Research Of Oil Spill Identification Based On GC-IRMS Analysis Technology

With the rapid development of extraction and transportation of offshore oil resources,the risks of oil spill will increase.Hence oil fingerprint identification technology with the increasing of oil spill is increasingly important.At present,the oil spill identification mainly by comparing and identifying the oil fingerprint of the spilled oil and the oil source to identify the source of oil spill.With the development of stable isotope analysis technology(IRMS),the source of the individual compound can be reflected from the molecular level by measuring the stable isotopic composition of monomeric hydrocarbon.A scientific and effective auxiliary method is provided for the oil fingerprint identification.This research mainly determined and analyzed different origin crude oils,as which is IRMS as the core,using gas chromatography-mass spectrometry(GC-MS)and gas chromatography-mass isotope ratio mass spectrometry(GC-IRMS)methods.In addition,two crude oils and two marine fuel oils were selected as research objects.And here,we demonstrated carbon stable isotope composition of oil spill under different weathering degree through the short-term simulated outdoor weathering experiment.The results showed that:(1)The results of crude oil identification showed that the original chromatograms of six oils had no significant difference except Oman crude oil.The differences of nC18/Ph and nC17/nC18 diagnostic ratios were obvious among different oil types,but the differences of(nC19+nC20)/(nC19?nC22),OEP1and CPI13-22 between crude oils were not significant,or even consistent.Stable isotope analysis showed that different types of crude oil had different carbon isotope distribution characteristics,which were mainly controlled by the sedimentary environment of source rocks.The single factor variance analysis results showed that there were significant differences between the bluk ?13C values and ?13C of the individual n-alkanes(P<0.05),validating the feasibility of the application of stable isotope techniques.(2)Repeatability limit test and relative standard deviation analysis showed that the characteristic ratios of LMW/HMW and(nC13+nC14)/(nC25+nC26)were weak resistance to weathering,which couldn't be used as weathering oil spill identification parameters.And OEP1,OEP2 and CPI ratios were less affected by weathering,but the differences in species of different oil not obvious.The carbon stable isotope of individual n-alkanes had no significant isotopic fractionation during weathering,the range of 813C values was in less than 3‰.The principal component analysis and t test based on carbon isotope ratios showed that the unweathered oil samples could completely matched with the oils with different weathering time and effectively distinguished between different kinds oils,improving the accuracy of oil spill identification.The results show that the stable isotope analysis technology has more ability and adaptability,which can make up the limitation of traditional oil fingerprint identification a certain extent.As an auxiliary supplement to the existing appraisal standards,stable isotope analysis technique has practical significance to enhance the level of judicial appraisal of oil spill accidents.