Photooxidation of crude petroleum maltenic fraction in natural simulated conditions and structural elucidation of photoproducts
Significant amounts of petroleum enter the marine environment from different sources such as; transportation, natural oil seeps, and oil spills each year (Etkin, 1998). It is estimated that 3.2 million tons of petroleum enters the world oceans each year (Heller, 1993). Most crude oils spilled at sea spread rapidly to form slicks with greatly increased surface area (Nicodem, 1998). Oil entering the seas can have a harmful impact, not only on the marine ecosystem, but also on commercial and recreational resources of coastal areas (Garrett, 1998). Oil is spilled immediately subject to a variety of abiotic processes and associated physical changes such as dispersion, photooxidation, evaporation, dissolution and spreading (Nicodem, 1998) with accompanying changes in density, viscosity and interfacial tension (Heller, 1993’) also biotic processes including microbial degradation, biodegradation (Nicodem, 1998). Thus, photooxidation is an important transformation pathway for oil spilled in the marine environment that between 5-40 percent of the oxygen produced by photosynthesis is used by photooxidation (Laane, 1985). The photochemical degradation of hydrocarbons yields a great variety of oxidized compounds, which are highly soluble in a water column (Jacquot, 1996). One year after the Persian Gulf War the seawater contained a high level of oxygenated photoproducts originating from spilled crude oil hydrocarbons (Manfred, 2003). On the other hand, some studies have shown that photoproducts could be greatly toxic (Lacaze, 1989; Jayanti, 1979; Lacaze, 1976; Qstgaard, 1987). Therefore to determine the effects of photooxidation it could be interesting to study the nature of the photoproducts and composition of the residual hydrocarbons (Jacquot, 1996).