interpret the Mesoproterozoic ages to represent fluid–rock interaction during the Mid-Continent Rift, whereas the Paleozoic to Mesozoic grouping may be related to alkalic/kimberlitic activity within the area associated with the Great Meteor Hotspot track. It is unclear if these fluids had compositions amenable for large-scale gold mobilization, but they may have played a role in locally distributing gold throughout the Island Gold deposit. An increasing number of reported Proterozoic dates from accessory minerals in Archean gold deposits suggests that post-Archean processes are a potential complication for understanding the distribution of gold and has regional implications for gold exploration in the Superior Province.
Use of Fe isotopes to examine Fe cycling in Boreal Shield lakes: implications for cyanobacterial bloom development and ancient biogeochemical cycling
(University of Waterloo, 2024-01-26) LIU, KAI
Stable iron (Fe) isotopes have only been used recently to explore biogeochemical Fe processes in terrestrial and aquatic ecosystems. The δ⁵⁶Fe values in natural samples range from −4‰ to 4‰. An increasing number of studies have focused on Fe isotopes in marine settings. However, few studies have focused on lake systems and only in extreme environments such as meromictic ferruginous lakes. This thesis has applications in two distinct fields, freshwater eutrophic research and early Earth evolution. Phytoplankton blooms have been studied extensively in lake ecosystems. Despite the fact that macronutrients phosphorus and nitrogen are commonly known as dominant factors controlling the blooms, the critical role of micronutrient Fe has been proposed in recent studies. However, current understanding of the sources and availability of Fe for phytoplankton blooms and Fe cycling in lakes in general remains limited. Although the mechanisms that result in the deposition of banded iron formation in the Archean ocean remain a subject of debate, it is proposed that photoferrotrophy played a significant role in the oxidation of Fe(II) in anoxic Archean oceans. Studies investigating the occurrence and significance of photoferrotrophy have primarily focused on meromictic and ferruginous lakes. However, such lakes are thought to be rare on a global scale. To explore the potential application of stable Fe isotopes for tracing biogeochemical Fe cycling in Boreal Shield lakes, δ⁵⁶Fe values of dissolved, particulate, and sediment Fe were measured in two small dimictic Boreal Shield headwater lakes: manipulated eutrophic Lake 227, with annual cyanobacterial blooms, and unmanipulated oligotrophic Lake 442. Within these small lakes, the range in δ⁵⁶Fe is large (ca. −0.9 to +1.8‰), spanning more than half the entire range of natural Earth surface samples. Two layers in the water column with distinctive δ⁵⁶Fe of dissolved (DFe) and particulate Fe (PFe) were observed in both lakes, despite large differences in trophic states. During cyanobacterial blooms in Lake 227, selective uptake of isotopically light Fe modifies δ⁵⁶Fe, resulting in Δ⁵⁶Fe dis-part of up to 1‰ between dissolved and particulate Fe in the epilimnion while little fractionation was observed in the epilimnion of Lake 442. In the anoxic layers in both lakes, upward flux from sediments dominates the dissolved Fe pool with an apparent Δ⁵⁶Fe dis-part of −2.2 to −0.6‰. Large Δ⁵⁶Fe dis-part and previously published metagenome sequence data suggest active Fe cycling processes in anoxic layers, such as microaerophilic Fe(II) oxidation or photoferrotrophy, could regulate biogeochemical cycling. Large fractionation of stable Fe isotopes in these lakes provides a potential tool to probe Fe cycling and the acquisition of Fe by cyanobacteria, with relevance for understanding biogeochemical cycling of Earth’s early ferruginous oceans. To further explore the effect of phytoplankton blooms on biogeochemical Fe cycling in the epilimnion and metalimnion of L227, seasonal variations in Fe concentrations, Fe speciation and Fe isotope compositions of dissolved Fe (DFe), particulate Fe (PFe) and total Fe (TFe) were reported in the oxic layers of L227 and L442. Biological uptake of Fe by phytoplankton results in a decrease in DFe, an increase in PFe and a decrease in TFe in the oxic epilimnion and metalimnion during the blooms. The prevalence of Fe(II) in the particulate Fe coupled with the depletion of Fe(II) in the dissolved Fe during the blooms suggest that diazotrophic cyanobacteria and chlorophytes in L227 likely utilize dissolved inorganic Fe(II) rather than organic complexed Fe(III), highlighting the importance of Fe(II) during iron acquisition. Uptake of isotopically light Fe by phytoplankton results in a diagnostic change in the dissolved and particulate δ⁵⁶Fe in the oxic