Understanding Thermal/Optical Understanding Thermal/Optical AnalysisAnalysis

Judith C. Chow (judy.chow@dri.edu)

John G. WatsonL.-W. Antony Chen

Desert Research Institute, Reno, NV

Presented at:

The Atmospheric Science Progress Review Meeting

Research Triangle Park, NCJune 21, 2007

ObjectivesObjectives• Reconcile different thermal/optical methods by

determining factors that influence OC/EC split

• Specify differences in optical properties between particles in the air, particles on a filter, and particles undergoing changes owing to thermal analysis

• Quantify differences in thermal carbon fractions determined by commonly used thermal/optical methods

• Optimize thermal/optical methods to meet multiple needs of health, visibility, global, and source apportionment

Large Temperature and Analysis Time Large Temperature and Analysis Time Variations in OC for Thermal/Optical Variations in OC for Thermal/Optical

MethodsMethods

(~120 to 900 °C)

*OGI OC performed at 600 °C only

(~30 to 580 sec)

*OGI Time is variable**HKUST-3 Time 150 s only

30 70 110 150 190 230

IMPROVE (to 580 s)

NIOSH

HKGL

HKUST-3**

CalTech

OGI*

Analysis Time (s)

STN

10 50 90 130 170 210100 200 300 400 500 600 700 800 900 1000

IMPROVE

STN

NIOSH 5040

HKGL (Hong Kong)

HKUST-3 (Hong Kong)

CalTech (ACE-Asia)

OGI*

Temperature (ºC)

Watson et al. (2005)

Large Temperature and Analysis Time Large Temperature and Analysis Time Variations in EC for Thermal/Optical Variations in EC for Thermal/Optical

MethodsMethods

(60 to 580 sec)

*HKUST-3 Time 150 s only

30 70 110 150 190 230

IMPROVE (to 580 s)

NIOSH

HKGL

HKUST-3*

CalTech

OGI

Analysis Time (s)

STN

10 50 90 130 170 210

100 200 300 400 500 600 700 800 900 1000

IMPROVE

STN

NIOSH 5040

HKGL

HKUST-3

CalTech (ACE-Asia)

OGI

Temperature (ºC)

Watson et al. (2005)

(400 to 920 °C)

IMPROVE vs. IMPROVE_AIMPROVE vs. IMPROVE_A** Thermal ProtocolsThermal Protocols

Original OGC/DRI Thermal Optical Analyzer (1986)

IMPROVE_A*

(DRI Model 2001)IMPROVE (DRI/OGC)

OC1 140 ºC 120 ºC

OC2 280 ºC 250 ºC

OC3 480 ºC 450 ºC

OC4 580 ºC 550 ºC

OP (POC) TOR/TOT TOR

EC1 580 ºC 550 ºC

EC2 740 ºC 700 ºC

EC3 840 ºC 800 ºC

*After temperature and O2 calibration. Implemented for samples acquired after January 1, 2005

DRI Model 2001 Thermal/Optical Analyzer

No difference in OC/EC split between No difference in OC/EC split between IMPROVE by DRI/OGC and IMPROVE by DRI/OGC and IMPROVE_A by Model 2001IMPROVE_A by Model 2001

OC_TOR (Sample Date 3/1/2004 - 9/30/2006)

y = 0.98x - 0.36R2 = 0.99N = 2037

0

50

100

150

200

250

300

350

400

450

500

0 100 200 300 400 500

IMPROVE_A by Model 2001 EC (µg/filter)

IMPR

OVE

by

DR

I/OG

C E

C (µ

g/fil

ter)

EC_TOR (Sample Date 3/1/2004 - 9/30/2006)

y = 1.010x + 0.980R2 = 0.970N = 2037

0

50

100

150

200

250

300

0 50 100 150 200 250 300

IMPROVE_A by Model 2001 EC (µg/filter)

IMPR

OVE

by

DR

I/OG

C E

C (µ

g/fil

ter)

Effect on Carbon Fractions by Effect on Carbon Fractions by Temperature and OTemperature and O22

LevelLevel

• Low temperature OC1 (140 °C) and OC2 (280 °C) are sensitive to temperature independent of the oxidant level

• As O2 > 100 ppmv in He atmosphere, changes in OC3 (480 °C), OP, and EC1 (580 °C) are found

