As conventional oil reserves deplete and more efficient refining technologies emerge, the use and transportation of heavy fuel oils such as dilbit is rising. Despite the risk of accidental dilbit spills, the fate and behaviour in aquatic systems is largely unknown. The objective of this thesis was to develop new approaches and insights to directly address knowledge gaps surrounding the fate and behaviour of diluted bitumen (dilbit) in freshwater systems. During the summers of 2017 and 2018, a large-scale collaborative field study was conducted at the International Institute for sustainable Development’s – Experimental Lakes Area (IISD-ELA), a world-renowned freshwater research station located in Northwestern Ontario, Canada. First, two tank-based dilbit spill simulations were carried out at oil:water ratios of 1:8000 and 1:800 v/v (Chapter 2). Here I examined the physical fate and behaviour of dilbit spilled onto the water’s surface for 11 days. In this chapter I provide, for the first time, experimental evidence of dilbit physically sinking after 8 days of environmental weathering in land-based tanks containing natural lake water. Building on the findings of chapter 2, the remaining four chapters focus on a series of 70-d long experimental dilbit spills carried out in limnocorrals (10 m diameter x 1.5 m depth) installed directly in a freshwater lake. Chapter 3 provides, to our knowledge, the most detailed temporal account to date of dilbit submergence in freshwater at multiple oil:water ratios. In Chapter 4 I provide the rates at which over 100 individual hydrocarbons are depleted over time from the dilbit slicks and apply diagnostic ratios to postulate which weathering processes are responsible for the observed depletions. As predicted, evaporation, dissolution, and photooxidation are prominent weathering processes whereas biodegradation is not. I then describe both the short- and long-term behaviour of these compounds as they partition from the dilbit slick to the air, water, and sediments of the limnocorrals in Chapter 5. While the concentrations of polycyclic aromatic hydrocarbons (PAHs) were elevated in the water columns of each treatment, they were orders of magnitude lower than concentrations that pose a toxicological risk. The same was true for all sediment samples except those that were in direct contact with sunken dilbit. This suggests that the major threat of dilbit spills from an ecotoxicological point of view is the dilbit-laden sediments produced by submergence. Finally, I demonstrated the successful application of a mass transfer model to predict the dissolution trends of the highly toxic benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX) compounds following the dilbit spills. In Chapter 7 I detail the implications and conclusions for each chapter and the thesis as a whole. I also describe areas where future research is needed. In the end, the conclusions of this thesis were: 1) dilbit has the propensity to sink following spills in freshwater, 2) prominent weathering processes include evaporation, dissolution, and photooxidation, 3) our regression design allowed for important relationships between contamination and spill size to be realized, 4) sunken dilbit poses a toxicological threat to aquatic biota, and 5) mass transfer models can accurately predict BTEX dynamics in the water column following a dilbit spill.

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Canadian bitumen is mainly transported in a diluted form via pipeline and train, all posing a risk as they can lead to the release of diluted bitumen (dilbit) in the environment. In the summer of 2018, a collaborative large-scale field experiment was conducted at the International Institute for Sustainable Development - Experimental Lakes Area (IISD-ELA), a world-renowned aquatic research facility. The research objectives of the Boreal lake Oil Release Experiment by Additions to Limnocorrals (BOREAL) project were to understand the fate, behaviour, and potential toxic effects of dilbit in a freshwater Boreal lake to inform evidence-based management strategies for the transport of dilbit. A range of controlled dilbit spills was performed in seven 10 m diameter limnocorrals (~100,000 L of water) resulting in environmentally realistic dilbit:water dilutions ranging from 1:69,200 to 1:504, representing the upper half of the distribution of oil spill sizes in North America in the last decade. Additionally, two limnocorrals not treated with dilbit were studied as controls. This thesis identifies the bioaccumulating compounds derived from naturally weathered dilbit in adult giant floater mussels (Pyganodon grandis), to determine the rates at which they were accumulated and excreted. More specifically, the bioaccumulation potential and toxicokinetic parameters of polycyclic aromatic compounds (PACs) and various metals were assessed in mussels exposed ex situ for 41 days (25 days of exposure and 16 days of depuration) to water from the limnocorrals. These compounds have shown to be toxic, carcinogenic, and mutagenic to aquatic organisms. Mussels exposed to dilbit-contaminated water experienced significantly greater TPACs concentrations (0.40 – 0.90 µg L-1, n=12) compared to mussels from the Control (0.017 µg L-1, n=4). Furthermore, dilbit-contaminated water had a higher proportion of alkylated PACs compared to their parent counterpart, demonstrating petrogenic PAC profiles. We detected significantly greater TPACs concentrations in mussels exposed to dilbit-contaminated