10/13/2012

1

ACSM Update

Phil Croteau

AMS Users Meeting 2012

Size: 19”D x 21”W x 32”H

Weight: 140 lbs

Power: 300W

universal AC power; 85-264 VAC, 47-63 Hz

Aerosol Chemical Speciation Monitor

ACSM-011 SN 140-109

Shown with Pfeiffer Pumps and Integrated Power Supply

10/13/2012

2

Particle Inlet (1 atm)

Thermal Vaporization

&Electron Impact

Ionization

Aerodynamic Lens40-1000 nm

Particle Beam Generation

Particle Composition

Aerosol Chemical Speciation Monitor

LaptopComputer

RG

A

Pumps (x3)

No Sizing

Commercial gradeMass Spectrometer

Pfeiffer Prisma

Slow scan rates, 0.2 sec/amu

RG

A

Automated Valve System for Instrument Zero

Sample mode

FilterFilter mode

Aerosol mass is determined from difference of ‘Sample – Filter”

3-way Valve

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37 Delivered – 17 since last users meetingACSMs have been on 6/7 continents

ACTRIS - Aerosols, Clouds, and Trace gases Research Infrastructure Network

15 ACSMs across Europe 1-year deployment started June 2012

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Long term measurements

• UNC – at Jefferson St. in Atlanta

• PSI Zurich 1-year of data

• Outside Paris (Jean Sciare) – 1 year

• DoE – 3 instruments; SGP site > 2 years

• Environment Canada – Alert, Whistler > 2 years

New Automated (Inlet) Valve

Changed from gear driven to direct drive. Eliminates forces on plug valve and safer

Old style

New style

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New Automated Filter Switching Valve

New style

Old style

Changed from gear driven to direct drive. Eliminates forces on plug valve and safer

Sample Line Flow Controller

3-20 LPM, 25mBar50W, 24VDC14” x 4” x 6”~2 lbs

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Aerosol Inlet

Thermal Particle Vaporization &Electron Impact

IonizationAerodynamic Lens

(0.1 LPM)

LaptopComputer

RG

A

Turbo Pumps

Quadrupole Mass Spectrometer

Ethernet connection

Diaphragm Roughing Pump

Fil

ter

Automated 3-way switching valve

Naphthalene Internal

Standard

Sampling pump3 LPM

(not supplied)

Drier System

Aerosol Drier System

dPElectronics

RH/T/P

RH/T

RH/T

To pump(Supplied by users)

CA Filter air

P2

P1

Nafion Drier

RH/T- Relative humidity and temperature

P1 and P2 - 860 torr absolute

dP – 50 torr differential pressure

CA – critical aperture

Aerosol Drier System Schematic

3 to 10 LPM to ACSM/AMS

Aerodyne Research

April 2012

USB interface to PC

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To pump

Critical aperture

Sample InSample Out

Aerosol Sample Line Drier System

(50 tube Permapure shown)

RH/T probeRH/T probe

Aerodyne Research

April 2012

Aerosol drier adapted to ACSM sampling manifold

Evaluating 50 and 200 tube systems for aerosol loss and drier performance

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Dryer data logging software – plots and saves all of the RH/T/P data

PD-50T-12 Performance

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PD-200T-12 Performance

ACSM Users Site is migrating from google to Aerodyne – stay tuned

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FlashVaporization

Positive Ion Mass Spectrometry

Vaporizer

e-

Filament

R+

Particle Trajectory no Bounce

600 C

Lost ion production

Vaporizer

e-

Filament

Particle Trajectory

with Bounce

600 C

Schematic representation of the bounce phenomena that is observed with the research grade AMS. The figure on the left illustrates efficient vaporization and ion production and on the right, the case of a particle trajectory with bounce which does not result in ion production.

Particle Bounce Illustration.

RIE NH4 = 6.2

Standard Vaporizer, 590 C Ammonium Nitrate

CE Determination Method

Sample DMA output aerosol and record CPC. Vary number concentration using an aerosol diluter. Compare measured and calculated mass loadings

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Collection Efficiency Results

Standard Vaporizer Xiamen City QAMS 600C

“calibration”CE = 22%

10

8

6

4

2

0

NO

3 m

easu

red

121086420

NO3 Calc'd

10

8

6

4

2

0

SO

4 m

easu

red

AN 300 nm T=610CCoefficient values ± one standard deviation

a =0.11875 ± 0.276b =1.0052 ± 0.0623

AS 300 nm 610C Coefficient values ± one standard deviation

a =0.13702 ± 0.228b =0.73511 ± 0.0188

Jan 3rd Databetween ~11am to 12am

Capture Vaporizer resultsshows ~74% CE for (NH4)2SO4

Improved CE of AS with new capture vaporizer

CE=1.0 (calibration)

CE=0.74

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NH4NO3 and (NH4)2SO4 IE calibration with capture vaporizer on ACSM (mass based IE → sum

of ions vs CPC calculated mass)NO3 IE = 1.3x10-11

NH4 IE = 8.9x10-11SO4 IE = 1.3x10-11

NH4 IE = 8.6x10-11

Suggests CE with (NH4)2SO4 is approaching 100% - typically ~20% with dry laboratory generated particles

0.12

0.10

0.08

0.06

0.04

0.02

0.00

-0.02

Ion

Sig

nal

0.0080.0060.0040.0020.000

pToF(s)

1.2

1.0

0.8

0.6

0.4

0.2

0.0

-0.2

300 nm 620CParticles entering Capture Vaporizer more m30 and broader than m46SO4 is broadend as expected

m64 m48 Sig_p30_R15430 Sig_p46_R15430

Capture Vaporizer pTOF Traces SO4 and NO3Sulfate is broadened as expected

More experiments needed…

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ACSM/ACSM Comparison

• ACSMs 140-149 with standard vaporizer and 140-150 with capture vaporizer were calibrated and run side-by-side sampling roof air at ARI 7/20-7/24.

• An airbeam correction was applied to each dataset relative to the conditions at the time of calibration.

All Species

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Org

NO3

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SO4

Org and NO3 are more or less as expected. SO4 is different

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Increased decomposition with capture vaporizer

Another view of the fragmentation difference

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Results are very encouraging but there’s much still to figure out

• Things to figure out:– Why 4-5x SO4 in ACSM/ACSM comparison?

– How much control do we have over fragmentation with temperature?

– If we can do that do other species (i.e. SO4) still vaporize?

– Put one in an HToF system - more to learn from pToF and high res. MS