Photooxidation of surface oil has been implicated as a critical weathering process in the environment after major oil spills (e.g., Deepwater Horizon (DWH)) and has been demonstrated to produce oil- and water-soluble oxygenated compounds. After the DWH oil spill, many laboratory studies have been conducted to mimic petroleum weathering in the environment. Due to the low availability of oil directly from the Mississippi Canyon (MC) 252 well from which the DWH spill occurred, several studies use surrogate crude oil, which is collected from various nearby wells in the Gulf of Mexico. Although chemically similar to the oil spilled in DWH, previous studies have shown minor differences between surrogate and MC 252 crude oils and suggest the production of different photooxidation products. For example, one study observed differences in the carbon number range for photochemical transformation products between the two oils, suggesting differences in boiling point. Our initial studies involved laboratory photoirradiation of MC252 and surrogate crude oils, and we observed notable differences between the sulfur content in the photooxidized products; thus, we focus here on sulfur functionality. Although light sweet crude oils (e.g., surrogate and MC252) typically contain very low amounts of sulfur (&lt;0.5%), the water-soluble fraction produced from irradiation of surrogate oil contained high levels of SOx species. Furthermore, sulfur-containing polyaromatic hydrocarbons from crude oil have been demonstrated to photooxidize and become water-soluble; however the role of sulfur chemistry in the formation of photogenerated water-solubles has not been extensively studied. Thus, surrogate and MC252 crude oil are separated into three fractions enriched in thiophene, sulfide, and thiol functionalities. Fractions are then irradiated in a solar simulator, which mimics photooxidation in the environment, and analyzed by ultrahigh resolution Fourier-transform ion cyclotron resonance mass spectrometry to reveal the sulfur functionalities of the water- and oil-soluble photooxidation products and allow for comparison of surrogate and MC252 sulfur-containing transformation products.

Role of sulfur functionality in the production of photogenerated water-soluble compounds from surrogate and MC252 crude oils

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.