water (25.92 – 27.79 µg g-1, ww Lipid, n=9, at day 25 of the uptake phase) compared to mussels from the Control (average of 2.62 ± 1.95 µg g-1, ww Lipid; ±SD, n=17). Alkylated PACs represented 96.4 ± 1.8%, ±SD, n=12 of TPACs in mussels from dilbit-contaminated treatments at day 25 of the uptake phase, indicating the importance of conducting a more inclusive assessment of petrochemical mixtures as most studies only focus on parent PACs. From first-order one-compartment models derived from nonlinear curve fitting of the accumulation phase or sequential modelling method, uptake (0.66 – 24.65 L g-1 day-1, n=87) and depuration (0.012 – 0.37 day-1, n=87) kinetic rate constants, as well as bioconcentration factors (log values from 3.85 – 6.12 L kg-1, n=87) for the 29 PACs that bioaccumulated in mussels suggested that alkylated PACs have greater bioaccumulation potential compared to their parent PAC counterpart. Results from this study also demonstrated that giant floater mussels could be used to biomonitor PAC contamination following oil spills as PACs accumulated in mussel tissue and were still present following the 16 day depuration phase. The results of this study are the largest, most comprehensive set of toxicokinetic and bioaccumulation information of PACs (44 analytes) in freshwater mussels obtained to date. Metal contamination following the controlled dilbit spill was minimal, but mussels exposed to water contaminated with naturally weathered dilbit experienced elevated concentrations of dissolved zinc (30.26 – 38.26 µg L-1, n=12) compared to the mussels in the uncontaminated water (6.75 ± 3.31 µg L-1, n=4), surpassing the Canadian water quality guidelines for the protection of aquatic life. However, it is not clear if dilbit contamination caused elevated zinc concentrations in the water as other factors, such as limnocorral building materials and/or galvanized minnow traps used in the limnocorrals, could have contributed to zinc contamination. Nonetheless, giant floater mussels did not accumulate zinc in their tissues.

Canada has become increasingly economically dependent on the exportation of bitumen to trans-oceanic international markets. As the export of Alberta bitumen from ports located in British Columbia increases, oil spill response and readiness measures become increasingly important. Although the frequency of ship-source oil spills has dramatically declined over the past several decades, they remain environmentally devastating when they occur. In the event of a marine spill, great lengths of shoreline are at risk of being contaminated. Once ashore, oil can persist for decades if shoreline hydraulic conditions are correct and remediation does not occur. Most commonly transported oils (e.g., fuel oils, Bunker C, crude oil, etc.) have been thoroughly studied, and their fate and behaviour in the event of a marine spill is well understood. In contrast, because diluted bitumen has been historically traded in relatively low quantities and has almost no spill history, there is a sizable knowledge gap regarding its effects and behaviour in both the marine environment and on coastal shorelines. The intent of this thesis was to develop a classification scheme to identify marine shorelines of high and low diluted bitumen (dilbit) retention for southeastern Vancouver Island, British Columbia. This study builds upon the outcome of former laboratory bench top dilbit and sediment research known as Bitumen Experiments (Bit_Ex). Bit_Ex investigated dilbit penetration and retention in six engineered sediment classifications ranging from coarse sand to very large pebble in accordance with the Wentworth Classification scheme. This research used Bit_Ex findings to predict dilbit retention in poorly sorted in-situ beach sediments found on shorelines representative of the southern coast of Vancouver Island, British Columbia, Canada. Field and laboratory measurements were conducted to document the occurrence of in-situ shoreline sediments and hydraulic conditions and were used to predict dilbit retention by comparing such characteristics between Bit_Ex and unconsolidated in-situ beach sediments. Saturated hydraulic conductivity (Ks) was measured using a double-ring constant-head infiltrometer. Measured Ks values were then compared to predicted Ks values generated by five semi-empirical Ks equations. A modified version of the Hazen Approximation was selected as the most appropriate. Using measured and calculated metrics, sediments were grouped as having either low or high dilbit retention. When sediments were analysed as homogenous samples, the experimental results suggested two of ten shorelines were composed of a combination of low and high retention sections, while the remaining eight sites were of low retention. Upon the isolation of coarse surface strata, results indicated two shorelines were entirely veneered with high retention sediments, and four shorelines were a combination of high and low retention. The residual four shorelines were found to be entirely composed of low retention sediments. The results illuminate the importance of shoreline stratification when predicting shoreline oil retention. This characteristic is a factor that current shoreline oil retention mapping techniques do not adequately consider. Additionally, the findings suggest that while sediments indicative of retaining weathered dilbit are relatively uncommon within Juan de Fuca and Harro Straits, high retention unweathered dilbit sediments are more common. / Graduate / 2018-06-26