State of the Science on Sources of State of the Science on Sources of Carbonaceous Aerosols and Their Carbonaceous Aerosols and Their

Contribution to Regional Haze Contribution to Regional Haze John G. Watson (johnw@dri.edu)

Judith C. ChowDesert Research Institute, Reno, NV, USA

Presented at:

WRAP Workshop on Fire, Carbon, and Dust

May 23-24, 2006Sacramento, CA

ObjectivesObjectives

• Describe sources of carbonaceous aerosol

• Identify and evaluate methods to identify and quantify carbon emissions and source contributions

• Review progress on reconciling different carbon measurement methods and instruments

Carbon contributes much to poor visibility at Carbon contributes much to poor visibility at many western sitesmany western sites(Yosemite National Park)(Yosemite National Park)

OC contributions vary spatially and differ by year, OC contributions vary spatially and differ by year, mostly due to firesmostly due to fires

(Annual Average OC for Western States)(Annual Average OC for Western States)

Fire contributions vary with time during the yearFire contributions vary with time during the year(Yosemite National Park)(Yosemite National Park)

Area and mobile sources contain more carbon than point Area and mobile sources contain more carbon than point sourcessources

0.0001

0.001

0.01

0.1

1

10

100

1000

Chlorid

e

Nitrat

e

Sulfat

e

Amm

onium

Soluble

Pot

assiu

m

Organ

ic Car

bon

Black C

arbo

n

Sodium

Mag

nesiu

m

Aluminu

m

Silicon

Phosp

horu

s

Sulfur

Chlorin

e

Potas

sium

Calcium

Titaniu

m

Vanad

ium

Chrom

ium

Man

gane

seIron

Nickel

Coppe

rZinc

Arsen

ic

Seleniu

m

Brom

ine

Rubidi

um

Stront

ium

Zircon

ium

Mer

curyLe

ad

Carbo

n m

onox

ide

Oxides

of n

itrog

en

Sulfur

diox

ide

Ions, Carbon Fractions, Elements, and Inorganic Gases

Pe

rce

nt

of

PM

2.5

Ma

ss

Average Abundance Variabilitya) Fugitive Dust

0.0001

0.001

0.01

0.1

1

10

100

1000

Chlorid

e

Nitrat

e

Sulfat

e

Amm

onium

Soluble

Pot

assiu

m

Organ

ic Car

bon

Black C

arbo

n

Sodium

Mag

nesiu

m

Aluminu

m

Silicon

Phosp

horu

s

Sulfur

Chlorin

e

Potas

sium

Calcium

Titaniu

m

Vanad

ium

Chrom

ium

Man

gane

seIron

Nickel

Coppe

rZinc

Arsen

ic

Seleniu

m

Brom

ine

Rubidi

um

Stront

ium

Zircon

ium

Mer

curyLe

ad

Carbo

n m

onox

ide

Oxides

of n

itrog

en

Sulfur

diox

ide

Ions, Carbon Fractions, Elements, and Inorganic Gases

Pe

rce

nt

of

PM

2.5

Ma

ss

Average Abundance Variabilityb) Coal-Fired Boiler

7200±1400

0.0001

0.001

0.01

0.1

1

10

100

1000

Chlorid

e

Nitrat

e

Sulfat

e

Amm

onium

Soluble

Pot

assiu

m

Organ

ic Car

bon

Black C

arbo

n

Sodium

Mag

nesiu

m

Aluminu

m

Silicon

Phosp

horu

s

Sulfur

Chlorin

e

Potas

sium

Calcium

Titaniu

m

Vanad

ium

Chrom

ium

Man

gane

seIron

Nickel

Coppe

rZinc

Arsen

ic

Seleniu

m

Brom

ine

Rubidi

um

Stront

ium

Zircon

ium

Mer

curyLe

ad

Carbo

n m

onox

ide

Oxides

of n

itrog

en

Sulfur

diox

ide

Ions, Carbon Fractions, Elements, and Inorganic Gases

Pe

rce

nt

of

PM

2.5

Ma

ss

Average Abundance Variabilityc) Gas Veh. Exhaust

0.0001

0.001

0.01

0.1

1

10

100

1000

Chlorid

e

Nitrat

e

Sulfat

e

Amm

onium

Soluble

Pot

assiu

m

Organ

ic Car

bon

Black C

arbo

n

Sodium

Mag

nesiu

m

Aluminu

m

Silicon

Phosp

horu

s

Sulfur

Chlorin

e

Potas

sium

Calcium

Titaniu

m

Vanad

ium

Chrom

ium

Man

gane

seIron

Nickel

Coppe

rZinc

Arsen

ic

Seleniu

m

Brom

ine

Rubidi

um

Stront

ium

Zircon

ium

Mer

curyLe

ad

Carbo

n m

onox

ide

Oxides

of n

itrog

en

Sulfur

diox

ide

Ions, Carbon Fractions, Elements, and Inorganic Gases

Pe

