Hickie, Brendan

Plastic pollution is a growing concern, owing to its durability, ubiquity, and potential health impacts. The overall objective of this study was to assess the abundance and distribution of microplastics within Lake Scugog catchment, Ontario. This was fulfilled through two tasks (i) the development of a microplastic particle budget for the lake catchment, and (ii) the determination of the dry deposition of atmospheric microplastics in Port Perry, Ontario. The total input of microplastics into Lake Scugog (atmospheric deposition and stream inflow) was 2491 x106 mp/day, while the output (lake outflow and sedimentation) was 1761 x106 mp/day, suggesting that 29% of inputs were retained in the lake. The dry deposition of microplastics in Port Perry was 1257 mp/m2/day, which was high when compared to bulk deposition (37 mp/m2/day) in the same area. By quantifying the major pathways of microplastics better management techniques can be implemented.

Author Keywords: Catchment, Dry Deposition, Microplastics, Ontario, Particle Budget, Plastic pollution

This thesis investigated coloured and fluorescent dissolved organic matter in the Canada Basin, Arctic Ocean from 2007 to 2017. The first interannual time-series of its kind in the Canada Basin incorporated the use of EEM-PARAFAC to validate a seven-component model. Statistical temporal tests revealed (1) an increasing protein-like intensity in the upper polar mixed layer (UPML); (2) increasing intensities of humic-like components in the halocline due to increasing freshwater content; and (3) no change in DOM composition in deeper Atlantic waters (AW) congruent with the long residence time of the water mass (> 30 years). The significant decline in sea ice concentration was related to a decrease in humic-like FDOM due to enhanced photodegradation and an increase in protein-like FDOM, likely the results of increased biological activities in surface layers. This research provides evidence that the changes in physical and biological environment in the Arctic regions have already profound impacts on the composition and distribution of FDOM.

Author Keywords: absorbance, Arctic Ocean, dissolved organic matter, fluorescence, parallel factor analysis, time-series

This thesis explored the contribution of mixed methods approaches to marine mammal science through the use of concurrent and sequential designs to study distribution and feeding ecology of bowhead whales (Balaena mysticetus) in the Arctic region of Nunavik, Quebec, Canada. The study combines Inuit knowledge (IK), collected through semi-directed interviews with Inuit harvesters, and analyses of stable isotopes and trace elements (SI/TE) in baleen plates. A systematic literature review found that mixed methods are increasingly used in marine mammal ecology studies in remote locations, yet are still relatively rare and face a number of challenges. Both IK and SI/TE, indicated that bowhead whales have a seasonal pattern in their distribution and feeding ecology. They are most commonly present in productive nearshore areas in summertime, feeding in areas of great prey diversity, and moving to offshore areas in winter to fast. Mixed methods approaches used in this case study enabled the collection of complementary knowledge about bowhead whale ecology important for local management in a changing climate. This study also shows the value of mixed methods approaches for future marine mammal studies in Nunavik and elsewhere.

Author Keywords: Arctic, bowhead whale, distribution, feeding ecology, mixed methods, traditional ecological knowledge

While there is an emerging body of literature on the role and effectiveness of community-based research (CBR) in addressing the needs of local communities, few studies have explored its promise in areas lacking established collaborative models. The purpose of this paper is to examine the potential of CBR to meet the sustainable community development needs of the primarily urban Durham Region in Southern Ontario. Semi-structured interviews with twenty sustainability-focused community members from the academic, municipal, private and non-profit sectors were conducted using Glaser and Strauss' grounded theory to develop a working hypothesis that was analyzed with the aid of the qualitative data software program ATLAS.ti. The results reveal that while the region's academic and community groups have little time to initiate formal community-campus collaborations, the additional manpower and expertise that a well-structured CBR model provides could significantly assist local organizations complete unfinished projects and undertake new initiatives.

Author Keywords: Community-based research, Community-campus collaboration, Cooperative education, Durham Region, Experiential education, Sustainable development

