ABSTRACT 2017-189
The crude oil released from the Macondo Well, also known for its location in Mississippi Canyon area as the MC252 well during the Deepwater Horizon Oil Spill, entered an environment already containing a complex mixture of hydrocarbons from both natural and anthropogenic sources, many of which have closely related chemical profiles. To understand the impact of the released oil in offshore areas, a method was needed to distinguish MC252-related hydrocarbons from other sources. A multiple lines of evidence approach was developed to identify weathered MC252 oil in offshore sediments in the Gulf of Mexico. Chemical data for alkanes, PAH, petroleum biomarkers and metals were combined with spatial, temporal, and observational information to examine the fingerprints for more than 4,000 sediment samples collected over the span of five years. The unique conditions of the Gulf of Mexico (GOM), with many natural petroleum seeps and tepid seas, provided an ideal environment to support microbial degradation of petroleum. As a result of these conditions, the initial fingerprint of the MC252 was rapidly and extensively altered in the environment including depletion of petroleum biomarkers, usually assumed to be recalcitrant and often used in ratios to identify petroleum residues. Revised biomarker match criteria were defined to account for biodegradation within this fraction. Applying this methodology to the offshore sediment data from the GOM provided a comprehensive understanding of the distribution of the MC252 oil in offshore sediment and an understanding of the various transport pathways which conveyed the oil to the sediments.
Impact of the Deepwater Horizon oil spill on a deep-water coral community in the Gulf of Mexico