Laboratory Generated Carbon Laboratory Generated Carbon SourcesSources

Wood Stove

Diesel Generator

Acetylene Flame

• Electric Arc Generator (PALAS) DR of 8; T = 20 or 40 min; Source, Source + NaCl

• Carbon Black and Graphite Powder

4 kW load Dilution ratios (DR) of 18, 40, 80 and 150

sample time (T) of 20 or 60 min

Source, Source + NaCl

White Oak DR of 18, 40, 105

T of 20 or 25 min

Source, Source + NaCl

2-inch flame

DR of 17

T of 20, 40, 70 min

Source, Source + NaCl

Dilution Sampling System

Miniature Dilution System

Re-suspension Chamber

For Diesel Exhaust

Acetylene Soot

Wood Smoke For Carbon Black

Source Characterization Systems for Reference SamplesSource Characterization Systems for Reference Samples

For Electric Arc Generator

Source Testing InstrumentationSource Testing Instrumentation

Particle Sizing Instruments (3 nm to 10 µm)

Photoacoustic

DustTrak

Aethalometer

Sampling ConePAS-2000

Dilution System

(PAH Monitor)

• TSI Nano-SMPS (TSI, St. Paul, MN)• Grimm SMPS+C (Grimm, Ainring,

Germany)• MSP Wide Range Spectrometer (MSP;

St. Paul, MN)

Most laboratory generated sources can Most laboratory generated sources can reproduce TC reproduce TC (Relative Standard Deviation(Relative Standard Deviation**, RSD < 15% , RSD < 15%

typically, except for Wood Smoke)typically, except for Wood Smoke)

RSD of IMPROVE_A TC

0

10

20

30

40

50

60

old

sam

ple

lin

e, D

R ~

150-1

65

old

sam

ple

lin

e, D

R ~

40,

T =

60

old

sam

ple

lin

e, D

R ~

40,

T =

20

pure

, D

R ~

80,

T =

60

pure

, D

R ~

80,

T =

20

pure

, D

R ~

40,

T =

20

pure

,DR ~

40,

T =

60

pure

, D

R ~

18,

T =

60

pure

, T =

20

pure

, T =

40

pure

, T =

70

pure

, 300 c

urr

ent,

T =

60

pure

, 950 c

urr

ent,

T =

20

pure

, 950 c

urr

ent,

T =

40

pure

, D

R 1

10-1

17,

T =

20

pure

, D

R ~

105,

T =

20

pure

, D

R ~

40,

T =

25

pure

, D

R ~

18,

T =

25

RS

D (

%)

Diesel AcetyleneFlame

PALAS Wood Smoke

*standard deviation divided by the arithmetic mean, expressed in percentage

IMPROVE, STN and French ProtocolsIMPROVE, STN and French ProtocolsIMPROVE_A_TOR/TOT

STN_TOT French 2-step

Gas Temp(°C)

Time(sec) Gas Temp

(°C)Time(sec) Gas Temp

(°C)Time(sec)

OC1 He 140 150 to 580 He 310 60

O2 340 7200

OC2 He 280 150 to 580 He 480 60

OC3 He 480 150 to 580 He 615 60

OC4 He 580 150 to 580 He 900 90

He n/a n/a He cool oven -

EC1 O2/He 580 150 to 580 O2/He 600 45

O2 1100 ~600

EC2 O2/He 780 150 to 580 O2/He 675 45

EC3 O2/He 840 150 to 580 O2/He 750 45

EC4 O2/He n/a n/a O2/He 825 45

EC5 O2/He n/a n/a O2/He 920 120

Detection Methanator / FID Methanator / FID Coulometric titration of CO2 forEC phase. TC from another punch. OC by difference.

