Analytical photochemistry of Prudhoe Bay crude petroleum in simulated oil spills: Identification of major lower molecular weight photooxidation products.

摘要

The primary and secondary goals of this research were to identify the major lower molecular weight photo-oxidation products and the major aromatic photooxidation products, respectively, which are formed by the interaction of natural sunlight and crude petroleum layered on water.; To simplify the inherently complex aqueous-phase sample extracts, the crude oil matrix was subjected to a pre-photolysis extraction process which involved the selective fractionation of the crude into three oil fraction types. This process also removed the more water-soluble and volatile components which would presumably be rapidly removed from the oil/seawater interface in a real spill situation. These oil fractions were utilized along with the whole crude for short-term photodegradation experiments. A simulated spill (long-term) study was also performed with whole crude on natural seawater.; The sample extracts from the photolyzed oil/water systems were initially simplified (fractionated) by liquid-solid chromatography to isolate the polar photooxidation products. Anion exchange chromatography and high performance liquid chromatography were employed to further simplify selected sample extracts.; Sample characterizations by capillary gas chromatography and infrared spectroscopy demonstrated that the polar photodegradation products rapidly passed into the underlying aqueous phase. Chromatographic profiles from aqueous-phase extract polar fractions demonstrated the effectiveness of the pre-photolysis extractions in reducing the sample complexity, thereby allowing for identification of lower molecular weight photooxidation products.; Characterizations by gas chromatography/mass spectrometry, with selective ion monitoring analysis, allowed for the identification of series of aliphatic carboxylic acids and numerous isomeric series of alkyl-substituted phenols as the major lower molecular weight photooxidation products. Individual aliphatic esters, aromatic acids, aromatic ketone and ketone-like species, and dibenzothiophene sulfoxides were also identified. A wide variety of previously reported photooxidation products were investigated with selective ion monitoring, but could not be found in the chromatographic profiles of this work.; The overall results of the short-term and long-term photodegradation studies appear to be applicable to real oil spill situations over the first several days of weathering.