Instrument Characterization and First Application of the Single Particle Analysis and Sizing System (SPASS) for Atmospheric Aerosols

We describe here the instrumental setup and first experiments with the mobile single particle analysis and sizing system (SPASS) for the on-line characterization of single atmospheric aerosol particles. Aerosols are introduced into the SPASS via a differentially pumped particle inlet system using an aerodynamic lens that forms a narrow particle beam. The particles are sized with a two-laser velocimeter and subsequently desorbed and ionized with a high-power pulsed Nd:YAG laser operating at 266 nm. Positive and negative ions formed are simultaneously detected in a bipolar time-of-flight mass spectrometer. Thus, the size and chemical composition of single aerosol particles can be characterized simultaneously in real time. The SPASS system has been installed inside a truck, creating a mobile unit. The performance of the SPASS in terms of mass resolution and sizing capabilities of the laser velocimeter has been evaluated. Positive and negative mass spectra from different types of particles have been obtained to identify “typical” peak patterns. The relative detection sensitivity depending on particle size and chemical composition was studied. Significant differences in detection sensitivities for different compounds were observed, demonstrating that the results obtained from ambient single particle measurements are strongly biased and dominated by “easy-to-detect” particles. The instrument performance is illustrated with results from a 24 h measurement period during winter in Milan, Italy. The period encompasses two meteorologically different episodes, a period of stagnant conditions, where regional background pollutants contribute significantly and the aerosol is dominated by ammonium nitrate and sulfate, and a North-Foehn event, where accumulation mode particles are scavenged and the urban aerosol population is dominated by organic matter due to local emissions.

[1]  Glen R. Cass,et al.  SOURCES OF FINE ORGANIC AEROSOL. 3. ROAD DUST, TIRE DEBRIS, AND ORGANOMETALLIC BRAKE LINING DUST: ROADS AS SOURCES AND SINKS , 1993 .

[2]  B. Morrical,et al.  Real-Time Analysis of Individual Atmospheric Aerosol Particles: Design and Performance of a Portable ATOFMS , 1997 .

[3]  P. Crutzen,et al.  Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry , 1997 .

[4]  D. S. Gross,et al.  Relative sensitivity factors for alkali metal and ammonium cations in single-particle aerosol time-of-flight mass spectra. , 2000, Analytical chemistry.

[5]  Donald W. Bouldin,et al.  A Cluster Separation Measure , 1979, IEEE Transactions on Pattern Analysis and Machine Intelligence.

[6]  Kenneth A. Smith,et al.  Aerosol mass spectrometer for size and composition analysis of submicron particles , 1998 .

[7]  P. Verheijen,et al.  ON THE PERFORMANCE OF AN ON-LINE TIME-OF-FLIGHT MASS SPECTROMETER FOR AEROSOLS , 1997 .

[8]  D. Murphy,et al.  Aerosol characteristics at Idaho Hill during the OH Photochemistry Experiment , 1997 .

[9]  J. A. Hartigan,et al.  A k-means clustering algorithm , 1979 .

[10]  Anthony S. Wexler,et al.  MS of INDIVIDUAL AEROSOL PARTICLES , 1995 .

[11]  R. Van Dingenen,et al.  Chemical mass closure and assessment of the origin of the submicron aerosol in the marine boundary layer and the free troposphere at Tenerife during ACE-2 , 2000 .

[12]  K. Prather,et al.  Real-time measurements of the chemical composition of size-resolved particles during a Santa Ana wind episode, California USA , 2001 .

[13]  P. Hopke,et al.  Classification of Single Particles Analyzed by ATOFMS Using an Artificial Neural Network, ART-2A , 1999 .

[14]  Bernhard Spengler,et al.  Data processing in on-line laser mass spectrometry of inorganic, organic, or biological airborne particles , 1999 .

[15]  Esa Alhoniemi,et al.  SOM Toolbox for Matlab 5 , 2000 .

[16]  A. Prevot,et al.  Climatology of ozone transport from the free troposphere into the boundary layer south of the Alps during North Foehn , 2002 .

[17]  J. Seinfeld,et al.  New particle formation from photooxidation of diiodomethane (CH2I2) , 2003 .

[18]  Bernhard Spengler,et al.  Simultaneous Detection of Positive and Negative Ions From Single Airborne Particles by Real-time Laser Mass Spectrometry , 1996 .

[19]  Kenneth A. Smith,et al.  Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles , 2000 .

[20]  W. Whitten,et al.  Tandem mass spectrometry of individual airborne microparticles , 1997 .

[21]  M. Johnston.  Sampling and analysis of individual particles by aerosol mass spectrometry. , 2000, Journal of mass spectrometry : JMS.

[22]  Esa Alhoniemi,et al.  Self-Organizing Map for Data Mining in MATLAB: The SOM Toolbox , 1999 .

[23]  David B. Kittelson,et al.  Generating Particle Beams of Controlled Dimensions and Divergence: I. Theory of Particle Motion in Aerodynamic Lenses and Nozzle Expansions , 1995 .

[24]  L. Peng.  Generating particle beams of controlled dimensions and divergence: I. Theory of particle motion in aerodynamic lenses and nozzle expansions , 1996 .

[25]  P. Bhave,et al.  Source apportionment of fine particulate matter by clustering single-particle data: tests of receptor model accuracy. , 2001, Environmental science & technology.

[26]  P. B. Farnsworth,et al.  A Differentially Pumped Particle Inlet for Sampling of Atmospheric Aerosols into a Time-of-Flight Mass Spectrometer: Optical Characterization of the Particle Beam , 2000 .

[27]  T. Peter.  Airborne Particle Analysis for Climate Studies , 1996, Science.

[28]  G. Petrucci,et al.  Analysis of ultrafine and organic particles by aerosol mass spectrometry , 2002 .

[29]  D. Murphy,et al.  Cluster Analysis of Data from the Particle Analysis by Laser Mass Spectrometry (PALMS) Instrument , 2003 .

[30]  K. Prather,et al.  Real-time measurements of the chemical composition of size-resolved particles during a Santa Ana wind episode, , 2001 .

[31]  John H. Seinfeld,et al.  Formation and cycling of aerosols in the global troposphere , 2000 .

[32]  S. Downey,et al.  Single particle characterization by time-of-flight mass spectrometry , 1995 .

[33]  David S. Thomson,et al.  Particle Analysis by Laser Mass Spectrometry WB-57F Instrument Overview , 2000 .