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1
AMS Introduction
Doug Worsnop
AMS Users Meeting
Caltech
Georgia Tech
FZ - Juelich
October 24, 2003
October 8, 2004
25 August, 2005
CE Issues – “magic” “fudge factor” ~ 0.5 +/− 0.1
NY, Tokyo, Ron Brown 2004, Chebogue Point
Aircraft: DoE G-1, Env Can King Air, BA146, ONR Twin Otter, NOAA P3
Beam width probe
ambient, soot (Boston College), ozonolysis of oleic acid (Harvard)
Lens transmission – standard, high throughput and high pressures lenses
Light Scattering Probe:
FIRST Direct Measurement of Bounce Eben Cross, Tim Onasch
HOA / OOA – Qi Zhangseparation of “primary” and “secondary” OMdirect estimate of OC content
Tof-AMS – C, V and W Frank Drewnick, Silke Hings, Peter Decarlo
Soft Ionization – VUV, Li+, neg ions Megan Northway, Achim Trimborn
Frag waves - updated diagnostics; SO4/SO3, MSA, orgainc/SO4 interference
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2
Aerosols in the Atmosphere
C.E. Kolb, Nature, 2002
Number Density
Surface Area
Mass “Remote Continental”Pandis and Seinfeld, 1998
Ultrafine Fine Coarse
Ambient Aerosol Size Distribution
Goal: Size-Resolved Chemical Composition of Ambient Aerosol
EPA, 1999
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3
Number Density
Surface Area
Mass “Remote Continental”Pandis and Seinfeld, 1998
Ultrafine Fine Coarse
Ambient Aerosol Size Distribution
Goal: Size-Resolved Chemical Composition of Ambient Aerosol
EPA, 1999
EPA limits on Aerosol Mass Loading:
Annual: PM2.5 < 15 µg/m3
Daily: < 65
Clean PM2.5= 4 µg m-3
Aerosol Impact on VisibilityUSX Tower
PollutedPM2.5= 45 µg m-3USX Tower
July 2, 2001
July 18, 2001
Taken from same location, same time of day in Pittsburgh(at PAQS main site)
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4
QuadrupoleMass Spectrometer
Thermal Vaporization
&Electron Impact
Ionization
Aerodynamic Lens
(2 Torr)
Chopper
Turbo Pump
Turbo Pump
Turbo Pump
TOF Region
Particle Beam Generation
Aerodynamic Sizing Particle Composition
QuadrupoleMass Spectrometer
Thermal Vaporization
&Electron Impact
Ionization
Aerodynamic Lens
(2 Torr)
Chopper
Turbo Pump
Turbo Pump
Turbo Pump
TOF Region
Particle Beam Generation
Aerodynamic Sizing Particle Composition
Aerosol Mass Spectrometer (AMS)
• Efficient transmission (40-1000 nm), aerodynamic sizing, linear mass signal
• Non-refractory PM1.0 mass loadings and chemically-speciated mass distributions
Particle Inlet (1 atm)
AMS Particle Detection Process
Universal and quantitative chemical analysis: 0.01µg/m3 sensitivity.Vaporization and analysis of most aerosol chemical constituents
- with primary exception of crustal oxides and elemental carbon.