layers. As a result, dissolved δ⁵⁶Fe is more positive than particulate δ⁵⁶Fe in the oxic layers of L227, with Δ⁵⁶Fe dis-part of 1.02 ± 0.33‰ (2σ) during the peak of the first bloom and Δ⁵⁶Fe dis-part of 0.56 ± 0.05‰ (2σ) during the second bloom. The difference in Δ⁵⁶Fe dis-part observed during the first bloom and the second bloom suggests that uptake of Fe by chlorophytes might produce distinct Fe isotope fractionation compared to diazotrophic cyanobacteria, possibly due to the differences in their uptake kinetics, the specific Fe-uptake mechanisms and associated enzymatic processes. The consistency in TFe concentration and Fe isotope composition of TFe in the epilimnion throughout the first and second blooms suggest that the settling flux of particulate Fe is limited during the blooms, likely due to efficient retention by phytoplankton. In contrast, during the decline of the bloom, the settling of isotopically light particulate Fe(II) associated with biomass to profundal sediment caused total δ⁵⁶Fe in the epilimnion to become isotopically heavier. During the peak of the first bloom, the large Δ⁵⁶Fe dis-part, the more negative particulate δ⁵⁶Fe, and the more particulate Fe concentrations in the metalimnion compared to what has been observed in the epilimnion suggest that cyanobacteria could migrate to the upper zone of the anoxic hypolimnion to uptake Fe under Fe-limited conditions. Modelling results showed that isotopically light PFe and TFe measured in the metalimnion during the peak of the first bloom are best explained by the migration of cyanobacteria below the redox boundary for the uptake of dissolved Fe(II). The observed seasonal variation in Fe concentration, speciation and isotope compositions associated with the progression of two annual blooms show great potential in understanding the role of Fe in the formation of cyanobacterial bloom and determining the availability and source of Fe for cyanobacterial uptake. To explore the Fe processes and Fe sources in the anoxic hypolimnia of Boreal Shield lakes, seasonal variation in Fe concentrations and Fe isotope compositions of dissolved Fe and particulate Fe in the anoxic hypolimnia along with the Fe concentrations and Fe isotope compositions of porewater Fe and bulk sediment Fe in bottom sediment cores were reported in four Boreal Shield lakes: one eutrophic Lake 227 and three oligotrophic Lake 221, Lake 304 and Lake 442. In the oxic layers of all lakes, dissolved δ⁵⁶Fe is more positive than particulate δ⁵⁶Fe, likely modified by a combination of multiple processes including biological uptake, photochemical reduction of particulate Fe(III), complexation of dissolved Fe and dissolved organic matter, photolysis and microbial decomposition. The observed Δ⁵⁶Fe dis-part in the oxic layers of all lakes ranges from 0.06 ± 0.09‰ (2σ) to 1.02 ± 0.33‰(2σ), with the higher values likely arising from biological uptake. In contrast, the δ⁵⁶Fe values of dissolved and particulate Fe are reversed in the anoxic hypolimnia of all lakes, with negative Δ⁵⁶Fe dis-part fractionations of −0.91 ± 0.58‰ (2σ) in L221, −0.87 ± 0.81‰ (2σ) in L227, −1.06 ± 0.26‰ (2σ) in L304 and −0.72 ± 0.25‰ (2σ) in L442. Particulate Fe from the epilimnia is likely reduced completely by dissimilatory iron-reducing bacteria at the redox boundary, supported by the similarity in δ⁵⁶Fe between dissolved Fe in the anoxic hypolimnia and particulate Fe in the epilimnia of all lakes. The highly positive δ⁵⁶Fe values of particulate Fe in the anoxic hypolimnion and the large Δ⁵⁶Fe dis-part fractionations indicate in situ active Fe cycling in the anoxic hypolimnion. The most plausible explanation for the large Δ⁵⁶Fe dis-part fractionations in the anoxic hypolimnion is microbial oxidation, possibly photoferrotrophy, supported by the 16S rRNA gene sequencing and genome-resolved metagenome sequencing analysis. An increase in the magnitude of Δ⁵⁶Fe dis-part with depth and over time was observed in L221, L227 and L304, likely due to the variation of the oxidation rates, supported by increased particulate Fe concentrations with depth and time. The high concentration and negative δ⁵⁶Fe values of porewater Fe(II) suggest that DIR dominates organic mineralization pathways in sediment cores from the bottoms of L227, L304 and L442. The DIR-produced porewater δ⁵⁶Fe is further modified by the diagenetic formation of siderite in the upper section of sediment cores and the diagenetic formation of pyrite in the deeper section. Temporal and spatial variation in Fe isotope fractionation in the anoxic hypolimnia, along with the Fe isotope signatures in the sediment, suggest active Fe cycling in four lakes, highlighting the potential of seasonally anoxic Boreal Shield lakes to serve as analogues of the late Archean ocean.
