Study On Weathering Process And Fingerprinting Diagnostic Ratios Optimization Of Ship Fuel Oil

In recent years, with the rapid development of China’s marine economy, the sizeof oil exploration and explotation has expanded, and the oil shipping in coastal hasincreased frequently. That contributed to the risk of our country’s oil spill seriously. Atpresent, technology about oil spilled identification of our country has not yet mature.The number of fingerprinting diagnostic ratios is big, which results in the process offingerprinting identification complex. What’s more, after oil spills into the marineenvironment, it will experienced complex weathering process. The inherentcharacteristic information of oil fingerprinting and some identified parameters aredamaged. It make diagnostic ratios lose their validity, and then, the identification offingerprinting become more difficult.This article selects three kinds of suspicious fuel oil from an oil spilled accidentfor screening and optimizating the diagnostic ratios.What’s more, in order to studythe weathering effects on the validity of the fuel oil’s diagnostic ratios, a weatheringsimulation experiment of some oil is performed under natural conditions for60days.On this basis, using the optimized diagnostic ratios to identify the residual oil andthree kinds of fuel oil. It will have important theoretical and realistic significance inenriching and consummating the oil fingerprinting identified methods. The mainconclusions of this paper are as follows:(1) In the process of oil fingerprinting identification using repeatability limit,when the relative standard deviation is in the same situation, the diagnostic ratiosscreening recognition ratio of different kinds of oil are different. While as the relativestandard deviation changing (reduce from5percent to2.5percent, then to1percent),the availability of fingerprinting diagnostic ratios in different kinds of oil is different,and there is no specific regularity. Therefore, the screening of diagnostic ratios inadvance is an indispensable program. Otherwise, it may cause misjudgment.(2) Based on the research of three kinds of fuel oil, some common priorities in the oil fingerprinting identification,(C19+C20)/(C19+C20+C21+C22)> CPI and MPI1>C3D/C3P> MPI2, are obtained. Even when the relative standard deviation reduces to1percent, the5ratios still keep good stability.(3) The results of60days’ natural weathering shows that: There is nearly anabsence of aliphatic compounds below n-C13; What’s more, middle molecular weightnormal alkanes (n-C15~n-C29) maybe more resistant to weathering than highmolecular weight normal alkanes (n-C30~n-C38). Some most alkylated membersmaybe depleted easier than the less substituted ones.(4) Weathering changes the effectiveness of the diagnostic ratios in the greatdegree:Among diagnostic ratios of n-alkanes,(C19+C20)/(C19+C20+C21+C22) and CPIremain the priority that (C19+C20)/(C19+C20+C21+C22)>CPI unchanges under60daysof weathering. Even if the relative standard deviation is2.5%,(C19+C20)/(C19+C20+C21+C22) are still applied in tracing oil spilled source,while CPI is not. While Pr/Phis no value after15days of weathering. The validity of diagnostic ratio is different indifferent oils. Therefore, the diagnostic ratios should be used carefully, when toidentify different species and different weathering extent oils. Otherwise, the resultsmaybe wrong.Among the terpane ratios, the relative standard deviation of Ts/Tm is alwaysmore than5percent. So this diagnostic ratio should be chosen selectively to be anidentification indicator. On the contrary, C31αβ(S/(S+R))~C35αβ(S/(S+R)) are alwaysstable. C31αβ(S/(S+R))~C33αβ(S/(S+R)) are still valid even the relative standarddeviation is1%, while C34αβ(S/(S+R)) and C35αβ(S/(S+R)) exceed1%from theseventh day, which suggests that it is not applied in the oil fingerprintingidentification of weathering oils.In the diagnostic ratios of sterane classes, C29ααα(S/(S+R)) ster andC29αββ/(C27-C29)αββ ster have maintained good stablity within60days’ weathering.However,5diagnostic ratios show poor stability, which indicates that they are notsuitable as the identification indicator of this fuel oil which experienced weathering.In PAHs’ diagnostic ratios, the C3D/C3P ratio is not used to tracking the oil spilled source from the third day of weathering.(5) Compare the fingerprinting of the residual oil and the fuel oil A, B and C,which from Zhou Shan oil spilled accident, using the screening and optimizeddiagnostic ratios. The results are that the residual oil is consistent with the fuel oil C,and it don’t agree with A and B. In conclusion, the fuel oil C is the oil spilled sourceof this accident.