Environmental Forensics Study of Crude Oil and Petroleum Product Spills in Coastal and Oilfield Settings: Combined Insights from Conventional GC-MS, Thermodesorption-GC-MS and Pyrolysis-GC-MS

Abstract

A representative set of five oil spill samples from four different regions displayed different product characteristics and different levels of weathering. Three of them were taken along shorelines affected by marine oil spill events, viz., Aboño and Prestige (Spain) and Deepwater Horizon (USA) and the other two were taken at inland oil spill sites (Angola and Kuwait). A multi-faceted environmental forensics approach revealed key molecular features. In addition to the conventional GC/MS analysis of saturated and aromatic fractions, the polar fractions also were analyzed, revealing a complex series of linear alkanones in those oil samples particularly enriched in aliphatics. Thermodesorption-GC-MS of the whole oils was also employed to further test its efficacy as a tool for the rapid fingerprinting of environmental contamination. The method was shown to accurately detect most of the essential features recognized in the conventional GC-MS analysis of the saturated and aromatic fractions, although in some instances with less sensitivity and poorer resolution. Characteristics so recognized included the distributions of normal and isoprenoid alkanes, saturate and aromatic biomarkers, and polycyclic aromatic compounds such as alkylphenanthrenes and alkyldibenzothiophenes. Sequential pyrolysis of the post-thermodesorption residue and asphaltene pyrolysis yielded similar results, indicating that the residue consists primarily of asphaltenes. Thermodesorption and pyrolysis GC-MS also recognized substances likely to be associated with spill cleanup efforts that were not detected by conventional analysis