Hydrogeochemistry and Trace Element Mobility in an Acidic High-Sulfide Tailings Impoundment After 40 Years of Oxidation
(University of Waterloo, 2024-01-25) Starzynski, Hannah Lucy
Abandoned mine sites can create a legacy environmental contamination issue when the generation of acid mine drainage is allowed to continue with insufficient or absent remediation measures. The South Bay mine, a former underground Cu-Zn mine located in northwestern Ontario, is once such site with historical contamination. The mine wastes at South Bay contain high concentrations of sulfide minerals which continue to oxidize decades following mine closure, leading to acidic seepage with high concentrations of dissolved metals impacting the surrounding lakes. This aim of this study is to provide a characterization of the current hydrogeology, geochemistry, mineralogy, and microbiology of the South Bay tailings so that this information can inform future remediation work. Instrument installation and collection of core samples of the tailings was performed at five locations within the tailings impoundment area. Pore-water samples were collected from piezometer and soil water sampler nests. Sub-samples of tailings cores were collected and analysed using optical microscopy, scanning electron microscopy, selective extractions, total carbon/sulfur, X-ray diffraction, X-ray fluorescence, synchrotron, and DNA sequencing techniques. Mineralogical analysis indicated that pyrite was the main sulfide mineral in the tailings, with lesser amounts of sphalerite and chalcopyrite and trace amounts of pyrrhotite, galena, and arsenopyrite. The oxidation zone in which sulfide minerals are depleted is restricted to the upper 0-15 cm of tailings. The moisture content within the tailings is relatively high, contributing to a low O2 diffusion rate into the tailings. High proportions of acidophilic microorganisms capable of catalyzing Fe and S oxidation reactions were found in the shallow tailings. Sulfide oxidation modelling has indicated that oxidation of sulfide minerals in the South Bay tailings may continue for decades to millennia before all sulfide minerals are depleted in the vadose zone. Prolonged sulfide mineral oxidation has led to acidic pore waters with pH as low as 1.26 with high concentrations of dissolved metals, including Fe, Zn, Cu, As, Pb, and Co. The lowest pH and highest concentrations of dissolved metals tends to occur in the shallow tailings near the region of active sulfide-mineral oxidation. High concentrations of dissolved rare earth elements (REEs), up to 9.45 mg/L total REEs, were also found within the shallow acidic pore-waters. Dissolution of gangue minerals and secondary minerals contributes to acid neutralization, with pH increasing to circumneutral values below the water table. Metals and metalloids may be attenuated through adsorption or co-precipitation with secondary mineral phases. Copper was found to be attenuated through covellite precipitation, Pb was attenuated through anglesite precipitation, and As was attenuated by adsorption or co-precipitation with Fe(III) (oxy)hydroxides. Metal(loid)s sequestered within Fe(III) (oxy)hydroxides may be susceptible to remobilization through reductive dissolution should environmental conditions imposed by future remediation efforts induce strong reductive conditions.
