Steroidal Aromatic ‘Naphthenic Acids’ in Oil Sands Process-Affected Water: Structural Comparisons with Environmental Estrogens

Abstract

The large volumes, acute toxicity, estrogenicity, and antiandrogenicity of process-affected waters accruing in tailings ponds from the operations of the Alberta oil sands industries pose a significant task for environmental reclamation. Synchronous fluorescence spectra (SFS) suggest that oil sands process-affected water (OSPW) may contain aromatic carboxylic acids, which are among the potentially environmentally important toxicants, but no such acids have yet been identified, limiting interpretations of the results of estrogenicity and other assays. Here we show that multidimensional comprehensive gas chromatography-mass spectrometry (GCxGC-MS) of methyl esters of acids in an OSPW sample produces mass spectra consistent with their assignment as C(19) and C(20) C-ring monoaromatic hydroxy steroid acids, D-ring opened hydroxy and nonhydroxy polyhydrophenanthroic acids with one aromatic and two alicyclic rings and A-ring opened steroidal keto acids. High resolution MS data support the assignment of several of the so-called 'O3' species. When fractions of distilled, esterified, OSPW acid-extractable organics were examined, the putative aromatics were mainly present in a high boiling fraction; when examined by argentation thin layer chromatography, some were present in a fraction with a retardation factor between that of the methyl esters of synthetic monoalicyclic and monoaromatic acids. Ultraviolet absorption spectra of these fractions indicated the presence of benzenoid moieties. SFS of model octahydro- and tetrahydrophenanthroic acids produced emissions at the characteristic excitation wavelengths observed in some OSPW extracts, consistent with the postulations from ultraviolet spectroscopy and mass spectrometry data. We suggest the acids originate from extensive biodegradation of C-ring monoaromatic steroid hydrocarbons and offer a means of differentiating residues at different biodegradation stages in tailings ponds. Structural similarities with estrone and estradiol imply that such compounds may account for some of the environmental estrogenic activity reported in OSPW acid-extractable organics and naphthenic acids.

Impact of petroleum coke characteristics on the adsorption of the organic fractions from oil sands process-affected water

“…The NAs found in OSPW were in the carbon range of 8-22 within 1-6 numbers of rings, indicating that there were no acyclic NAs compounds present. Consistently with previous results Rowland et al 2011), monocyclic NAs were the least predominant species among all the Z groups; whereas, bicyclic and tricyclic acids within the carbon range of 12-16 were the most abundant compounds. For the PC (Fig.…”

“…However, low nitrogen content of the PC suggests that H-bonding does not significantly contribute to the adsorption. NAs with higher molecular weights may contain aromatic rings or double bonds which may increase the adsorption affinity of these compounds through the p-p interactions to the graphitelike surface of the adsorbents (Kavanagh et al 2009;Lin and Xing 2008;Rowland et al 2011;Zhu and Pignatello 2005). Given that NAs are highly hydrophobic compounds, the hydrophobic interactions between the NAs and the surface of PC are suggested as a dominant adsorption mechanism.…”

Biodegradation of naphthenic acid surrogates by axenic cultures

“…Estradiol was also selected because it has the same chemical formula as some NAs and similar structures have been shown to be present in OSPW (Rowland et al 2011b). …”

“…They have been shown to have an estrogenic effect (Reinardy et al 2013) and polycyclic monoaromatic compounds have been suggested to pose the ''greatest environmental threat'' because they were predicted to be among the most toxic NAs ). Although few chemical structures have been identified, they are known to coelute with fluorene-9-carboxylic acid in two-dimensional gas chromatography-mass spectrometry and some monoaromatic structures such as dehydroabietic acid, and C 19 and C 20 hydroxyl steroid acids similar to estrone and estradiol have been shown to be in OSPW (Rowland et al 2011b). Ochrobactrum, and Brevundimonas to a lesser extent, demonstrated good metabolism of estradiol and the more toxic polycyclic aromatic surrogates.…”

“…NAs are toxic to fish (Allen 2008;Nero et al 2006b;Siwik et al 2000), phytoplankton (Hayes 2005;Leung et al 2001), other aquatic organisms (Rogers et al 2007), mammals, and plants (Kamaluddin and Zwiazek 2002). Endocrine disruption has been demonstrated in fathead minnows (Kavanagh et al 2011;Siwik et al 2000), goldfish (Lister et al 2008) and T47D-kbluc and MDAkb2 cells (He et al 2011) with exposure to OSPW and the aromatic NAs have been implicated (Reinardy et al 2013;Rowland et al 2011b). Because of the potential adverse environmental impact, the Alberta Environmental Protection and Enhancement Act (1993) has imposed a zero discharge policy on OSPW, resulting in [720 million m 3 of it being currently stored in tailing ponds.…”