Award: OCE-1333148

When an oil spill occurs, responders face multiple challenges to assure the safety of humans and reduce damages to the environment. Simply put, the goal of a responder is preventing a bad thing from getting worse. To overcome these challenges, it is critical for responders to know the composition of oil spilled into the environment and its behavior after the spill. In our previous studies, we were surprised to find that in less than a year after the Deepwater Horizon disaster, which occurred in the Gulf of Mexico in 2010, approximately 50% of the oily residues collected in the environment had a different composition compared to the oil initially spilled into the Gulf; the oily residues were signficantly oxidized. However, the cause of the oxidation was not known. One goal of this project was to determine the relative importance of sunlight (photochemistry) or microbes, the two most likely drivers in the production of these oxidized residues. From the analysis of >100 field samples and laboratory experiments, we found that sunlight-driven processes contributed substantially to the formation of oxidized hydrocarbons following the Deepwater Horizon. This research also provided the first insights into the photochemical mechanisms governing the formation of oxidized oil residues. These findings should pave the way for additional work that will address if the oxidation of oil affects how responders combat future spills. For example, is in-situ burning, a frequently used tool to combat spilled oil, as effective for oxidized oil as it is for unoxidized oil? There are currently 29 rigs extracting oil from off-shore waters of the Gulf of Mexico. With this unwavering commitment to extract fossil fuels comes the risk of spills. Our work has determined that sunlight was a key process that rapidly changed the composition of oil and may impact the approach responders take to reduce damages from future spills. We have made great efforts to communicate these results to our academic colleagues, as well as leaders in United States government and oil industry charged with planning and responding to future spills. Last Modified: 03/03/2017 Submitted by: Christopher M Reddy