PyrolysisCorrection Reflectance & Transmittance Transmittance None

580

780

840

n/an/a

n/a

140

280

480

580

n/a

Temp((°°C)C)

600

675

750

825825

920

310

480

615

900

cool oven

Temp((°°C)C)

11001100

340340

TempTemp((°°°°C)C)

O2/He/He

O2/He/He

O2/He/He

OO22/He/He/He/He

O2/He/He

He

He

He

He

He

GasGas

O2/He

O2/He

O2/He

OO22/He/He

O2/He

He

He

He

He

He

Gas

O2

O2

Gas

150 to 580150 to 580

150 to 580150 to 580

150 to 580150 to 580

n/an/a

n/a

150 to 580150 to 580

150 to 580150 to 580

150 to 580150 to 580

150 to 580150 to 580

n/a

Time(sec)(sec)

TimeTime(sec)(sec)(sec)(sec)

6060

6060

6060

9090

-

4545

4545

4545

45454545

120120

Time(sec)(sec)

7200

~600

SourceSource--toto--source variations in EC are source variations in EC are apparent (EC is similar between protocols, apparent (EC is similar between protocols,

except for wood smoke)except for wood smoke)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

IMP

ST

N

FM

IMP

ST

N

FM

IMP

ST

N

FM

IMP

ST

N

FM

IMP

ST

N

FM

IMP

ST

N

FM

EC

/TC

Rat

io

IMP

ST

N

FM

Doraiswamy (2007)

Diesel ElectricArc

AcetyleneFlame

CarbonBlack

Graphite

WoodSmoke

Carbon fractions vary by sourceCarbon fractions vary by source

Chow et al. (2007b)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Die

sel @

4kW

D.R

. ~40

Woo

d sm

oke,

Dilu

tion

Rat

io 2

0 -

120

Ace

tyle

ne F

lam

e(2

"); D

.R. ~

16.5

PA

LAS

@ 9

50st

rom

cur

rent

Mas

s P

erce

ntag

e (%

) OC1OC2OC3OC4OPREC1-OPREC2EC3

IMPROVE_A protocolE

lect

ric A

rc @

950

Presence of NaCl shifts EC to Presence of NaCl shifts EC to lower temperature fractionslower temperature fractions**

* Higher NaCl -> greater shift from EC2 to EC1

0%

20%

40%

60%

80%

100%

0.02 nmol 0.3 nmol 12 nmol 300 nmol

1.17 ng 17.6 ng 702 ng 17.5 ug

STRSQ017-8 STRSQ017-7 STRSQ017-6 STRSQ017-5Amount of NaCl added

% o

f tot

al c

arbo

n OC1OC2OC3OC4EC1EC2EC3

NaCl has the largest effect among NaCl has the largest effect among halogen salts on EC fractionshalogen salts on EC fractions

• For NaCl, shift of EC2 to EC1.• For NaBr, no shift at 0.3 nmol but shift at 0.75

nmol• For NaI, no shift for both 0.3 and 0.75 nmol

82

92

102

112

122

132

142

152

162

172

182

FID

Sig

nal

NaCl NaBr NaI

EC1EC2

0.75 nmol

Catalytic reactivity: NaCl > NaBr > NaI

82

92

102

112

122

132

142

152

162

172

182

FID

Sig

nal

NaCl NaBr NaI

EC1

EC2

0.30 nmol

0%10%20%30%40%50%60%70%80%90%

100%

Diesel

Diesel

(+ NaC

l)Ace

tylen

e Flam

e

Acetyl

ene F

lame (

+ NaC

l)W

ood S

moke

Woo

d Smok

e (+ N

aCl)

Electric

Arc

Electric

Arc

(+ NaC

l)

Mas

s P

erce

ntag

e (%

) OC1OC2OC3OC4OPEC1-OPEC2EC3

Addition of NaCl shifts EC to Addition of NaCl shifts EC to lower temperature fractionslower temperature fractions

Chow et al. (2007b)IMPROVE_A protocol (front filter)

Carbon fractions in biomass burning varied Carbon fractions in biomass burning varied by fuel and combustion conditionsby fuel and combustion conditions

Chen et al. (2007a)

80

57

17

51

36

6

79

36

30

20

40

60

80

100

120

Pon

dero

saP

ine

Woo

d .

Pon

dero

saP

ine

Nee

dles

Whi

te P

ine

Nee

dles

Sag

ebru

sh

Exc

elsi

or

Dam

bo G

rass

Mon

tana

Gra

ss

Tund

ra C

ore

Ker

osen

e S

oot

Mas

s Pe

rcen

tage

(%) i

n P

M

OC1OC2OC3OC4EC1EC2EC3EC

Higher NHHigher NH44

Cl results in lower EC2Cl results in lower EC2• Higher NH4 Cl shifts more EC2 to EC1 • Effects at micro-mole/micro-gram level• No effect on OC speciation