Integrated hydrologic model calibration under non-stationary climates
(University of Waterloo, 2024-01-17) Song, Mohan
With global climate change, quantifying water availability for management under non-stationary conditions is, and will continue to be, a major challenge. When hydrologic models are calibrated to historic climatic conditions, they may lack the ability to simulate future extreme climates. This research quantified changes in model calibration under non-stationary climate conditions using the Harold L. Disney Training Center (HLDTC) site in Kentucky, USA for demonstration. An integrated hydrologic model of the site was developed using HydroGeoSphere (HGS) and was calibrated using PEST. Hydraulic conductivity (K), specific storage (Ss), and surface friction coefficient parameters were calibrated under four different climate scenarios based on two moderately-extreme precipitation events during the observation period: a. the entire observation record, including the two moderately-extreme precipitation events (base scenario), b. the entire observation record minus the short duration event (April 2017), c. the entire observation record minus the long duration event (February 2018), and d. the observation record without either event. The results demonstrate that the inclusion of observations from extreme precipitation events impact the calibration of the hydrologic model. The variations in K and Ss were the highest between scenarios of all the calibration parameters tested, while the ridge surface friction, topsoil hydraulic conductivity, or clayey sand specific storage remain unchanged. K has the greatest decrease in lateral K (x and y direction) of the clayey sand layers in Scenario D, and greatest increase in lateral K of fractured rock formation in Scenario C. This indicates the importance of lateral flow in the fractured rock during the shorter duration precipitation event. Ss changed in the fractured rock formation in Scenario B, indicating the importance of storage in the fractured rock during the longer duration precipitation event. The model constructed by this study can better capture shorter duration moderately-extreme precipitation events, demonstrated by a better match between observed and simulated hydraulic heads in Scenario C. The results also suggest that not only the presence or absence of these events informs model calibration, but the timing and duration of these events influences the parameters it informs.
Modelling effects of stormwater best management practices on urban stormwater runoff phosphorus
(University of Waterloo, 2024-01-15) Zhou, Bowen
Phosphorus (P) is a key limiting nutrient for algal growth in freshwater whose excess loading to freshwater bodies contributes to cultural eutrophication and the associated symptoms of water quality deterioration. Urban stormwater is a significant contributor of P to downstream ecosystems from various point and non-point sources and via a variety of transport and emission pathways. Stormwater best management practices (BMPs) such as stormwater ponds (SWPs, a type of traditional stormwater BMP) and bioretention cells (BRCs, a type of low-impact development (LID) BMP) have the potential to attenuate P loads from urban areas and hence mitigate eutrophication risks to aquatic ecosystems. Despite their rapidly growing implementation worldwide, the effects of these stormwater BMPs on urban stormwater P concentrations and loads remain poorly understood. In this thesis, I assess the effects of urban stormwater BMPs on P export, with the goal of determining (1) what are the knowns and unknowns regarding the sources, pathways, and influence of stormwater BMPs on urban P export, (2) what are the dominant internal processes that control P reduction in BRC, based on process-based modelling, (3) what are the general effects of BRCs on urban stormwater runoff P and how are they different from the effects on nitrogen (N), and (4) how to predict the effects of BMPs on urban stormwater runoff P through the use of data-driven models, and what are the potential influencing factors. I address these research questions by reviewing urban P sources discussed in the literature, quantifying P mass balance in a BRC facility in Mississauga, ON, assessing effects of urban stormwater BMPs on P export based on data from the International Stormwater BMP Database, and through the development of process-based and data-driven BMP P models. In Chapter 2, I review the existing literature and analyze data from the International Stormwater BMP Database (ISBD) to summarize the sources, pathways and speciation of urban stormwater P, and the effects of urban stormwater BMPs on P export. This study acts as an introduction to the issues of P in urban stormwater runoff and identifies the research gaps associated with understanding effects of stormwater BMPs on urban stormwater P export. I show, based on both previous literature and the data in the ISBD, that the effects of stormwater BMPs on urban P export remain highly uncertain and unknown. There is a lack of predictive tools for estimating effects of stormwater BMPs on urban P export, and I go on to fill this research gap in Chapters 3, 4, and 5. Following Chapter 2, I address my research questions by developing a process-based P model for a BRC facility