Monomethylmercury (MMHg), the most bioavailable form of mercury (Hg) and a potent neurotoxin, is present at elevated concentrations in Arctic marine mammals posing serious health threats to the local populations relying on marine food for their subsistence living. The sources of MMHg in the Arctic Ocean surface water and the role of dimethylmercury (DMHg) as a source of MMHg remain unclear. The objective of this research was to determine the sources and fate of methylated Hg species (MMHg and DMHg) in the marine ecosystem by investigating processes controlling the presence of methylated Hg species in the Arctic Ocean marine boundary layer (MBL) and surface waters. A method based on solid phase adsorption on Bond Elut ENV was developed and successfully used for unprecedented measurement of methylated Hg species in the MBL in Hudson Bay (HB) and the Canadian Arctic Archipelago (CAA). MMHg and DMHg concentrations averaged 2.9 ± 3.6 (mean ± SD) and 3.8 ± 3.1 pg m-3, respectively, and varied significantly among sampling sites. MMHg in the MBL is suspected to be the product of marine DMHg degradation in the atmosphere. MMHg summer (June to September) atmospheric wet deposition rates were estimated to be 188 ± 117.5 ng m-2 and 37 ± 21.7 ng m-2 for HB and CAA, respectively, sustaining MMHg concentrations available for bio-magnification in the pelagic food web. The production and loss of methylated Hg species in surface waters was assessed using enriched stable isotope tracers. MMHg production in surface water was observed from methylation of inorganic Hg (Hg(II)) and, for the first time, from DMHg demethylation with experimentally derived rate constants of 0.92 ± 0.82 x 10-3 d-1 and 0.04 ± 0.02 d-1 respectively. DMHg demethyation rate constant (0.98 ± 0.51 d-1) was higher than that of MMHg (0.35 ± 0.25 d-1). Furthermore, relationships with environmental parameters suggest that methylated Hg species transformations in surface water are mainly biologically driven. We propose that in addition to Hg(II) methylation, the main processes controlling MMHg production in the Arctic Ocean surface waters are DMHg demethylation and deposition of atmospheric MMHg. These results are valuable for a better understanding of the cycle of methylated Hg in the Arctic marine environment.

Author Keywords: Arctic Ocean, Atmosphere, Demethylation, Dimethylmercury, Methylation, Monomethylmercury

This thesis was designed to quantify absorbance and fluorescence characteristics of dissolved organic matter (DOM) in North Atlantic, Pacific and Arctic Oceans. DOM was described in water masses of distinct sources and formation pathways as well as in regions where environmental forcings such as deep water upwelling, enhanced biological activity and receipt of freshwater discharge were prevalent. Influence of sea ice on DOM in Beaufort Sea mixed layer (0 to 30 m) seawater was investigated based on sea ice extent as well as freshwater fractions of meteoric (f_mw) and sea ice melt water (f_sim) calculated from oxygen isotope ratio (δ18O). The effect of DOM exposure to simulated solar radiation was also assessed to determine the resilience of fluorescent fractions of DOM to photodegradation. This research aims to further our ability to trace DOM in marine environments and better understand its transformation pathways and predict its fate as part of the oceanic carbon cycle in a changing climate.

Author Keywords: Absorbance, Arctic Ocean, Dissolved organic matter, Fluorescence, Parallel Factor Analysis, Sea Ice

Models of partitioning, uptake, and toxicity of neutral organic chemicals in fish

Alena Kathryn Davidson Celsie

A novel dynamic fugacity model is developed that simulates the uptake of chemicals in fish by respiration as applies in aquatic toxicity tests. A physiologically based toxicokinetic model was developed which calculates the time-course of chemical distribution in four tissue compartments in fish, including metabolic biotransformation in the liver. Toxic endpoints are defined by fugacity reaching a 50% mortality value. The model is tested against empirical data for the uptake of pentachloroethane in rainbow trout and from naphthalene and trichlorobenzene in fathead minnows. The model was able to predict bioconcentration and toxicity within a factor of 2 of empirical data. The sensitivity to partition coefficients of computed whole-body concentration was also investigated. In addition to this model development three methods for predicting partition coefficients were evaluated: lipid-fraction, COSMOtherm estimation, and using Abraham parameters. The lipid fraction method produced accurate tissue-water partitioning values consistently for all tissues tested and is recommended for estimating these values. Results also suggest that quantum chemical methods hold promise for predicting the aquatic toxicity of chemicals based only on molecular structure.

Author Keywords: COSMOtherm, fish model, fugacity, Partition coefficient, tissue-water, toxicokinetics

Silver nanoparticles (AgNP) released into aquatic environments could threaten natural bacterial communities and ecosystem services they provide. We examined natural lake bacterioplankton communities' responses to different exposures (pulse vs chronic) and types (citrate and PVP) of AgNPs at realistic environmental conditions using a mesocosm study at the Experimental Lakes Area. An in situ bioassay examined interactions between AgNPs and phosphorus loading. Bacterial communities exposed to high AgNP concentrations regardless of exposure or capping agent type accumulated silver. We observed increases in community production during additions of polyvinylpyrrolidone (PVP) -capped AgNPs and that site and nutrient-specific conditions are important to AgNPs toxicology in aquatic systems. Toxicological effects of AgNP are attenuated in natural conditions and differ from results from laboratory studies of AgNP toxicity. Our results demonstrate more studies are needed to fully assess the risk posed by these novel chemicals to the environment. This work could be useful in forming risk assessment policies which are largely based on lab studies and typically demonstrate strong toxic effects.