Positive IonMass
Spectrometry
Vaporizer
e-
Electron EmittingFilament
R+
Focused Particle Beam
FlashVaporization
of Non-RefractoryComponents (NR)
600 C Electron Impact Ionization
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5
Operating Modes: Alternate between two modes
Size
Dis
trib
utio
n • Beam Chopped• Spectrometer is fixed (subset of 0-300 amu)
• Beam Open• Spectrometer is scanned (0-300 amu)
Mass Loadings20
15
10
5
0
Mas
s C
once
ntra
tion
(µg
m-3
)12:00 PM4/15/2003
1:00 PM 2:00 PM 3:00 PM 4:00 PM
Date and Time
Ammonium Sulphate Nitrate Organics
14
12
10
8
6
4
2
0
dM/d
logD
va (µ
g m
-3)
2 3 4 5 6 7 8 9100
2 3 4 5 6 7 8 91000
2
Vacuum Aerodynamic Diameter (nm)
Ammonium Nitrate Sulphate Organics
Ion
Sig
nal
0.0060.0040.0020.000Particle TOF (s)
(limited comp. info)
0.001
0.01
0.1
1
10
100
Nitr
ate
Equ
ival
ent M
ass
Con
cent
ratio
n (µ
g m
-3)
120110100908070605040302010m/z
Species
Air 188Water -0.0591Ammonium 1.02Nitrate 1.24Sulphate 1.81Chloride 0.0413PAH 0.00169Organics 7.93Others 0.883
(no size info)
Ave
rage
Com
posi
tion
Mass Distributions
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Nitr
ate
Equi
vale
nt M
ass
Con
cent
ratio
n (µ
g m
-3)
1412010080604020m/z (Daltons)
Ammonium 4.8 ug/m3Nitrate 5.8Sulphate 9.4Organics 13.4Chloride 0.15
Mexico City 2/2002
43 44
57
Urban organic aerosol is a mixture of hydrocarbon and oxygenated components
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6
MS Signatures for Aerosol Species Identificationcolor coded to match spectra
Water H2O H2O+ , HO+ , O+ 18, 17, 16Ammonium NH3 NH3+, NH2+, NH+ 17, 16, 15Nitrate HNO3 HNO3+, NO2+, NO+ 63, 46, 30
Sulfate H2SO4 H2SO4+, HSO3+, SO3+ 98, 81, 80SO2+, SO+ 64, 48
Organic CnHmOy H2O+, CO+, CO2+ 18, 28, 44(Oxygenated) H3C2O+, HCO2+, Cn’Hm+ 43, 45, ...
Organic CnHm Cn’Hm’+ 27,29,41,43,55,57,69,71...(hydrocarbon)
Group Molecule/Species Ion Fragments Mass Fragments
e-e-
e-
e-
e-
e-
Standard electron impact ionization @ 70 eVEasy to quantify: ca. NIST MS libraryEasy to separate inorganic and organic componentsSpeciation of organic composition is challenging
ELECTRON IMPACT (EI) IONIZATION
Measure all ions:
Ion Rate = Σ Ri+
independent of parent or fragment (neutral or ion)molecular mass
EI Cross Section (σ) ∝ electrons/molecule ∝ mass/molecule
Ion Rate = 2ndary electrons/sec ∝ σ • molecules/sec
Ion Rate = Σ Ri+ ∝ total mass/sec
σR + e- → R+ + e- + e-
↓Ri
+ + Rj
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7
Mass Loading A ∝ (MWA/IEA) ∑ Ion Signal
EI Ionization: A + e- ----> A+ ----> ai+
Calibration Factor * (MWNO3/IENO3)
EI Ionization Cross Sections
6
4
2
0
Nitr
ate
Equi
vale
nt C
ross
Sec
tion
200150100500
Molecular Mass
Oxygenated Organics = 1.5 X NITRATE
Diesel Fuel
NitrateSulfate
Inorganics NITRATE = 1.0
Chloride
AMS Particle Detection
Universal / quantitative chemical analysis: 0.01µg/m3 sensitivity.
“EVERTYHING AT THE SAME TIME” No Separation - bulk analysis
[ no dust (oxides) or elemental (black) carbon ]
Positive IonMass
Spectrometry
Vaporizer
e-
Electron EmittingFilament
R+
Focused Particle Beam
FlashVaporization
of Non-RefractoryComponents (NR)
600 C Electron Impact Ionization
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8
Aerosol Composition
• Organic aerosols are composed of thousands of compounds.
• Chemical analysis of organics is a significant challenge.
• Compound specific study can only explain a small fraction of total organic mass. Large fraction unidentified.
Figure 3.10. Speciation results for organic aerosol in Southern California (Rogge et al., 1993). Even if a hundred or so individual organic compounds were identified and quantified they represented only 15 percent or so of the total organic mass.
