How Does the Sample Affect the Measurement of Different Carbon Fractions?
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Transcript of How Does the Sample Affect the Measurement of Different Carbon Fractions?
How Does the Sample How Does the Sample Affect the Measurement of Affect the Measurement of Different Carbon Fractions?Different Carbon Fractions?
Judith C. Chow Desert Research InstituteReno, NV
presented at the
International Workshop for the Development of Research Strategies for the Sampling and Analysis of Organic and Elemental Carbon Fractions in Atmospheric Aerosols
Durango, Colorado
March 4, 2003
Types of Sample EffectsTypes of Sample Effects
• Filter samples
• Carbon particle composition
• Chemical and physical interactions between carbon and other constituents
Filter Sample BiasesFilter Sample Biases
• Non-uniform filter deposit biases scaling from punch to whole filter
• Non-uniform filter punch deposit biases optical monitoring and charring
• Too light or too dark particle deposits make pyrolysis correction uncertain
• More heavily loaded samples require longer combustion time at each temperature step
• Organic vapor adsorption and volatilization in filter biases OC and pyrolysis correction
Non-Uniform Sample DepositsNon-Uniform Sample Deposits(Chow, 1995)(Chow, 1995)
Carbon Particle CompositionCarbon Particle Composition• Ambient mixtures, source mixtures, and pure
carbon substances do not respond to heating in the same way
• Thermal evolution protocols are poorly documented and characterized
• Thermal evolution temperatures are not optimized to bracket compositions
• Carbonates are not present in most ambient PM2.5 samples, and CaCO3 evolves at >800 °C if they are present
• Samples do not respond the same as calibration standards
At Least 15 International Thermal At Least 15 International Thermal Combustion Carbon MethodsCombustion Carbon Methods
• Oregon Graduate Institute thermal optical reflectance (TOR) (Huntzicker et al., 1982)
• IMPROVE TOR and thermal optical transmittance (TOT)
(Chow et al., 1993, 2001)
• NIOSH TOT (NIOSH, 1999)
• ACE-Asia TOT (Mader et al., 2001)
• Hong Kong University of Science and Technology UST-3 TOT (Yang and Yu, 2002)
At Least 15 International Thermal At Least 15 International Thermal Combustion Carbon Methods Combustion Carbon Methods (continued)(continued)
• Meteorological Service of Canada MSC1 TOT (Sharma et al., 2002)
• U.S. Speciation Trends Network (STN) TOT
• General Motors Research Laboratory two temperature (Cadle et al., 1980)
• Brookhaven National Laboratory two temperature (Tanner et al., 1982)
• Japanese two temperature (Mizohata and Ito, 1985)
At Least 15 International Thermal At Least 15 International Thermal Combustion Carbon Methods Combustion Carbon Methods (continued)(continued)
• Two-temperature thermal manganese oxidation (Fung, 1990)
• R&P two temperature (Rupprecht et al., 1995)
• French two-temperature pure oxygen combustion (Cachier, 1989a, 1989b)
• Lawrence Berkeley Laboratory continuous temperature ramp (Novakov, 1982)
• German VDI extraction/combustion(Verein Deutcher Ingenieure, 1999)
Differences among Operating Differences among Operating ParametersParameters
• Combustion atmospheres
• Temperature ramping rates
• Temperature plateaus
• Residence time at each plateau
• Optical monitoring configuration and wavelength
• Standardization
• Sample aliquot and size
• Oxidation (C to CO2) catalyst
• Evolved carbon detection method
• Carrier gas flow through or across the sample
• Location of the temperature monitor relative to the sample
Laboratory Laboratory intercomparisointercomparisons are not ns are not consistent consistent (Schmid et al., (Schmid et al., 2001)2001)
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TO
T
10
TO
T
11
bT
OT
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TO
T
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TO
T
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TO