Author Keywords: bacterial production, bacterioplankton communities, ecological stoichiometry, Experimental Lakes Area, mesocosms, silver nanoparticles

Environmental monitoring and investigation of metal biogeochemical cycling has been

carried out in the Pearl River Estuary (PRE), an important and complex system in Southern

China. In this study, rare earth element (REE) patterns as well as isotope ratios (i.e., Zn and Cd)

were evaluated as tools to identify contamination sources in environmental compartments (i.e.,

water and suspended particles (SP)) as well as in oysters collected from estuarine sites. Results

show elevated concentrations (also called anomalies) of Pr, Nd, Dy and Ho, relative to other

REE elements, in water samples, potentially from REE recycling and other industrialized

activities in this area. Unlike water samples, no REE anomalies were found in SP or oysters,

suggesting that the dominate REE uptake pathway in oysters is from particles. Secondly, site to

site variations in Zn isotope ratios were found in water and SP, showing the complexity of the

source inputs in this area. Also, in estuarine locations, larger spatially differences in Zn isotope

ratios were found in water collected in wet season than those in dry season, which may due to

mixing of different source inputs under the water circulations in different seasons.

A series of laboratory experiments were conducted during which changes in Zn isotope

ratios were measured during uptake under varying salinity and Zn concentrations and during

depuration. Neither in vivo Zn transportation among the various tissues within the oysters nor

water exposure conditions (i.e., different salinities or Zn concentrations) caused Zn isotopic

fractionation in the oysters.

Cd and Zn isotope ratios were also determined in oysters obtained from the PRE. Large variations in Cd and Zn isotope ratios suggest that oysters were receiving contaminants from different input sources within the PRE. A consistent difference (approximately 0.67‰) was observed for Zn isotope ratios in oysters collected from the east side of the PRE compared to those from sampling locations on the western side of the PRE, suggesting different Zn sources in these two areas. Ultimately, by combining biogeochemistry with physiology, this study represents a first attempt to assess pollution status, monitor contaminants using oysters and model/identify contamination sources using both REEs and metal isotope ratios.

Road runoff is a vector for the transport of potentially toxic chemicals into receiving waters. In this study, selected tire-derived chemicals were monitored in surface waters of rivers adjacent to two high traffic highways in the Greater Toronto Area in Ontario, Canada. Composite samples were collected from the Don River and Highland Creek in the GTA during 5 hydrological events that occurred in the period between early October 2019 and late March 2020, as well as an event in August 2020. Grab samples were collected from these rivers during a period of low flow in August 2020, as well as during a storm event in July of 2020. Analysis was performed using ultra-high pressure liquid chromatography with high resolution mass spectrometric detection (UHPLC-HRMS). Hexamethoxymethylmelamine (HMMM), a cross-linker of tire material, was detected at elevated concentrations (> 1 µg/L) during rain events in the fall and winter of 2019-20 and during a period of rapid snow melt in early March of 2020. These samples were also analyzed for the tire additive, 6PPD, and its oxidation by-product, 6PPD-quinone, as well as 1,3-diphenylguanidine (DPG). In many samples collected from the Don River and Highland Creek during storm events, the estimated concentrations of 6PPD-quinone exceeded the reported LC50 of 0.8 µg/L for Coho salmon exposed to this compound. Temporal samples collected at 3-hour intervals throughout rain event the October 2020 showed that there was a delay of several hours after the start of the event before these compounds reached their peak concentrations. In addition, 26 candidate transformation products and precursor compounds of HMMM were monitored; 15 of these compounds were detected in surface waters in the GTA. The maximum total concentration of this class of methoxymethylmelamine compounds in surface water samples was estimated to be 18 µg/L. There is limited knowledge about the properties of HMMM, its precursor contaminants, and its transformation compounds, as well as their fate in the environment. COSMO-RS solvation theory was used to estimate the physico-chemical properties of HMMM and its derivatives. Using the estimated values for these properties (e.g., solubility, vapour pressure, log Kow) as inputs to the Equilibrium Criterion (EQC) fugacity-based multimedia model, the compounds were predicted to readily partition into aqueous media, with mobility in water increasing with the extent of loss of methoxymethyl groups from HMMM. Overall, this study contributes to the growing literature indicating that potentially toxic tire-wear compounds are transported via road runoff into urban surface waters. In addition, this study provides insight into the environmental behaviour of HMMM and its transformation products.

Author Keywords: 6PPD-quinone, COSMOtherm, Fugacity, Hexamethoxymethylmelamine, Road runoff, Tire wear