Grant: Discovery Grants Program - Individual

The remediation of mining landscapes in the Athabasca Oil Sands Region (AOSR) is a significant environmental issue in Canada. Vanadium and naphthenic acids are two significant contributors to the environmental toxicity of bitumen-derived contaminants. Despite both vanadium and naphthenic acids existing in high concentrations in the AOSR and having known toxicity, the interaction between these two contaminate classes remains unexplored. Vanadium is the most prevalent trace metal in Athabasca bitumen and leaches from petroleum coke at toxicologically relevant concentrations. This research's primary objective is to determine how vanadium speciation and coordination are determined by the environmental conditions in the AOSR: presence of coordinating naphthenic acid, pH, redox, and metal concentration. Speciation and coordination have a direct effect on vanadium's environmental fate, bioavailability, and toxicity. Additionally, there is little understanding of the transformation of vanadium from the insoluble vanadyl porphyrins observed in heavy oil to the soluble vanadium species leaching from coke. Therefore, unraveling these key aspects of vanadium's chemistry will be essential for mitigating the environmental risk of a significant pollutant in the AOSR. My research program's long-term objective is to determine how the formation of vanadium complexes with naphthenic acid affects these species' bioavailability/toxicity and contributes to the leaching of vanadium from coke upon contact with oil sands process-affected waters. A detailed understanding of vanadium sources, speciation and mobility is critical for assessing and mitigating long-term environmental risk. To achieve this long-term objective, the following specific short-term objectives will be addressed: 1)Characterize the structure, reactivity, and stability of vanadium-naphthenic acid (V-NA) complexes In Theme 1, foundational knowledge on V-NA physical and electronic structure will first be acquired. Studies will then be expanded to investigate V-NA properties under relevant environmental conditions. Specifically, we will explore the stability of these complexes and their redox chemistry as a function of solution pH and vanadium concentration. Establishing the reactivity and stability of V-NA complexes under environmental conditions is essential for understanding the likelihood of these species forming and persisting in the environment. 2)Tracking the formation of the labile vanadium species in petroleum coke In Theme 2, we will determine how vanadyl porphyrin transformation is affected by reaction conditions during the coking process and, specifically, which conditions lead to the formation of the labile vanadium species in coke and subsequent V-NA complex formation. Understanding the chemistry leading to vanadium leaching from coke will provide strategies for preventing/mitigating the impact of vanadium in the AOSR.