Not all oils photodegrade equally: The dependence of petroleum composition on photochemical production of hydroxyl radical and singlet oxygen.
Phoebe Zito Ray1, Matthew A Tarr2 and David C Podgorski2, (1)National High Magnetic Field Laboratory, FT-ICR MS Facility, Tallahassee, FL, United States, (2)University of New Orleans, Department of Chemistry, New Orleans, LA, United States
Abstract:
Photochemistry plays a major role in the fate of oil spilled in areas with sunlight exposure. Oil spilled in aquatic systems is exposed to sunlight, resulting in important photochemical processes. In order to study the fundamental and mechanistic pathways of these processes, the production rate, scavenging rate and steady state concentrations for hydroxyl radical and singlet oxygen were determined. Thin oil films (120 µm thick) over ten milliliters of seawater from crude oils with different compositions were exposed to simulated sunlight. The scavenging and production rates were calculated using a competition kinetics approach using selective chemical probes. The steady state concentration for hydroxyl radical produced from thin oil films in the aqueous layer, was ten times the concentration found in previous literature for photoproduction of hydroxyl radical in unaltered sea water. Steady state concentrations for singlet oxygen produced from five aromatic ring fractions chromatigraphically separated from Deepwater Horizon oil were higher than reported results for whole oil. This study illustrates not only how physical and chemical properties of crude oils play a role in the photochemical fate of oil but also how each individual ring fraction contributes to these processes.
