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

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??

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…

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)

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

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?

Comparison of Average Diurnal Meteorological Conditions

Comparison of Average Diurnal Trace Gas Concentrations

Comparison of Average Diurnal Photochemical Products

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?

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?

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.

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).

Supplementary Material

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

PCM

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

Seasonal and Regional Differences in Composition

Seasonal and Regional Differences in OC/EC

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)?

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