2003 NARSTO Assessment
CE Issues – “magic” “fudge factor” ~ 0.5 +/− 0.1
NY, Tokyo, Ron Brown 2004, Chebogue Point
Aircraft: DoE G-1, Env Can King Air, BA146, ONR Twin Otter, NOAA P3
Beam width probe
ambient, soot (Boston College), ozonolysis of oleic acid (Harvard)
Lens transmission – standard, high throughput and high pressures lenses
Light Scattering Probe:
FIRST Direct Measurement of Bounce Eben Cross, Tim Onasch
HOA / OOA – Qi Zhangseparation of “primary” and “secondary” OMdirect estimate of OC content
Tof-AMS – C, V and W Frank Drewnick, Silke Hings, Peter Decarlo
Soft Ionization – VUV, Li+, neg ions Megan Northway, Achim Trimborn
Frag waves - updated diagnostics; SO4/SO3, MSA, orgainc/SO4 interference
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9
Observed ‘Traffic’ Mode in Size Distributions
Scotland SASUA-3
Remote Site Mono-modal Aged-Transported
Urban Site Bi-modalLocal Sources
ACE ASIA
Allan, Alfarra et al. (U. Manchester)
5 6 7 8 9100
2 3 4 5 6 7 8 91000
2 3
3
2
1
04 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 35 6 7 8 9
1002 3 4 5 6 7 8 9
10002 35 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3
SulfateOrganicsNitrate
Cheju-Do Island, KoreaApril, 2001
3
2
1
04 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3
3
2
1
04 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3
3
2
1
04 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3
3
2
1
04 5 6 7 8 9
1002 3 4 5 6 7 8 9
10002 3
Aerodynamic Diameter (nm)
OrganicsNitrateSulfate
Edinburgh, ScotlandNovember, 2000
dM/d
logD
(µg
m-3
)
Aerodynamic Diameter (nm)Accumulation modeAccumulation mode‘Traffic’ mode
NO3= SO4= NH4+ nss-Cl-
OM vs OC
Takegawa et al., 2005Assumed CE = 0.5
OM CnHmOp⎯⎯ = ⎯⎯⎯⎯OC Cn
-
10
46
45
44
43
42
41
40
Latit
ude
-74 -72 -70 -68 -66
Longitude
Boston
New York City
Ronald H. BrownNEAQS 2004Cruise Track
outflow
ICARTT – International Consortium for Atmospheric Resaerchon Transport and Transformation
Onasch, Quinn, Bates et al
AMS (NR-PM1) quantification
25
20
15
10
5
0
AMS
SO
4
2520151050PILS SO4
5
4
3
2
1
0
AMS
NH
4
543210PILS NH4
14
12
10
8
6
4
2
0
AMS
Org
6420OCEC
35
30
25
20
15
10
5
0
AMS
tota
l
35302520151050DMPS mass
Slope = 1.0R2 = 0.92
Slope = 1.94R2 = 0.71
Slope = 1.16R2 = 0.87
Slope = 0.87R2 = 0.81
1:1 line
1:1 line
1:1 line
2:1 line
• Composition/phase-dependent collection efficiency (CE) applied• Correction for smaller cut diameter in AMS lens compared to PM1 impactors
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11
1.0
0.8
0.6
0.4
0.2
0.0
CE
3.02.52.01.51.00.50.0
NH4/SO4 Ratio
0.4
0.3
0.2
0.1
0.0
AM
S W
ater Mass Fraction
Apparent CE depends on NH4/SO4 ratio
14
12
10
8
6
4
2
0
AMS
SO
4=
14121086420Impactor nss SO4=
12
10
8
6
4
2
0
ug/m
3
220210200190
DOY
y = 1.2x - 0.52, r^2 = 0.86
Impactor nssSO4 AMS SO4
ICARTT Chebogue Point AMS - Impactor Comparison
AMS SO4 vs Impactor nssSO4 (Quinn, NOAA PMEL)
CE = 0.5
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12
PMTACS-NY 2004 Weimer, Drewnick, Demerjian et al
CE = 0.42
4) Measurements of Particulate Water with the AMS
• Using Brendan’s CE data, we looked at the water mass fraction/total mass (water plus dry mass) as f(RH) for both ammonium sulfate and ammonium nitrate particles
• For both particle compositions, the gas phase water was subtracted from the difference signal as a f(RH) before the particulate water was derived.
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13
Gas phase water calibration
• Measure RH and Temperature (water vapor pressure)
•Subtract gas phase water contribution using water vapor pressure and calibration
Middlebrook, Matthews 2005
6000
4000
2000
0
dM/d
T (µ
g m
-3 s
-1)
5x10-343210Time of Flight (s)
Water
Gas phase Particle source
4) Ammonium Sulfate Water Content
-1.0
-0.5
0.0
0.5
1.0
Mw
ater
/Mto
tal
100806040200
Sampling Line Relative Humidity (%)
Ammonium Sulfate Particles hydration expts.
dehydration expts. Tang, 1980
Ddma,dry = 343 nmDdma,dry = 199 nmDdma,dry = 100 nm
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14
4) Ammonium Nitrate Water Content
-1.0
-0.5
0.0
0.5
1.0M
wate
r/Mto
tal
100806040200
Sampling Line Relative Humidity (%)
Ammonium Nitrate Particles hydration expts.
