1. Air Pollution Control: Transboundary Air Pollutants
EPA Science Advisory Board workshop
Emerging Scientific Topics
Air Pollution Control: Transboundary Air Pollutants
December 11, 2003
Russell Dickerson, Univ. Maryland

2. Thunderstorms convert local air pollution problems into global atmospheric chemistry problems.

3. Tropospheric Ozone Formation
NOx is the limiting reagent outside urban areas.
Efficiency of ozone production falls as NOx concentration increases.
Lifetimes, wind speeds, and photolysis rates all higher aloft.

4. Atmospheric Residence Time Increases with Height
Stratosphere
Aerosol Layers
Troposphere
Clouds
Boundary Layer
NASA Astronaut Limb Photo
Fine Particle residence time in the boundary layer, is 3-5 days.
Residence time in the free troposphere is weeks and the transport is hemispheric
Photo prepared by R. Husar, Washington Univ.

5. AEROCE Finding: Transport of pollutants from North America to the North Atlantic via linked cold fronts (Prados, 2000)

6. Aircraft observations show how cold fronts lift and transport air pollutants to the east. Colored line shows King Air flight track.

7. TOMS tropospheric ozone (Thompson & Hudson)

8. Remote sensing of Ozone Surface network TOMS 

9. Seasonal cycle in mean afternoon surface O3 over the US
Based on the Harvard global model and surface observations
Fiore et al., JGR 2003.
Regional pollution: ppbv
Hemisph. pollution: ppbv
Natural ozone: ppbv
Stratospheric ozone: ppbv
US Trend: Peaks are falling but bottom is coming up.

10. The ambient EC concentration decreased ~50% in 11 yr.

11. INDOEX: Indian Ocean Experiment

12. Indian Today, 1996.

13. Mean Aerosol Optical Depth over INDOEX region from Dec 2001 to May 2003 from MODIS (Ramanathan & Ramana, Environ. Managers, Dec. 2003).

14. Global Fossil Fuel Black Carbon. Emissions (Cooke et al
Global Fossil Fuel Black Carbon* Emissions (Cooke et al.,1999; Penner et al., 1993; Dickerson et al., 2002)
Region
BC Emissions Tg yr-1
W. Europe
0.58
Eastern Europe
0.68
Africa
0.17
N. America
0.49
C. & S. America
0.26
Former USSR
0.69
China & Oceania
1.18
Rest of Asia
2.00
Total fossil fuel
6.17
Biomass Burning
5.97
*Major greenhouse substance.

15. South Asia emits large quantities of VOC’s and POM, but little NOx.
Little ozone is observed over India or the Northern Indian Ocean. VOC/NOx ratio too high(?).
This could change as vehicle fleet shifts from 2-stroke to 4-stroke engines.

16. Nitrogen Deposition Past and Present mg N/m2/yr
5000
2000
1000
750
500
250
100 50 25 5
1860
1993
Galloway et al., 2003

17. “A systems approach integrating both animal and crop productions is necessary to evaluate air emissions…. “
NRC 2003

18. Summary & Conclusions
Nonlinearities in chemistry and longer lifetimes of trace gases and aerosols in the free troposphere promote long-range transport.
Much of the growth in emissions in the coming decades will come from the developing world.
Asia is different from North America:
Organic aerosol & soot from biofuels & 2-stroke engines.
Conversion to high-tech combustion could lead to more ozone.
We need interdisciplinary and international colaboration.

19. The End.

20. Modeled Carbon Monoxide TRACE-P/ACE-Asia
Pickering et al., 2002

21. Forecasts & Observations of Air Pollution Over the Mid Atlantic
Shot from UMD Research Aircraft
Dickerson, Doddridge, Piety et al.

22. Impactor Sample from INDOEX

23. Global distribution of AOD (550 nm) for April & May, 2001 and 2002; from MODIS. (Ramanathan and Ramana, 2003).

24. Cruise Track and Air Flow During INDOEX 1999