0%

20%

40%

60%

80%

100%

2.0 umol 7.5 umol 22.5 umol

33.7 ug 134 ug 404 ug

STRSQ017-7 STRSQ017-6 STRSQ017-5Amount of Ammonium Chloride added

% o

f Tot

al C

arbo

n

OC1OC2OC3OC4OPEC1EC2EC3

Presence of (NHPresence of (NH44

))22

SOSO44

minimizes pyrolysisminimizes pyrolysis

a)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Analysis Time (sec)

Tran

smitt

ance

, Ref

lect

ance

, and

Tem

pera

ture

80

130

180

230

280

330

380

FID

Sig

nal

LaserTLaserROven TemperatureFID_8

Pure He 98% He/2% O2

TOR OC/EC Split

TOT OC/EC Split

Charring

b)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Analysis Time (sec)

Tran

smitt

ance

, Ref

lect

ance

, and

Tem

pera

ture

80

130

180

230

280

330

380

FID

Sig

nal

LaserTLaserROven TemperatureFID_8

Pure He 98% He/2% O2

TOR OC/EC Split

TOT OC/EC Split

Spiked with 3.0 µmol of ammonium sulfate

Original Filter

• Melting point = 280oC• Suppression of pyrolyzed carbon formed• No EC shift was observed

NaNa22

SOSO44

does not suppress pyrolysisdoes not suppress pyrolysis• Melting point = 884 oC.• Shift of EC 2 to EC1 but no suppression of

charring.

Spiked with 3.0 µmol of sodium sulfate

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Analysis Time (sec)

Tran

smitt

ance

, Ref

lect

ance

, and

Tem

pera

tu

80

130

180

230

280

330

380

FID

Sig

nal

LaserTLaserROven TemperatureFID_8

Pure He 98% He/2% O2

TOR OC/EC Split

TOT OC/EC Split

Charring

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Analysis Time (sec)

Tran

smitt

ance

, Ref

lect

ance

, and

Tem

pera

ture

80

130

180

230

280

330

380

FID

Sig

nal

LaserTLaserROven TemperatureFID_8

Pure He 98% He/2% O2

TOR OC/EC Split

TOT OC/EC Split

Charring

Original Filter

Optical Modeling of Filter Reflectance Optical Modeling of Filter Reflectance and Transmittanceand Transmittance

3mm

5mm

0.44 mm

Reflectance Light Pipe

Transmittance Light Pipe

Quartz-fiber Filter

)ln( )0(,F

FATNL T

T−=τ

ATNLATNa V

Ab ,, τ=

• Multiple scattering?

• Effect of loading?

A=Filter Surface Area

V=Sample Volume

(Apparent) Absorption Efficiency (Apparent) Absorption Efficiency Varies between EC and OPVaries between EC and OP

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0.00 0.05 0.10 0.15 0.20[Carbon ]after_o 2 (EC + POC) Mass (g/m2)

Max

Abs

orba

nce

( τA

TN,E

C +

τA

TN,P

OC

)

Fresno SamplesIMPROVE Samples

Estimated E a,EC (~20 m2/g)

Estimated E a,POC

(~50 m2/g)

OPa

OPATN

ECa

ECATNOafter EE

OPECCarbon,

,

,

,_ ][][][

2

ττ+=+=

Chow et al. (2004)After O2

OP

Monte Carlo Model Estimation of Reflectance Monte Carlo Model Estimation of Reflectance (R) and Transmittance (T)(R) and Transmittance (T)

0

0.5

1

1.5

2

2.5

3

0 1 2 30 L,a

-ln(R

F/R

F(0

))

MCMLMAAPK-M Diffuse

0

1

2

3

4

5

6

0 1 2 30 L,a

-ln(T

F/T

F(0

))

K-M DiffuseMAAPMCML

• MCML: Monte Carlo Simulation (reference method for two-layer model)

• MAAP: Code used by Multiple Angle Absorption Photometer

• K-M: Kubelka-Munk theory

τa τa

Chen et al. (2007b)

Filter Loading Filter Loading

Concurrent R and T Measurements Allow Concurrent R and T Measurements Allow Estimation of Absorption Optical DepthEstimation of Absorption Optical Depth

