Source Identification of Oil Spills Using Compound-Specific Carbon Isotope Analysis Based on “7–16” Oil Spill in Dalian, China

A set of sequentially weathered oils residue in sediments collected from Dalian Bay in different time after “7-16” oil spill accident, were analyzed by Gas chromatography–mass spectrometry (GC-MS) and Gas chromatography–isotope ratio mass spectrometry (GC-IRMS) to analyze the weathering process and evaluated the possibilities of GC-IRMS as a correlation tool in oil spill identification. Although some temporal variation was observed, no significant temporal shifts in the δ13C values for n-alkanes were measured in moderated weathered oils. The standard deviations of δ13C values of individual n-alkanes varied from 0.07% to 0.20%, which showed that the weathering has no significant effect on values of individual n-alkanes over 120 days. The results suggest that stable carbon isotope profile of n-alkanes can be a useful tool for tracing the source of an oil spill, particularly for the weathered oils absence of sterane and terpane biomarkers.