1. Global Modeling of Organic PM: State of the Science and Major Gaps Daniel J. Jacob with Rokjin J. Park 1, Colette L. Heald 2 Tzung-May Fu 3, Hong Liao 4 and funding from EPRI, EPA, NSF 1 now asst. prof. at Seoul National University 2 now asst. prof. at Colorado State University 3 now asst. prof. at Hong Kong Polytechnic University 4 Caltech, now at Chinese Academy of Sciences

2. ORGANIC PM IN STANDARD GEOS-Chem MODEL fuel/industry open fires OH, O 3,NO 3 SOGSOA POA K vegetation fuel/industry open fires 700 isoprene terpenes oxygenates… 30 alkenes aromatics oxygenates… alkanes alkenes aromatics… VOC EMISSIONPRIMARY EMISSION VOC 50 20100 20 Global sources in Tg C y -1 secondary formation

3. TOP-DOWN CONSTRAINTS ON U.S. SOURCES IMPROVE obs (1998) Park et al. [JGR 2003] annual U.S. source: 3.1 Tg yr -1 0.52 0.89 0.60 1.10 Fit GEOS-Chem sources of organic PM to monthly 1998 data at IMPROVE sites

4. IMPROVED MODEL WITH 1 o x1 o RESOLUTION, SOA FORMATION BY PANKOW/SEINFELD MECHANISM (2001, annual) Park et al. [AE 2006] IMPROVE  g m -3

5. SENSITIVITY OF NATURAL OC PM CONCENTRATIONS TO PRE-EXISTING POA AVAILABILITY Is SOA formation limited by availability of primaryorganic aerosol (POA)? YESNO Park et al. [AE 2006] Major implications for natural visibility objective of the Regional Haze Rule

6. QUANTIFYING THE BIOMASS BURNING SOURCE OF PM2.5 FROM CORRELATION OF TOTAL CARBON (TC) WITH NON-SOIL K + AT IMPROVE SITES Non-soil K + : West: summer max, low background East: winter and summer maxes, high background Background ns-K + (traces industrial biofuel) Park et al. [AE 2007] use TC vs. ns-K + linear regression together w/satellite data to quantify TC from open fires d[TC]/d[ns-K + ]

7. FIRE AND BIOFUEL CONTRIBUTIONS TO TC PM2.5 Annual mean C concentrations, 2001-2004 Mean values for W and E at top of plot Park et al. [AE 2007]

8. IMPLICATIONS FOR AQ STANDARDS AND EMISSION INVENTORIES PM2.5,  g m-3 (x1.8 for TC) WestEast Summer wildfires0.470.25 Other fires0.490.56 Residential biofuel0.130.52 Industrial biofuel0.130.32 Total fire+biofuel TC (this work) 1.21.6 Observed TC2.23.4 Observed total PM2.5 3.88.2 Tg C y -1 Top-down This work Open fires Biofuel Park et al. [2003] Open fires Biofuel 0.90 0.51 (40% industrial) 0.68 0.96 (80% industrial) Bottom-up Bond et al. [2004] Open fires Biofuel NEI99 Biofuel 0.89 0.42 (<10% industrial) 0.23 (<10% industrial) Source attribution at IMPROVE sites (annual means) Emissions for contiguous U.S. (climatological estimate for fires) Park et al. [AE 2007]

9. FIRST MASS CONCENTRATION MEASUREMENTS OF OC AEROSOLS IN FREE TROPOSPHERE ACE-Asia aircraft data over Japan (April-May 2001) Observed (Huebert) GEOS-Chem (Chung & Seinfeld for SOA) Observed (Russell) OC/sulfate ratio Heald et al. [GRL 2005] Chung and Seinfeld scheme: Observations show 1-3  g m -3 background; model too low by factor 10-100

10. LITTLE TRANSPACIFIC INFLUENCE OF ASIAN ORGANIC PM ON U.S. SURFACE AIR Spring 2001 IMPROVE sulfate data Days of max Asian influence (diagnosed by GEOS-Chem) March-May mean Days of max Asian influence sulfate0.691.04 nitrate0.220.24 OC1.081.19 Mean PM concentrations observed in NW U.S. (  g m -3 ) [Heald et al., JGR 2006a] Other studies (Randall Martin, Rodney Weber) find no OC enhancement in transpacific Asian plumes sampled from aircraft

11. ITCT-2K4 AIRCRAFT CAMPAIGN OVER EASTERN U.S. IN JULY-AUGUST 2004 water-soluble organic carbon (WSOC) aerosol measurements by Rodney J. Weber (Georgia Tech) 2-6 km altitude Alaska fire plumes Values ~2x lower than observed in ACE-Asia; excluding fire plumes gives mean of 1.0  gC m -3 (3x lower than ACE-Asia) Heald et al. [JGR 2006b]

