Measurements of Trace Gases and PM2.5 Mass and Composition near the Ground and at 254 m agl During

TexAQS 2000 and Comparison with Other Regions

K. Baumann, F. Ift, J.Z. Zhao, M.H. Bergin, A.G. Russell, W.L. Chameides

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta

Tools and data quality

PM2.5 and O3 relationships

Episodes

Seasonal and regional trends in PM2.5 mass and composition

Acknowledgement: J. Lester, University of Houston, Clearlake

R. Weber, D. Orsini, D. DiPasquale, W. Younger, all Georgia Tech

Work sponsored by U.S. EPA through NCER Grant R826372

2

Particle Composition Monitor “PCM”

More details described in paper accepted to JGR

“Atlanta Supersite” special section, coming

out soon…

3

Assessing Accuracy of PCM Measurements

S-compounds and mass agree well, volatile species esp. NO3- more difficult to measure accurately

15

10

5

0

30 m

in P

ILS

(u

g m

-3)

12108642

discrete PCM (ug m-3

)

SO42-

r = 0.97

slope = 1.04 +-0.04i-cept = 0.12 +-0.21

70

60

50

40

30

20

10

0

30 m

in T

EO

M (

ug

m-3

)

403020100

discrete PCM (ug m-3

)

Will. TowerMass r = 0.92slope = 0.96 +-0.07i-cept = 2.52 +-1.23

3

2

1

0

30 m

in P

ILS

(u

g m

-3)

1.51.00.50.0

discrete PCM (ug m-3

)

NO3- r = 0.61

slope = 0.47 +-0.09i-cept = 0.18 +-0.05

excl 1st 2 PCM

30

20

10

0

30 m

in T

EC

O (

pp

bv)

1086420

discrete PCM (ppbv)

SO2 r = 0.99

slope = 1.38 +-0.033i-cept = 0.00 +-0.08

70

60

50

40

30

20

10

0

30 m

in T

EO

M (

ug

m-3

)

403020100

discrete PCM (ug m-3

)

LaPorteMass r = 0.95slope = 1.01 +-0.05i-cept = 0.98 +-0.81

excl 1st 3 PCM

6

5

4

3

2

1

0

30 m

in P

ILS

(u

g m

-3)

4321

discrete PCM (ug m-3

)

NH4+

r = 0.92

slope = 0.91 +-0.06i-cept = 0.26 +-0.11

4

Motivation

During SOS’99, 16 June - 22 July 1999,

measurements near Nashville, TN, between

4 and 42 m agl showed positive vertical

gradients for 60-70 % of all daytime, and

70-80 % of all nighttime samples of

PM2.5 mass, SO4=, NO3

-, and NH4+!!

Direct emissions and/or secondary formation of

fine PM aloft

5

Differences in [O3] and [PM2.5] Based on 30 min Averages

100

80

60

40

20

0

Ozo

ne

(p

pb

v)

00:00 06:00 12:00 18:00 00:00

LaPorteWill.Tower

30

25

20

15

10

5

TE

OM

mas

s

(µg

m-3

)

00:00 06:00 12:00 18:00 00:00Time (CST)

LaPorteWill.Tower

WT-O3 levels are significantly

higher early mornings and

lower at midday

-30

-20

-10

0

10

20

Ozo

ne

WT-

LP

(

pp

bv

)

00:00 06:00 12:00 18:00 00:00

Δ-O3

center 67 %

10

5

0

-5

-10

PM

WT-

LP

(

µg

m-3

)

00:00 06:00 12:00 18:00 00:00Time (CST)

Δ-PM2.5

center 67 %

Positive vertical [PM2.5]

‘gradients’ favored more often at night than at day, similar to

Hendersonville

6

High Ozone and Biomass Burning Episodes

60

40

20

0

μg

m-3

PM2.5 Mass PCM LP WT TEOM LP WT

200

150

100

50

0

pp

bv

O3 LP WT

NOy(LP)

80

60

40

20

0

-20

ne

m-3

8/29/2000 8/31/2000 9/2/2000 9/4/2000 9/6/2000 9/8/2000Date (CST)

PM2.5 Acidity (SO4=/NO3

-/NH4

+) LP WT

LP max [O3] on 08/30 is more than twice WT-[O3], which more seems to follow a “rising tide”.

In contrast: [PM2.5] only slightly different and in fact higher average on 08/29.

BB plume on 9/5: max [NOy] and alkaline aerosol at LP only (!) but joint increase in mass.

7

High Ozone and Biomass Burning Episodes, continued

1.0

0.8

0.6

0.4

0.2

0.0

pp

mv

%TOC LP WT

CO (LP)

4.7 ±0.8 / 266 ±51 / 0.80 CO vs NOys= 1.7 ±0.6i= 372 ±40r= 0.67

6.9 ±1.2 / 143 ±36 / 0.84

7.4 ±1.0 / 112 ±34 / 0.89

4.7 ±0.8 / 202 ±26 / 0.81

15

10

5

0

pp

bv

8/29/2000 8/31/2000 9/2/2000 9/4/2000 9/6/2000 9/8/2000

Date (CST)

LOAg LP WT NH3 LP WT

Increases in SO4= mass fraction preceded by high [SO2] episodes, coinciding with max [O3].

Largest increase in TOC m.f. on day w/max [O3] & [SO2] and signature of traffic emissions.

Maximum [CO] & [LOA]g associated with BB plume on 9/5 but [NH3] high at LP only!

