Effects of weathering process on the stable carbon isotope compositions of polycyclic aromatic hydrocarbons of fuel oils and crude oils.

Two fuel oils and two crude oils were subjected to a 60-day weathering simulation experiment, and the effects of weathering on some common parameters for aromatics and aromatic δ13C values were studied. The results show that weathering of all oil samples affected little the DBT/P (dibenzothiophene/phenanthrene) ratio and methylphenanthrene distribution fraction. Four oil samples could be distinguished only by the DBT/P ratio. The effect of weathering on isotopes in polycyclic aromatic hydrocarbons was small. The results show that the types of four oil samples can be distinguished, while Kuwait and Russia crude oils cannot be discriminated from each other totally by double-coordinate two-dimensional maps for aromatic δ13C; all of the oil samples can be distinguished by principal component analysis of δ13C for aromatics, the relationship of DBT/P and PAHs δ13C values. Therefore, the δ13C value of aromatics can be used as an alternative index for the analysis of oil spills.