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Atmospheric Particles
Size range: 0.003 to 50 m, 0.003 m particle contains ~1000
molecules
Concentration ranges: 10-5 - 105 cm-3 = 10 - 1011 m-3
Sources: combustion, organic emissions, volcanoes, earths
surface, gas to particle conversions,
Mass concentrations: 1 - 100 g m-3 (density of air 1 kg m-3)
ppbm
Composition: sulfates, nitrates, ammonium, organics, carbon,
crustal material, silicates, water,
Removal: sedimentation, cloud processes, evaporation.
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Complete characterization of atmospheric aerosol requires time
and space resolved measurements of aerosol:
numbersize (geometric, optical, aerodynamic)surface
areavolumemasscompositionoptical properties (scattering +
absorption = extinction)shape (droplets to chain
aggregates)phasechargenucleating characteristics (nucleation of
water, ice, nitric acid hydrates)
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|( Nucleation Mode ---(||(Accumulation Mode(||(Coarse Mode
------
10-3 10-2 10-1 100 101 102
|______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|
Diameter ((m)
|( Filters
-------------------------------------------------------------------------------
|( Diffusion --------------(|
|( Impaction/Interception, Centrifuge/Cyclone
|( Cascade Impactors ---------------(|
|( Thermal Precipitation ---------------------(|
|( Electrostatic Precipitation ----------(|
|(Transmission Electron Microscope (|
|( Scanning Electron Microscope ---------------(|
|( Optical Microscope -------------------
|(Diffusion Analysis(|
|( Electrostatic Analysis -------(|
|( Laser cavity (|
|(Optical Particle Counter (|
~|( Nephelometer/Backscattersonde -------
|( Condensation Nuclei,
Ultrafine-----------------------------------------
|( Condensation Nuclei,
Conventional--------------------------
~|( Cloud Condensation Nuclei -------------------
~|( Ice Nuclei ------------------------------------------
- |( Single particle composition ---------------------
10-21 10-18 10-15 10-12 10-9
|______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|
Mass (g, density = 1 g cm-3)
10-6 10-5 10-4 10-3 10-2 10-1 100 101
__________|__________________|__________|__________|___________|_______|__________|_______|_____
Terminal Velocity (km d-1)
10-3 10-2 10-1 100 101 102
|______|______|_____|______|______|_____|______|______|_____|______|______|_____|______|______|_____|
Diameter ((m)
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PCASP -Passive Cavity Aerosol Spectrometer,r > 0.05 - 1.5
m
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FSSP - Forward Scattering Spectrometer Probe, r > 0.2 - 15.0
m
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MASP - Multi-angle Aerosol Scattering Probe, r > 0.2 - 10.0
m
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Nephelometer - aerosol scattering, hemispheric backscatter
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Aethalometer - aerosol absorption
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Aerosol Composition Mass Spectrometer
(ACMS)MagneticElectron50C
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AerodyneAerosolMassSpectrometer
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The FactsAtmospheric aerosol have a global impact on the
atmosphere far exceeding their mass concentration. These impacts
include pivotal roles in the hydrologic, radiative, and chemical
balance of the atmosphere.Atmospheric aerosol are difficult to
measure, and instrument selection depends heavily on measurement
goals and ranges of interest.Measurement errors/variations are
inherently large due to small sample sizes and large geophysical
variations.Measurement quality depends heavily on frequent and
careful instrument calibration and characterization.A complete
characterization of atmospheric aerosol populations is only
addressable with a suite of instruments.Atmospheric aerosol
ranges:size: 1 - 10,000 nmconcentrations: 10-4 - 104 cm-3shape
droplets to chain aggregatescompositions - large fraction of the
periodic table
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The ChallengesProvide a climatology of tropospheric aerosol
which reduces uncertainties in our understanding of earths
radiation budget, particularly over continents.Address questions
related to the variation of single scatter albedo from hemisphere
to hemisphere, maritime - continental, urban - ruralRefine our
understanding of the processes of water, ice, and hydrate
nucleation, and characterize the populations of cloud condensation
nuclei, ice nuclei, and hydrate nuclei.Establish proper
extrapolations: from surface aerosol measurements to atmospheric
aerosol profiles from local to global measurementsfrom global
satellite measurements to global geophysical parameters
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http://www.iac.ethz.ch/staff/krieger/pdf/SpektroskopischeMethoden2.pdfAcknowledging
some of the material sourcesTSI Inc web site
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optimized to focus particles between 0.1 and 2 m transmission
better than 90% at 40 70 mbar, decreases towards larger paricles
transition time 30 ms, composition changes negligibleAerodynamic
Lens - Focussing Principle