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
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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