Dispersed oil fingerprinting in marine environments

Song, Xing (2019) Dispersed oil fingerprinting in marine environments. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The occurrence of offshore oil spills can induce various negative effects on marine environments. Oil fingerprinting is a key technology to identify the sources of crude oil and associated refined products spilled into the environments. Spill oil fingerprinting can be achieved by investigating the diagnostic relationships among specific hydrocarbons, known as biomarkers. Biomarkers in oils can be uniquely distributed to pinpoint the oil geographic source and weathering status. Dispersants are widely used marine oil spill treatment agents, containing surfactants and solvents. It can reduce interfacial tension between oil and seawater by enhancing the generation of small and stable oil-surfactant micelles (i.e., oil-in-water emulsion). By using dispersants, the spilled oil in a water emulsion bridged by surfactants, called chemically dispersed oil (CDO), can dwell in seawater for a longer period under proper conditions. CDO fingerprinting is essential for assessment of its environmental impact, selection of further response countermeasures, and for a better understanding of the fate and behaviors of CDO in marine environments. However, dispersant application could change the physicochemical properties of spilled oil, which is challenging for the applicability of current environmental forensics for CDO fingerprint and limits the research on the topic reported. To address this challenge, this thesis carried out investigations on dispersed oil fingerprinting in marine environments in the following aspects: 1) investigation of the applicability of existing typical biomarkers for fingerprinting of short-term weathered CDO, 2) identification of relatively long-term weathered CDO through screening eight types of aliphatic and aromatic biomarkers, 3) differentiation of CDO from non-dispersed oil using principal component analysis, 4) assessment of the impacts of biodegradation of weathered dispersed oil (treated by a shrimp-waste based new dispersant) on fingerprinting of CDO, and 5) comprehensive evaluation of environmental factors on CDO fingerprinting. The research outputs lead to a group of identified biomarkers for effective dispersed oil identification and oil weathering assessment, a better understanding of the characteristics of spilled oil treated by dispersants, and a more robust means for tracking fate and behaviors of CDO in marine environments.

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