rce

nt

of

PM

2.5

Ma

ss

Average Abundance Variabilityd) Hardwood Burning

Emissions relevant to carbonaceous PMEmissions relevant to carbonaceous PM

• PM Fugitive dust from wind erosion, agricultural activities, construction, storage piles, and vehicle traffic on paved and unpaved roads.

• VOC Vegetation, surface coatings, fuel storage and distribution, solvents.

• PM, VOC Burning and cooking from stoves, charbroilers, trash, forest fires, and agricultural burning.

• PM, NOx, VOC Ducted exhaust from industrial facilities (e.g., coal- and oil-fired power stations, smelting, cement plants, chemical plants, petroleum extraction and refining, glass manufacturing, paper making, shipping). Vehicle exhaust from cars, trucks, motorcycles, and buses. Exhaust from non-road generators, small engines, non-road vehicles.

Potassium is a reaonsable indicator of fire Potassium is a reaonsable indicator of fire contributions, but there’s still noisecontributions, but there’s still noise

0

5

10

15

20

25

30

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

Potassium (ug/m3)

Org

anic

Car

bo

n (

ug

/m3 )

Yosemite National Park1988-2004

Limited Limited 1414C measuements also show much C measuements also show much contemporary carbon (Bench, 2004)contemporary carbon (Bench, 2004)

Urban carbon levels decrease rapidly with distance(Summer and Winter OC averages from the CY2000 CRPAQS

Nitrate at FresnoSummer

Winter

Winter

There are many manmade burning sourcesCRPAQS 2000 Annual Average

Summer

WinterSummer WinterAnnual Avg Winter Avg*

FEL 6 26CHL 7 32YOSE 9 38EDW 12 52OCW 14 58HELM 19 81PIXL 19 82ANGI 23 98COP 32 138BAC 49 209BTI 50 215SNF 57 244SJ4 58 247S13 63 269LVR 68 291FEDL 75 323M14 101 433FRS 121 521SDP 128 551FSF 202 868

Levoglucosan Concentrations (ng/m3)

* Predicted concentration based on mass concentration measurements

Annual OC Distribution

Issues for PM Carbon Emission Issues for PM Carbon Emission Rates and CompositionsRates and Compositions

• Many carbon compounds are semi-volatile and condense or evaporate depending on vapor pressure, temperature, and surface availablility on other particles

• Different (certification) test methods for different source types result in different emission rates and compositions for the same equipment, fuels, and operating conditions

• Organic vapors adsorb onto quartz fiber filters used to measure carbon

• Size distributions, compositions, and gas/particle phases continue to change within and emissions inventory grid. Grid scaling affects equivalent emissions

Source Measurement MethodsSource Measurement Methods• Hot stack sampling: Samples taken directly from

exhaust duct at duct temperatures.• Vehicle dynamometer testing:

Simulate driving cycles on fixed roller. • Continuous emissions monitoring: In-duct or on-board

(motor vehicle) measure continuously• Diluted duct sampling:

Samples drawn into aging chamber and cooled with clean air.

• Vehicle on-road testing: Roadside or tunnel, integrated or individual vehicle samples, in-plume or remotely sensed.

• Source-dominated sampling: Samples taken at locations and times when a single source dominates ambient concentrations (e.g roadside, tunnel, .

Hot Stack ComplianceHot Stack ComplianceMethod 201/202 Filter/Impinger MethodsMethod 201/202 Filter/Impinger Methods

EPA Methods PRE4 & 202

Filterable PM

Condensable PM (<1 µm)

PM10 and PM2.5cyclones and

filter(in-stack)

VTT

Filter

Glass orTeflon®

probe liner(heated) Teflon®

tubing(heated)

Sample gas is cooled to 60-70 °F in iced

impingers

Analysis:

• Organic extraction

• Titration of inorganic fraction

• Dry and weigh organic and inorganic residue

• SO4= and Cl-

Analysis:

