1. NATURAL AND TRANSBOUNDARY INFLUENCES ON PARTICULATE MATTER IN THE UNITED STATES: IMPLICATIONS FOR THE EPA REGIONAL HAZE RULE Daniel J. Jacob and Rokjin J. Park Sponsored by the Electrical Power Research Institute Project Manager: Naresh Kumar

2. EPA REGIONAL HAZE RULE Federal class I areas (including national parks, other wilderness areas) to return to “natural visibility” conditions by 2064 State Implementation Plans to be submitted by 2007 for linear improvement in visibility over the 2004-2018 period EPA [2001]

3. AEROSOLS ARE TRANSPORTED ON REGIONAL SCALE  REGIONAL HAZE RULE HAS NATIONAL IMPLICATIONS Acadia National Park ( http://www.hazecam.net/ ) “clean day” (“heavily polluted day” is not worth showing) …2064 endpoint would require nationwide elimination of anthropogenic emissions “moderately polluted day” Visibility reduction at Acadia is caused by emissions from the entire Northeast Corridor, industrial Midwest, and probably beyond

4. TRANSBOUNDARY TRANSPORT COMPLICATES THE DEFINITION OF “NATURAL VISIBILITY” Glen Canyon, AZ Clear dayApril 16, 2001: Asian dust! Should foreign anthropogenic influences from Canada, Mexico, Asia be considered part of the “natural aerosol”?

5. EPA HAS PROPOSED “DEFAULT ESTIMATED NATURAL PM CONCENTRATIONS” FOR APPLICATION OF THE REGIONAL HAZE RULE PM mass concentration (  g m -3 ) Extinction coefficient (Mm -1 ) These defaults are not traceable to actual data in the literature. What do they mean in terms of actual natural vs. anthropogenic influences?

6. OBJECTIVES OF PROJECT Determine present-day natural PM concentrations in the U.S., compare to EPA “default” values. –Do the EPA default values allow for practical implementation of the Regional Haze Rule? What are the implications for the 2004-2018 1 st implementation period? Determine the contributions from foreign anthropogenic emissions (Canada, Mexico, Asia) to visibility degradation in the U.S. –Transboundary transport of pollution is not addressed by the Regional Haze Rule. Long-term global trends in PM emissions, associated in particular with industrialization of Asia, may compromise the definition of a 2064 visibility endpoint based on present-day estimates of natural aerosol concentrations. Determine the pervasiveness of natural fires and dust events, particularly from outside the U.S, in decreasing natural visibility in the U.S. –The role of these events is not adequately addressed in the EPA definition of default natural PM concentrations.

7. GENERAL APPROACH OF PROJECT GENERAL APPROACH OF PROJECT Assessment of EPA “default estimated natural PM concentrations” Assessment of transboundary pollution influences Start from best a priori estimates of natural and anthropogenic PM sources Conduct global PM simulation with GEOS-CHEM chemical tracer model Evaluate with aerosol data from IMPROVE, CASTNET, other networks Improved emission estimates carbonaceous aerosols [Park et al., JGR, 108, 10.1029/2002JD003190, 2003] H 2 SO 4 -HNO 3 -NH 3 -H 2 O aerosols [Park et al., ms. in prep.] dust [Fairlie et al., in progress] Conduct sensitivity simulations APPLICATIONS SO FAR:

8. GEOS-CHEM GLOBAL CHEMICAL TRANSPORT MODEL (http://www-as.harvard.edu/chemistry/trop/geos) Driven by GEOS assimilated meteorological data from the NASA Global Modeling and Assimilation Office (GMAO) Horizontal resolution 1 o x1 o to 4 o x5 o (user-selected), 48 levels in vertical Ozone-NO x -VOC (“oxidant”) chemistry: ~80 species, 400 reactions Aerosols: H 2 SO 4 -HNO 3 -NH 3, organic carbon (OC), elemental carbon (EC), soil dust (four size classes), sea salt (two size classes) Oxidant and aerosol simulations coupled by photolysis frequencies, heterogeneous chemistry, sulfate/nitrate formation, HNO 3 (g)/NO 3 - partitioning Multi-process wet deposition scheme evaluated with 210 Pb/ 7 Be tracers Previous global evaluation of aerosol simulation by Chin et a.. [JAS 2002] using GOCART model (same meteorological data source, similar emissions) FOR THIS PROJECT: Coupled aerosol-oxidant model (4 o x5 o resolution) Aerosol-only model (2 o x2.5 o resolution) Archived oxidant/HNO 3 3-D fields … applied to 1-year simulations for 1998 and 2001 (with 6-month initialization)