33.25

3.253.5

3.53.5

3.753.75

3.75

44

4

4.254.25

4.25

4.5

4.54.5

4.75

4.75

4.75

55

5

6 7

8

8

9

9

9

10

10

10

11

11

11

12

12

12

13

13

13

14

14

14

15

15

15

16

16

16

17

17

τL1,a

τ L2,a

0 0.5 1 1.5 20

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

• τL1,a : absorption in the first layer

• τL2,a : absorption in the second layer

• Blue line: reflectance measure

• Red line: transmittancemeasure

•Absorption in the second layer has no impact on the reflectance

•Absorption in the first layer does not affect transmittance as much as absorption in the second layer

: absorption in

Estimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical DepthEstimation of Absorption Optical Depth

Retrieve OP and EC Absorption Retrieve OP and EC Absorption based on R and T Measurementsbased on R and T Measurements

0.2

0.2

0.4

0.4

0.6

0.6

0.8

0.8

11

1

1.21.

2

1.4

1.4

1.6

1.6

1.8

1.8

2

2

0.2

0.2

0.2

0.4

0.4

0.4

0.6

0.6

0.6

0.8

0.8

0.8

1

1

1

1.2

1.2

1.2

1.4

1.4

1.4

1.6

1.61.8

1.8

-ln(Rop)

-ln(T

op)

3 3.5 4 4.5 5

6

8

10

12

14

16

18

Pure EC

Pure POC

•Blue line: absorption in the first layer

•Red line: absorption in the second layer

Chen et al. (2007b)

Pure OP

Sources Ambient

Mass absorption efficiency varied Mass absorption efficiency varied by source by source (1047 nm)(1047 nm)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

Diesel

Diesel

+ NaC

lAce

tylen

e Flame

Acetyl

ene Flame + N

aCl

Electric

Arc

Electric

Arc + N

aCl

Wood Smok

e

Wood Smok

e + N

aCl

Carbon B

lack

Fresno: S

ummer

Fresno: W

inter

Mas

s ab

sorp

tion

effic

ienc

y (m

2 /g)

IMPROVE_A TORIMPROVE_A TOT

1 10 100 1000Size (nanometer)

Rel

ativ

e Vo

lum

e C

once

ntra

tion

(dV/

dLog

D)

Carbon Black

Electric Arc

Wood Smoke

Diesel

Acetylene

Size distribution varies by sourceSize distribution varies by source

1 10 100 1000

Size (nanometer)

Rel

ativ

e N

umbe

r Con

cent

ratio

n (d

N/d

LogD

)

AcetyleneDieselPalasWood smokeCarbon Black

By WPS (Chow et al. 2007b)

MieMie--Scattering ModelScattering Model2

2

3

3

3

3

4

4

4

4

4

5

5

5

5

6

6

6

7

7 78

8 8

Particle Size (μm)

BC

Mas

s F

ract

ion

0.1

0.1

0.1

0.2

0.2

0.2

0.3

0.3

0.30.

4

0.4

0.4

0.43

0.43

0.43

0.5

0.5

0.5

0.5

0.6

0.6 0.6

0.7

0.7 0.7

0.80.8

0.1 0.2 0.3 0.4 0.5 0.6 0.70.80.911.1

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

The blue lines indicate BC σabs at 1047 nm in m2/g and the red lines indicate the single scattering albedo, ω. The refractive index and density for EC/BC are assumed to be 1.96 – 0.66i and 1.7 g/cm3, respectively (Chen et al., 2006). OM is modeled with a refractive index of 1.42 – 0.001i and density of 1.2 g/cm3.

3

02

0.0.333 0.0.4 00.4Acetylene Soot

300000.555Diesel Soot

Spectral Dependence of Light Spectral Dependence of Light Absorption (Angstrom Power Law; Absorption (Angstrom Power Law; λλ--αα))

0.000.200.400.600.801.001.201.401.601.80

Diesel

Diesel

+ NaC

lAce

tylen

e Flam

e

Acetyl

ene F

lame +

NaC

lElec

tric A

rc

Electric

Arc

+ NaC

lWoo

d Smok

e

Wood S

moke +

NaC

lCarb

on B

lack

Fresno

: Sum

merFres

no: W

inter

Source / Ambient Sample

Ang

stro

m a

bsor

ptio

n ex

pone

nt

Estimate of the Angstrom absorption exponent, α, using 7-AE (seven wavelength aethalometer) measurements for different source and ambient samples. Error bars shown are one standard deviation from the mean.

