Oxygen isotopes (delta O-18) trace photochemical hydrocarbon oxidation at the sea surface
Ward, Collin P.
Sharpless, Charles M.
Valentine, David L.
Sutherland, Kevin M.
Wankel, Scott D.
Reddy, Christopher M.
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Keywordpetroleum hydrocarbons; photochemical oxidation; Deepwater Horizon; stable oxygen isotopes; organic carbon
Although photochemical oxidation is an environmental process that drives organic carbon (OC) cycling, its quantitative detection remains analytically challenging. Here, we use samples from the Deepwater Horizon oil spill to test the hypothesis that the stable oxygen isotope composition of oil (δ18OOil) is a sensitive marker for photochemical oxidation. In less than one‐week, δ18OOil increased from −0.6 to 7.2‰, a shift representing ~25% of the δ18OOC dynamic range observed in nature. By accounting for different oxygen sources (H2O or O2) and kinetic isotopic fractionation of photochemically incorporated O2, which was −9‰ for a wide range of OC sources, a mass balance was established for the surface oil's elemental oxygen content and δ18O. This δ18O‐based approach provides novel insights into the sources and pathways of hydrocarbon photo‐oxidation, thereby improving our understanding of the fate and transport of petroleum hydrocarbons in sunlit waters, and our capacity to respond effectively to future spills.
Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 46(12), (2019): 6745-6754, doi:10.1029/2019GL082867.
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Suggested CitationWard, C. P., Sharpless, C. M., Valentine, D. L., Aeppli, C., Sutherland, K. M., Wankel, S. D., & Reddy, C. M. (2019). Oxygen isotopes (delta O-18) trace photochemical hydrocarbon oxidation at the sea surface. Geophysical Research Letters, 46(12), 6745-6754.
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