Photooxidation of crude oils

Photooxidation is a potentially significant process in the degradation of c rude oil spilled at sea. Moreover, a fundamental understanding of the effec t of photochemical degradation on crude oil is a prerequisite for providing an accurate description of the recent history and potential fate of oil sp illed in a marine environment. In this report we examine the effect of ultr aviolet illumination on crude oil using a variety of techniques including g as chromatography/mass spectroscopy and X-ray absorption spectroscopy. The saturated compounds are resistant, but the aromatic compounds are particula rly sensitive to photooxidation. Greater size and increasing alkyl substitu tion increase the sensitivity of aromatic compounds to photochemical oxidat ion. The photooxidized products appear in the resin and polar fractions as determined by thin-layer chromatography. Thus, the effect of photooxidation is distinctly different from that of biodegradation, where larger and more substituted compounds are more resistant to degradation. Perhaps surprisin gly, X-ray absorption spectroscopy indicates that the aliphatic sulfur comp ounds are more readily oxidized than the thiophenic compounds with the sulf ur being oxidized to sulfoxides, sulfones, sulfonates, and sulfates in appr oximately equal amounts.