in Mississauga, ON. This model is calibrated using field monitored data for flow, water quality and filter media soil chemistry (from core samples). In Chapter 3, the model simulates the multi-year P partitioning, accumulation and export in this stormwater BMP. I show, via the analysis of model simulation results, that exfiltration to underlying native soil was principally responsible for decreasing the surface water discharge from the BRC (63% runoff reduction), while accumulation in the filter media layer was the predominant mechanism responsible for the reduction in P outflow loading (57% retention of total P (TP) inflow load). Of the P retained within the filter media layer, only 11% was stored in easily mobilizable forms. There were no signs that the P retention capacity of the BRC was approaching saturation after 7 years of operation. Thus, my results demonstrate sustained efficient P load reduction by this BRC. In Chapter 4 I evaluate the general effects of BRCs on urban stormwater runoff P concentration and loading by analyzing data from a large number of BRCs in the ISBD from across the United States. I further compare the influence of BRCs on P and N export. I also introduce the data-driven approach in Chapter 4 by training a random forest model to predict the reduction and enrichment effects of BRCs and compare the importance of different explanatory variables. I show that while BRCs typically enrich concentrations of TP and soluble reactive P (SRP), the corresponding outflow loads of TP and SRP, were generally lower, mainly because of reductions to surface runoff volumes via exfiltration to the subsurface. This finding raises questions regarding the relative importance of this infiltrating P to the subsurface environment and potential impacts to groundwater quality. Because they are generally more efficient in reducing N loads than P loads, BRCs tended to decrease the N:P ratio of stormwater runoff, potentially altering nutrient limitation patterns in receiving aquatic ecosystems. My findings also imply that the impacts of BRCs on P and N concentrations, speciation, and loads in urban runoff are highly variable. This variability can be partly accounted for by some explanatory variables related to the climate, watershed and BRC characteristics, and predicted by machine learning (ML) methods such as the random forest model. Random forest modeling identified inflow concentrations and BRC age as key variables modulating the changes in TP, SRP, and total N concentrations between inflow and outflow. For dissolved inorganic N, the BRC’s storage volume and drainage area also emerged as important explanatory variables. Chapter 5 also focuses on the ISBD, similar to Chapter 4, but the analysis of P control performance is expanded to six categories of BMPs. I compare the accuracy of different data-driven models for the prediction of BMP P reduction/enrichment factors, through the use of different ML methods. I show that although LID BMPs are generally more efficient at reducing runoff quantity, they are more likely to enrich TP and SRP concentrations compared to traditional BMPs leading to poorer P load reduction performance amongst LID BMPs. Both traditional and LID BMPs are more likely to enrich SRP concentration when influent SRP concentration is low, in watersheds with higher imperviousness and in drier climates. The influence of LID BMPs on SRP concentration is also more sensitive to climate, watershed and BMP characteristics compared to traditional BMPs. I show that the random forest model provides the most accurate estimation of BMPs effects on urban stormwater P concentrations when compared to models produced using other ML methods. This study suggests that switching to LID BMPs has the potential to increase eutrophication risks and requires further examination. It also proposes that ML methods, especially use of the random forest model can represent a more robust approach to estimate the effects of stormwater BMPs on urban runoff P by accounting for both P reduction and enrichment effects. My results show that that BRCs and other stormwater BMPs have highly variable effects on urban P export. I show that although the BRC I investigated in Mississauga, ON, exhibits efficient reduction of P export, it appears to be atypical and that BRCs and other LID BMPs are generally more likely to enrich P concentration compared to traditional BMPs based on data from a large number of BMP systems in the ISBD. This concentration enrichment may further impact the quality of groundwater and surface waterbodies. Considering the global environmental policy trend to promote replacement of traditional stormwater BMPs with LID BMPs, the findings of this thesis should serve as a caution to policy makers, as understanding of the effects of stormwater BMPs on urban P export remain incomplete.
EVOLUTION OF MULTI-ARC ACCRETION SYSTEMS: A CASE STUDY FROM THE SOUTHERN BEISHAN OROGEN, CENTRAL ASIAN OROGENIC BELT, NW CHINA
(University of Waterloo, 2023-12-18) Hong, Tong