dehydration expts. Tang, 1980
Ddma,dry = 343 nmDdma,dry = 199 nm
Do we have a chance to get information about xH2O – at least a lower limit ? (calculations with Pitzer + Unifac)NH4HSO4 / Glutaric Acid - mole fractions from AMS data
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15
Beam Width Probe
Alex Huffman et al – detailed description in press
Dara Salcedo – analysis of Mexico City Data
also James Allan
Interesting but not critical
…. “all” ambient particles are focused on the oven
BWP analysis from Mexico City0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
sigm
a
4/11/2003 4/16/2003 4/21/2003 4/26/2003 5/1/2003dat
sigma (pt every 34 min) 90% : 0.28 - 0.50 95% : 0.265 - 0.55 98% : 0.25 - 0.60
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16
Figures from Huffman et alRed line is the fit that I used in order to calculate sigma for the BWP data
100
80
60
40
20
0
% o
f Tot
al
807060504030Wire sector (arbitrary units)
100
80
60
40
20
0
No cooling 90 % RH
QUEST (Finland) Beam Width Probe Attenuation
Allan et al
DRY (Ambient)
90% RH (Cooled)
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17
0.4
0.3
0.2
0.1
0.0 ∆M
/ ∆L
ogD
aero
(µg
m-3
)
102 3 4 5 6 7 8
1002 3 4 5 6 7 8
10002
Daero (nm)
1.0
0.8
0.6
0.4
0.2
0.0
Collection E
fficiency
Queens Surface Corp.
Flame generated soot in the lab(Slowik et al, 2005; DeCarlo et al., 2005)
Diesel particles on the road
(Canagaratna et al., 2003)
What is the nature of the small mode organics?8
4
0
-4
2 3 4 5 6 7 8 9100 2 3 4 5 6 7 8 91000Vacuum Aerodynamic Diameter (nm)
2.01.00.0-1.0
dM/d
logD
va (µ
g m
-3)
3210-1
m/z 57
m/z 202
m/z 226
Dmob100 nm150 nm200 nm250 nm300 nm350 nm400 nm
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18
Calculation of Black Carbon Content, Particle Density, and Dynamic Shape Factor
Assumptions: 1. No internal voids2. Dynamic shape factor is the same in continuum and free-molecular regimes3. BC, PAH, aliphatic species are immiscible4. Component densities estimated (ρBC = 2.0 g/cc, ρPAH = 1.3 g/cc, ρAL = 0.85 g/cc)
System of equations relating equivalent diameter and mass:
dm = dve χCc(dm)Cc(dve)
dva = dveρpρ0
1χ mp = mBC + mPAH + mAL = (π/6) dve
3 ρp
The system is underdetermined (3 equations, 4 unknowns: dve, ρp, χ, mBC). However, using assumptions 3 and 4, ρp may be expressed as:
ρp =mBC + mPAH + mALmBCρBC
mPAHρPAH
mALρAL
+ +
The system has been reduced to 3 equations with 3 unknowns, and can be solved for mBC, ρp, and χ.
D_mob = d * X
D_va = pro * d / X
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19
Aging of fractal combustion particles
100
0
200
300
400
500
100
0
200
300
400
500
12
8
4
dM/d
logD
a(µ
gm
-3)
12
8
4
dM/d
logD
a(µ
gm
-3)
20
15
10
5
03 4 5 6 7
1002 3 4 5 6 7
10002
20
15
10
5
03 4 5 6 7
1002 3 4 5 6 7
10002
20
15
10
5
03 4 5 6 7
1002 3 4 5 6 7
10002
Aerodynamic Diam. (nm)
0
Ammonium Nitrate Sulphate Organics Chloride Diesel Truck Emission
~1 sec average
Fixed Site~100 min average(morning rush hour)
Photochemical processing and
transport(afternoon)
EMISSIONS
URBANAging/Processing
Urban Down WindOxidized and internally mixed
with secondary organicand inorganic compounds
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20
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
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Sig
nal (
arb.
uni
ts)
2 3 4 5 6 7 8 9100
2 3 4 5 6 7 8 91000
Dva (nm)
TransEff, NH4NO3nh4no3_sep0104_CE, Peter Liu, N transeff_countsEl_model_new_585torr, Deng calc Trans_760torr, Deng, calc. AN_ObsCalcRat (AN_ARI) DEHS_ObsCalcRat (DEHS_ARI) SN_ObsCalcRat (NaNO3_ARI) DEHS_dec1304_CE dehs_small_dec1404_CE NaNO3_CE_dec1304 ARI2_Na_TOF_CPC ARI2_NH4_TOF_CPC SN_2_obspredrat
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21
High Pressure Lens Assembly
-0.36 -0.30 -0.24 -0.18 -0.12 -0.06 0.00-0.015
-0.010
-0.005
0.000
0.005
0.010
0.015
Nozzle
Diameter of pinhole is 120/140/160 microns.Diameters of connection and lens tube are 4.4mm.Diameter of the nozzle is 0.8mm.
