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

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

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.

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.

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

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

TOMS tropospheric ozone (Thompson & Hudson)

Remote sensing of Ozone Surface network TOMS  

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: 10-30 ppbv Hemisph. pollution: 5-15 ppbv Natural ozone: 15-25 ppbv Stratospheric ozone: 0-10 ppbv US Trend: Peaks are falling but bottom is coming up.

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

INDOEX: Indian Ocean Experiment

Indian Today, 1996.

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

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.

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.

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

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

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.

The End.

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

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

Impactor Sample from INDOEX

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

Cruise Track and Air Flow During INDOEX 1999