• Evaporation of rinses

• Gravimetric analysis

Post Test Purge with N2 or AirRange of chemical

speciation techniques is limited due to high

temperatures, moisture, interfering particles &

gases

Dilution sampling better represents what gets is emitted to Dilution sampling better represents what gets is emitted to environment, allows more variables to be measuredenvironment, allows more variables to be measured

aa

StackGas

HEPAFilter

CarbonFilter

Rotameter

VenturiProbe

T

RH

AmbientAir

Flow Control

Pump

ResidenceTime

ChamberPM2.5

Cyclones

To SampleCollection

Trains

•Stainless steel

•Cross-flow jet mixing

•Dilution Ratio >20:1

•Residence time >10 sec

Sample gas is cooled to ambient

temperature by dilution with ambient air

Flow meter

PM10 Cyclone

Hildemann,L.M., Cass,G.R. and Markowski,G.R. (1989) A dilution stack sampler for collection of organic aerosol emissions: Design, characterization and field tests. Aerosol Sci. Technol. 10(10-11):193-204.

Difference in PMDifference in PM2.52.5 Mass between Mass between

In-Stack and Dilution SamplingIn-Stack and Dilution SamplingGas-Fired Boiler - Field Data

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

Run 1 Run 2 Run 3 Run 1 Run 2 Run 3 AP42

lb/M

MB

tu

inorganic condensable (M202)organic condensable (M202)Filterable PM (M201A)PM2.5 (dilution)

Dilution Method

In-Stack Methods

Chang,M.C. and England,G.C. (2004) Development of fine particulate emission factors and speciation profiles for oil and gas-fired combustion systems, Update: Critical review of source sampling and analysis methodologies for characterizing organic aerosol and fine particulate source emission profiles. Irvine, CA: GE Energy and Environmental Research Corp.

Mobile source certification requires Mobile source certification requires dilutiondilution

Dilution tunnel and sampling ports Put generator on wheels and move it and it is certified by dilution sampling

Install the generator permanently and itis certified by hot stack sampling and hasdifferent emissions

Mobile and area source emissions may have more semi Mobile and area source emissions may have more semi volatile PM components than point source emissionsvolatile PM components than point source emissions

Lipsky,E.M. and Robinson,A.L. (2006) Effects of dilution on fine particle mass and partitioning of semivolatile organics in diesel exhaust and wood smoke. Environ. Sci. Technol. 40(1):155-162.

Difficulties with OC and EC Difficulties with OC and EC Sampling and AnalysisSampling and Analysis

• No common definition of EC for atmospheric applications– It’s not graphite, diamond, or fullerenes

• Light absorption efficiencies are not constant– They vary depending on particle shape and

mixing with other substances

• OC and EC properties on a filter differ from those in the atmosphere

• OC gases are adsorbed onto the quartz filter at the same time that semi-volatile particles evaporate

Thermal Evolution Methods are Thermal Evolution Methods are Conceptually SimpleConceptually Simple

Lavoisier's Oil Analysis "Traité Élémentaire de Chimie" (1789) vol. II, chap.VII, p. 493-501

T150,150,150,150

650,750,850,950

150,150,150,150

250,500,650,850

99%He1%O2

HeHKUST-3 (Hong Kong)

T45,45,45,45,120

600,675,750,825,

920

60,60,60,90

310,480,615,900

98%He2%O2

HeSTN(Variation of NIOSH)

R100,120,>200

400,500,600

Variesa60098%He2%O2

HedOGI(Variation of IMPROVE)

T45,45,45,45,45,120

550,675, 700,775, 880,900

60,60,80,90

310,450,575,870

90% He10% O2

HeACE-ASTA (Cal Tech)

T10,50,40,30,30,70

550,600,700,750,800,850

70,70,110350,550,850

95%He5%O2

HeHKGL (Hong Kong)

(Variation of NIOSH)

T30,30,30,>120

650,750,850,940

60,60,60,90

250,500,650,850

98%He2%O2

HeNIOSH 5040

R150 – 5801550,700,800

150 – 5801120,250,450,550

98%He2%O2

HeIMPROVE

Opticalcorrection

Time for

EC (s)

Temp. for

EC (ºC)

Time forOC (s)

Temp. forOC (ºC)

Carrier Gas(EC)

Carrier Gas (OC)

Protocol

T150,150,150,150

650,750,850,950

150,150,150,150

250,500,650,850

99%He1%O2

HeHKUST-3 (Hong Kong)

T45,45,45,45,120

600,675,750,825,

920

60,60,60,90

310,480,615,900

98%He2%O2

HeSTN(Variation of NIOSH)