LensConnectionPinhole
Y (m
)
X (m)
Deng Rensheng (MIT)
Transmission Efficiency
O140, Q=149.2sccm, Window: 0.21- 4µm
10 100 1000 10000
0.0
0.2
0.4
0.6
0.8
1.0
10 100 1000 10000
O160 O140 O120
Tran
smis
sion
effi
cien
cy
Dp, nm
O120, Q=108.0sccmWindow: 0.135-4.5µm
O160, Q=198.0sccmWindow: 0.33-3.4µm
Deng Rensheng (MIT)
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22
Light Scattering Probe – Eben Cross (Tim Onasch)
In-situ quantification of the refractory and/or particle bounce events for single particles
30
20
10
0
ls_s
ig
5x10-343210time-of-flight
1.00.80.60.40.20.0
tof_sig
50
40
30
20
10
0
ls_s
ig
4x10-33210time-of-flight
250
200
150
100
50
0
tof_sig
Refractory or Particle Bounce Event
Non-Refractory Particle Event NH4NO3
(NH4)2SO4
-
23
15
10
5
0
Mas
s C
once
ntra
tion
(µg
m-3
)
12:00 PM8/12/2004
3:00 PM 6:00 PM 9:00 PM
Date and Time
Ammonium Nitrate Sulphate Chloride Organics PAH
High and Low RH Nitrate600
500
400
300
200
100
0
dN/d
LogD
va
3 4 5 6 7 8 9100
2 3 4 5 6 7 8 91000
Dva
3
2
1
0
ce_b
ounc
e
dNdLogD_LS dNdLogDtoflsd_30_46 ce = 1.08+/- 0.3
NH4NO3
15
10
5
0
Mas
s C
once
ntra
tion
(µg
m-3
)
12:00 PM8/12/2004
3:00 PM 6:00 PM 9:00 PM
Date and Time
Water Ammonium Nitrate Sulphate Chloride Organics PAH
RH = 54% Sulfate
150100
500dN
/dLo
gDva
3 4 5 6 7100
2 3 4 5 6 71000
Dva
0.40.30.20.10.0 ce
_bou
nce
dNdLogD_LS dNdLogDtoflsd_48_64_80_81_98 ce = 0.16 +/- 0.15
DRY (NH4)2SO4
-
24
15
10
5
0
Mas
s C
once
ntra
tion
(µg
m-3
)
12:00 PM8/12/2004
3:00 PM 6:00 PM 9:00 PM
Date and Time
Water Ammonium Nitrate Sulphate Chloride Organics PAH
RH = 84% Sulfate
600
400
200
0
dN/d
LogD
va
3 4 5 6 7100
2 3 4 5 6 71000
Dva
1.2
0.8
0.4
0.0
ce_b
ounc
e
dNdLogD_LS dNdLogDtoflsd_48_64_80_81_98 ce = 0.81 +/- 0.12
WET (NH4)2SO4
250
200
150
100
50
0
dNdL
ogD
_LS
4 5 6 7 8 91000
2
Dva
1.2
0.8
0.4
0.0
ce_bounce
dNdLogD_LS dNdLogD_NO3_30_46 dNdLogD_org_43_44 dNdLogD_SO4_48_64
Sulfate Event 7/30/04 Species Mean ce sdev
NO3 0.53 0.10
SO4 0.62 0.17
Org 0.65 0.12
Region over which the mean was calculated
Ambient Particles
Chebogue Point
Nova Scotia
-
25
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
AMS/
PIL
S C
E (S
O4
or N
O3)
1.61.41.21.00.80.60.40.20.0
Light Scattering CE
85
80
75
70
65
60
55
Relative H
umidity (%
)
Polydisperse Aerosols Ammonium sulfate Ammonium nitrate 25:75 AS:Org mixture 50:50 AS:Org mixture 75:25 AS:Org mixture Organic acid mixture 50:50 AN:Org mixture Ambient
Peter Decarlo
-
26
20
15
10
5
0
ug/m
^3
7/25/2004 7/27/2004 7/29/2004 7/31/2004dat
1.81.71.61.51.41.31.2d
ensi
ty(g
/cc)
1.4s
SO4 Org NH4 NO3 MAAP
Aerodynamic and Optical Diameters Particle Density
Eben Cross, Boston College
Density:OpticalChemical
CnH2n+0,2 ----> CmH2m±1+27, 29, 41, 43, 55, 57, 69, 71, ...
