Characterization of Oxidation Products of Crude Oil in the Sea Ice Environment using Time-of-Flight High-Resolution Mass Spectrometry

Abstract

As global warming progresses, the Arctic sea-ice extent has decreased rapidly over the past decades, leading to an increase in oil and gas exploration and marine transportation in the Arctic. It is thus important to develop and evaluate oil spill remediation strategies to deal with the increasing risk of crude oil spilled in the Arctic marine environment. Integral to this is understanding the potential for photochemical and microbial transformation processes to degrade the oil in an Arctic marine environment and in the presence of sea ice. This thesis reports a mesocosm-scale oil-in-sea-ice experiment involving a light crude oil conducted at the University of Manitoba’s Sea-ice Environmental Research Facility (SERF) in January–April 2018. The degradation of the oil and production of polar, oxygen-containing compounds were studied by direct infusion electrospray ionization ion mobility time-of-flight high-resolution mass spectrometry (ESI-IM-TOF-HRMS). The data suggests that degradation takes place even when spilled oil is encapsulated in sea ice, as supported by an increase in the occurrence of polar oxygen-containing compounds over time, and a growth of microbial degraders of hydrocarbons as the oil-brine contact increases. Interestingly, ion mobility drift time data shows a decline in cross sectional area of oxidized by-products, despite the fact that the addition of oxygen typically increases molecule size of intermediate by-products. Challenges encountered in non-targeted analysis of oil-in-ice samples are also documented and discussed. This study furthers our understanding of the weathering processes that affect crude oil in a sea ice-covered marine environment and gives detailed information regarding efficient analysis of the relevant oxidized by-products.