SP-AMS Soot Particle – Aerosol Mass Spectrometer

Onasch, Timothy1; Trimborn, Achim1,2; Fortner, Edward1; Kok, Greg3; Jayne, John1; and Worsnop, Douglas1

1Aerodyne Research, Inc., 45 Manning Road, 01821, Billerica, USA2AeroMegt GmbH, Verbindungsstraße 27, 42723 Hilden, Germany3Droplet Measurement Technologies, 5710 Flatiron Parkway Suite,

Boulder, USA

Final Optical Component Design for SP-AMS

Final SP-AMS Design

Pictures of the (A) laser mount from the top, (B) laser mount from theside, (C) laser mount from the bottom, and (D) output coupler with CCD cameraused to image intra-cavity laser beam profile.

• Sold # and shipped 2 to date

Schematic of SP-AMS module

0

Coating Evaporating

Coated Soot Particle

Laser Beam

Core Evaporating

10

Transit of Soot Particles Across

Laser Beam5-20 microsecond

evaporation time

Coatings evaporate first at relatively low temperatures (<600oC) potentially dependent upon vapor pressures

Core evaporates last at high temperature (>1000oC) under SP2-like incandescence conditions

Coating and core material ionized and detected with mass spectrometry

20Gao et al. 2007

ConfigurationsLaser Vaporizer

• Sensitive to black carbon containing particles only

• Readily quantify coating materials

• More difficult to calibrate IE and RIE’s

Laser and Tungsten Vaporizers

• Provides measure of nonrefractory PM and black carbon

• Characterize coating material by turning laser on/off

• Readily calibrate IE and RIE’s with ammonium nitrate (etc.)

CHEMICAL AND PHYSICALINFORMATION

MS info4000

3000

2000

1000

0

Ion

rate

(Hz

s-1)

120010008006004002000m/z

small medium Fullerenes

70x103

60

50

40

30

20

10

0

Sig

nal

10080604020m/z

C8m/z=96

C7m/z=84

Air Beam Organics Elemental Carbon

C6m/z=72

C5m/z=60

C3m/z=36

C4m/z=48

C2m/z=24

C1m/z=12

H2Om/z=18

N2m/z=28

Carbon Signals: Fullerene Series4000

3000

2000

1000

0

Ion

rate

(Hz

s-1)

120010008006004002000m/z

C32 C50 C60 C70

small medium large carbon cluster ions

BC2 Exp 104 Fullerene Soot

0.001

0.01

0.1

1

10

100

1000

Nitr

ate

equi

vale

nt m

ass

(µg

m-3

s-1

)

1000900800700600500400300200100m/z

BC2 EXP#104 Fullerene Soot 100 nm

Ionizer ON Ionizer OFF

10-1

100

101

102

103

104

105

106

Ion

rate

(Hz

s-1)

Fullerene Soot

10-1

100

101

102

103

104

105

106

Ion

rate

(Hz

s-1)

Premixed Ethylene Flame Soot

10-1

100

101

102

103

104

105

106

Ion

rate

(Hz

s-1)

3500300025002000150010005000m/z

Cabot Regal Black Pigment

‘Black Carbon’ Chemical Composition

0.0 0.2 0.4 0.6 0.8 1.0

Regal black

Flame soot

Fullerenesoot

Bla

ck c

arbo

n ty

pe

Fraction

FullereneMedium carbon clustersSmall carbon clusters

Coating Signals: DEHS Mass Spectra

Less fragmentation in SP2-AMS than in Q-AMSLarge parent ion signal and fragmentation pattern more similar to

NIST data base spectrumCoating evaporating at temperatures < 600oC

Inte

nsity

(arb

uni

ts)

20015010050m/z

NIST MS for DEHS

SP2-AMS MS for DEHS

QAMS MS for DEHS

Vaporized from laser-heated soot particles

Vaporized from600oC vaporizer

NIST database

AMS organic signal is linear with respect to coating thickness

Organic Signal of DEHS Coatings30

25

20

15

10

5

0

Org

anic

Sig

nal (

arb.