9. CARBONACEOUS AEROSOL SIMULATION Best a priori sources (1998) ORGANIC CARBON (OC) ELEMENTAL CARBON (EC) GLOBAL UNITED STATES 130 Tg yr -1 22 Tg yr -1 2.7 Tg yr -1 0.66 Tg yr -1

10. NORTH AMERICAN BIOMASS BURNING SOURCE HAS LARGE INTERANNUAL VARIABILITY From TOMS Aerosol Index [Duncan et al., 2002] 1998 fires from ATSR satellite data: Apr-May fires in Mexico Jul-Sep fires in U.S/Canada Biomass burning source for 1998 in GEOS-CHEM uses climatology from Duncan et al. [2002], scaled to 1998 using satellite data (TOMS and ATSR)

11. ANNUAL MEAN OC AND EC (1998): GEOS-CHEM vs. IMPROVE (45 sites) 45 sites High OC in southeast U.S.: vegetation High OC in Mexico, Canada: fires

12. SEASONAL VARIATION OF OC AND EC Circles: IMPROVE Lines: model & model tracers of sources Seasonal variations driven by vegetation and fires for OC, fires and fossil fuel for EC

13. LEAST-SQUARES FIT OF MODEL TO OBSERVATIONS GENERATES OPTIMIZED A POSTERIORI SOURCES Fossil fuel  15% Biofuel  65% Biomass burning  17% Biogenic  11%

14. CARBONACEOUS AEROSOL IN THE U.S.: contributions from natural sources and transboundary pollution OC (  g m -3 as OMC) West East EC (  g m -3 ) West East Baseline (1998)2.03.20.300.68 Zero anthropogenic emissions in U.S. – GEOS-CHEM (w/ climatological fires) – EPA default values 1.3 0.5 1.2 1.4 0.06 0.02 0.04 0.02 Contributions from transboundary anthropogenic sources Canada and Mexico Asia 0.05 0.013 0.05 0.007 0.02 0.005 0.02 0.003 Annual regional means from GEOS-CHEM standard and sensitivity simulations We find that EPA default natural concentrations are too low by factors of 2-3 except for OC in eastern U.S. – quantifying fire influences is critical Transboundary pollution influences are relatively small except for EC from Canada/Mexico

15. H 2 SO 4 -HNO 3 -NH 3 -H 2 O AEROSOL SIMULATION GEOS-CHEM emissions (2001) GLOBAL UNITED STATES Sulfur, Tg S yr -1 Ammonia, Tg N yr -1 NO x, Tg N yr -1 788.3 55 2.8 437.4

16. ANNUAL MEAN SULFATE (2001): GEOS-CHEM vs. IMPROVE (141 sites) Highest concentrations in industrial Midwest (coal-fired power plants)

17. SULFATE AT IMPROVE, CASTNET, NADP (deposition) SITES: model vs. observed for different seasons High correlation, no significant model bias except NADP summer (excessive scavenging of SO 2 in convective updrafts?)