The Central Asian Orogenic Belt (CAOB) is characterized as an accretionary orogen, evolved for ca. 800 m.y from late Mesoproterozoic to early Mesozoic. Its terminal collision and accretion generally commenced in the west and terminated in the east, creating the Tien Shan suture and Solonker suture, respectively. The Beishan Orogen is a southern-central segment of the Central Asian Orogenic Belt, located in Northwest China. It connects the two sutures and contains some of the youngest ophiolitic complexes, arc terranes, and sedimentary basins in the CAOB. Hence, investigations of the southern Beishan Orogen can contribute to correlating the geology on both sides and establishing an integrated tectonic history of the Paleo-Asian Ocean’s closure. Through detailed mapping at 1:25000 scale in southern Beishan, five distinctive tectono-stratigraphic packages have been identified, from south to north, including the Shiyaozi Complex, the Baidunzi Complex, the Ganquan Complex, the Liuyuan Complex, and a cover sequence forming the Heishankou Basin. The Baidunzi Complex comprises a mixture of sheared and transposed metasedimentary and syn-kinematic meta-plutonic rocks, ranging from greenschist to amphibolite facies. The metasedimentary sequences contain Carboniferous-Permian marble and meta-calcareous clastic rocks, which were intruded by syn-tectonic arc magmatic rocks (Baidunzi Intrusive Suite). Collectively these rocks represent a continental arc setting. A massive sheet of bedded quartzite in this complex, displaying no age signatures younger than 1.0 Ga, stands as the most probable candidate for Precambrian basement, with an inferred affinity to the Tarim Craton. The Baidunzi Complex was overthrusted by the Ganquan Complex, which primarily consists of two sequences separated by unconformities and thrust faults. The lower sequence exhibits minimal reworking and lacks continent-derived materials in its stratigraphy. U-Pb zircon dating of this sequence yielded ages ranging from 295 to 285 Ma, without zircon inheritance. In contrast, the upper sequence is dominated by epiclastic sedimentary rocks, structurally and/or unconformably overlying rocks of the lower sequence. Both sequences display geochemical characteristics typical of island arcs, with an increase of εHf values over time. They correlate temporally and tectonically with the adjacent back-arc ophiolitic rocks within the Liuyuan Complex, an ophiolite mélange formed in a backarc setting. Together they represent an arc-backarc system, with arc-trench migration leading to the progressive incorporation of juvenile components in the source. A cover sequence forming a Permian foreland basin, with typical fold-and-thrust style deformation, developed unconformably on the Ganquan and Liuyuan Complexes. From bottom to top, it consists of black shale, an unconformably overlying flysch-like sedimentary unit, and a syn-orogenic conglomerate with clasts of rocks from all the underlying sequences. The sedimentary record and structural analyses of this basin suggest south-verging deformation, associated with a collisional event involving the Ganquan arc-Liuyuan Backarc system over the Baidunzi Complex. Subsequently, this thrust-and-fold belt experienced a phase of north-verging deformation, aligning with the amalgamation of the Shiyaozi Complex from the southernmost region toward the Baidunzi Complex. The overall field relationships record a transition from a passive to an active margin (Baidunzi Complex), formation and accretion of a relatively juvenile arc, and collision during the Permian.
The Role of Transverse Faults in Late Gold Mineralization: A Structural Study of the Maskinonge Lake Fault, Michipicoten Greenstone Belt, Ontario
(University of Waterloo, 2023-10-25) Adam, Zachary
The Maskinonge Lake fault is a late NW-striking fault that occurs at a high angle to the structural features of the gold-producing Goudreau Lake Deformation Zone (GLDZ) in the Michipicoten greenstone belt. The fault is populated with zones of high-grade gold mineralization along its strike and represents an uncommon setting for orogenic gold deposits in the Superior Province. Three phases of fault movement (D4–D6) are identified that postdated the main structural features of the GLDZ (D1–D3). D4 dextral shearing resulted in the initiation of the Maskinonge Lake fault and the development of fault-parallel foliation. The fault was reactivated during D5 sinistral progressive brittle-ductile deformation and included the emplacement of steeply dipping fault-parallel quartz vein arrays and extensional en echelon veins. Structural analysis of these veins shows that structures associated with D5 deformation are subvertical and occurred during transpression. D6 sinistral faulting is responsible for the brecciation of earlier features and ~1 km of strike-slip stratigraphic displacement with little to no vertical movement. The Pine-Breccia gold occurrence is found along the Maskinonge Lake fault and consists of rocks that have undergone pervasive silica alteration within the fault zone. The centre of the alteration halo contains a gold- and copper-bearing fault-filling “main vein”. Both the fault and main vein are located along the contacts of a NW-trending Matachewan dyke, while gold concentrations in the main vein are enhanced at the intersection between the Maskinonge Lake fault and ENE-striking shear zones. These structural controls provide additional constraints for favourable sites of mineralization along late high-angle transverse faults and support these structures as viable gold exploration targets.
