Analysis of biomarkers in crude oils, processed oils, and spilled oils

Abstract

Oil spills in marine are commonly come from crude oils, fuel oils and lubricating oils by accidental leakages or purposeful discharges to the surroundings. As crude oil and fuel oil which refined from the heavy fraction of crude oil have similar physical properties especially if they were weathering, it is difficult to differentiate that the spill has the origin from crude oil or fuel oil. In this study, five crude oils, two fuel oils, one fresh and one used lube oil that are typically used in Thailand were investigated. All crude oils, fuel oils, and used lube oil were weathered in the sea water. All samples were characterized using GC-FID and GCxGC TOFMS. The attention of this work is focused on the distribution pattern of polycyclic aromatic hydrocarbons (PAHs) such as phenanthrenes (P), anthracenes (A), dibenzothiophenes (D) and their alkylation, and biomarkers in hopanes group. The statistic method was applied to distinguish crude oils, fuel oils and lube oil. The results from GC-FID showed a useful basis information of hydrocarbon in oils which could distinguish lube oil from other oil type due to the huge unresolved complex mixture (UCM). The distribution patterns of methyl-phenanthrenes (MP) and methyl-anthracenes (MA) were different in most crude oils and processed oils. The double ratio plots of MP and MA showed the most positive method to differentiate two refined products and crude oils. The results from weathering simulation showed that biomarkers were high degradation-resistant, however, hopanes distribution patterns were different between fuel oils and their crude oil feedstocks. In addition, the distribution pattern of hopanes biomarker in fresh or unused lube oil and used lube oil were dissimilar as they were generated or degraded during the combustion in the engine.