SP2-AMS

AMS User Meeting 2008, Manchester

Achim M. Trimborn, Timothy B. Onasch, John T. Jayne, Sally NgLeah Williams, Douglas R. Worsnop

Aerodyne Research, Inc.

Gregory L. Kok, Darrel BaumgardnerDroplet Measurement Technologies

Eben Cross, Billy Wrobel, Adam Ahern, Paul DavidovitsBoston College

ICCPA August 2008

Happy Birthday

Astrid

Need for new soot particle instruments

Black carbon (BC) particles− Absorb light efficiently, contributing to radiative forcing − Significant anthropogenic sources

BC particles typically coated in the atmosphere− Primary combustion products− Secondary organic and inorganic condensates− Compositions and fate of BC containing particles are not well

knownNeed new instruments capable of measuring the refractory and non-refractory mass, size and composition of soot containing particles

Instrument conceptSP2 + AMS => SP2-AMS

SP2: Single Particle Soot Photometer(Droplet Measurement Technologies) ‏

- little information on absorbed compounds, particle chemistryAMS: Aerosol Mass Spectrometer (Aerodyne Research, Inc.) ‏

- Lack of sensitivity to refractory particles (i.e. black carbon soot) ‏

SP2-AMS: new combined instrument− Intracavity laser vaporization of the coatings and refractory

cores of absorbing (λ = 1 µm) particles − Electron impact ionization− Measures both the non-refractory components of the

coatings (e.g. organics, sulfates, nitrates, etc.) and the refractory carbon cores (i.e. black carbon) via Time-of-Flight mass spectrometry

AMS Schematic

Measures non-refractory aerosol chemical composition and massInsensitive to refractory aerosol (e.g. black carbon)‏

How to build a SP2-AMS

Remove vaporizer

SP2-AMS schematic

Install SP2 module

Schematic of the SP2-AMS module

Absorbing particles (coating and core) vaporize in laserVapor is ionized by electron impact ionizationDetection of the ions by Time-of-Flight mass spectrometryReadily installed in any exiting AMS instrument

0

Coating Evaporating

Coated Soot Particle

Laser Beam

Core Evaporating

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

Oil Lamp Soot Particles

Obtain chemical information on elemental carbon clusters and organic compounds coating the soot cores

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

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

225 nm Glassy Carbon Spheres uncoated and coated with DEHS oil

No coating

3 nm coating

50 nm coating Organics / 15

` organic signal

carbon signa;

6

4

2

0

µg/m

3

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

PToF size, nm

0.10

0.08

0.06

0.04

0.02

0.00

Time delay for fullerenes

Cn

fullerenes

H2SO4coating

Coating Signals: DEHS Mass Spectra

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

NIST data base spectrumMost of the coating material evaporates at temperatures < 600oC

Vaporized from laser-heated soot particles

Vaporized from600oC vaporizer

NIST database

Carbon Signals: Fullerene Series4000

3000

2000

1000

0

Ion

rate

(Hz

s-1)

120010008006004002000m/z

C32 C50 C60 C70

small medium large carbon cluster ionsfullerenesmedium carbonclusters

small carbonclusters

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

Ambient Measurements

Quantification and Detection LimitsCarbon 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 SP2AMS due to faster particle velocities

157 nm (1 fg) Ethylene Flame Soot

Carbon Signal vs MAAP CBC10x103

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

Total carbon signal is constant for different monodisperse soot particles

2 .5

2 .0

1 .5

1 .0

0 .5

Org

sig

nal

1 0 08 06 04 02 00C o a t i n g th ic k n e s s ( n m )

8 x 1 0- 3

6

4

2

FR

sig

nal

1 0 08 06 04 02 00C o a t in g t h i c k n e s s ( n m )

Signal vs coating thickness

10-10

10-9

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10-4

10-3

10-2

10-1

100

101

Run

136

, no

coat

ing

10-10

10-9

10-8

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10-6

10-5

10-4

10-3

10-2

10-1

100

101

Run 141, coating = 105 nm

12

14

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26 27

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353637

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4243

4748

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5253 5658

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616364

656667 69 70

727374

7576

77 79

81

82 848586

8788

9091 9394 95

96 9798100

101102

103105106108109110

111112

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132133134135136

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555557559560561562 565566567 569570571572573

576577578579581 582583586588

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11071111111311191121112511281129113011421149

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3336 333933403350 33523363

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3483349034923493 3495349634993503

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35213524352635313533

Coefficient values ± one standard deviationa =0 ± 0b =1.0112 ± 0.000623

SummarySP2AMS: Successfully adapted SP2 module into AMS− Separate volatilization and ionization mechanisms− Only sensitive to absorbing particles (soot or metals) ‏− Chemical and size information obtain for elemental carbon cores and non-

refractory organic coatingsMeasure of organic coating mass and size− Shows less fragmentation than standard AMS spectra

Measure of particulate elemental carbon mass and size− Provides chemical information on ‘black carbon’ particles− Linear correlation between MAAP absorption and carbon cluster ion signals from

SP2-AMS for several different types of soot particles− Fully vaporizes 160 nm (~1 fg) soot particles under higher laser powers

Quantification studies have been carried out and are being analyzed− Boston College – Aerodyne Soot Project 2

Department of Energy (DOE) SBIR