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The formation of crude oil occurred many millions of years ago from decaying plants and animals. Sediment and rock covered the organic material creating an anaerobic environment that eventually, under temperature and pressure conditions, formed crude oil. Crude oils from various regions differ in the plant and animal source materials, as well as the time, temperature, and pressure conditions that occurred during formation. Therefore, each crude oil has a unique fingerprint that can potentially be determined using biomarkers. Biomarkers play a very important role in characterization, correlation, differentiation, and source identification in environmental forensic investigations of oil spills. Biomarkers such as steranes and hopanes are one of the most important hydrocarbon groups in petroleum for chemical fingerprinting, 15 they are complex molecules derived from formerly living organisms. The biomarkers found in crude oils, rocks, and sediments are stable and show little or no changes in structures from their parent organic molecules, or so-called biogenic precursors (e.g. bacteriohopanetrol, sterols), in living organisms, and thus carry information about the nature, source, type, geological conditions, and thermal history of these organisms. Biomarkers can be detected in low quantities (ppm and subppm level) in the presence of a wide variety of other types of petroleum hydrocarbons using the gas chromatography/mass spectrometry (GC/MS). Relative to other hydrocarbon groups such as alkanes and most aromatic compounds, biomarkers, hopanes and steranes are more degradation-resistant in the environment. |
