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Instrumentation for the Measurement of Aerosol Optical Properties
• Simple in Operation• Rugged• Inexpensive Components• Stable• State-of-the Art Performance
Cavity Attenuation Phase Shift Extinction Spectrometer
(CAPS PMex)
• Use Low-Loss Optical Cavity to Produce km Pathlengths• Square Wave Modulate Light Souce• Detect Distorted Waveform Emitted from Cavity• Phase Shift Provides Information on Particle Extinction
cotϑ = cotϑ0 + (c/2πf) σe
where ϑ = Measured Phase Shift ϑ0 = Phase Shift for Particle-Free Cell f = Modulation Frequency σ
e = Extinction
WHY
• Near-Confocal Optical Cavity 25 cm Base Length• Light Emitting Diode (LED) Light Source 445 nm, 530 nm or 630 nm
CalNex-LA Ground Site, Pasadena, CA
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ical
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-1)
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CAPS extinction AE absorption
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ical
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CAPS Extinction AE Absorption
November 2010-April 20111
Aerosol light extinction measurements by Cavity Attenuated Phase Shift Spectroscopy (CAPS): laboratory validation and field deployment of a compact aerosol extinction monitor,” P.Massoli, P. Kebabian, T. Onasch, F. Hills, and A. Freedman, Aerosol Sci. Technol., 44:428–435 (2010)
System and method for trace species detection using cavity attenuated phase shift spectroscopy with an incoherent light source, P.L. Kebabian and A. Freedman, U.S. Patent No. 7301639 (issued November 27, 2007)
Optical Extinction Monitor Using CW Cavity Enhanced Detection, P.L. Kebabian, W.A. Robinson and A. Freedman, Rev. Sci. Instrum., 78, 063102 (2007)
REFERENCES
South Coast Air Basin: Emissions Map
NOAA National Emission Inventory (http://map.ngdc.noaa.gov/website/al/emissions/viewer.htm )
Total pollutant emissions
Caltech
UC-Riverside
Downtown LA
530 nm
630 nm
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50
0Sca
tterin
g [E
XT
- AB
S] (
Mm
-1)
3002001000
Exrtinction (Mm-1
)
<Albedo> = 0.97 (Sub-1 µm, RH< 35%)
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250
200
150
100
50
0Sca
tterin
g [E
XT
- AB
S] (
Mm
-1)
3002001000
Extinction (Mm-1
)
<Albedo> = 0.97 (Sub-1 µm, RH< 35%)
Funding for Aerodyne participation provided by the NIH and NASA through the Small Business Innovation Research program. We also acknowledge Ian McCubbin (SPL) and the AMF2 team for their assistance.
Storm Peak Laboratory
Optical Property Measurements of Urban and Regional ParticulatesUsing the CAPS PMex Particle Extinction Monitor
P. Massoli* [1], A. Sedlacek [2], G. Hallar [3], , P. Kebabian [1],T. Onasch [1], J. Allan [4], J. Taylor [4] and A. Freedman# [1][1] Aerodyne Research, Inc.; [2] Brookhaven National Laboratory; [3] Desert Research Institute; [4] University of Manchester ( U.K.)
WHERE
CAPS PMex Particle Extinction Monitor
• Time Response ~1 s (10-90%)• LOD (3σ, 1s) = 2 Mm-1• Rack Mount, 12 kg, 50 W, 0.85 l min-1 Flow
StormVex Campaign
AERODYNE
RESEARCHInc.
LEDLED
Mixer+
PreAmp
L O o u t
Signal
t t
Bandpass Filter VacuumPhotodiode
σe, σs
VFCs
TimersCounters
CPU
PMT
IntegratingVolumeSample
Flow
Purge Flow
StormVex CampaignSteamboat Springs, CO
• Two Sites Storm Peak Laboratory (DRI) (alt. 3220 m) ARM AMF2 Deployment at Christie Peak (alt. 2440 m)
• Fully Instrumented for Particle Optical Property Measurement - Absorption (PSAP) - Scattering (Nephelometer) - Extinction (CAPS PMex)
CALNEX CAMPAIGNMay-June, 2010
#[email protected]*[email protected]
• Sub-1 µm Dried (RH < 35%) Particles• Measure Extinction at ~ 530 nm and 630 nm Combine with Aetholometer Absorption Data• Absorption Contributes Little to Total Extinction - <Albedo> = 0.97 ± 0.01
• Two Sites Storm Peak Laboratory (DRI) (alt. 3220 m) ARM AMF2 Deployment at Christie Peak (alt. 2440 m)
• Fully Instrumented for Particle Optical Property Measurement - Absorption (PSAP) - Scattering (Nephelometer) - Extinction (CAPS PMex)
• Four Months of Continuous Data - Strong Correlation Between Sites - Occasional Local Events Snow Clearing Equipment Vehicular Traffic - Some Meteorological-Linked Events
• Future Analysis - SSA at Both Sites - Effects of Meteorology (Thermal Inversion) on Loadings
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ctio
n (
= 63
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, Mm
-1)
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