12. MODEL OC AEROSOL SOURCES DURING ITCT-2K4 ~10% yield~2% yield Large fires in Alaska and NW Canada: 60% of fire emissions released above 2 km (pyro-convection) Heald et al., [JGR 2006b]

13. ITCT-2K4 OC AEROSOL: VERTICAL PROFILES SO x = SO 2 + SO 4 2- : efficient scavenging during boundary layer ventilation Observations Model hydro- phobic Data filtered against fire plumes (solid) and unfiltered (dotted) Model source attribution Total Biomass burning Anthropogenic Biogenic SOA Heald et al. [JGR 2006b]

14. IRREVERSIBLE DICARBONYL UPTAKE BY AQUEOUS AEROSOL Chamber AMS experiments of glyoxal uptake by Liggio et al. [JGR 2005] Organic aerosol mass growth with time Inferred reactive uptake coefficient  median  = 2.9x10 -3 observed for aqueous surfaces; evidence for oligomerization similar  observed for methylglyoxal on acidic surfaces [Zhao et al. ES&T 2006] glyoxalmethylglyoxal

15. POSSIBLE MECHANISMS FOR DICARBONYL SOA FORMATION GASAQUEOUS Oligomers OH Organic acids H* ~ 10 5 M atm -1 Ervens et al. [2004] Crahan et al. [2004] Lim et al. [2005] Carlton et al. [2006, 2007] Warneck et al. [2005] Sorooshian et al. [2006, 2007] Altieri et al. [2006, 2008] Schweitzer et al. [1998] Kalberer et al. [2004] Liggio et al. [2005a,b] Hastings et al. [2005] Zhao et al. [2006] Loeffler et al. [2006] glyoxal H* ~ 10 3 M atm -1 methylglyoxal oxidation oligomerization

16. GLYOXAL/METHYLGLYOXAL FORMATION FROM ISOPRENE GEOS-Chem mechanism based on MCM v3.1 Fu et al. [JGR, in press] 6%25% molar yields

17. GLOBAL GLYOXAL BUDGET IN GEOS-Chem Including reactive uptake by aq. aerosols + clouds with  =2.9x10 -3 [Liggio et al., 2005] Global SOA formation of 6.4 Tg yr -1 (1.0 in clear sky + 5.4 in cloud); compare to 16 Tg yr -1 from terpenes/isoprene by semivolatile mechanism Fu et al. [JGR, in press]  = 2.9 h (biomass burning)

18. GLOBAL METHYLGLYOXAL BUDGET IN GEOS-Chem Including reactive uptake by aerosols and clouds with  =2.9x10 -3 Global SOA formation of 16 Tg yr -1 (2 in clear sky + 14 in cloud); compare to 16 Tg yr -1 from terpenes/isoprene by semivolatile mechanism  = 1.6 h Fu et al. [JGR, in press] (biomass burning)

19. MODEL COMPARISON TO IN SITU OBSERVATIONS Glyoxal Methylglyoxal Continental boundary layer (all northern midlatitudes summer) Continental free troposphere Marine boundary layer Indication of a missing marine source in the model Fu et al. [JGR, in press]

20. SCIAMACHY SATELLITE OBSERVATION OF GLYOXAL General spatial pattern reproduced over land, SCIAMACHY is 50% higher than model SCIAMACHY sees high values over oceans correlated with chlorophyll: unidentified marine source? 100 pptv glyoxal in marine boundary layer would yield ~1  g C m -3 SOA; could contribute to observed OC aerosol concentrations in marine air Fu et al. [JGR, in press]

21. SIMULATION OF WSOC AEROSOL OVER EASTERN U.S. Water-soluble OC (WSOC) aerosol observations by Rodney Weber (GIT) from NOAA aircraft during ICARTT campaign out of Portsmouth, NH (Jul-Aug 04) Observed Model w/ dicarbonyl SOA added Model w/ standard SOA Model hydrophilic primary OA biomass burning plumes excluded Boundary layer data (<2 km) Fu et al., in prep. IMPROVE (surface) ICARTT model w/ dicarbonyls w/out dicarbonyls Dicarbonyl source in summer is mainly Biogenic (isoprene)

22. CORRELATIONS OF FREE TROPOSPHERIC WSOC WITH OTHER VARIABLES MEASURED ON NOAA AIRCRAFT Observed Model with dicarbonyl SOA Model without dicarbonyl SOA WSOC is observed to correlate with toluene and methanol (anthro+bio?) sulfate (aqueous-phase production?) alkyl nitrates (photochemistry?) Model does not reproduce observed WSOC variability but does better with correlations, particularly when dicarbonyl SOA is included (sulfate, alkyl nitrates) Fu et al., in prep.