R100,120,>200

400,500,600

Variesa60098%He2%O2

HedOGI(Variation of IMPROVE)

T45,45,45,45,45,120

550,675, 700,775, 880,900

60,60,80,90

310,450,575,870

90% He10% O2

HeACE-ASTA (Cal Tech)

T10,50,40,30,30,70

550,600,700,750,800,850

70,70,110350,550,850

95%He5%O2

HeHKGL (Hong Kong)

(Variation of NIOSH)

T30,30,30,>120

650,750,850,940

60,60,60,90

250,500,650,850

98%He2%O2

HeNIOSH 5040

R150 – 5801550,700,800

150 – 5801120,250,450,550

98%He2%O2

HeIMPROVE

Opticalcorrection

Time for

EC (s)

Temp. for

EC (ºC)

Time forOC (s)

Temp. forOC (ºC)

Carrier Gas(EC)

Carrier Gas (OC)

Protocol

Various Thermal/Optical ProtocolsVarious Thermal/Optical Protocols

}{

Temperature and Analysis Time in OC Temperature and Analysis Time in OC varies in Thermal/Optical Protocolsvaries in Thermal/Optical Protocols

*OGI OC performed at 600 ºC only *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 90 130 170 210

100 200 300 400 500 600 700 800 900 1000

IMPROVE

STN

NIOSH 5040

HKGL (Hong Kong)

HKUST-3 (Hong Kong)

CalTech (ACE-Asia)

OGI*

Temperature (ºC)

Temperature and Analysis Time in EC Temperature and Analysis Time in EC also varies for Thermal Analysisalso varies for Thermal Analysis

*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)

11

TO

T

10

TO

T

11

bT

OT

12

TO

T

12

TO

T

11

TO

T

10

TO

T

11

bT

OT

13

TO

R

13

TO

RSchmid et al., 2001, Atmos. Environ. 35:2111-2121

Different Thermal Evolution

Protocols Give Different EC

Results, but TC Results

Generally

Agree!

Learned much in transition from old Learned much in transition from old to new IMPROVE analyzersto new IMPROVE analyzers

DRI Model 2001 Analyzer

DRI/OGC Analyzer

Several variables might affect OC/EC Several variables might affect OC/EC split and carbon fractionssplit and carbon fractions

• Carrier gas composition• Temperature ramping rates• Temperature plateaus• Residence time at each plateau• Optical pyrolysis monitoring configuration/wavelength• Standardization• Oxidation and reduction catalysts• Sample aliquot and size• Evolved carbon detection method• Carrier gas flow through or across the sample• Location of the temperature monitor relative to sample• Oven flushing conditions

Low-temperature protocol corrects for pyrolysis by reflectance (TOR), has low initial temperatures (120 and 250 ˚C), long residence time at each temperature (150-580 seconds),

carbon peaks back to baseline, 550 ˚C max in He

0

0.25

0.5

0.75

0 500 1000 1500 2000 2500 3000

Analysis Time (sec)

Car

bon

Evo

lved

(µ

gC c

m -2

s-1

)

0

200

400

600

800

1000

1200

1400

1600

Lase

r R

efle

ctan

ce, T

rans

mitt

ance

T

empe

ratu

re (

ºC)

Carbon (FID)

Reflectance

Transmittance

Temperature

TOT split

TOR split

He 98%He/2%O2

LowT Protocol (Sample 02/14/03, medium loading)

FID tailing

IMPROVE (Low-Temperature) ProtocolIMPROVE (Low-Temperature) Protocol

High-temperature protocol corrects for pyrolysis by transmittance (TOT), has high initial temperature (310 ˚C),

fixed and short residence times (45-120 seconds), 900 ˚C max in He

0

0.25

0.5

0.75

0 500 1000 1500 2000 2500 3000

AnalysisTime (sec)

Car

bon

Evo

lved

(µ

gC c

m -2

s-1

)

0

200

400

600

800

1000

1200

1400

1600

Lase

r R

efle

ctan

ce, L

aser

Tra

nsm

ittan

ce

T

empe

ratu

re (

ºC)

Carbon (FID)

Reflectance

Transmittance

Temperature

TOT split

TOR split

He 98%He/2%O2

HighT Protocol (Sample 02/14/03, medium loading)

STN (High-Temperature) ProtocolSTN (High-Temperature) Protocol

EC differs within Protocol between EC differs within Protocol between Reflectance (TOR) and Transmittance Reflectance (TOR) and Transmittance

(TOT) Pyrolysis Corrections(TOT) Pyrolysis CorrectionsFRESNO SAMPLES

y = 0.67x - 0.12

R2 = 0.93 n = 58

y = 0.29x + 0.97

R2 = 0.82 n = 58

0

5

10

15

20

25

30

0 5 10 15 20 25 30

TOR EC (µg cm-2)

TO

T E

C (

µg

cm-2

)

IMPROVE ProtocolSTN Protocol

Chow et al., 2001, Aerosol Sci. Technol. 34:23-34

IMPROVE-TOR and STN-TOR yield the IMPROVE-TOR and STN-TOR yield the Same EC. Why?Same EC. Why?

