The Characteristics Of Stable Carbon Isotope Fingerprint Of Polycyclic Aromatic Hydrocarbons In Oil Spills

Some oil products from different regions and types were selected to carry out simulated weathering experiments on some of them.The chemical fingerprints and carbon stable isotope fingerprints of polycyclic aromatic hydrocarbons(PAHs)were analyzed by statistical methods and their weathering laws during weathering were analyzed based on Gas Chromatography-Mass Spectrometer(GC-MS)and Gas Chromatography-Isotope Ratio Mass Spectrometer(GC-IRMS).The non-weathering and weathering oils were analyzed by the above fingerprints of PAHs to apply to identification and distinction.This study supplemented the stable and effective identification indexes and methods for the tracing of oil spills.The results showed that:(1)From the crude oil PAHs relative contents distributions,rich information of oil samples could be obtained,but crude oils can not be identified only on the basis of them;One-way analysis of variance of PAHs diagnostic ratios in crude oils showed that the maturity parameters in different oils were little difference,while other indicators of the difference was obvious.The principal component analysis of crude PAHs diagnostic ratios failed to distinguish between Angola(AGL)and Oman(AM)crude oil from different regions.Therefore,the diagnostic value of PAHs should be considered carefully when it is used to identify crude oils.As the number of aromatic rings and methyl groups increase,the overall trend of PAHs 813C tended to be negative.The Principal component analysis(PCA)of stable carbon isotope compositions of PAHs demonstrated different oil features.The combination of PAHs characteristic ratios and aromatics 81 C of seven kinds of crude oils showed significant differences and all oils could be more detailed and clearly discriminated.PAHs stable carbon isotope composition can be used as an effective tool to identify oil sources.(2)The PAHs weathering patterns of different oils are obviously different.Crude oils PAHs are more susceptible to weathering than fuel oils.The results of relative standard deviation(RSD)and repeatability limit analysis showed that the Dibenzothiophene/Phenanthrene(DBT/P)ratio and Methylphenanthrene Distribution Fraction(MPDF1)ratio were more resistant to weathering and higher stability in all oil samples.The one-way analysis of variance(ANOVA)results of the two diagnostic ratios indicated that only the DBT/P ratio could distinguish all the oil samples.Therefore,the DBT/P ratio can be used as a reference for identification of oil spills.The RSD of the same PAHs in the same oil sample in ?13C for aromatics at different weathering stages didn't exceed 1.2 ‰,PAHs ?13C values changed have a limited impact.The principal component analysis of PAHs SILC could distinguish between oil samples.The two-dimensiolal scatter plots of two kinds of PAHs ?13C can identify the sources of oil samples.This study provides some effective reference methods for oils identification.