AMS Introduction Doug Worsnop. AMS Users Meeting

Transcription

1 AMS Introduction Doug Worsnop AMS Users Meeting Aerodyne Caltech Georgia Tech FZ - Juelich University of Minnesota Desert Research Institute October 21/22 October 24, 23 October 8, August, September, September, 27 AMS Introduction AMS Users Meeting Aerodyne Caltech Georgia Tech FZ - Juelich University of Minnesota Desert Research Institute October 13, 22 October 24, 23 October 8, August, September, September, 27 Nitrate Sulfate Ammonia Organics (44,57) OOA, HOA OOA1, OOA2 1

2 Aerosols in the Atmosphere C.E. Kolb, Nature, 22 Ambient Aerosol Size Distribution Number Density EPA, 1999 Surface Area Mass Remote Continental Pandis and Seinfeld, 1998 Ultrafine Fine Coarse Goal: Size-Resolved Chemical Composition of Ambient Aerosol 2

3 Org SO 4 2- NO 3 - NH 4 Manchester center Small particles <2nm Hydrocarbon organics Vancouver center Rural (outside Vancouver) Larger particles (>2 nm) m/z 44 CO 2 dominates 3

4 e - Organic Mass Spectra C n H 2n,2 ----> C m H 2m±1 27, 29, 41, 43, 55, 57, 69, 71,... C 3 H 5 C 4 H 7 C 5 H 9 e - C n H m O y ----> H 2 O, CO, CO 2, C 2 H 3 O , 55,. Following flash vaporization at ~6 o C Organic Aerosols: Urban vs. Rural/Remote 4

5 AMS (PMF) Factors 6C, e- m/z HOA: C n H m C n-x H m-y 27,29,41,43,55,57,69,71, LESS OXIDZED OOA2 C n H m O C 2 H 3 O, C 3 H 3 O, R 43,55, MORE OXIDZED OOA1 C n H m O 2 CO 2, HCO 2, R 44,45, BBOA R R, C 2 H 4 O 2, C 3 H 3 O 2 6,73,. levoglucosan O:C ratio: HOA << OOA2 ~ BBOA < OOA1 Factors are not unique or identical among campaigns, platforms CONSISTENT TRENDS CO O x Residual Layer Fresh Urban Airmass from T Photochemistry 5

6 SOA: measurements vs. models Johnson et al. DeGouw et al. Heald et al. Volkamer et al. SOA correlates with photochemistry: O x Volkamer, Jimenez, et al GRL, 26 Aerosol Mass Spectrometer (AMS) Particle Beam Generation Aerodynamic Sizing Particle Composition Quadrupole Mass Spectrometer Chopper Aerodynamic Lens (2 Torr) TOF Region Thermal Vaporization & Electron Impact Ionization Particle Inlet (1 atm) Turbo Pump Turbo Pump Turbo Pump Efficient transmission (4-1 nm), aerodynamic sizing, linear mass signal Non-refractory PM1. mass loadings and chemically-speciated mass distributions 6

7 Q C-ToF W-ToF-AMS MCP Signal to ADC Particle Beam Generation Aerodynamic Sizing Quadrupole Mass Spectrometer Particle Composition Chopper Aerodynamic Lens (2 Torr) TOF Region Thermal Vaporization & 7 ev EI Ionization Particle Inlet (1 atm) Turbo Pump DeCarlo et al., Anal. Chem., in preparation, 25. Turbo Pump Turbo Pump AMS Particle Detection Process Focused Particle Beam Electron Emitting Filament e - Vaporizer Flash Vaporization of Non-Refractory Components (NR) R 6 C Positive Ion Mass Spectrometry Electron Impact Ionization Universal and quantitative chemical analysis:.1μg/m 3 sensitivity. Vaporization and analysis of most aerosol chemical constituents - with primary exception of crustal oxides and elemental carbon. 7