T
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TO
T
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bT
OT
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TO
R
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TO
R
Same method intercomparisons Same method intercomparisons show differences show differences (Schauer et al., 2003)(Schauer et al., 2003)
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0.5
1
1.5
2
TOTE TOTB TOTH TOTC TOTD TOTF TOTG TOTA
Analysis Method
EC
(µ
g c
m-2
)
Denv1 AVG
STD+ STD-
0
4
8
12
16
TOTF TOTG TOTC TOTD TOTA TOTB TOTH TOTE
Analysis Method
EC
(µ
g c
m-2
)
ACE Kosa1 AVG
STD+ STD-
Comparison of EC Concentrations Comparison of EC Concentrations between TMO and TOR Methodsbetween TMO and TOR Methods
(Fung et al., 2002)(Fung et al., 2002)
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10
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0 10 20 30 40 50
IMPROVE TOR Elemental Carbon (EC) (µg/cm2)
TM
O E
lem
enta
l C
arb
on
(E
C)
(µg
/cm
2 )
Non-Urban IMPROVE
Korean Urban
Carbon Black
Hong Kong Urban
y=0.73x, R2=0.79
y=0.78x, R2=0.91
y=1.07x, R2=0.98
y=1.22x, R2=0.97
IMPROVEIMPROVEcarbon carbon
thermogramthermogram
STNSTNcarbon carbon
thermograthermogramm
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Process Time (sec)
FID
res
pons
e (c
ount
s)
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3000
Lase
r R
efle
ctan
ce,
Lase
r T
rans
mitt
ance
, T
empe
ratu
re (
ºC)
FID
Laser Reflectance
Laser Transmittance
Filter Temperature
OC/EC split
Sample ID: Q20204
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Process Time (sec)
Tem
per
atu
re (
ºC)
FID_8
SOTmp
LaserT
LaserR
He
ECT
ECR
Sample from Sample from Hong Kong urban Hong Kong urban site on 04/17/01 site on 04/17/01 with with 9.9 ± 0.8 ug/m9.9 ± 0.8 ug/m33 OCOCand and 7.8 ± 0.8 ug/m7.8 ± 0.8 ug/m33 ECEC
Carbon Source ProfilesCarbon Source Profiles(Watson et al., 1994)(Watson et al., 1994)
Diesel-fueled vehiclesGasoline-fueled
vehicles
Hong Hong Kong Kong Vehicle Vehicle Exhaust Exhaust Profiles Profiles (Cao et al., (Cao et al., 2003)2003)
OC1OC2OC3OC4EC1EC2EC3OP
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Diesel LPG Gasoline
Figure 11.5 Distribution of the concentration and percentage of 8 carbon fractions in diesel,gasoline and LPG vehicle exhaust
Con
cent
rati
on
g m
-3P
erce
ntag
e (%
)
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30
Source Differences in Carbon Fractions
BRAVO BRAVO Source Source Profiles Profiles (Chow et al., (Chow et al., 2003)2003)
Motor Vehicle Composite (BVRDMV)
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Vegetative Burning Composite (BURN)
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Coal-Fired Boiler Composite (CFPP)
0
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Cement Kiln Composite (CEM)
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Cooking Composite (COOK)
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Catalytic Cracker Composite (CAT1)
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OC1120 °C
OC2250 °C
OC3450 °C
OC4550 °C
OP EC1550 °C
EC2675 °C
EC3750 °C
Carbon Fraction and Thermal Evolution Temperature
Pe
rce
nt
of
PM
2.5
Ma
ss
Source Differences in Carbon Fractions
No relationship between No relationship between EC and carbonate by acidificationEC and carbonate by acidification
(Chow and Watson, 2002)(Chow and Watson, 2002)
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-5
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Measured Carbonate Carbon (µg/sample)
Dif
fere
nc
e B
etw
een
No
n-A
cid
ifie
d a
nd
Ac
idif
ied
E
C a
nd
EC
3 (µ
g/s
am
ple
)
EC EC3
IMPROVE samples and IMPROVE protocol
Carbon Standards Should be Carbon Standards Should be Similar to SamplesSimilar to Samples• Water-soluble organics
(e.g., sucrose, KHP, organic acids)
• Carbon dioxide and methane
• Nebulized charcoal resuspension
• Carbon blacks
