Performance Characterization and Application Study of a Single Particle Aerosol Mass Spectrometry
|Keywords||single particle aerosol mass spectrometry performance characterization online analysis cigarette smoke|
Aerosols are solid or liquid particles suspended in the air。For example, dust,fog, smoke or smog. Aerosols are ubiquitous in the air, they are closely related to ourdaily life. Aerosols are becoming more widely recognized throughout the world dueto their significant local, regional, and global impacts. Local impacts includevehicular emissions, wood burning fires, industrial processes, and other aerosolsources that can lead to urban air pollution and possible adverse health effects.Regional problems comprise aerosol transport from areas of high emissions torelatively clean remote regions, while global warming and heterogeneous chemistryin both the troposphere and stratosphere influence the entire planet. Traditionalaerosol analytical methods are primary bulk analysis and off line analytical methods,such as IC and LMMS. However, these methods need to pre collect aerosol particles,which will take too much labor power and time. Moreover, aerosols wouldcondensation; undergo reaction, gas to solid transition etc during the process ofsampling, storing, and conservation, which will make the results deviate the originalconstitution condition. Single particle aerosol mass spectrometry, as a new styledaerosol analytical tool, has high time and spatial resolution, which can detect theaerosol particles from the single particle level. However, these technologies aremostly mastered by developed countries. Aerosol mass spectrometry technologieswere above around in the past years, but are still have a long way to go. Our groupsuccessfully developed a single particle time of flight mass spectrometry with thefinancial aid by National 863 Program. This thesis is primary divided into four parts:principal representation, calibration and characterization, ambient experiment, andcigarette smoke determination.(1) Single particle aerosol mass spectrometry. This is the second chapter of thethesis, structures of the single particle aerosol mass spectrometry were described allsidely, including vacuum system, aerosol inlet system, two laser sizing system, laserdesorption/ionization TOFMS system, data acquisition system and data processing methods.(2) Calibration and performance characterization. This is the third chapter of thethesis, which is completed by myself. Firstly, the calibration method of singleparticle mass spectrometry is described. Standard PSL particles are use forcalibration. The inlet pressure has large effect on the particle sizing. Results showthat little changes of the inlet pressure will cause the changes in the particle time offlight, which is especially significant when concern to large particles. The sizedistribution for the 720nm PSL particles is very consistent to the nominal values,which manifests the single particle aerosol mass spectrometry’s sizing ability.Moreover, laser energy on the fragment production and detection rate ofdi 2 ethylhexyl phthalate (DOP) were investigated. Lastly, sizing efficiency of thesingle particle aerosol mass spectrometry is described as well. These basicexperiments are very important to ensure the single particle mass spectrometry’snormal working. Moreover, outdoor aerosols were determined in Guangzhou,ART 2a based data processing method was used to classify the detected particles,which were then further, merged into five different types. Results show the practicalability of single particle mass spectrometry, which lays the first stone for its nextapplication.(3) Ambient experiment and preliminary results. This chapter describes thepractical environmental monitor application of the aerosol mass spectrometry duringthe Asia Olympic, the search criteria of the data analysis, and also the temporal trendof the detected particles. Some characteristic and possible sources of the mealcontaining particles are analyzed by combination of the size distribution, temporaltrends, and average mass spectrum. The function of the aerosol mass spectrometry instudying the mixing state of single particles are introduced by showing four differentspecies particles. At last, the heterogeneous of Pb containing particles in theatmosphere is confirmed by referring the method described form other reference,which manifested the reliability of the home built aerosol mass spectrometry. It is notably that this chapter merely introduce the experiment data result in a brief level,detailed and specific analysis are just about my next work.(4) Single particle aerosol mass spectrometry determination of cigarette smoke.This is the fifth chapter of the thesis, which is primary completed by myself. Thischapter shoes that single particle mass spectrometry detect the main stream, sidestream and 24 hour old smoke from the burning of several different brands ofcigarette. Results show the fraction of nicotine particles in main stream is higherthan that in side stream. The fraction of nicotine particles in old smoke is higher thanthat in the new generated smoke. The fractions of nicotine particles in the mainstream are all nearly over 50%. Experiments also show that there are big differencesbetween the negative spectra of side stream particles and side stream particles. Thefraction of large particles in the old smoke is higher than that in the new generatedsmoke. Moreover, combustion smokes contain more or less heavy metal particlesfrom all the brands. But the content rates are different from each other.