Chemical and toxicological characterization of an unresolved complex mixture‐rich biodegraded crude oil

Abstract

Chemical and toxicological characterization of unresolved complex mixtures in the water-soluble fraction of an artificially weathered Norwegian Sea crude oil was determined by a combination of chemical analysis and toxicity testing in fish in vitro bioassays. The water-soluble fraction of the crude oil was separated into 14 increasingly polar fractions by preparative high-pressure liquid chromatography. The in vitro toxicity (7-ethoxyresorufin O-deethylase activity, estrogenicity, and metabolic inhibition) of these fractions was characterized in a primary culture of liver cells (hepatocytes) from rainbow trout (Oncorhynchus mykiss). The main contributor to toxicity was one of the most polar fractions, accounting gravimetrically for more than 70% of the organic material in the water-soluble fraction and dominated by an unresolved complex mixture. Chemical analysis by gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography-time of flight-mass spectrometry identified a large number of cyclic and aromatic sulfoxide compounds and low amounts of benzothiophenes (<0.1% of total mass) in this fraction. Commonly monitored toxic components of crude oil (e.g., naphthalenes, polycyclic aromatic hydrocarbons, and alkylated phenols) eluted in less polar fractions, characterized by somewhat lower toxicity. Normalization of in vitro responses to the mass in each fraction demonstrated a more even distribution of toxicity, indicating that toxicity in the individual fractions was related to the amount of material present. Although polar and nonpolar compounds contribute additively to crude oil toxicity, the water-soluble fraction was dominated by polar compounds because of their high aqueous solubility and the high oil-water loading. Under these conditions, the polar unresolved complex mixture-rich fraction might account for a large portion of crude oil toxicity because of its high abundance in the water-soluble fraction.

Organic Pollutants in Coastal Waters, Sediments, and Biota: A Relevant Driver for Ecosystems During the Anthropocene?

“…This is not because they are not there, but because of the amount of work that such a study would involve and because it is methodologically impossible to analyze and characterize all pollutants. Even for fossil fuel residues found in the environment, the chemical structure of some fractions remains largely uncharacterized (Rowland et al 2001;Donkin et al 2003;Melbye et al 2009). Furthermore, the list of chemicals present in the environment must be several orders of magnitude longer than those ever reported, since hundreds of thousands of organic chemicals have been used by humankind.…”

Toxicity of sediment-associated unresolved complex mixture and its impact on bioavailability of polycyclic aromatic hydrocarbons

“…Most studies on crude oil spills have focused on polycyclic aromatic hydrocarbons (PAHs), and have shown that these contaminants caused detrimental effects on various aquatic organisms [2][3][4][5][6]. Conversely, other constituents in the oil matrix, which were commonly referred to as an unresolved complex mixture (UCM) were less studied [7][8][9][10]. The UCM was composed of weathered oils, which originated from natural and/or anthropogenic sources, and was first recognized as the "hump" in the quantification of petroleum-contaminated sediment samples using gas chromatography (GC) [11].…”

“…Recent studies, however, have showed that the UCM constituents in sediment not only accumulated in benthic organisms, but also caused sub-lethal effects to these organisms [7][8][9][10][11]15]. For example, UCM contributed to the overall toxic effects of oils to the marine amphipod Corophium volutator and its contribution was separate from the PAHs [7].…”

Compositional properties characterizing commonly transported oils and controlling their fate in the marine environment

“…Their main characteristic is higher polarity which, as a consequence, affords higher water solubility and bioavailability/toxicity. [62][63][64] Furthermore, this fraction can also contain transformation products generated through weathering, such as oxidated polycyclic compounds which can be present at even higher concentrations than the parent compounds. 65 These have been reported in marine environmental matrices at toxic levels 66,67 and can be persistent.…”