Dr. Matthew Tarr at the University of New Orleans was awarded and RFP-II grant at $1,469,125 to lead the RFP-II project entitled, “Effect of Photochemistry on Biotransformation of Crude Oil”, which took place between January 1, 2013 and December 31, 2015 with an additional No Cost Extension period through September 30, 2016. This project consisted of 11 research team members and 3 institutions. Through this work, Dr. Tarr and his team aimed to 1) gain a fundamental understanding of the behavior of Deepwater Horizon crude oil components when exposed to sunlight at the marine surface under a range of relevant conditions, and 2) understand how the photochemical transformations impact toxicity and biodegradation.
Dr. Tarr’s research included 4 outreach products and activities and resulted in 29 scientific presentations, 7 peer-reviewed publications, and 5 datasets submitted to the GoMRI Information and Data Cooperative (GRIIDC), which are available to the public. Dr. Tarr also engaged 24 students over the course of his award. Significant outcomes of his research are highlighted below.
Theme 2: Chemical/Biological Processes
Research in this project has provided several important insights into the effects of sunlight on oil spilled in marine systems. The formation of reactive transients from solar irradiated oil was demonstrated, including reports for hydroxyl radical, singlet oxygen, and organic triplet formation from oil films on water exposed to simulated sunlight. The rates of formation and scavenging of these reactive transients was also determined. Through the use of high resolution mass spectrometry, changes in molecular composition of oil were observed after exposure to sunlight in the presence of water and oxygen. Results indicated that oxygen atoms were added across all classes of oil molecules (low to high carbon number, aliphatic and aromatic, with or without heteroatoms). Furthermore, addition of oxygen occurred for oxygenated molecules, so that increasing oxygen content per molecule was observed with increasing irradiation time. The oxygenation resulted in increased water solubility of the photoproducts, altering the bioavailability and toxicity compared to oil that was not irradiated. In studies with sand patties collected from beaches, exposure to simulated sunlight dramatically changed the amount and structures of molecules released into surrounding water. These released photoproducts stimulated aerobic microbial activity, indicating that solar irradiation enhances the bioavailability of even heavily weathered oil. Such enhancements demonstrate the role of sunlight in the fate and transport of spilled oil.