ConclusionsConclusions• The IMPROVE_A protocol was developed to

represent actual sample temperature and to maintain consistency in OC/EC measurements for IMPROVE and other networks.

• Temperature calibration and O2 <100 ppb auditing is necessary for thermal/optical methods.

• Small (20 to 40 °C) temperature differences do not affect the OC/EC split in TOR, but they do affect the TOT split and the carbon fractions.

• OC/EC split is insensitive to analytical conditions as long as reflectance correction is used.

Conclusions Conclusions (continued)(continued)• The presence of salts in samples increases

EC oxidation rate at lower temperatures, thereby shifting thermal carbon fractions to lower temperature plateaus.

• Charring is minimized in the presence of (NH4 )2 SO4 , but not Na2 SO4 .

• Due to the formation of char and EC decomposition at high temperatures w/o O2 , optical correction is necessary in thermal methods to separate OC from EC.

• EC and OP have different absorption efficiencies. Optical correction should minimize the effects of the OP char.

Conclusions Conclusions (continued)(continued)• Pyrolyzed carbon (OP) is more abundant in

ambient and wood smoke samples than in diesel and acetylene flame soot. This results in less consistent OC/EC splits for vegetative burning than for other EC sources.

• Low-temperature OC and high-temperature EC are relatively abundant in diesel soot but low in wood smoke PM.

• Under laboratory-controlled conditions, source samples can be reproduced within ±10-15% for diesel, acetylene flame, and electric arc soot, and within ±40-50% for wood combustion.

• Biomass fuel and combustion conditions (e.g., temperature) result in EC/TC abundances of 3 to 80%.

Conclusions Conclusions (continued)(continued)• Absorption efficiencies at 1047 nm from

photoacoustic instruments yield 3 – 5 m2/g for EC from the IMPROVE, but are different for different sources.

• The absorption exponent is smaller for diesel and acetylene soot (~0.8) and larger for electric arc (PALAS) and wood smoke PM (>1).

• Optical properties cannot be fully explained by Mie theory (especially for wood smoke and electric arc PM) due to uncertain refractive indeces and irregular particle shapes.

• Filter characteristics condition (thickness, refractive indices, particle penetration depth) need to be better specified to model OC/EC splits.

• Chen, L.-W. A., Chow, J.C., Watson, J.G., Moosmüller, H., Arnott, W.P. (2004). Modeling reflectance and transmittance of quartz-fiber filter samples containing elemental carbon particles: Implications for thermal/optical analysis. J. Aerosol Sci. 35, 765-780, doi: 10.1016/j.jaerosci.2003.12.005.

• Chow, J.C., Watson, J.G., Chen, L.W., Arnott, W.P., Moosmüller, H., Fung, K.K. (2004). Equivalence of elemental carbon by thermal/optical reflectance and transmittance with different temperature protocols. Environ. Sci. Technol. 38 (16), 4414-4422.

• Ho, K.F., S.C. Lee, C.K. Chan, J.C. Yu, J.C. Chow, and X.H. Yao (2003). Characterization of chemical species in PM2.5 and PM10 aerosols in Hong Kong. Atmos. Environ., 37(1), 31-39.

• Ho, K.F., J.J. Cao, S.C. Lee, Y.S. Lee, J.C. Chow, J.G. Watson, and K. Fung (2004). Variability of levels, water soluble and isotopic composition of organic and elemental carbon in Hong Kong urban atmosphere. Environ. Sci. Technol., submitted.

• Sin, D.W.M., W.H. Fung, Y.Y. Choi, C.H. Lam, P.K.K. Louie, J.G. Watson, and J.C. Chow (2004). Seasonal and spatial variation of solvent extractable organic compounds in fine suspended particulate matter in Hong Kong. JAWMA, 55(3):291-301.

2003 - 2004STAR GrantSTAR Grant--Related PublicationsRelated Publications

• Arnott, W.P., B. Zielinska, C.F. Rogers, J. Sagebiel, K. Park, J.C. Chow, H. Moosmüller, J.G. Watson, K. Kelly, D. Wagner, A. Sarofim, J. Lighty, and G. Palmer (2005). Evaluation of 1047-nm Photoacoustic Instruments and Photoelectric Aerosol Sensors in Source-Sampling of Black Carbon Aerosol and Particle-Bound PAHs from Gasoline and Diesel Powered Vehicles. Environ. Sci. Technol., 39(14):5398-5406.

