Characterization And Identification Of Spilled Oils Using Synchronous Fluorescence Spectroscopy And Gas Chromatography-Mass Spectrometry

Nowadays, the marine exploitation industry of crude oil develops rapidly. Because of the imbalance of oil distributing and consumption and the cheapness of sea transport, the quantity of oil transported by sea mounts up year after year. At the same time, sea transport accidents happen frequently. Oil spill badly affects the marine environment and natural resources, and therefore it has become a global pollution problem. Thus great attention has been paid to characterization and identification of spilled oils. The rapid and reliable characterization and identification of spilled oils is of great significance for assessing the damage to the environment and natural resources caused by the released petroleum, for settling liability dissension and for providing an effective cleanup strategy.In this paper, twenty-one oils including two gasoline, one diesel oil, one lubricating oil and seventeen crude oils were studied. These oils were analyzed by synchronous fluorescence spectroscopy (SFS) in three oil concentrations (5 mg/L,500 mg/L,5000 mg/L) and chromatography– mass spectrometry (GC-MS) for n-alkanes, polycyclic aromatic hydrocarbons and biomarkers fingerprinting. Four crude oils among seventeen crude oils were set outdoors for natural weathering. The weathered oils after 1, 3, 5, 10, 15 and 35 days were also analyzed by SFS in three oil concentrations. The main research work is as follows:1. Seeing about the SFS of different oil types. Gasoline, diesel oil and lubricating oil all had distinct characteristics, which were obviously different from crude oils. As for the 17 crude oils studied in the research, SFS were different as the concentration increased. Oil solution of 5 mg/L, 500 mg/L and 5000 mg/L had characteristic peaks in excitation wavelength 260-460 nm, 300-600 nm and 400-850 nm respectively. SFS of oil solution of low concentration (5 mg/L) had less distinction, while SFS of oil solution of high concentration (500 mg/L and 5000 mg/L) had more distinguishing feature.2. The SFS of original and weathered oils were studied, and a fingerprint database based on SFS feature was built. First, visually comparing SFS of weathered oil with those of its original oil, we find that the peak intensity of SFS minished as weathering processed; the shape of SFS of oil solution of 5 mg/L and 500 mg/L had little alteration, while the shape of 5000 mg/L changed to some extent. All SFS were analyzed using principal component analysis (PCA). The principal component scores charts showed that the SFS of the oil solution of 500 mg/L and 5000 mg/L had better distinguishing ability than that of 5 mg/L; Although the SFS of oil solution of 5000 mg/L had best distinguishing ability, SFS were influenced a lot by weathering; the SFS of 500 mg/L had preferable stability. Thus, SFS of 500 mg/L between 300 nm and 600 nm were selected as spectrum feature of crude oils, and used to build oil fingerprint data base for approximately differentiating crude oils.3. A fingerprint database based on GC-MS was built. Concentrations of detailed hydrocarbons including target n-alkanes, Poly Aromatic Hydrocarbons (PAHs) were determined by GC-MS. Besides, a series of diagnostic ratios based on n-alkanes, PAHs and biomarkers were also analyzed. All the information was used as oil feature to build oil fingerprint data base for matching crude oils.4. The origin of one weathered crude oil was identified. A weathered oil of 17 crude oils was selected as an unknown oil sample. Firstly, SFS of 500 mg/L were analyzed by PCA to find similar oils. Then GC-MS data were used to match oils. The results suggest the newly developed protocol in which oils firstly distinguished by SFS of 500 mg/L and then matched by GC-MS may become a useful means in spilled oils identification.In sum, this study for the first time suggests the application of SFS of high concentration (500 mg/L) to approximately differentiating crude oils and the novel protocol in which oils firstly distinguished by SFS of 500 mg/L and then matched by GC-MS; build oil data bases both for approximately differentiating crude oils and matching crude oils; apply PCA to digitally identify the origin of weathered oil samples. The results suggest that it is reliable and rapid to identify spilled oils using the newly developed system, which may become a useful means in spilled oils identification.