Identification of crude oils and fuel oils after weathering using biomarkers, pyrogenic index and asphaltenes contents

Abstract

Oil spills have become a global problem. This is one of the serious problems in marine environment. The spills are generally from reservoir zipping, accident or unauthorized drainage. Typically, the spilled oils are fuel oils or crude oils which are difficult to differentiate. After oil spill incident, oils are undergone weathering processes such as evaporation, dissolution, and biodegradation etc., which are main factor of depleting hydrocarbon. This work focuses on the distribution of hydrocarbon and diagnostic ratio of polycyclic aromatic hydrocarbons such as pristane, phytane, phenanthrene, pyrene, chrysene and biomarker in hopane group after weathering processes. Moreover, measuring of Al, Si and asphaltenes contents also study in this research. Five crude oils and four fuel oils were weathered in the sea water for 60 days. All samples were characterized by GC-FID and GCxGC-TOFMS followed NORDTEST methodology. Moreover, all samples were measured for asphaltenes contents and Al, Si contents in order to differentiate the types of oil. The result from weathering simulation showed that weathering had significantly affected the distribution of n-alkanes and generally used diagnostic ratio (pristane/phytane) including Al and Si contents changed seriously. However, pyrogenic index and asphaltenes contents can be used as indicators to differentiate fuel oils and crude oils since both of them are strong anti-weathering.