FRESNO SAMPLES

y = 1.01x - 0.87

R2 = 0.97 n = 58

0

5

10

15

20

25

30

0 5 10 15 20 25 30

IMPROVE_TOR EC (µg cm-2)

ST

N_T

OR

EC

(µ

g cm

-2)

Chow et al., 2001, Aerosol Sci. Technol. 34:23-34

Charring Correction is the KeyCharring Correction is the Key

(Chow et al., 2004)

• Charring could occur throughout the filter. Therefore, the transmittance is more influenced by the charred material within the filter than reflectance.

• EC is oxidized and removed earlier than POC in an oxidative environment.

Example of Negative OP ThermogramExample of Negative OP Thermogram(Site: Sipsey Wilderness Area, AL 12/29/2004)(Site: Sipsey Wilderness Area, AL 12/29/2004)

Early Split

Introduction of O2

Zero OP in IMPROVE Samples Zero OP in IMPROVE Samples between 2000-2004between 2000-2004

(12,730 samples out of 93,438 samples)

0%

5%

10%

15%

20%

25%

30%

35%

Jan

-00

Ap

r-0

0

Jul-0

0

Oct

-00

Jan

-01

Ap

r-0

1

Jul-0

1

Oct

-01

Jan

-02

Ap

r-0

2

Jul-0

2

Oct

-02

Jan

-03

Ap

r-0

3

Jul-0

3

Oct

-03

Jan

-04

Ap

r-0

4

Jul-0

4

Oct

-04

Month

% o

f N

eg

ati

ve

Py

roly

sis

%

of

Zer

o O

P

(12,730 out of 93,438 samples)

Carbon Fractions vary by SourcesCarbon Fractions vary by Sources

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

100%

Diesel

@ 4

kW D

.R. ~

40

Woo

d sm

oke,

Dilu

tion

Ratio

20 -

120

Acetyl

ene

Flame

(2");

D.R

. ~16

.5

PALAS @

950

stro

m cu

rrent

Carbo

n Blac

k

Graph

ite

Mas

s P

erce

ntag

e (%

)

OC1OC2OC3OC4OPREC1EC2EC3

Configuration of DRI Model Configuration of DRI Model 2001: Sample Holder2001: Sample Holder

19.12 mm

2 mm

Thermocouple Shield

Bare Thermocouple Tip (unshielded)

Sample

Sample Holder

8.46 mm

Example of Multi-point Example of Multi-point Temperature CalibrationTemperature Calibration

0

400

800

1200

1600

2000

2400

2800

0 200 400 600 800 1000 1200 1400 1600 1800 2000Time (sec)

-35

-25

-15

-5

5

15

25

35

Fir

st/

Se

co

nd

De

riv

ati

ve

La

se

r R

efl

ec

tan

ce

/Tra

ns

mit

tan

ce

(m

V)

(Tempilaq’s melting point 184 ± 2 ºC)

Transmittance

Reflectance

1st Reflectance Derivative

1st Transmittance Derivative

2nd Reflectance Derivative2nd Transmittance Derivative

y = 1.012x + 12.908

R2 = 0.999

0

100

200

300

400

500

600

700

800

900

0 100 200 300 400 500 600 700 800 900

Thermocouple (Measured) Temperature (°C)

Sam

ple

(Ind

icat

ed)

Tem

pera

ture

(°C

) DRI Model 2001 (CA#7)

•Tempilaq G indicator used for temperature calibration: 121 2, 184 2, 253 3, 510 6, 704 8, and 816 9 C (Chow et al., 2005)

IMPROVE vs. IMPROVE_A* IMPROVE vs. IMPROVE_A* Thermal ProtocolThermal Protocol

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

*Implemented for samples acquired after January 1, 2005

Comparison of Carbon Fractions Comparison of Carbon Fractions between Model 2001 IMPROVE_A and between Model 2001 IMPROVE_A and DRI/OGC IMPROVE ProtocolsDRI/OGC IMPROVE Protocols

y = 1.1227xR2 = 0.5759

0

5

10

15

20

0 5 10 15 20

MODEL 2001 Carbon (μg cm-2)