CnHmOy ----> H2O+ , CO+ , CO2+ , C2H3O+18 28 44 43
29, 55, ….
Organic Mass Spectra
Following flash vaporization at ~600oC
e-
e-
C5H9+C4H7+C3H5+
-
27
Organic Mass Distributions
• Small mode, hydrocarbon-based, primary traffic organic PM• Accumulation mode oxidized organic PM
Morning Rush Hour
Accumulation mode
m/z = 57C4H9+
‘Traffic’ mode m/z = 44CO2+
Organic Mass Spectra
m/z = 44CO2+
Accumulation mode
‘Traffic’ mode
m/z = 57C4H9+
Morning Rush Hour
Investigate specific mass spectra during morning rush hour and late afternoon
-
28
Hydrocarbon and oxidized organics
2.0
1.5
1.0
0.5
0.0
Nitr
ate
Equi
vale
nt M
ass
Con
cent
ratio
n (µ
g m
-3)
150140130120110100908070605040302010m/z
Species
Air 295 ± 0.2Water 1.62 ± 0.1Ammonium 0.896 ± 0.02Nitrate 0.486 ± 0.007Sulphate 1.98 ± 0.01Chloride 0.0727 ± 0.007PAH 0.00739 ± 0.004Organics 13.1 ± 0.05Others 1.38 ± 0.2
m/z = 44CO2+
16
14
12
10
8
6
4
2
0
dM/d
logD
va (µ
g m
-3)
2 3 4 5 6 7 8 9100
2 3 4 5 6 7 8 91000
2
Vacuum Aerodynamic Diameter (nm)
Organics
5
4
3
2
1
0
Nitr
ate
Equi
vale
nt M
ass
Con
cent
ratio
n (µ
g m
-3)
150140130120110100908070605040302010m/z
Species
Air 293 ± 0.3Water 1.53 ± 0.2Ammonium 1.81 ± 0.03Nitrate 1.79 ± 0.02Sulphate 2.29 ± 0.03Chloride 0.901 ± 0.02PAH 0.066 ± 0.008Organics 39.2 ± 0.1Others 2.77 ± 0.2
m/z = 43C3H7+
30
20
10
0
dM/d
logD
va (µ
g m
-3)
2 3 4 5 6 7 8 9100
2 3 4 5 6 7 8 91000
2
Vacuum Aerodynamic Diameter (nm)
Organics
Small traffic mode
Hydrocarbonseries
m/z = 57C4H9+
AMS Mass Spectral Tracersm/z 57 (mostly C4H9+): Hydrocarbon-like Organic Aerosol (HOA; likely POA)
m/z 44 (mostly CO2+): Oxygenated Organic Aerosol (OOA; likely SOA)
Gas & EC data from E. Wittig & R. Subramanian (CMU)
-
29
0.00
0.05
0.10
0.15
0.20
0.25
0.30
050
100150
200250
23:20:00 23:30:00 23:40:00
23:50:00 00:00:00 00:10:00 00:20:00
Sign
al In
tens
ity
m/z
Sampling timet0t1
t2t3
......
Organic Mass Spectra
Deconvolve AMS Organic Data: MathematicsAn AMS organic mass spectrum is the linear superposition of the mass spectra of individual organic species.
= + E
Residual matrix
×
mass spectra matrix of n components
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
nttt
n
n
ccc
cccccc
,2,1,
,22,21,2
,12,11,1
L
LLLL
L
L
Conc. matrix of n components
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
300,2,1,
300,22,21,2
300,12,11,1
nnn msmsms
msmsmsmsmsms
L
LLLL
L
L
⎥⎥⎥⎥
⎦
⎤
⎢⎢⎢⎢
⎣
⎡
300,2,1,
300,22,21,2
300,12,11,1
ttt mmm
mmmmmm
L
LLLL
L
L
t
iRow: mass spec
Column: t series
?Our approach:
Custom PCA initializes with
unique MS tracers
Nt: 1,000 ~ 10,000
-
30
Indications of other (small) components or small variation in the spectra
Hydrocarbon-type OAOxygenated OA
HOA and OOA Time Series in Pittsburgh
-
31
Mexico City Map
Measurements were obtained at several fixed sites in Mexico City(Xalostoc, Merced, Cenica, Pedregal, and Santa Ana)
with differing influences of air pollution sources and meteorology.
