| Usually,semi-volatile organic compounds are the kinds of compounds whichboiling points and vapor tensions are between 70℃and 300℃,101×10-6 and 0.101respectively.They can make the balance between the gas and particles phase inatmosphere.SVOCs comprise major components in aerosols and play important rolesin atmospheric chemistry.Their species are various,the structure is complex andanalysis method is difficult.The traditional methods for the analysis of SVOCs in aerosol samples,such asGC-MS,HPLC,capillary electrophoresis and IC usually involve pretreatmentprocedures such as extraction,preconcentration and preseparation.These proceduresare labor intensive and time consuming.Moreover,they may cause the change or lossof certain components during analysis (for example,due to low extractionefficiency).This paper aims at resolving the problems of traditional methods for theanalysis of SVOCs,applied a direct,rapid traditional technology-desorptionelectrospray ionization mass spectrometry ( DESI-MS ) to the analysis of SVOCs inaerosol samples.This paper mainly accomplished three parts of work below:The optimization of experimental conditions of DESI,the determination ofcalibration and the limit of detection were achieved.Experimental parameters forDESI-MS were carefully optimized to enhance the signal intensity by using thestandard PAHs,oxalic acid and oleic acid solution.First we used the standardsolutions of PAHs,oxalic acid and oleic acid with different concentrations depositedon the quartz filter to calibrate the intensities of ion signals.A dynamic range of 4orders of magnitude was observed for PAHs with good linearity (R2＞0.97).TheRSD was less than 15% for PAHs.A dynamic range of 5orders of magnitude wasobserved for both oxalic acid and oleic acid with excellent linearity (R2＞0.99).TheRSD was less than 10% for oxalic acid and within 15% for oleic acid.The LOD forthe above compounds was estimated as 1 pg/mm2 respectively with 5～10 s samplingtime using this particular mass spectrometer.DESI-MS was applied in the qualitative and quantitative analysis of PAlls.oxalic acid and oleic acid in rice straw burning aerosol and ambient aerosol.Under theoptimized condition,DESI-MS can selectively detect the above target compounds from the aerosol samples with reliable results comparing with the traditionalmethods.Besides the above compounds,DESI-MS also detected the signals of organicacids,sugars and inorganic salts in aerosols.Which indicates DESI-MS can beapplied in the analysis of SVOCs and some inorganic components in aerosol.Thecompositions of PAHs in biomass burning and ambient aerosol are different.Weconclude that the mass concentrations of large PAHs are higher than those of smallPAHs in aerosols from rice straw burning.In ambient sample,the ion signalintensities for the observed PAHs are close to one another except for the strong 179(Ant and Phe) ion.During the sampling period,the average concentration of PM2.5 inshanghai was 110.0μg/m3,which was 1.7 times of the standard values 65μg/m3 forPM2.5(US EPA,1997).This indicates the particle pollution especially fine particlepollution in winter of shanghai is very serious.The average concentrations of oxalicacid and oleic acid are 289.0 and 11.3 ng/m3 respectively.Compared with other citiesin China,the concentration of oxalic acid in Shanghai is much lower than Hongkongand Nanjing,little lower than Beijing,higher than Urumqi,and close to Shenzhen.Based on the data of DESI-MS and IC,analysed the composition constitute inrice burning aerosol,measured their emission factors through laboratory methods andestimated their emission mass.A kinds of inorganic acids ions and organic acids werealso analyzed.In 2006,the TSP emitted from rice straw burning for domestic fuel usewas about 64.52 million tons.The content of contamination in TSP is in the order ofCl-＞SO42-＞NO2-＞HCOO-＞F-＞H2C2O4＞NO3-＞MSA＞PAHs＞OA.In PM2.5,the concentrations of the most abundant species followed the order of SO42-＞NO3-＞Cl-＞F-＞NO2-＞C2＞C3＞C4＞MSA＞HCOOH＞OA.The mass ratio of NO3-/SO42-was 0.65,which indicated that with the rapid modernization and motorization ofShanghai,the pollutants from vehicle emissions (mobile source) became severercompared with that of a few years ago.However,NO3-/SO<sup>4(2-) was lower than 1 inShanghai,revealing that stationary source emissions are still the important contributorto atmospheric particles.The C3/C4 ratio was 1.15,which indicated the secondaryproduction from photochemical oxidation should be more important in Shanghai.
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