IMPROVE Corrects OC and EC for a Positive Artifact

The positive artifact correction causes the organic and elemental carbon to approach zero as fine mass goes to zero

Shenandoah, VA 1999, IMPROVE

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 5 10 15 20 25 30

Fine Particle Mass (g/m3)

Car

bo

n M

ass

(

g/m

3)

Light Abs. CarbonOrganic Carbon

Burlington, VT 2001, EPA STN

0

1

2

3

4

5

6

7

8

0 10 20 30 40

Fine Particle Mass (g/m3)

Ca

rbo

n M

as

s (

g/m

3 )

SASS_ECSASS_OC

IMPROVE: Artifact CorrectedOC ~ 0.3, EC ~0.02 g/m3

EPA STN monitoring site: No carbon artifact correction

IMPROVE and STN Fine Mass Budgets

• OC is scaled by 1.4 to account for oxygen and hydrogen mass• OC accounts for ~20% of fine mass at Washington, ~43% at Baltimore• EC accounts for ~6% of fine mass at Washington, ~4.4% at Baltimore

Reconstructed fine mass:

Washington, DC 2001 - IMPROVE

0%

20%

40%

60%

80%

100%

Jan Mar May Jul Sep Nov

Per

cen

t F

ine

mas

s

Organic EC Amm. SulfateAmm. Nitrate Soil Other

Baltimore, MD 2001 - STN

0%

20%

40%

60%

80%

100%

120%

Jan Mar May Jul Sep Nov

Per

cen

t F

ine

mas

s

Organic EC Amm. SulfateAmm. Nitrate Soil Other

Biogenic vs Fossil Carbon

0

2

4

6

8

10

2 3 4 5 6 7 8 9 10

Biogenic carbon massFossil carbon mass

y = -0.69929 + 0.99973x R= 0.99069

Bio

gen

ic o

r f

oss

il

carb

on

con

ten

t in

aeroso

l (

g/m

3)

Total carbon content in aerosol (g/m3 )

Washington

Great Smoky

Jarbidge

OC/EC Ratio Winter 2001, Dec, Jan, Feb Summer 2001, Jun, Jul, Aug

• OC/EC ratio varies between 3 - 5, indicative of more primary urban emissions

• OC/EC > 7 throughout upper West and Texas, Fires?

• OC/EC ~ 3 in Industrial Midwest, primary urban?

• OC/EC > 4-6 in southeast, increased secondary organics?

FRACTION OF CARBON ATTRIBUTTED TO FIRE/SOA

END