8 Real Time Chemical and Physical Composition of Aerosols Aerosol Sampling AMS dm/dlogd a (µg m -3 ) Aerosol Mass Concentration (µg m -3 ) Nitrate Sulphate Ammonium Organics Alkanes Aromatics Etc Aerodynamic Diameter (nm) m/z (Daltons) Sp Mass distribution Chemical composition Nitrate Equivalent Mass Concentration (µg m -3 ) Urban organic aerosol is a mixture of hydrocarbon and oxygenated components Ammonium 4.8 ug/m3 Nitrate 5.8 Sulphate 9.4 Organics 13.4 Chloride.15 Mexico City 2/ m/z (Daltons)

9 Same AMS, same issues, new issues CE collection efficiency particle bounce CE ~.5, except RIE relative ionization efficiency - particularly RIE_org ~ 1.4 ToF threshold & baseline - single ion determination linearity of large and small signals (dynamic range) Real Time Chemical and Physical Composition of Aerosols Aerosol Sampling AMS dm/dlogd a (µg m -3 ) Aerosol Mass Concentration (µg m -3 ) Nitrate Sulphate Ammonium Organics Alkanes Aromatics Etc Aerodynamic Diameter (nm) m/z (Daltons) Sp Mass distribution Chemical composition 9

10 MS Signatures for Aerosol Species Identification color coded to match spectra Group Molecule/Species Ion Fragments Mass Fragments e - Water H 2 O H 2 O, HO, O 18, 17, 16 Ammonium NH 3 e - NH 3, NH 2, NH 17, 16, 15 Nitrate HNO 3 e - HNO 3, NO, 2 NO 63, 46, 3 e - Sulfate H 2 SO 4 H 2 SO 4, HSO 3, SO 3 98, 81, 8 SO 2, SO 64, 48 Organic C n H m O y e - H 2 O, CO, CO 2 18, 28, 44 (Oxygenated) H 3 C 2 O, HCO 2, C n H m 43, 45,... e - Organic C n H m C n H m 27,29,41,43,55,57,69,71... (hydrocarbon) Standard electron impact 7 ev Easy to quantify: ca. NIST MS library Easy to separate inorganic and organic components Speciation of organic composition is challenging ELECTRON IMPACT (EI) IONIZATION σ R e- R e- e- R i R j EI Cross Section (σ) electrons/molecule mass/molecule Ion Rate = 2 ndary electrons/sec Ion Rate = Σ R i total mass/sec Measure all ions: Ion Rate = Σ R i σ molecules/sec independent of parent or fragment (neutral or ion) molecular mass 1

11 EI Ionization: A e > A ----> a i Mass Loading A (MW A /IE A ) Ion Signal Calibration Factor * (MW NO3 /IE NO3 ) EI Ionization Cross Sections Nitrate Equivalent Cross Section Oxygenated Organics = 1.5 X NITRATE Inorganics NITRATE = 1. Chloride 5 Nitrate 1 Sulfate 15 Molecular Mass 2 Diesel Fuel AMS Particle Detection Focused Particle Beam Electron Emitting Filament e - Vaporizer Flash Vaporization of Non-Refractory Components (NR) R 6 C Positive Ion Mass Spectrometry Electron Impact Ionization Universal / quantitative chemical analysis:.1μg/m 3 sensitivity. EVERTYHING AT THE SAME TIME No Separation - bulk analysis [ no dust (oxides) or elemental (black) carbon ] 11

12 NO 3 = SO 4 = NH 4 nss-cl - OM vs OC Takegawa et al., 25 Assumed CE =.5 OM OC C n H m O p = C n AMS (NR-PM 1 ) quantification AMS Org Slope = 1.94 R 2 =.71 2:1 line 35 AMS total Slope = 1.16 R 2 =.87 1:1 line Slope = 1. R 2 =.92 4 OCEC 6 1:1 line Slope =.87 R 2 = DMPS mass :1 line AMS SO AMS NH PILS SO PILS NH4 Composition/phase-dependent collection efficiency (CE) applied Correction for smaller cut diameter in AMS lens compared to PM 1 impactors

