Characterization of naphthenic acid fraction compounds in water from Athabasca oil sands wetlands by Orbitrap high-resolution mass spectrometry

Classical naphthenic acids (NAs) are known to be primary aquatic toxicants of concern in the Athabasca oil sands region (AOSR), and are a component of naphthenic acid fraction compounds (NAFCs). Recent studies conducted in the AOSR have examined metals and polycyclic aromatic hydrocarbons in regional wetlands. However, few studies have described NAs and/or NAFCs in AOSR wetlands. To address this gap, we examined NAFC profiles in the water of different wetlands in the AOSR, including naturalized borrow pits (i.e., abandoned pits created by excavation of road-building materials), and opportunistically-formed wetlands associated with reclamation activities. For comparison, NAFC profiles from these wetlands were compared to an opportunistic wetland formed from tailings pond dyke seepage. Samples were prepared using solid-phase extraction and analyzed using negative-ion high-resolution Orbitrap mass spectrometry. Principal component analyses (PCA) revealed patterns to the NAFC profiles in the wetlands. The first distinct grouping of wetlands included water bodies associated with reclamation activities that are located on and/or adjacent to mining overburden. One other wetland, HAT\\S5w, separated from all other wetlands during PCA, and had a unique NAFC profile; detailed examination of NAFCs revealed HAT\\S5w contained the heaviest (i.e., high m/z components) and most unsaturated NAFCs among study locations, demonstrating the usefulness of high-resolution mass spectrometry for characterizing

Automated summary

This study investigated the profiles of naphthenic acid fraction compounds (NAFCs) in wetlands of the Athabasca oil sands region. Utilizing high-resolution mass spectrometry, the research found distinct NAFC profiles in different wetlands, with some wetlands exhibiting unique characteristics in their NAFC compositions.