How a dry year affects spatial variability of ground thaw and changes the hydrology of a small Arctic watershed
(University of Waterloo, 2023-09-28) Dakin, Brampton
The summer of 2021 in the Inuvik area, NWT was warm and dry. As recorded in Siksik Creek, a sub-catchment of Trail Valley Creek located 50 km north-east of Inuvik, this was the 7th warmest summer and driest July recorded to date. This presented a unique opportunity to study the drying phenomena of Arctic ecosystems. This is pertinent to the study of permafrost degradation, as the drying phenomena is still vastly understudied and there are few datasets available that record abnormally dry conditions in Arctic catchments. These data sets are needed to properly show the influence that this has on active layer thicknesses. It is unknown whether these conditions may pose a risk to permafrost, if this is spatially variable, and what other processes might amplify or hinder this. The main objective of this thesis is to explore how a dry year affects active layer thaw and the hydrology of Siksik Creek so that we may better understand how catchments such as Siksik will respond to ongoing climate change. To do this a mix of field results and modelling was used to show and quantify how these may affect active layer thaw as well as water balance components. The three main research chapters of this thesis divide this by analyzing active layer thaw as physically measured in the catchment to previous years, by using the model GEOtop to assess how this affects water balance components, and then by simulating wetter conditions to show the affect soil moisture has. Field data were collected from May 25th to August 29th in Siksik Creek during the summer of 2021, where the data collected included active layer thicknesses, depth to the water table, as well as stratigraphy and soil thicknesses across a variety of terrain type throughout the entirety of the catchment. This study specifically focused on measuring these data across hummocks and inter-hummocks throughout the catchment, as these features are ubiquitous in the Mackenzie uplands. In addition to analyzing the 2021 field data, the GEOtop physically based hydrology model was used to explore the processes controlling active layer thicknesses, water table depths, and various water balance components over the course of the summer of 2021. GEOtop is designed to handle microtopographies, such as hummocks and other terrain features. Further, we compare the physical and simulated results from the summer of 2021 to a more normal and wetter year (2016) to assess the differences that soil moisture has on the hydrology and active layer thaw of Siksik Creek. We explored how the movement of water impacted thaw depths in these landscapes, how spatial variability of thaw is influenced by soil moisture, and by the terrain features that control this. We found that peat thicknesses in this area are controlled by the presence of hummocks, where peat is thickest between hummock mounds in an area called the inter-hummock zone. This variability of peat thicknesses directly controls the spatial variability of soil moisture, and this had implications on thaw. In Chapter Two it was found that thaw for the summer of 2021 was shallower than expected in the inter-hummock zones by as much as 20cm compared to similar studies in Siksik and in similar landscapes in Alaska. This chapter also showed that the overlying vegetation, specifically lichens and mosses, were statistically linked to peat thicknesses representative of hummocks and inter-hummocks - where lichens tended to be overtop of hummocks, and mosses overtop of inter-hummocks. This correlation was then used with UAV imagery, taken in mid-June, to map mosses and lichens across the catchment and by proxy the locations of hummocks and inter-hummocks. This map was built into the model GEOtop to simulate Siksik Creek for the summer of 2021. Starting in Chapter Three, the modelled portion of this thesis covered a wide aspect of simulations, where the influence of hummocks was assessed, as well as shrubs and snow when they were added to the model, and finally assessing the role soil moisture plays within all of these various processes. It was found that hummocks, when they were specifically discretized and compared to a simple soil column, reached freshet and max discharge sooner by as much as two days, a lag that existed in the evapotranspiration outputs as well. However, these results were relatively consistent and the only major difference between these two simulations was seen in the 2d active layer depth maps. It was found that microtopography by the end of the summer seemed to influence local patterns of thaw more than larger topographical features such as natural depressions in the landscape did. When shrubs and snow were added to the model domain and simulated it was found that the presence of snow or lack thereof was the main component of difference in the discharge and evapotranspiration data. The active layer depth maps changed between simulations, with the shrub only simulations having the lowest degree of thaw, with a degree of variability seen between simulations. In comparison, the water table depths hardly changed between simulations, and it was hypothesized that the dryness of the summer and the lack of soil moisture was the main culprit for this. To test if this was the case, in Chapter Four, precipitation and snow water-equivalent data was taken from a wetter year (2016) and replaced the values for the dry summer of 2021. This was done so that only moisture available to the system was changed. It was found that soil moisture was in fact the main cause for this lack of variability. The wetter simulations because of this had deeper thaw throughout the catchment, with both the extent, max thaw depths, and min thaw depths increasing. The water table depths on the other hand became shallower and the ground surface was much more inundated with water. The spatial variability in the water table depth maps was found to match where the presence of taller shrubs in the catchment exist, where these areas had the least amount of soil moisture and the shallowest thaw depths. Whereas the areas with the highest amount of soil moisture content had the deepest thaw depths in the catchment. Overall, this thesis helps to improve our understanding of how peat catchments similar to Siksik Creek might respond to either the wetting or drying of the Arctic. This thesis also advances our understanding on the controls of soil moisture variability and ground thaw, as well as its spatial variability. One can infer from this study that for posterity it is the warm and wet summers rather than the warm and dry summers that pose the largest risk to permafrost and its degradation.
