McMartin, Dena

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https://hdl.handle.net/10133/7003

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    Multi-year trends in the spatiotemporal occurrence and fate of naphthenic acid fraction compounds in a pilot-scale engineered treatment wetland
    (Elsevier, 2025) Vander Meulen, Ian; Ahad, Jason M. E.; Martineau, Christine; Muench, Douglas G.; McMartin, Dena; Headley, John V.
    In the Athabasca Oil Sands region (AOSR) of Alberta, Canada, there are ∼1.4 billion m3 of fluid tailings containing known toxic constituents which will require treatment and must be reclaimed before closure. One class of contaminants of concern are naphthenic acid fraction compounds (NAFCs). While various treatment strategies have been considered, constructed wetland treatment systems (CWTSs) have emerged as a semi-passive, high throughput, and potentially cost-effective option. Here, non-targeted Orbitrap high-resolution mass spectrometry was applied to assess the NAFC remediation efficacy of a 1-ha CWTS operated over two field seasons (2021 and 2022) at a site situated in the Northern of Alberta. Concentrations of total NAFCs decreased consistently during a closed CWTS operation with OSPW recirculation at each field seasons. Concurrently, O2-NAFCs (i.e., classical NAs) steadily decreased while more-oxygen-rich formulae increased in spectral abundance, consistent with oxidative degradation. Attenuation rates of NAFCs were more rapid at the outset of the season (∼0.53 mg/L/d), where treatment rates eventually decreased (∼0.25 mg/L/d). Molecular-level characterization of treatment outcomes showed that the highest molecular weight O2-NAFCs detected (i.e., #C > 14) decreased the most, whereas all O3- and O4-NAFCs generally increased in relative spectral abundance. Shallow, heavily vegetated cells of the wetlands tended to have lower NAFC concentrations and more oxygen-rich compounds, suggesting substantial attenuation of NAFCs in these segments. These results demonstrate that this field-scale CWTS effectively in depletes and transforms OSPW-derived NAFCs under environmental conditions found in the AOSR
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    On the occurrence, behaviour, and fate of naphthenic acid fraction compounds in aquatic environments
    (Elsevier, 2025) Vander Meulen, Ian J.; Headley, John V.; McMartin, Dena
    Naphthenic acids and naphthenic acid fraction compounds (NAFCs) are associated with production of unconventional petroleum resources, especially the Athabasca Oil Sands of Alberta, Canada. This complex mixture of acidic organic compounds is toxic to a variety of taxa, and so represents an important environmental management challenge. Thus, there is clear motivation to better understand the occurrence and characteristics of NAFCs in aquatic environments, their chemical behaviour, and environmental fate. Empowered by modern high-resolution mass spectrometry analyses, improved descriptions of the environmental occurrence of NAFCs have emerged. These studies include spatiotemporal survey studies describing the characteristics and quantities of NAFCs, as well as forensic methods working towards reliable source differentiations. Work has also proceeded in earnest to advance mechanistic understandings of how NAFCs are affected by passive phenomena, such as soil and sediment sorption, and chemically reactive mechanisms such as photolysis and biodegradation. Further advances describe the environmental fate and behaviour of NAFCs as they are transported and transformed across environmental compartments. In the context of Canadian oil sands, the available data describe NAFCs as a dynamic compound class that both affects and is affected by their receiving environment. By working towards a comprehensive understanding of the behaviour and fate of NAs and NAFCs, we might better anticipate the extent to which residual toxic effects may persist in reclaimed landscapes.