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Oxygen Isotopes (δ 18 O) Trace Photochemical Hydrocarbon Oxidation at the Sea Surface
Author(s) -
Ward Collin P.,
Sharpless Charles M.,
Valentine David L.,
Aeppli Christoph,
Sutherland Kevin M.,
Wankel Scott D.,
Reddy Christopher M.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082867
Subject(s) - environmental chemistry , hydrocarbon , oxygen , isotopes of oxygen , oxygen 18 , fractionation , chemistry , isotopes of carbon , stable isotope ratio , petroleum , isotope fractionation , photochemistry , total organic carbon , nuclear chemistry , organic chemistry , physics , quantum mechanics
Abstract 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 (δ 18 O Oil ) is a sensitive marker for photochemical oxidation. In less than one‐week, δ 18 O Oil increased from −0.6 to 7.2‰, a shift representing ~25% of the δ 18 O OC dynamic range observed in nature. By accounting for different oxygen sources (H 2 O or O 2 ) and kinetic isotopic fractionation of photochemically incorporated O 2 , which was −9‰ for a wide range of OC sources, a mass balance was established for the surface oil's elemental oxygen content and δ 18 O. This δ 18 O‐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.