Application of a Multimolecular Marker Approach to Fingerprint Petroleum Pollution in the Marine Environment

In an attempt to investigate the suitability of a multibiological marker approach for defining the origin of petroleum pollution in marine systems, the aliphatic hydrocarbon compositions of tar ball samples collected from the beaches of a small island impacted by heavy tar loads were determined by gas chromatography and gas chromatography/mass spectrometry. The tar ball samples, as collected, were at low stages of biodegradation and had diverse physical appearance. The majority of the samples (as many as 7 of the 10) appeared to be heavy fuel oils—possibly Bunker C. The GC traces for the other three tar balls, however, indicated that they were crude oils probably from tanker ballast washings or other non-point sources like the oil entering from the adjacent North Mediterranean. The biomarkers of the sterane and hopane series in these samples, however, had remained unaffected by weathering, and their distributions revealed significant differences among the samples suggesting multiple sources of the tar balls. The tar ball samples could be genetically subdivided into four groups on the basis of their biomarker fingerprints. A marine carbonate or evaporite, hypersaline, anoxic depositional environment of the petroleum source rock for Type I residues could be inferred from the even-carbon-number predominance of n-alkanes, the high relative abundance of gammacerane and the predominance of C35 relative to C34 17α(H)-homohopanes. Higher plant contribution and a deltaic environment of source rock deposition could be concluded for Type II residues from the high concentrations of oleanane and diasteranes. On the other hand, Type III residues possessed geochemical characteristics consistent with a normal marine carbonate or evaporite source depositional environment under normal saline, reducing conditions. Finally, type IV residues had biomarker signatures intermediate between Types II and III.