uni

ts)

50403020100DEHS Coating Thickness (nm)

8

4

0

(µg/

m3 ) /

(dlo

gDva

)

2 3 4 5 6 7 8100

2 3 4 5 6 7 81000

Dva (nm)

8

4

0

8

4

0

Size Distributions for uncoated and coated particles

Obtain chemical mass distribution information for both carbon and organic signals

PTOF show size and particle mass signals increasing with particle coatings

Carbon SignalOrganic Signal

225 nm Glassy Carbon Spheres uncoated and coated with DEHS oil

No coating

3 nm coating

50 nm coating Organics / 15

CALIBRATIONS

Size calibrationsLaser Vaporizer

• Done with tungsten vaporizer and PSL prior to removal

• Can detect some absorbing PSL with laser vaporizer only

• Potentially with spherical metal particles

• Light scattering detection of PSL

Laser and Tungsten Vaporizers

• PSL using tungsten vaporizer

IE and RIE calibrationsLaser Vaporizer

• IE potentially done with spherical metal particles

• IE for Black Carbon done with independent measure of BC mass loading (e.g. SP2, PAS, MAAP, etc.)

• IE’s for carbon ion cluster types (small vs fullerene) may vary and may need to be calibrated separately

• RIE’s for nonrefractory material done with coated spherical metal particles or black carbon particles and an independent measure of mass loadings

Laser and Tungsten Vaporizers

• Standard AN IE calibration• RIE for Black Carbon done with

independent measure of BC mass loading (e.g. SP2, PAS, MAAP, etc.)

• RIE’s for carbon ion cluster types (small vs fullerene) may vary and may need to be calibrated separately

• May have different fragmentations/RIE’s for nonrefractory materials vaporizing from laser or tungsten vaporizers

Metal Particle Detection

(7 – 120 nm)

Silver

SilverGold

Fullerene and Regal Black CalibrationsSP-AMS vs SP2

• Calibrations done with toner and high fullerene soot

• Suggests more efficient fullerene detection than small carbon ion cluster detection (i.e. RIE_fullerene > RIE_lowCarbon

Carbon cluster (Cn) distributions

30x103

25

20

15

10

5

0

m/z

24,

36,

48,

or 6

0

20x103151050m/z 12

2.0

1.5

1.0

0.5

0.0

Abun

danc

e re

lativ

e to

12C

6543210Carbon Number (Cn)

225 nm Glassy Carbon Spheres 350 nm Norit SX Activated Carcoal

m/z 24 m/z 36 m/z 48 m/z 60 m/z 72

The ratio of Cn to 12C is observed to be nearly constant for a range of soot particles

The relative abundance of carbon clusters formed (Cn) follows the predicted stability pattern of odd number of carbons in the cluster

Raghavachari and Binkley, 1987

Comparison of low carbon ratios from burn to burn in HR

C1-C7 proportions for calibrations and measurements

C1 C2 C3

C4

C6 C7

C5

AMS Carbon Signal vs MAAP CBC(laser vaporizer)

10x103

8

6

4

2

0

AMS

Car

bon

Sign

al

50403020100MAAP CBC (ug/m3)

NoritSXNoritSXNoritSXNoritSXNoritSXNoritSX

CarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNanoCarbonNano

GlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbonGlassyCarbon

PSLPSL

SP2-AMS vs MAAP V_Pr= 0.962059

a = -23.695 ± 26.7 b = 176.82 ± 8.02

V_Pr= 0.930573 a = -40.253 ± 29.6 b = 194.62 ± 3.01

V_Pr= 0.70619 a = 4.3244 ± 26.2 b = 204.01 ± 7.74

AMS Carbon signal is constant for different monodisperse soot particles

Chemical measure of the amount of elemental carbon in soot particles

SP-AMS mz 36 vs MAAP(laser and tungsten vaporizers)

