Date of Award

Spring 4-17-2015

Document Type


Degree Name

Master of Science (MS)

First Advisor

Karl G. Linden

Second Advisor

Fernando Rosario-Ortiz

Third Advisor

Joann Silverstein


Chemical dispersants, such as Corexit 9500 and 9527, are approved by the U.S. government to reduce the environmental impact of crude oil spills on marine habitats. Such chemicals are effective as oil dispersants but the implications of their use remains largely unknown. Laboratory studies have yielded conflicting evidence regarding the toxicity of dispersed oil. Marine environments are dynamic and difficult to replicate in the laboratory; therefore, little is known about the effects of natural elements, such as sunlight, on dispersed oil mixtures. In this study, dispersed oil in artificial seawater was studied under direct sunlight and deep UV. Crude oil dispersed by Corexit is particularly difficult to characterize by analytical methods because of its tendency to form oil-dispersant emulsions. A method of extraction was developed to disrupt the emulsions formed by Corexit and extract both hydrophilic and hydrophobic fractions for chemical analysis. The chemical composition of these fractions was characterized using fluorescence spectroscopy and gas chromatography with a flame ionization detector. The degradation rates of extractable petroleum hydrocarbons and fluorescent components were calculated assuming pseudo-first order kinetics. A bioluminescence inhibition assay using the marine bacterium Vibrio fischeri indicated that 48 hours of equivalent sunlight exposure decreased the toxicity of dispersed oil (oil + Corexit) by 13% compared to oil only or Corexit only samples in which the toxicity increased following sunlight exposure by 8% and 6%, respectively. Additionally, mucilage extracted from prickly pear cactus, has been shown to be a non-toxic, yet effective oil dispersant. A bioluminescence inhibition assay of gelling and non-gelling cactus mucilage extracts suggests that sunlight exposure significantly increases the bioavailability of both mucilage-dispersed oil and mucilage only samples. The results presented in this report suggest photodegradation is an important mechanism in oil spill remediation and a vital first step in improving the biodegradability of crude oil in the environment.