Abstract
The photo-oxidation of oil is becoming more recognized as an important weathering process after oil is spilled in the environment, occurring in the hours to days post-oil spill rather than during the weeks to months as previously thought. Understanding how oil weathers under solar irradiation can improve models that forecast the fate and transport of oil spills and also better inform oil spill responders on the types of cleanup and mitigation techniques to use. This study builds off previous work which examined the chemical and physical changes that occur in floating oil (Louisiana Sweet Crude; LSC) exposed to ultraviolet light (UV-A) at different temperatures. Initial results indicated that oil exposed to UV light formed tar ball-like features, regardless of temperature, whereas non-UV exposed oil generally remained sheen-like throughout the duration of the exposure. However, from a chemical standpoint, only minor changes, related to polycyclic aromatic hydrocarbons, were detected. This next phase of research explores how the saturate, aromatic, resin, and asphaltene fractions (SARA analysis) change as oil (both Louisiana Sweet Crude and Alaska North Slope Crude Oil) is exposed to UV light and different temperatures (10, 21 and 30°C) over a ten day period. Physical changes in the oil, related to changes in oil surface area, were documented through the use of photography and FIJI analysis. Results from this study will be used to improve models that forecast the fate of floating oil in the environment and inform future directions for additional research.
Key Findings:
LSC oil exposed to UV light, regardless of temperature, formed tar balls by the end of the exposures; tar balls were only observed at 10°C for ANSCO.
Using a three way ANOVA, the interaction of light, temperature and time was found to have a significant impact on the aromatic and asphaltene fraction in LSC and only the asphaltene fraction in ANSCO.
Three way ANOVA results showed that the interaction of light, temperature and time had significant impacts on oil surface area for both LSC and ANSCO.