DR

I/O

GC

Ca

rbo

n (

μg

cm

-2)

OC1

y = 0.7407xR2 = 0.9351

0

5

10

15

20

0 5 10 15 20

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

OC2

y = 1.1186xR2 = 0.8537

0

10

20

30

40

0 10 20 30 40

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

OC3

y = 1.0872xR2 = 0.9109

0

10

20

30

40

0 10 20 30 40

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

OC4

y = 0.7812xR2 = 0.5642

0

5

10

15

20

0 5 10 15 20

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

OP

y = 0.9461xR2 = 0.8537

0

10

20

30

40

0 10 20 30 40

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

EC1

y = 0.8427xR2 = 0.598

0

2

4

6

8

10

0 2 4 6 8 10

MODEL 2001 Carbon (μg cm-2)

DR

I/OG

C C

arb

on

(μ

g c

m-2

)

EC2

y = 0.89xR2 = 0.0252

0.0

0.5

1.0

1.5

2.0

0.0 0.5 1.0 1.5 2.0

MODEL 2001 Carbon (μg cm-2)

DR

I/O

GC

Ca

rbo

n (

μg

cm

-2)

EC3

IMPROVE TOR

0%

20%

40%

60%

80%

100%

He+>1

000p

pmO2

He+80

0ppm

O2

He+16

0ppm

O2

He+40

ppm

O2

He+10

ppm

O2

He+2p

pmO2

Pure

He

Per

cen

t o

f T

ota

l Car

bo

n

IMPROVE OC/EC Split not Affected by OIMPROVE OC/EC Split not Affected by O22 in He, in He,

but an early split might occur. Carbon Fractions but an early split might occur. Carbon Fractions not Affected by Onot Affected by O22<40 ppm<40 ppm

OC1

OC2

OC3

OC4

POCOC/EC Split

EC1-POC

EC2

Minerals increase EC oxidation rate at higher Minerals increase EC oxidation rate at higher temperatures in 100% He atmosphere. More early splits temperatures in 100% He atmosphere. More early splits for high temperature STNfor high temperature STN

0.0001

0.001

0.01

0.1

0.0008 0.0009 0.001 0.0011

1/Temperature (°K-1)

Gra

ph

ite

Lo

ss R

ate

(mas

s fr

acti

on

s-1

)

Fe2O3

CuO

TiO2

MnO2

900 °C

850 °C

800 °C750 °C

700 °C

NaCl and other catalysts affect carbon NaCl and other catalysts affect carbon fractions and can cause an early splitfractions and can cause an early split

IMPROVE Protocol (Front Filter)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Diesel

Soot

Diesel

Soot (

+ NaC

l)

Woo

d Som

ke

Woo

d Sm

oke

(+ N

aCl)

Acetyl

ene

Soot

Acetyl

ene

Soot (

+ NaC

l)

PALAS

Palas +

NaC

l

Mas

s P

erce

ntag

e (%

)

OC1OC2OC3OC4OPREC1EC2EC3

More specific detectors can give more carbon More specific detectors can give more carbon fractions on existing samples fractions on existing samples

(examples from a GC/MS detector a(examples from a GC/MS detector at 275 degrees)t 275 degrees)

Gasoline

Diesel Roadside dust

Coal power plant

How can we Maximize Utility of STN How can we Maximize Utility of STN and IMPROVE for Different and IMPROVE for Different Purposes?Purposes?• Understand OC and EC

– Report both TOT and TOR corrections– Report negative pyrolysis corrections– Report initial, minimum, and final reflectance and

transmittance– Re-analyze fraction of samples on old analyzers

• Source attribution (also needed in source samples)– Define temperature plateaus that bracket

dominant compounds– Use more specific detectors

ConclusionsConclusions• Very large carbon concentrations are often due to fire.

These can be identified by spatial and temporal changes in carbon

• Urban carbon concentrations decrease rapidly with distance

• Need more specific markers for non-fire sources and for fire contributions at normal carbon levels

• OC/EC split appears to be independent of temperature of program.

• Oxygen in the carrier gas, catalysts such as NaCl, and mineral oxides affect carbon fractions and may cause a negative OC/EC pyrolysis correction

• More information can be obtained from the same samples with more specific carbon detectors