Products of polycyclic aromatic sulfur heterocycles in oil spill photodegradation.

Photo-oxidation is a potentially significant process in the degradation of crude oil spilled in the environment. The polycyclic aromatic sulfur heterocycles (PASHs) in an Egyptian crude oil (0.8 % sulfur) were photo-oxidized as a film on the surface of water in the presence of anthraquinone as photosensitizer under simulated solar irradiation. The polar photoproducts were characterized using negative ion electrospray ionization with time of flight mass spectrometry and, after trimethylsilylation, gas chromatography with mass spectrometry. The photoproducts identified revealed the presence of a large variety of sulfonic acids, aliphatic and aromatic acids, and alcohols. The data also give new information on the substituents of the aromatic compounds in the unexposed oil and indicate the presence of cyclohexyl substituted aromatic compounds.