13 LS-C-ToF-AMS LS-SP Mode PMT Laser Coincident Particles: Evidence of External Mixing Light Scattering Signal particle #1 particle #2 6x LS Signal Chemical Ion Signal 5x Total Ion Signal particle #1 particle # x1-3 Time-of-Flight (s) PARTICLE PROPERTY Velocity (m/s) Vacuum Aerodynamic Diameter (nm) Optical Diameter (nm) Predicted Physical Diameter (nm) Chemical Density (g/cc) Optical Density (g/cc) [dva/dopt] Measured Total Mass (fg) Predicted Total Mass (fg) [Chemical Density] Predicted Total Mass (fg) [Optical Density] Particle # Particle #

14 Collection Efficiency: Particle Counting Count CE Count-Based Collection Efficiency Optically detected: Chemically detected: 5542 Fast Vaporization/Ionization: Counts Vacuum Aerodynamic Diameter (dva) (nm) Apparent CE depends on NH4/SO4 ratio CE AMS Water Mass Fraction NH4/SO4 Ratio Onasch et al, Ron Brown, 24 14

15 NH4/SO4 NO3/SO4 >>1 CE =.4 1 H2O/Total 1 Tim Onasch, Ann Middlebrook: particle phase Junying Sun, Yangmei Zhang Beijing July ratio of AMS with fixed CE =.5 to dry SMPS_vol_adj 1..8 AMS Mass SMPS Mass ORG / TOTAL AMS H2O AMS Total Note: cluster of highest org fraction have low H2O and CE 15

16 Lens Transmission issues Reasonable understanding of current lenses Peter Liu, Leah Williams, John Jayne Ann Middlebrook, Brendan Matthew, Ken Docherty standard vs high throughput some variability New high pressure lens modification of Schreiner lens Summary of Lab Transmission Experiments Standard Lens Williams et al Signal (arb. units) TransEff, NH4NO3 nh4no3_sep14_ce, Peter Liu, N transeff_counts El_model_new_585torr, Deng calc Trans_76torr, Deng, calc. AN_ObsCalcRat (AN_ARI) DEHS_ObsCalcRat (DEHS_ARI) SN_ObsCalcRat (NaNO3_ARI) DEHS_dec134_CE dehs_small_dec144_ce NaNO3_CE_dec134 ARI2_Na_TOF_CPC ARI2_NH4_TOF_CPC SN_2_obspredrat Dva (nm) 16

17 Comparison of Standard and High Pressure Lenses August, Standard Lens (Liu et al, AS&T, 27) Experiment CFD High Pressure Lens NH4NO3 Lens # 2 PSLs Lens # CFD Model.8 TE Dva [ nm ] How to build a SP2-AMS Install SP2 module 17

18 7x Oil Lamp Soot Particles C 1 m/z=12 N 2 m/z=28 C 2 m/z=24 H 2 O m/z=18 C 3 m/z=36 Air Beam Organics Elemental Carbon Signal C 4 m/z=48 C 5 m/z=6 C 6 m/z=72 C 7 m/z=84 C 8 m/z= m/z Obtain chemical information on BC and Organics Ion signal for carbon (C n ; n=1..4) 1.4x Comparison SP2-AMS and MAAP carbon nano powder a=89. r 2 =.997 Norit SX a=52.1 r 2 = MAAP signal MAAP: Multi Angle Aerosol Photometer (Thermo Fisher) 2 Strong correlation between SP2-AMS carbon signals and the MAAP absorption measurement 18

19 6C, e- m/z HOA: C n H m C n-x H m-y 27,29,41,43,55,57,69,71, OOA2 C n H m O C 2 H 3 O, C 3 H 3 O, R 43,55, OOA1 C n H m O 2 CO 2, HCO 2, R 44,45, BBOA R R, C 2 H 4 O 2, C 3 H 3 O 2 6,73,. levoglucosan SP2 e- Graphitic C C n BETTER ORGANIC FACTORS CHEMICAL (MOLECULAR) ANALYSIS 19