0.5

0.4

0.3

0.2

0.1

0.0

10

0•p

pb

v%SO4

= LP WT

SO2(LP)

8

Regional Comparison of Average PM2.5 Composition in 2000

29%

3%

9%

5%18%

7%

9%

4%

16%

30%

3%

10%4%20%

8%

6%

4%

15% SO4=

NO3-

NH4+

EC

OC

OOE

LOA

Others

Un-ID

Entire period mid August to mid September

Williams Tower

16.4+-8.8

La Porte

16.0+-8.0

22%

4%

7%

2%

29%

11%

5%

2%

18%

34%

2%

10%1%21%

9%

4%

3%

16%

27%

1%

9%

2%35%

14%

5%2% 5%

Macon, GA

Late June

Augusta, GA

Early July

Columbus, GA

Late July

12.1+-2.8 22.2+-8.3 19.7+-4.6

Sequential measurements at GA sites captured different episodes !

9

Seasonal Comparison of Average PM2.5 Composition

33%

2%

11%2%18%

7%

4%

1%

22%

33%

1%

10%

1%17%

7%

5%

0%

26%

Summer ‘99

Dixon

Hendersonville26.0+-11.7

29.6+-12

23%

6%

11%

1%34%

13%

3%

2% 7%

25%

7%

14%

1%29%

11%

10%1%2%

Fall ‘99

15.2+-5.7

19.0+-9.3

18%

9%

11%

3%34%

14%

4%

1% 6%

Winter’99/’00

19%

12%

12%2%

31%

12%

5%

1%

6%

SO4=

NO3-

NH4+

EC

OC

OOE

LOA

Others

Un-ID

13.0+-4.7

11.5+-4.0

•Differences in composition are insignificant regionally but not seasonally•Differences in mass related to different BL dynamics

10

PM2.5 Mass Balance and Maximum Hourly Ozone

0

10

20

30

40

50

60

70

80

90

100

Hen

.vill

e

O3

Dix

on

O3

Atl

anta O3

Hen

.vill

e

O3

Dix

on

O3

Sh

eSh

an O3

Hen

.vill

e

O3

Dix

on

O3

Mac

on O3

Au

gu

sta

O3

Co

lum

bu

s O3

La

Po

rte O3

W.T

ow

er O3

PM

2.5

(m g

m-3

)

0

20

40

60

80

100

120

140

160

180

200

O3

(pp

bv

)

Ca++ K+ Na+ NH4+ Cl- NO3- SO4= Acetate Formate Oxalate OC OOE EC Unid. O3-hrly max

Summer '99 Fall '99 Winter '99/'00 Summer '00

Comparison of Seasonal and Regional Averages - incl. China

• Significantly higher [PM2.5] at Yangtze sites in fall, even relative to U.S. summer• [O3] comparable in fall, but much higher in summer, esp. in U.S. metro areas

•[O3] build-up observed in both summers and regions, TN&GA / GA&TX•[PM2.5] generally correlates with max [O3] (“rising tide”), except for TexAQS2k

11

Seasonal/Regional Aerosol Acidity Based on [SO4=/NO3

-/NH4+]

Slightly alkaline aerosol in fall and winter, as opposed to Yangtze sites.Different emission patterns, e.g. post-harvest burns at Yangtze: [K+]mean= 2.2 ±1.4 mg m-3.

LP & WT closely neutralized, only occasionally alkaline, esp. ~9/5.

PM2.5 Charge Balance

-400

-300

-200

-100

0

100

200

300H

en.v

ille

Dix

on

Atl

anta

Hen

.vil

le

Dix

on

Sh

eSh

an

Hen

.vil

le

Dix

on

Mac

on

Au

gu

sta

Co

lum

bu

s

La

Po

rte

W.T

ow

er

(ne

m-3

)

SO4= NO3- NH4+ Net Acidity

Summer '99 Fall '99 Winter '99/'00 Summer '00

12

Summary

• Positive vertical gradients of PM2.5 mass and sulfate point to atmospheric aerosol formation with the

ground being a net sink, confirming Hendersonville observations

• Localized plume on 8/30 carrying max [O3] at LaPorte, coincided with high [SO2] and showed max TOC

increase relative to PM2.5 mass possibly indicating high aerosol forming potential

• Average PM composition at LaPorte and Williams Tower are very similar, showing sulfate and organics

each contributing ~1/3 to total fine mass

• Insignificant regional differences in fine particle composition, but noticeable seasonal differences, esp. wrt

C-species and sulfate, likely due to higher primary (SO2) emissions and photochemical activity in summer

• Based on SO4=/NO3

-/NH3+ system, PM2.5 in SE-US is slightly alkaline in winter but more acidic in summer

• Significantly (~3x) lower PM2.5 mass in SE-US compared to Yangtze Delta region, which has a potential

impact on American continent due to long-range transport across Pacific

• Use of OOE factor 1.4 possibly too low for Houston aerosol; different factors might have to be applied for

OC from quartz and XAD coated quartz backup filters due to different volatilities, which has been shown

to be valid for the Atlanta Supersite data

13

PCM

14

La Porte Wind Rosesday = 0901-1900 CST, night = 1901-0900CST

N

E

S

W3.5 7

WindFrequency

day night

Daytime sea breeze dominated with prevailing

SE flows.Those SE air masses were

low in primary gaseous pollutants.

Highest average Ozone with flows from SW and N.

Photochemical precursors moved in from N and NW;

with nighttime levels >> daytime indicating BL

dynamics.

SO2 points to possible point sources to W and NW

N

E

S

W5.5 11

SO2 (ppbv)

day night

N

E

S

W203.5 407

CO (ppbv) day night

N

E

S

W22 44

NOy (ppbv) day night