Resolving Biodegradation Patterns of Persistent Saturated Hydrocarbons in Weathered Oil Samples from the Deepwater Horizon Disaster

• Published in: Environmental science & technology Vol. 48; no. 3; pp. 1628 - 1637
• Main Authors: Gros, Jonas, Reddy, Christopher M, Aeppli, Christoph, Nelson, Robert K, Carmichael, Catherine A, Arey, J. Samuel
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 04-02-2014
• Subjects: Applied sciences; Biodegradation; Biodegradation, Environmental; Chemical compounds; Chromatography; Chromatography, Gas; Disasters; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Monitoring; Exact sciences and technology; Gulf of Mexico; Hydrocarbons; Hydrocarbons - analysis; Mexico; Natural water pollution; Oil spills; Petroleum - analysis; Petroleum Pollution - analysis; Pollution; Pollution, environment geology; Seawaters, estuaries; Water treatment and pollution; Gulf of Mexico; Mexico; ASW, Mexico Gulf; Biodegradation; Oil spill; Offshore production; Two dimensional chromatography; Hydrocarbon; Pollutant behavior; Multicomponent mixture; Ageing; Accidental explosion; Polycyclic aromatic compound; Persistent organic pollutant; Persistence; Carcinogen; Gas chromatography; Oil industry; Selfpurification; Water pollution; Organic compounds; Seawater
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es4042836

Biodegradation plays a major role in the natural attenuation of oil spills. However, limited information is available about biodegradation of different saturated hydrocarbon classes in surface environments, despite that oils are composed mostly of saturates, due to the limited ability of conventional gas chromatography (GC) to resolve this compound group. We studied eight weathered oil samples collected from four Gulf of Mexico beaches 12–19 months after the Deepwater Horizon disaster. Using comprehensive two-dimensional gas chromatography (GC×GC), we successfully separated, identified, and quantified several distinct saturates classes in these samples. We find that saturated hydrocarbons eluting after n-C22 dominate the GC-amenable fraction of these weathered samples. This compound group represented 8–10%, or 38–68 thousand metric tons, of the oil originally released from Macondo well. Saturates in the n-C22 to n-C29 elution range were found to be partly biodegraded, but to different relative extents, with ease of biodegradation decreasing in the following order: n-alkanes > methylalkanes and alkylcyclopentanes+alkylcyclohexanes > cyclic and acyclic isoprenoids. We developed a new quantitative index designed to characterize biodegradation of >n-C22 saturates. These results shed new light onto the environmental fate of these persistent, hydrophobic, and mostly overlooked compounds in the unresolved complex mixtures (UCM) of weathered oils.