Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Characterization of Athabasca Oil Sand Process-Affected Waters Incubated in the Presence of Wetland Plants

Abstract

Naphthenic acid fraction compounds (NAFCs) are naturally present in the oil sand. These compounds become integrated into the oil sands process-affected water (OSPW) during the bitumen extraction process. NAFCs have been identified as causing toxicity in the OSPW to aquatic organisms. Water treatment technologies that are largely passive, such as constructed treatment wetlands, are a sought-after technology for the degradation of NAFCs in aquatic environments, partly because of their low energy intensity. However, it can be challenging to accurately assess the performance regarding decreased NAFC concentration and biodegradation characteristics in water samples that have been exposed to such systems. This is due to interferences of biological products such as fatty acids and humic-like materials, which may give false-positive information on NAFCs estimation with conventional analytical sample cleanup methods such as liquid–liquid extraction (LLE). It is recognized that this same issue exists when attempting to characterize NAFCs in natural wetlands for environmental monitoring purposes and, therefore, an analytical method that can remove background interferences in water samples is desirable on several fronts. Studies were thus conducted to develop and compare methods for NAFC isolation in an experimental wetland setting. A controlled greenhouse experiment was conducted with sedge (Carex aquatilis), bulrush (Schoenoplectus acutus), and cattail (Typha latifolia) grown in OSPW. Two methodsthe Isolute Biotage ENV+ SPE method and a new weak anion exchange (WAX SPE)were assessed for their ability to isolate, clean up, and concentrate NAFCs in OSPW and municipal tap water (control) that were exposed to samples of plants and associated microbes. Negative-ion-electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) data revealed that WAX SPE method has better relative enhancement (5%–50%) of O2 classes in OSPW exposed to wetland plants, compared to ENV+ SPE method. The WAX SPE method is a good candidate for the isolation of organic compounds in complex environmental matrices and supports the development of analytical protocols for isolation and characterization of NAFCs. Compound classes from negative-ion ESI-FT-ICR-MS data were further probed using principal component analysis (PCA) to evaluate the NAFCs that are potential indicators of efficiency of engineered wetlands for monitoring in future wetland studies. Given the PCA results, future wetland NAFC degradation investigations should target O2 classes for detailed evaluation of the performance of treatment systems, or measurement of the fate and distributions of NAFCs in natural wetlands exposed to OSPW.

Characterization of dicarboxylic naphthenic acid fraction compounds utilizing amide derivatization: Proof of concept

“…OSPW was provided by the Environment Canada National Hydrology Research Centre (Saskatoon, SK, Canada). The source of the OSPW was a study on the wetland microbial degradation of NAFCs . The sample used was an influent sample, and as such would not yet have experienced biodegradation as a result of the study.…”

“…Samples were extracted from OSPW using weak anion‐exchange SPE (WAX‐SPE) as previously described . For underivatized samples, the eluent was dried under nitrogen gas and reconstituted in 1 mL 50:50 acetonitrile/water with 0.1% NH 4 OH.…”

Solubilized Chitosan Biopolymers for Sequestration of Organic Acids in Aquatic Environments after Biodegradation in a Constructed Wetland Treatment System

“…As a consequence of the toxicity of OSPW, there is restriction on their release, and therefore, they are kept in large-scale tailings containment sites (Giesy et al, 2010). OSPW confined in storage containment sites requires further treatment of potentially toxic components before release of contained water to the aquatic environment (Limited, 2014;Hughes et al, 2017). This situation has led to innovative technologies and treatment strategies for OSPW remediation.…”

Chitosan Biopolymers for Analysis of Organic Acids in Aquatic Environments of Treatment Wetlands

“…Various methods have been proposed for the remediation of OSPW [4]. One of them includes the use of wetland plants to metabolize NAFCs to form by-products that are less toxic [5] [6]. However, the limitation of this method is in the quantification of NAFCs after the wetland treatment where fatty acids and humic-like materials that are produced may yield false positive NAFC concentration levels, based on conventional extraction methods such as liquid-liquid extraction.…”

“…However, the limitation of this method is in the quantification of NAFCs after the wetland treatment where fatty acids and humic-like materials that are produced may yield false positive NAFC concentration levels, based on conventional extraction methods such as liquid-liquid extraction. As well, such conventional methods have shown to favour isolated chemical species with higher carbon chains and molecular weight [6] [7]. Background effects (salinity, suspended and dissolved solids, etc.)…”