Urban Aerosols – City Center and Down Wind
• City center
• Residential urban
• Boundary site
-
32
Oxygenated organic composition from AMS
0.8
0.6
0.4
0.2
0.0
m/z
44
6420Organics
6
4
2
0
Org
anic
s (u
g/m
3)
12:00 AM7/9/2004
Date and Time
High O:C Ratio (m = 0.17) Medium O:C Ratio (m = 0.10) Low O:C Ratio (m = 0.03)
-
33
0.25
0.20
0.15
0.10
0.05
0.00
m/z
44 (C
O2+
) /
orga
nic
6050403020100
Ozone (ppb)
350300250200150100500
Wind Direction
Secondary Organic Oxidation CO2+ (m/z 44) vs Ozone
Sulfate NR Organic Nitrate
Northwest – Southerly Aerosol Loading
14
12
10
8
6
4
2
0
dM/d
logD
va (µ
g m
-3)
5 6 7 8 9100
2 3 4 5 6 7 8 91000
2
Vacuum Aerodynamic Diameter (nm)
Nitrate Sulphate Organics Ammonium
4
3
2
1
0
dM/d
logD
va (µ
g m
-3)
5 6 7 8 9100
2 3 4 5 6 7 8 91000
2
Vacuum Aerodynamic Diameter (nm)
Nitrate Sulphate Organics Ammonium
1 0
8
6
4
2
0
7 /2 6 /20 0 4 7 /2 9 /200 4 8 /1 /2004d a t
-
34
1 .0
0 .8
0 .6
0 .4
0 .2
0 .0
Nitr
ate
Equ
ival
ent M
ass
Con
cent
ratio
n (µ
g m
-3)
1 5014 013012 01101 0090807 0605040302 010m/z
Sp ecies
Air 89.6 ± 0.03W ater 0 .424 ± 0.02Am monium 0.2 93 ± 0.005Nitrate 0.07 65 ± 0 .0008MSA 0 ± 0Sulphate 1.59 ± 0.0 03Chlo ride 0 .0008 83 ± 0.0006PAH -0.000 657 ± 0.001Orga nics 1.27 ± 0.006Others 0.149 ± 0.004
Southerly airflow
0 .8
0 .6
0 .4
0 .2
0 .0
Nitr
ate
Equ
ival
ent M
ass
Con
cent
ratio
n (µ
g m
-3)
1 501401301 201101009 08070605040302010m /z
Spe cies
A ir 89 .6 ± 0 .03W ater -0.11 4 ± 0 .02A mm on ium 0.23 6 ± 0 .005N itrate 0.192 ± 0.0 01S ulphate 0.411 ± 0.0 02C hloride 0.00525 ± 0.0 006P AH 0.000 348 ± 0.000 9O rgan ics 3.96 ± 0.00 7O th ers 0 .643 ± 0.00 7
Northwest airflow
0 .6
0 .5
0 .4
0 .3
0 .2
0 .1
0 .0
Nitr
ate
Equ
ival
ent M
ass
Con
cent
ratio
n (µ
g m
-3)
1 501401301 201101009 08070605040302010m /z
S pec ies
Air 89.6 ± 0.03W ate r -0. 114 ± 0.02Am mo niu m 0. 236 ± 0.00 5Nitrate 0.19 2 ± 0 .001Sulpha te 0.4 11 ± 0 .002Chloride 0.005 25 ± 0 .0006PA H 0.00 0348 ± 0.0 009O rg anic s 3.9 6 ± 0.007O thers 0.643 ± 0.007
Northwest airflow
0 .30
0 .25
0 .20
0 .15
0 .10
0 .05
0 .00
Nitr
ate
Equ
ival
ent M
ass
Con
cent
ratio
n (µ
g m
-3)
1 501 401301201 10100908070605040302010m /z
Sp ec ies
A i r 8 9 .6 ± 0.03W ater 0 .424 ± 0.02Am m o nium 0.2 93 ± 0 .005N itrate 0 .07 65 ± 0 .0008M SA 0 ± 0Sulphat e 1.59 ± 0.0 03C hlo ride 0 .0008 83 ± 0 .000 6PA H -0.000 657 ± 0.001Orga nic s 1.27 ± 0.0 06Ot hers 0.149 ± 0.0 04
Southerly a irflow
CO2+ (m/z 44)
C2H3O+ (m/z 43)
-
35
“First” Single Particle - Mixed (NH4)2SO4 and Organic
Drewnick, Hings, DeCarlo, Jimenez et al.
