Characterization and determination of naphthenic acids species in oil sands process-affected water and groundwater from oil sands development area of Alberta, Canada

This work reports the monitoring and assessment of naphthenic acids (NAs) in oil sands process-affected water (OSPW), Pleistocene channel aquifer groundwater (PLCA), and oil sands basal aquifer groundwater (OSBA) from an active oil sands development in Alberta, Canada, using ultra performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) analysis with internal standard (ISTD) and external standard (ESTD) calibration methods and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) for compositional analysis. PLCA was collected at 45–51 m depth and OSBA was collected at 67–144 m depth. Results of Ox−NA concentrations follow an order as OSPW > OSBA > PLCA, indicating that occurrences of NAs in OSBA were likely related to natural bitumen deposits instead of OSPW. Liquid-liquid extraction (LLE) was applied to avoid the matrix effect for the ESTD method. Reduced LLE efficiency accounted for the divergence of the ISTD and ESTD calibrated results for oxidized NAs. Principle component analysis results of O2 and O4 species could be employed for differentiation of water types, while classical NAs with C13−15 and Z (-4)−(-6) and aromatic O2−NAs with C16−18 and Z (-14)−(-16) could be measured as marker compounds to characterize water sources and potential temporal variations of samples, respectively. FTICR-MS results revealed that compositions of NA species varied greatly among OSPW, PLCA, and OSBA, because of NA transfer and transformation processes. This work contributed to the understanding of the concentration and composition of NAs in various types of water, and provided a useful combination of analytical and statistical tools for monitoring studies, in support of future safe discharge of treated OSPW. [Display omitted] •NA species were analyzed in 30 OSPW and groundwater samples.•Characterization and determination of NAs were done using UPLC-TOF-MS and FTICR-MS.•Semi-quantification by external and internal standards for calibration was conducted.•Source differentiation and marker compounds screening were done by PCA analysis.•Distinct compositions of NA species were found with different water types.