• Graphite powders
• Organic dyes (e.g., nigrosin, C48N9H51)
• Carbon arc emissions
• Simulated source emissions
• Neutral density filters
Some Organic Compounds Absorb LightSome Organic Compounds Absorb Light(Justus et al., 1993)(Justus et al., 1993)
Transmission through nigrosin (C48N9H51) dye
Chemical Composition of Chemical Composition of Carbon Black and Fresh SootCarbon Black and Fresh Soot
(Watson and Valberg, 2001)(Watson and Valberg, 2001)
Soot - Woodburning Fireplace Chimney
Other20%
Soluble Organics
14%
Ash19%
Elemental Carbon
47%
Soot - Diesel EngineSulfate
and Other8%
Elemental Carbon
61%
Metals1%
Soluble Organics
30%
Carbon Black
Elemental Carbon
98%
Ash1%
Soluble Organics
1%
Chemical and Physical Chemical and Physical Interactions of Carbon with Interactions of Carbon with Other ConstituentsOther Constituents
• Oxidation interactions
• Catalytic reactions
• Optical interactions
Increasing rate Increasing rate of graphite of graphite oxidation by oxidation by MnOMnO22 (Fung, 1990)(Fung, 1990)
1000°K
900°K
833°K
800°K
Catalytic reactions with glass-fiber filter Catalytic reactions with glass-fiber filter (525 °C)(525 °C)
(Lin and Friedlander, 1988a, 1988b, 1988c)(Lin and Friedlander, 1988a, 1988b, 1988c)
Na, K, Pb, Mn, Fe, Ca, V, Cu, Ni, Co, and Cr compounds are known catalysts
Carbon Fractions are Probably Carbon Fractions are Probably Different for Different ApplicationsDifferent for Different Applications
• Visibility and radiation balance
– Visible light absorption and scattering by particles in the atmosphere
• Source attribution
– Consistently define fractions in source and receptor samples
• Health effects
– Absorption of toxic substances on EC
• Chemical and physical models
– Reaction surfaces, catalytic properties
Research NeedsResearch Needs• Critically summarize and review non-
atmospheric carbon literature• Document methods (combustion
temperatures, ramping rates, residence times, optical pyrolysis corrections)
• Prepare different standards representing different black carbon sources
• Perform optical modeling to verify changes in absorption and scattering properties
Research NeedsResearch Needs (continued)(continued)
• Optimize carbon fractions for source identification
• Quantify effects of pyrolysis on and within a filter to resolve reflectance/transmittance differences
• Quantify effects of non-absorbing particles, optical monitoring wavelengths, initial darkness, carbonate deposits, and oxygen-supplying minerals
• Calibrate reflectance and transmittance measurements and report with carbon fractions at beginning, minimum, oxygen introduction, and end of analysis
ReferencesReferences
Cachier, H.; Bremond, M.P.; and Buat-Ménard, P. (1989a). Thermal separation of soot carbon. Aerosol Sci. Technol., 10(2):358-364.
Cachier, H.; Bremond, M.P.; and Buat-Ménard, P. (1989b). Determination of atmospheric soot carbon with a simple thermal method. Tellus, 41B(3):379-390.
Cadle, S.H.; Groblicki, P.J.; and Stroup, D.P. (1980). An automated carbon analyzer for particulate samples. Anal. Chem., 52(13):2201-2206.
Cao, J.J.; Ho, K.F.; Lee, S.C.; Fung, K.; Zhang, X.Y.; Chow, J.C.; and Watson, J.G. (2003). Characterization of roadside fine particulate carbon and its 8 fractions in Hong Kong. Sci. Total Environ., submitted.
Chow, J.C.; Watson, J.G.; Pritchett, L.C.; Pierson, W.R.; Frazier, C.A.; and Purcell, R.G. (1993). The DRI Thermal/Optical Reflectance carbon analysis system: Description, evaluation and applications in U.S. air quality studies. Atmos. Environ., 27A(8):1185-1201.
ReferencesReferences (continued)(continued)
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ReferencesReferences (continued)(continued)
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ReferencesReferences (continued)(continued)
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ReferencesReferences (continued)(continued)
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