The influence of soil moisture, oxygen, and temperature on naphthalene biodegradation and CO2 and CH4 effluxes
(University of Waterloo, 2023-09-22) Ye, Jane
Petroleum hydrocarbons (PHCs) are essential to the functioning of the industrialized world yet serve a potential threat to human and ecosystem health when they inadvertently enter the environment. In recent decades, recognition of natural attenuation as a viable approach to PHC remediation is increasing. Natural attenuation includes the biodegradation of PHCs through respiration, fermentation, and methanogenesis, processes which are also central to the biodegradation of natural background soil organic matter. Biodegradation of both PHCs and natural soil organic matter are a major component of the global carbon cycle and an important source of atmospheric greenhouse gases (GHGs). As a biologically mediated set of reactions, environmental factors like temperature and moisture are important controls on the rates and pathways of biodegradation. It is therefore important to understand the influence of these environmental factors on PHC biodegradation and associated carbon dioxide (CO2) and methane (CH4) effluxes to improve predictions of PHC remediation efficiency and soil GHG emissions under ongoing and future climate change. In Chapter 2, I investigated the effect of soil moisture on PHC biodegradation kinetics, using naphthalene as a representative PHC compound. I performed microcosm incubations with naphthalene-spiked soil at 60, 80, and 100% water-filled pore space (WFPS) under oxic headspace, and at 100% WFPS under anoxic headspace. Incubations lasted 44 days. The results showed that the total naphthalene in soil decreased to below detection after Day 9, 17, and 44 in incubations at 60, 80, and 100% WFPS under oxic headspace, respectively. At 100% WFPS under anoxic headspace, total soil naphthalene concentrations decreased over time but were still detectable past Day 44. Fitting of the naphthalene data to first order decay equations revealed two distinct kinetic regimes of degradation in the oxic incubations: an initial fast regime characterized by an apparent first order rate constant on the order of 10-1 day-1 followed by dominance of a slower degradation regime. In the anoxic incubations, only the slow end-member regime was observed with a corresponding rate constant of 10-2 day-1. Porewater electron acceptor and organic acid data indicated that in the fast regime, naphthalene degradation was dominated by microbial respiration pathways, while in the slow regime fermentative pathways dominated. Results from Chapter 2 imply that spatial and temporal fluctuations in soil moisture – and the associated oxygen (O2) availability – can cause order-of-magnitude variability in the degradation kinetics of PHCs in the vadose zone. In Chapter 3, I investigated the effect of temperature and O2 availability on CO2 and CH4 accumulations in the presence of naphthalene. I performed naphthalene-spiked microcosm incubations under oxic or anoxic headspace at temperatures of 10, 20, and 30°C. Time series data of net accumulated CH4, accumulated CO2, consumed O2, accumulated dissolved inorganic carbon (DIC), and consumed organic acids (OAs) were analyzed using Arrhenius temperature sensitivity curve-fitting. Q10 temperature sensitivity quotients were estimated from this analysis, indicating a greater temperature sensitivity of anaerobic CO2 and CH4 production processes than their aerobic equivalents. I observed that methanogenesis under anoxic conditions had a particularly high Q10 of 9. Overall, findings from this research confirm our understanding of field biodegradation rates. PHC biodegradation in oxic, drier zones is expected to be 10 times faster than in anoxic, saturated zones. The two distinct regimes of biodegradation activity identified in Chapter 2 could also be used as simplified representations of PHC biodegradation when modelling variable moisture and oxygen conditions. Chapter 3 additionally suggests that the CH4:CO2 ratio of soil carbon emissions from anoxic soils may potentially increase with warming temperature. Thus, PHC contaminated sites may see increasing GHG emissions potential, but also increasing contaminant biodegradation rates, in a warming climate, especially those located in saturated soils and cold regions. These expected alterations in soil carbon fluxes are important for the consideration of site managers concerned with site-scale carbon cycling and GHG emissions.

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