• Chow, J.C., J.G. Watson, P.K.K. Louie, L-W.A. Chen, and D. Sin (2005). Comparison of PM2.5 Carbon Measurement Methods in Hong Kong, China. Environ. Poll., 137(2):334-344.

• Chow, J.C., J.G. Watson, L.W.A. Chen, G. Paredes-Miranda, M.C.O. Chang, D. Trimble, K. Fung, H. Zhang, and J.Z. Yu (2005). Refining Temperature Measures in Thermal/Optical Carbon Analysis. Atmos. Chem. And Physics Discuss., 5:4477-4505.

• El-Zanan, H.S., D.H. Lowenthal, B. Zielinska, J.C. Chow, and N. Kumar (2005). Determination of the organic aerosol mass to organic carbon ratio in IMPROVE samples. Chemosphere, 60(4):485-496.

• Watson, J.G., J.C. Chow, and L.W.A. Chen (2005). Summary of Organic and Elemental Carbon/Black Carbon Analysis Methods and Intercomparisons. AAQR, 5(1):65-102.

2005STAR GrantSTAR Grant--Related PublicationsRelated Publications

STAR GrantSTAR Grant--Related PublicationsRelated Publications• Chen, L.-W.A.; Moosmüller, H.; Arnott, W.P.; Chow, J.C.; Watson, J.G.; Susott, R.A.;

Babbitt, R.E.; Wold, C.; Lincoln, E.; and Hao, W.M. (2006). Particle emissions from laboratory combustion of wildland fuels: In situ optical and mass measurements. Geophys. Res. Lett., 33(L04804):1-4.

• Chow, J.C.; Watson, J.G.; Lowenthal, D.H.; Chen, L.-W.A.; and Magliano, K. (2006). Particulate Carbon Measurements in California’s San Joaquin Valley. Chemosphere, 62(3):337-348.

• Chow, J.C.; Watson, J.G.; Park, K.; Lowenthal, D.H.; Robinson, N.F.; and Magliano, K. (2006). Comparison of Particle Light Scattering and Fine Particulate Matter Mass in Central California. JAWMA, 56(4)398-410.

• Chow, J.C.; Watson, J.G.; Lowenthal, D.H.; Chen, L.-W.A.; Zielinska, B.; Rinehart, L.R.; and Magliano, K. (2006). Evaluation of organic markers for chemical mass balance source apportionment at the Fresno Supersite. Atmos. Chem. Phys., http://www.atmos-chem-phys.net/7/1741/2007/acp-7-1741-2007.pdf.

• Chow, J.C., J.G. Watson, D.H. Lowenthal, L.-W.A. Chen, and K. Magliano (2006). Particulate Carbon Measurements in California’s San Joaquin Valley. Chemosphere, in press.

• Park, K.; Chow, J.C.; Watson, J.G.; Trimble, D.L.; Doraiswamy, P.; Arnott, W.P.; Stroud, K.R.; Bowers, K.; Bode, R.; Petzold, A.; and Hansen, A.D.A. (2006). Comparison of continuous and filter-based carbon measurements at the Fresno Supersite. J. Air Waste Manage. Assoc., 56(4):474-491.

• Park, K., J.C. Chow, J.G. Watson, W.P. Arnott, D. Trimble, K. Stroud, K. Bowers, R. Bode, A. Petzold, and A.D.A. Hansen (2006). Comparison of Continuous and Filter- Based Carbon Measurements at the Fresno Supersite. JAWMA, in revision.

2006

STAR GrantSTAR Grant--Related PublicationsRelated Publications

• Chen, L.-W.A.; Chow, J.C.; Watson, J.G.; Lowenthal, D.H.; and Chang, M.C. (2007). Particle emissions from laboratory combustion of wildland fuels: Emission factors and source profiles. Environ. Sci. Technol., in press.

• Chow, J.C.; Watson, J.G.; Chen, L.-W.A.; Chang, M.C.O.; Robinson, N.F.; Trimble, D.L.; and Kohl, S.D. (2007). The IMPROVE_A temperature protocol for thermal/optical carbon analysis: Maintaining consistency with a long-term data base. J. Air Waste Manage. Assoc., 57:accepted.

2007