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ASSESSING ORGANIC MASS FROM MASS CLOSURE: COMPARING ATLANTA ‘99 WITH ESP’01 AND ‘02.

ASSESSING ORGANIC MASS FROM MASS CLOSURE: COMPARING ATLANTA ‘99 WITH ESP’01 AND ‘02. 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. K. Baumann, M.E. Chang, V. Dookwah, S. Lee, A.G. Russell

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ASSESSING ORGANIC MASS FROM MASS CLOSURE: COMPARING ATLANTA ‘99 WITH ESP’01 AND ‘02.

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  1. ASSESSING ORGANIC MASS FROM MASS CLOSURE:COMPARING ATLANTA ‘99 WITH ESP’01 AND ‘02. 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 K. Baumann, M.E. Chang, V. Dookwah, S. Lee, A.G. Russell School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta • 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 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. downwind Griffin 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! Source – Receptor Considerations: CO/NOy 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. downwind Atlanta JST Griffin Source – Receptor Considerations: O3/NOz as “OPE” 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”

  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

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