Environmental Chemistry Modeling Laboratory, GR C2 544, Swiss Federal Institute of Technology at Lausanne (EPFL) , Station 2, CH-1015 Lausanne, Switzerland.
Environ Sci Technol. 2014;48(3):1628-37. doi: 10.1021/es4042836. Epub 2014 Jan 22.
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.
生物降解在石油泄漏的自然衰减中起着重要作用。然而，由于常规气相色谱（GC）解析此化合物组的能力有限，尽管油主要由饱和烃组成，但有关不同饱和烃类在地表环境中的生物降解的信息有限。我们研究了在深水地平线灾难发生 12-19 个月后从墨西哥湾四个海滩采集的八个风化油样。使用全面二维气相色谱（GC×GC），我们成功地分离、鉴定和量化了这些样品中的几个不同的饱和烃类。我们发现，在 n-C22 后洗脱的饱和烃主导了这些风化样品中 GC 可处理的部分。该化合物组代表了从 Macondo 井中最初释放的 8-10%，或 38-68 万吨石油。在 n-C22 到 n-C29 洗脱范围内的饱和烃被发现部分生物降解，但降解程度不同，易生物降解性按以下顺序降低：正构烷烃>甲基烷烃和烷基环戊烷+烷基环己烷>环状和非环状异戊二烯。我们开发了一种新的定量指数，旨在表征 >n-C22 饱和烃的生物降解。这些结果为风化油中未解析复杂混合物（UCM）中这些持久、疏水且大多被忽视的化合物的环境命运提供了新的认识。