• SP-AMS operating 1 s MS and 60 s MS/PTOF with laser on/off

• Correlation of mz36 vs MAAP is incredibly tight, working on making quantitative sense of calibrations vs measurements

Diesel Truck PlumesCaldecott Tunnel

Collection Efficiency IssuesLaser Vaporizer

• Laser – Particle beam overlap (will vary with particle shape/focusing and laser mode/quality)

• Large coating, small BC core detection and large BC particle detection issues (laser intensity and duration of particle in laser beam)

Laser and Tungsten Vaporizers

• Particle bounce (partial vaporization) off of tungsten vaporizer

• Laser – Particle beam overlap

• Different CE’s for two methods

Carbon Signal vs Laser Power

6x10-6

5

4

3

2

1

0

Blac

k ca

rbon

sig

nal

1086420

Laser Power

Hyperbolic tangent functionf(x) = b*((exp(a*x)-exp(-a*x))/(exp(a*x)+exp(-a*x))) Coefficient values ± one standard deviation

a =0.32 ± 0.05b =5.4 ± 0.3e-6

SP2 instruments operate at laser powers of ~2

Higher laser powers required in SP-AMS due to faster particle velocities

157 nm Ethylene Flame Soot

Laser Beam Width Calculations

• Laser Beam 1/e2 diameter at Particle Beam is ~20/23*CCD Camera diameter, FWHM ~1.2 mm

• Laser Beam 1/e diameter ~0.5 mm, FWHM ~ 0.56 mmBarry McManus, ARI

Laser Beam Width Determination300 nm Regal Black Particles

IF, the convolution of two Gaussian functions (i.e. laser beam and particle beam) generates a gaussianfunction with c = sigma of c = sqrt(c1^2+c2^2),

Then in the case of the laser beam = c1 (unknown) and particle beam = c2 (0.34 mm from horizontal -i.e. along laser axis - BWP measurements) and the convolution of the two = particle beam walk experiment, c (0.72 mm from particle ).

Thus, laser beam width, c1 = sqrt(c^2-c2^2) = sqrt(0.72^2 - 0.34^2) = 0.63 mm (FWHM = 1.5 mm)

Laser Profile Camera

Vertical

Camera is inverted

AMBIENT RESULTS

Ambient Measurements

SP-AMS versus MAAP

0.4

0.3

0.2

0.1

0.0

SP2A

MS

Car

bon

Sig

nal (

NO

3 E

q. u

g/m

3)

0.60.50.40.30.20.10.0

MAAP BC (ug/m3)

Coefficient values ± one standard deviationa =0.0028837 ± 0.000764b =0.63088 ± 0.0127

Carbon = m/z 12, 24, 36, 48m/z 36 ~ 50% carbon

Size Distributions

Black Carbon Plume

Organic Plume

SP-AMS projects/deployments• 2007 BC/ARI laboratory development• 2007 and 2008 Karlsruhe AIDA campaigns (two)• 2008 BC weekend measurements of ambient• 2008 Boston College Black Carbon (BC2) project• 2009 NYC results• 2009 FLAME 3• UTRC laboratory tests• Po Valley• Aerodyne laboratory investigations of metal nanoparticles• Metals in Finland dynanometer tests• May 2010 CalNex on board R/V Atlantis• May 2010 CalNex at CalTech site• July 2010 Caldecott Tunnel study• September 2010 John Zink Flare project

Summary• SP-AMS successful instrument• Two configurations (laser vaporizer, combo

laser+tungsten vaporizers) that provide two unique measurement capabilities (i.e. BC-containing particles only, or NR PM1 + BC PM1)

• Provides Black Carbon (Elemental Carbon) measurements (chemistry, mass loading, size distributions) as well as metal particle measurements

• EC/OC and Coated-BC measurement capabilities in real-time