SootParticle-AMS or LaserVaporizer-AMS. Aerodyne Research, Inc. et al.

Transcription

1 SootParticle-AMS or LaserVaporizer-AMS Aerodyne Research, Inc. et al.

2 Outline SP-AMS instrument design Nomenclature Collection Efficiency Refractory carbon ion distributions

3 SP-AMS Instruments in the Field # Research Group Instrument Status 1 Aerodyne Research, Inc. SP module delivered 2 Aerodyne Research, Inc. SP module delivered 3 University of Manchester SP module delivered 4 University of Toronto SP-AMS delivered 5 Lund University, Sweden SP module delivered 6 ETH, Switzerland SP module delivered 7 FMI Helsinki SP module delivered 8 Drexel University SP-AMS delivered 9 Environment Canada SP-AMS delivered

4 Laser Vaporizer

5 SP-AMS Orthogonal Detection Axes Ion Extraction and MS detection Sampled Particles Characterization of particle-laser interaction region: Vertical Particle Beam Walk Horizontal/Vertical Beam Width Probe Horizontal/Vertical Laser Beam Walk

6 Ionizer Configurations Standard AMS Filaments on sides of ion chamber Filament position is mechanically set Filament wire is typically well positioned with respect to well formed slits in ion chamber walls SP-AMS Filament is on bottom of ion chamber Filament position is moveable (vert & horz) Filament slit width and breadth may vary due to custom procedure Large holes in sides to accommodate laser beam

7 Detection Scheme The laser is not the vaporizer, the absorbing particles are the vaporizer!!

8 Ambient Results

9 Absorbing Refractory Particles Refractory Black Carbon Metals Metalloids Schwarz et al., 2004

10 Mensah and Corbin Nomenclature NR-PM R-PM LR-PM Metals & Minerals rbc Sampling Temp. 600 o C ~2000 o C 4000 o C NR-PM = Nonrefractory Particulate Matter R-PM = Refractory Particulate Matter LR-PM = Light absorbing Refractory Particulate Matter Metals/Minerals = Refractory Metals and Metalloids rbc = Refractory Black Carbon

11 Nascent Flame Soot Refractory Oxygen Laser and Tungsten Vaporizers

12 Particle Temperature Profiles Laser Vaporizer Particle Temperature Tungsten Vaporizer R-PM 600 o C NR-PM Time Time

13 SP-AMS PMF HR-AMS HOA SVOOA 1 SVOOA 2 LVOOA Similar PMF factor identification - slightly different spectra Massoli et al, 2012

14 SP-AMS Vaporizer Configurations Vaporizer Tungsten Laser Measured Species NR-PM * E B (rbc + R-PM ǂ + NR-PM ǂ ) * E S Laser and Tungsten (rbc + R-PM ǂ + NR-PM ǂ ) * E S + (NR-PM - NR-PM ǂ * E S ) * E B NR-PM = Nonrefractory Particulate Material measured by a standard AMS [Jimenez et al., 2003 ] R-PM = Refractory Particulate Material measured by the SP-AMS (see text for details) rbc = Refractory black carbon measured by the SP-AMS (and SP2) [Schwarz et al., 2006 ] ǂ = Particulate Material on rbc particles as mesaured by the SP-AMS (see text for details) E B = Particle bounce related Collection Efficiency of the AMS E S = Size and shape related Collection Efficiency of the SP-AMS

15 SP-AMS Onasch et al. (AS&T 2012)

16 Laser Vapor Collection Efficiencies E L = Aerodynamic lens transmission E B = Particle bounce off the Tungsten vaporizer E S = Particle beam divergence E L ~ 1 (Dva = nm) E B = 1 (No bounce issue on laser vaporizer) E s < 1 (Particle beam width > laser beam) E S governs the overall CE for black carbon Beam width probe measurement Mass concentration of species s

17 Beam Width Probe (BWP) Measurement wire motion Particle beam laser BWP wire diameter

18 Experimental setup BC standard: Regal black Coating: Bis(2-ethylhexyl)sebacate (BES) SP-AMS configuration: Dual vaporizers Coating thickness depends on temperature Measures particle mass before and after coating M.D. Willis, A.K.Y. Lee, J.P.D. Abbatt

19 M.D. Willis, A.K.Y. Lee, J.P.D. Abbatt Beam Width Probe (BWP) Measurement Block % at the center Beam sigma (mm) 95% beam width (mm) NO 3 RB RB with coating

