Oil Weathering after the Deepwater Horizon Disaster Led to the Formation of Oxygenated Residues

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• 作者：Christoph Aeppli ; Catherine A. Carmichael ; Robert K. Nelson ; Karin L. Lemkau ; William M. Graham ; Molly C. Redmond ; David L. Valentine ; Christopher M. Reddy
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2012
• 出版时间：August 21, 2012
• 年：2012
• 卷：46
• 期：16
• 页码：8799-8807
• 全文大小：463K
• 年卷期：v.46,no.16(August 21, 2012)
• ISSN：1520-5851

文摘

Following the Deepwater Horizon disaster, the effect of weathering on surface slicks, oil-soaked sands, and oil-covered rocks and boulders was studied for 18 months. With time, oxygen content increased in the hydrocarbon residues. Furthermore, a weathering-dependent increase of an operationally defined oxygenated fraction relative to the saturated and aromatic fractions was observed. This oxygenated fraction made up >50% of the mass of weathered samples, had an average carbon oxidation state of 鈭?.0, and an average molecular formula of (C₅H₇O)_n. These oxygenated hydrocarbon residues were devoid of natural radiocarbon, confirming a fossil source and excluding contributions from recent photosynthate. The incorporation of oxygen into the oil鈥檚 hydrocarbons, which we refer to as oxyhydrocarbons, was confirmed from the detection of hydroxyl and carbonyl functional groups and the identification of long chain (C₁₀鈥揅₃₂) carboxylic acids as well as alcohols. On the basis of the diagnostic ratios of alkanes and polycyclic aromatic hydrocarbons, and the context within which these samples were collected, we hypothesize that biodegradation and photooxidation share responsibility for the accumulation of oxygen in the oil residues. These results reveal that molecular-level transformations of petroleum hydrocarbons lead to increasing amounts of, apparently recalcitrant, oxyhydrocarbons that dominate the solvent-extractable material from oiled samples.