18. ANNUAL MEAN AMMONIUM (2001): GEOS-CHEM vs. CASTNET (79 sites) Highest concentrations in upper Midwest (livestock) (no ammonium data at IMPROVE sites)

19. ANNUAL MEAN NITRATE (2001): GEOS-CHEM vs. CASTNET (79 sites) Highest concentrations in upper Midwest (NH 4 NO 3 formation limited by ammonia availability)

20. AMMONIUM AND NITRATE AT CASTNET AND IMPROVE SITES: model vs. observed for different seasons Ammonium Nitrate Nitrate High bias for NH 4 + in fall: error in seasonal variation of livestock emissions High bias for NO 3 -, esp. in summer/fall, results from bias on [SO 4 2- ]-2[NH 4 + ]

21. SEASONAL VARIATION OF NH 3 EMISSION Standard seasonal dependence of NH 3 emissions used in GEOS-CHEM produces a fall high bias in U.S., as shown previously in inverse modeling of NADP NH 4 + precipitation data by Gilliland et al. [JGR 2003]

22. SEASONAL VARIATION OF AEROSOL ACIDITY Aerosol is mostly neutralized (highest acidity in eastern U.S. in summer); aerosol phase is therefore a major issue for visibility assessment CASTNET GEOS-CHEM CASTNET sites Except in the upper Midwest, NH 4 NO 3 formation is limited by NH 3 rather than by HNO 3 availability  better knowledge of NH 3 emissions is critical

23. SULFATE, AMMONIUM, NITRATE AT EUROPEAN EMEP SITES (1998): model vs. observed for different seasons sulfate simulation is unbiased similar ammonium and nitrate high biases as for U.S.

24. SULFATE-NITRATE-AMMONIUM AEROSOL IN THE U.S.: contributions from natural sources and transboundary pollution Ammonium sulfate (  g m -3 ) West East Ammonium nitrate (  g m -3 ) West East Baseline (2001)1.524.111.533.26 Zero anthropogenic emisions in U.S. – GEOS-CHEM – EPA default values 0.43 0.11 0.38 0.23 0.27 0.1 0.37 0.1 Contributions from transboundary anthropogenic sources Canada and Mexico Asia 0.15 0.13 0.14 0.12 0.20 -0.02 0.25 -0.02 Achievability of EPA default estimates is compromised by transboundary pollution influences Transboundary pollution influence from Asia is comparable in magnitude to that from Canada + Mexico Annual regional means from GEOS-CHEM standard and sensitivity simulations

25. INTERCONTINENTAL TRANSPORT OF ASIAN AND NORTH AMERICAN ANTHROPOGENIC SULFATE As determined from GEOS-CHEM 2001 sensitivity simulations with these sources shut off

26. CONSEQUENCES FOR 2004-2018 IMPLEMENTATION OF EPA REGIONAL HAZE RULE WESTEAST Baseline dv (current conditions)15.622 Estimated natural dv – EPA default – This work 4.7 8.8 7.4 8.8 Required improvement in dv, 2004-2018 –using EPA default –using this work 2.5 1.6 3.4 3.1 Required % improvement in b ext, 2004-2018: –using EPA default –using this work 21% 13% 29% 27% Visibility (deciviews: dv = 10ln(b ext /10) Illustrative calculation assuming f(RH) = 2 (west) or 3 (east), adopting EPA default values for dust, and using mean eastern/western U.S. PM concentrations.

27. FUTURE WORK 1.PROVIDE UNCERTAINTIES ON OUR NATURAL PM ESTIMATES Critical issue: better evaluate the ability of the model to simulate natural and transboundary influences –Use frequency distributions at IMPROVE sites –Use aerosol optical depth data from AERONET network and from satellite (MODIS, MISR) –Use aircraft observations as constraints on transboundary simulation (TRACE-P, NOAA/ITCT, INTEX) 2. REDUCE THESE UNCERTAINTIES THROUGH MODEL IMPROVEMENTS –Improve representation of NH 3 emissions, SO 2 wet scavenging –Increase horizontal resolution to 1 o x1 o –Include representation of aerosol phase for characterization of optical properties –Develop microphysical representation

28. FUTURE WORK (cont.) 3. EXTEND APPLICATION OF MODEL TO OTHER REGIONAL HAZE RULE ISSUES –Quantify frequency distributions for “natural” visibility –Quantify the role of dust (domestic, Asian, Saharan) in visibility reduction –Assess the effect of future changes in Asian and other foreign anthropogenic emissions on “natural” visibility in U.S. –Assess the effect of changes in aerosol size, aerosol phase –Assess the impact of climate change (including effects on transport, scavenging, thermodynamics)