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Hélène CACHIER Laboratoire des Sciences du
Climat et de lEnvironnement
What are the important parameters that need to be
defined for a carbonaceous aerosol analysis ?
How should these be documented for different
analysis protocols ?
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Carbonaceous Combustion Aerosols
Physical and chemical diversity their own
story due to their origin source due to the
atmospheric environment due to their age
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Carbonaceous Combustion Aerosols
morphology
porous fly ash (carbonaceous)
Courtesy of A. Lefèvre
diesel microsoots
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Carbonaceous Combustion Aerosols
morphology
fresh diesel microsoots
Courtesy of A. Gaudichet
Biomass burning particles
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Carbonaceous Combustion Aerosols
Atmospheric aging
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Carbonaceous Combustion Aerosols
Chemical complexity of EC (BC) and OC
Difficult to find a chemical separation Difficult
to find a thermal separation Fate of attached
VOC?
From D. Smith et al., 1989
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Carbonaceous Combustion Aerosols
Chemical complexity of the aerosol mix
Biomass burning aerosols (savanna fires)
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Carbonaceous Combustion Aerosols
Chemical complexity of the aerosol mix
Weekly samples from Finokalia (Crete) nov 01-jun02
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What type of method to be used?
2-step thermal method (Oxygen)  blind 
method TOA under Oxygen better TOA
under He and He/O2
Pyrolysis vs Combustion dont mix
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I
Interlaboratory comparisons Are not
consistent Discrepancy is sample
dependent Schmid et al, 2001
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What to avoid ?
Overlap of the 2 EC and OC components
Charring of the Organic Component
Untimely removal of EC
Value of optical correction ?
Interferences with other species carbonates
dusts salts (K)
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TOA / Oxygen
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2 -step TOA example
OC1 OC2 OC3 OC4 OP EC
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2- Step TOA He/He-Ox
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First type of 2-step TOA
From Chow et al.,2001
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Second type of 2-step TOA
From Chow et al.2001
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Thermograms of levoglucosan in the (a) absence
and in the (b) presence of ammonium bisulfate
using the UST-2 thermal method
Thermal evolution of Organic species altered by
inorganic species
!!! use of standard
Yu et al., 2002
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Yu et al., 2002 An important part of the
charred OC(PEC) is from water soluble
aerosol
Use aerosol water extract as PEC surrogate
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Thermograms of a same aerosol water extract using
(a) the NIOSH and (b) the UST-3 thermal methods.
Prolonging the duration at each temperature
step reduces charring
Yu et al., 2002
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Charring corrections primarily rely on the
hypothesis that charred carbon (PEC) evolves
prior to EC (Native EC NEC)
Hypothetic thermograms of pure PEC, pure NEC, and
a mixture of the two in a HeO2 atmosphere
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Thermograms of (a) an untreated aerosol sample
and its water extract and (b) charcoal
Charred OC (PEC) does not evolve prior to EC
(NEC)b
Nor do PEC and NEC have the same absorption
coefficient
From Yang and Yu, 2002
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Analysis of a  dust sample by the Niosh method
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Recommendations
Reduce charring correction uncertainty reduce
charring by increasing plateau duration reduce
charring of the high temperature
plateau increase the resolution around the OC/EC
split point Avoid interactions with dusts (iron
oxides) Proceed to removal of carbonates prior to
analysis if necessary Avoid untimely departure
of EC during the He step Need to find an
experimental design to evaluate if OC remains on
sample after the He step of the thermal
procedure
charring cannot be predefined
Define an acceptable concentration range (mgC/cm2)
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Analysis of Crete samples Minos experiment, Aug
2001
Why does the DRI-Improve mebbhod insensitive to
industrial BC? Why is it very sensitive to
Biomass Burning BC?
From Sciare et al., 2003
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Analysis of impactor samples
Heterogeneity of the deposit
Concentration of particles on small areas
Role of the substrate (quartz vs aluminium)
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Are you really wanting to change your own
protocole??