20 DOS coated Regal black Regal black Particle Beam Width Comparisons SP-AMS Laser Width Particle beam widths: DOS coated RB ~ pure DOS/AN particles Laser beam width is <= s ~ 0.1 to 0.25 mm M.D. Willis, A.K.Y. Lee, J.P.D. Abbatt

21 Brief Laser Desorption of rbc Material History 1. Late 1970 s to early 1980 s developed laser heating of soot detection using (a) incandescence and (b) mass spectrometry (Melton et al., 1985). Typical MS applications include Laser Desorption and Ionization (LDI), where a focused, pulsed laser beam desorbs and ionizes refractory carbon material Incandescence (ensemble and single particle) applications typically use CW lasers 2. Fullerenes were first discovered using LDI (Kroto et al., 1985) 3. Initial applications of LDI to ambient and extra-terrestrial samples implied the presence of fullerenes; however, subsequent studies showed LDI can generate fullerenes, with laser power a significant issue (Kasuya et al., 2001) 4. Currently, analytical results for ambient rbc chemical/structural detection include many different off-line techniques (including HR-TEM, XPS, STXM, NEXAFS, Raman Spectroscopy) (Isaacson et al., 2009) 5. The real time, on-line SP-AMS uses relatively low laser power densities (~10 5 W/cm 2 ) and may provide useful chemical information on refractory black carbon particles. It does not generate fullerenes from laboratory samples where it is not expected. These observations suggest that the SP-AMS carbon ion signals reflect the fullerene content of the rbc particulate material but the fraction of the ions signal associated with the nascent fullerene content of the rbc material has not been quantitatively determined

22 Atmospheric Applications 1 Source Characterization of rbc particles Atmospheric rbc particles Graphitic Chemical information on the structure of the refractory carbon material Source characterization of rbc particles Fullerene containing

23 Emissions Measurements Caldecott Tunnel Dallmann et al., EST 2010 Distinct combustion sources generate different SP-AMS refractory carbon ion mass spectra Potential to provide insights into ambient particulate sources FLAME3 McMeeking et al., JGR 2009

24 Ambient Observations rbc Source Finger Prints Vehicle Emissions Wood Burning Emissions 2012 Clearflo Site in Detling Clearflo 2012 in prep. Williams et al. 2012

25 SP-AMS Papers 1. Cross et al Soot Particle Studies Instrument Inter-Comparison Project Overview. Aerosol Science and Technology 44 (8) (June 30): Onasch et al Soot Particle Aerosol Mass Spectrometer: Development, Validation, and Initial Application. Aerosol Science and Technology 46 (7) (July): Cappa et al Radiative Absorption Enhancements Due to the Mixing State of Atmospheric Black Carbon. Science 337 (6098) (August 30): Cross et al Real-Time Measurements of Engine-Out Trace Elements: Application of a Novel Soot Particle Aerosol Mass Spectrometer for Emissions Characterization. Journal of Engineering for Gas Turbines and Power 134 (7): Massoli et al Pollution Gradients and Chemical Characterization of Particulate Matter from Vehicular Traffic Near Major Roadways: Results from the 2009 Queens College Air Quality Study in NYC. Aerosol Science and Technology 46 (11) (November): Fortner et al Particulate Emissions Measured During the TCEQ Comprehensive Flare Emission Study. Industrial & Engineering Chemistry Research 51 (39) (October 3): Liu et al Ambient Black Carbon Particle Hygroscopic Properties Controlled by Mixing State and Composition. Atmospheric Chemistry and Physics 13 (4) (February 21): Nordin et al Secondary Organic Aerosol Formation from Idling Gasoline Passenger Vehicle Emissions Investigated in a Smog Chamber. Atmospheric Chemistry and Physics 13 (12) (June 28): more submitted and many more in preparation/planning

26 Sunday Afternoon Breakout Session

27 Summary SP-AMS technology has matured and is opening new avenues for applying MS to refractory particles Nomenclature: Corbin et al. have set out a proposed set of terminology based on temperature (instrument and particle specific) 1. NR-PM and R-PM {LR-PM is a subset of R-PM} 2. SP-AMS laser vaporizes LR-PM and associated NR-PM & R- PM material at temperatures below sublimation/incandescence Collection efficiency: Willis et al. show that CE S dominates in SP-AMS measurements, requiring BWP measurements Successful applications of SP-AMS technique are starting to grow rapidly Please join the Breakout Session Sunday afternoon