Chemistry Department Seminar Christoph Aeppli "Where did all the oil go? The chemistry of oil weathering after the Deepwater Horizon oil spill"
- 12/6/2013 |
3:00 PM – 4:00 PM
Location: Druckenmiller Hall, Room 020
Event Type: Lecture
The 2010 Deepwater Horizon oil spill led to the release of approx. 5 million barrels of oil in the Gulf of Mexico, making it the larges marine oil spill in US history. Whereas approx. 40% of the released hydrocarbons were burnt, recovered or evaporated, 45% dissolved in a deep plume in the water phase, and the remaining 15% formed surface slicks that ended up on beaches or formed near-shore submersed oil mats. These mats are a long-term source of oil and still today, oil-soaked sand aggregates are washed on beaches along the Gulf of Mexico. Analyzing these samples provides a unique opportunity to gain new insights in the fate of oil on time scales of years. Oil is a complex mixture of thousands of hydrocarbons with various physico-chemical properties. Recent analytical development, such as comprehensive two-dimensional gas chromatography now allows analyzing relative changes in the composition of petroleum on a molecular level. This technique allowed us to identify Deepwater Horizon oil on the sea surface and on beaches, based on relative amounts of various petroleum biomarker compounds (“oil fingerprinting”). Furthermore, we analyzed compositional changes in the petroleum hydrocarbon over time. This showed that abiotic (photooxidation) and biotic (biodegradation) oil degradation processes efficiently remove many – but not all – hydrocarbons on time scales of years. However, these degradation processes also led to the formation of highly oxygenated oil degradation products. These compounds are recalcitrant on the observed time scale, form a pool of compounds that are currently overlooked, and might contain products with ecotoxic effects. Overall, taking advantage of the complexity of oil allowed us to gain new knowledge about oil weathering processes. This knowledge will be useful to prepare for future potential oil spills.