1. ASSESSING ORGANIC MASS FROM MASS CLOSURE: COMPARING ATLANTA ‘99 WITH ESP’01 AND ‘02.
K. Baumann, M.E. Chang, V. Dookwah, S. Lee, A.G. Russell
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta
Acknowledgement: E. Edgerton, ARA Inc.,
M. Bergin, H. Park, K. Patel, L. Sun, R. Weber, W. Younger, all GA Tech
Funding provided by US-EPA and GA-EPD
Motivation & Instrumentation
Site Locations, Met and Gas Characteristics
Estimate Photochemical Activity
Link to Changing Organic Mass

2. Derived OM/OC from Mass Closure for Urban / Rural Sites
Regional Difference: Higher OM/OC and OC/EC at more rural site!
Seasonal Difference: Lower OM/OC and higher (?) OC/EC in winter.
WHY??

3. Particle Composition Monitor “PCM”
For each PCM sample 17 (!) components (incl. 5 field blanks) are being analyzed via IC & TOT.
The following species are being quantified and reported.
Channel 1:
NH3
Na+, K+, NH4+, Ca+2
Channel 2:
HF, HCl, HONO, HNO3, SO2,
HCOOH, CH3COOH, (COOH)2
F-, Cl-, NO3-, SO4=,
HCOO-, CH3COO-, C2O4=
Channel 3:
EC, OC, “SVOC”
Special tests and procedures for eliminating positive water bias, OC artifacts and other details described in paper accepted to JGR “Atlanta Supersite” special section, coming out soon…

4. Sites Locations and Measurements in Georgia
Name
Period
Met CO
SO2 NO
NOx
NOy O3
PM2.5
Atlanta JST
08/99 X XX
Atlanta TUC
Since 03/99
Atlanta FTM
Atlanta SDK
Griffin
Since 06/01
(X)
Macon
Since 06/00
Columbus
Since 07/00
Augusta
Tifton
Since 07/01
Atlanta Supersite (Solomon) ASACA (Russell) FAQS (Chang)

5. Site Locations and PM2.5 Wind Roses: Summer / Winter

6. Summertime PM2.5 – Max(O3) Relationship
Tighter correlation in July 2001.
“Downwind” Griffin site offset to higher PM2.5 mass.
What was different in August 1999?

7. Comparison of Average Diurnal Meteorological Conditions

8. Comparison of Average Diurnal Trace Gas Concentrations

9. Comparison of Average Diurnal Photochemical Products

10. Summary of Met and Trace Gas Comparison
August 1999 in Atlanta was…
Hotter, dryer, more polluted with precursor species, incl. NH3!
How can this, in addition to higher [O3] and [PM2.5], lead to the observed differences, suggesting more OC (SOA?) in Aug’99 and more oxygenated POCs away from Atlanta?

11. Source – Receptor Considerations: CO/NOy
Air mass arriving at Griffin has significantly higher CO/NOy ratio in summer than in winter:
Loss of more abundant summertime HNO3 due to surface deposition!
Griffin
downwind
Atlanta JST
Higher intercept points to elevated regional background CO!
Long-range transport of wild fires’ plumes (see SOS’95)?
Or other high-CO/low-NOx sources?

12. Source – Receptor Considerations: O3/NOz as “OPE”
Atlanta JST
Griffin
downwind
Elevated regional O3 background reflected in regression’s intercept: higher in Aug 99!
At JST higher intercept and slope during Aug ’99 (OPE= 4 vs 3): more efficient P(O3).
OPE in air mass arriving at Griffin is likely larger given by upper and lower limits.
Lower limit assumes 1st order loss of HNO3 due to surface deposition at k ≈ 0.22 h-1.

13. Summary
Photochemical processes leading to high ozone levels also lead to high PM fine.
Elevated levels of primary pollutants (CO, NOx, SO2 and NH3) under hot and relatively dry conditions responsible for high PM fine mass concentrations during August 1999.
Possible regional impact from distant wild fires (similar to 1995?) causing high OC/EC and elevated background CO in August 1999?!
As the Atlanta urban plume is advected over BHC-rich terrain, it transitions to a more NOx-limited regime, i.e. with greater RO2 abundance, indicated by an increasing OPE.
This transition bears great potential for the formation of SOA and more oxygenated POC, explaining the observed increase in OM/OC downwind from Atlanta.
Subset of Jul’01 and Jan’02 Griffin samples show 65 vs 55 ±5 % WSOC fraction.
No biomass burn ban in winter causing a shift to higher OC/ECp
Outlook
Investigate influence from distant plumes of wild fires in August ’99.
Quantify SOA by careful determination of (OC/EC)p.
Detailed analyses of selected days/episodes for OPE and WSOC.
Air quality impacts of biomass burning (in collab w/ M. Zheng).

14. Supplementary Material

15. Assessing Accuracy of PCM Measurements
S-compounds and mass agree well, volatile species esp. NO3- more difficult to measure accurately

16. PCM

17. OM/OC Estimates With & Without “SVOC”
OM/OC for closure
OM/OC {svoc} for closure
AVG
STD
August-99
Atlanta
2.1
0.7
1.5
0.3
Summer-00
Macon
2.5
0.6
1.7
0.1
Augusta
3.4
Columbus
2.0
0.5
1.6
LaPorte
3.5
3.8
2.3
2.6
W.Tower
3.2
2.4
July-01
Atlanta JST
1.2
Atlanta TUC -
Atlanta FTM
1.0
Griffin
2.7
Dec-01
1.1
0.9
Jan-02
1.8
0.8

18. Seasonal and Regional Differences in Composition

19. Seasonal and Regional Differences in OC/EC

20. Seasonal/Regional Aerosol Acidity Based on [SO4=/NO3-/NH4+]
Aerosol is closely neutralized / slightly alkaline in winter but more acidic in summer
Acidity caused by insufficient NH3, or unaccounted for organic amines (with higher OM/OC)?

21. From CO/NOy regressions JST vs GRF:
NOyinit = 31/9 *NOy
NOylost = NOyinit - NOy
= NOyinit*(1-9/31)
= 0.71*NOyinit
Assume 1st order loss:
NOyinit = NOy / exp(-kt)
Assume 2.5 m/s N-ly flow throughout CBL:
Then t = 5.6 h
And k = 0.22 h-1