2003-12-09 International Transport of Air Pollutants (ITAP)

International Transport of Air Pollutants (ITAP) Terry J. Keating, Ph.D. Office of Air & Radiation U.S. Environmental Protection Agency

Animation of CO Concentrations Observed by NASA’s MOPITT/TERRA

What have we learned about International Transport? While most air quality problems are due to local or regional sources, the U.S. is both an importer and exporter of air pollution.

Transboundary Flows with Canada & Mexico Transboundary flow can be important during exceedances of the NAAQS, as well as during exceedances of Canadian & Mexican policy objectives. What do we know? Major emissions sources have been located along both borders, and new sources continue to be built. SO 2 Ann Emiss, BRAVO

What do we know? Some of the most dramatic examples of international transport are not anthropogenic. On July 8, 2002, forest fires in Quebec created a smoke plume that blanketed the U.S. East Coast. [NASA MODIS image]

Imports from Central America In May 1998, fires in Central America create a smoke plume across the central U.S. Flows from Central America carry smoke, as well as other pollutants, including pesticides. Pesticide use per acre in Central America exceeds the US by a factor of 10. What do we know? GOES-8 Satellite Image, CIMSS Univ of Wisconsin

Imports from Africa Dust, metals, and other pollutants are transported from North Africa across the Atlantic to the Caribbean and the Southeastern U.S. Saharan Dust over Miami = 10 – 100  g/m 3 24 hr PM NAAQS = 65  g/m 3 PM 2.5 150  g/m 3 PM 10 [Prospero 1999] Pathogens in Saharan Dust have been linked to coral decline in the Caribbean. [Shinn et al 2000] What do we know?

Exports to Europe The U.S. exports ozone precursors, mercury, and other pollutants to the North Atlantic. The impact on attainment of European policy objectives may be significant. Days predicted to exceed the EU ozone standard that would not exceed the standard in the absence of North American emissions. [Li et al. , 2001] What do we know?

Imports to Alaska & Arctic Mercury, POPs, and other pollutants are carried into the Arctic, by circulation patterns and “global distillation.” Air Transport Pathways Arctic Air Mass In Summer and Winter [Crane & Galasso, 1999] What do we know?

Mercury Deposition

~40% of all Hg deposition to the lower 48 states comes from emission sources outside the U.S. or from U.S. emissions that have been transported across international boundaries

What do we know? [EPA, 1997] From Travnikov, EMEP MSC-E Global mercury emissions inventory for 1995 (provided by AMAP) Emissions distribution Contribution of different continents

Imports from Asia Dust from Chinese Deserts, fossil fuel emissions, and other pollutants travel across the Pacific and impact the Western U.S. What do we know? [Aerosol Index, NASA TOMS] World Energy Use [EIA, 2002] Emissions in Asia are expected to grow with further economic development, offsetting emissions decreases in the United States.

Simulated increase in mean U.S. surface ozone (ppbv) from tripling of Asian emissions (1985 to 2015). Future ozone impacts could be enough to offset the benefits of 25% decrease in U.S. emissions! Jacob et al. [1999] Imports from Asia What do we know?

The Tightening Vise Implications for the U.S.? From Keating, West, and Farrell (in press) Ozone concentration Historical Future (alternate view) Hemispheric background Regional Local Standard Future

IPCC-SRES global emission trends vs. national medium-term projections Implications for the U.S.? From Markus Amann, IIASA What will future emissions be? NO x VOC CO SO 2

The International Challenge