-
36
1.5
1.0
0.5
0.0
1600155015001450140013501300
QMSApproximately 1.5 ug/m3 of sulfate, 30 second acquisition
m/z 48, SO+ m/z 64, SO2+
FIG 2a
-
37
1.0
0.8
0.6
0.4
0.2
0.0
4100400039003800370036003500
40
30
20
10
0
x10-
3
4100400039003800370036003500
ToF-AMSApproximately 1.5 ug/m3 of sulfate, 30 second acquisition
m/z 48, SO+m/z 64, SO2+
x40
“organics”
FIG 2b
IONS
IONS
C-ToF
W-ToF
-
38
0 . 6
0 . 4
0 . 2
0 . 0
W M
ode
Sign
al (b
its)
4 3 . 1 04 3 . 0 84 3 . 0 64 3 . 0 44 3 . 0 24 3 . 0 04 2 . 9 8
3 0
2 0
1 0
0
V Mode S
ignal (bits)
H N 3C H N OC H 3 N 2
C 2 H 3 O C 2 H 5 NC 3 H 7
N 2H 2C OC H 2C H 4C 2 HC 2 HC 3H NC H NC H 3C 2 HC 2 HC 2 HC 3 HC 3 HC 4
D ie s e l D if f e r e n c e S p e c t r a W M o d e V M o d e
H N 3C H N O
C H 3 N 2C 2 H 3 O C 2 H 5 N
C 3 H 7
r e n c e S p e c tr a
Diesel Exhaust
WToF-AMS: m/z 43
Albumen (protein)
C2H3O+ C3H7+
DeCarlo et al,
unpublished results (2005)
V-Mode
W-Mode
FIG 4
High Resolution MS
OOA Marker
m/z 44: dominated by CO2+HOA Marker
m/z 57: dominated by C4H9+
Albumen (protein) particles Diesel Exhaust
-
39
VUV (10.5 eV) lamp assembly in ionization region of AMS
“softer”
ionization
Switch between EI and Photoionization
8
6
4
2
0
-2 8 910
Energy (eV)
150 140 130 120 110
Wavelength (nm)
AlkanesAlcohols
AldehydesKetones
EthersAromatic
O Kr
LiFCaF2
ArLampWindow
Acids
Organic Groups
11 1210
Single Photon - Ionization Kr at 10/10.5 eV
MgF2
-
40
40
30
20
10
0
500400300200100
40
30
20
10
0
x10-3
Cigarette Smoke – ToFAMS with VUV (JARI)
EI
VUV
Akiyama (JARI)
12
10
8
6
4
2
0
12010080604020
NO2- (m/z = 46)
NO3- (m/z =62)
HCOO- (m/z = 45)
CH3COO- (m/z = 59)
C2H5COO- (m/z = 73)
HSO4- (m/z = 97,99)
SO2- (m/z = 64)
SO3- (m/z = 80)
Cl- (m/z = 35,37)
CNO- (m/z = 42)
NO- (m/z = 30)
CN- (m/z = 26)
OH- (m/z = 17)
O- (m/z = 16)
Electron attachment (neg ion) spectrum of ambient (Riverside)
-
41
Li attachment spectrum of pinene – ozon experiment
220210200190180170160150140130m/z
220210200190180170160150140130m/z
pinic acid + Li+ (m/z = 192)
pinonic acid + Li+ (m/z = 190)
norpinic acid + Li+ (m/z = 178)
norpinonic acid + Li+ (m/z = 176)
pinonaldehyde + Li+ (m/z = 174)
norpinonaldehyde + Li+ (m/z = 160)
dialdehyde + Li+ (m/z = 146)
Cs+ (m/z = 133)
Findings from EPA’s Findings from EPA’s Particulate Matter Particulate Matter
Supersites ProgramSupersites Program
Cover of JGR-Atmospheres, in press
Data from:Zhang et al., ES&T 38, 4797, 2004
JGR 110 (D07S09), 2005Stainer et al, ES&T; JGR