HR: 1330h
AN: A12B-0077    [PDF]
TI: Global Simulation of Ammonium-sulfate-nitrate Inorganic Aerosols: Implications for Natural Visibility in the United States and Intercontinental Transport of Pollution
AU: * Park, R J
EM: rpark@fas.harvard.edu
AF: Harvard University, 29 Oxford St. Div. Engineering & Applied sciences, Cambridge, MA 02138 United States
AU: Jacob, D J
EM: djacob@fas.harvard.edu
AF: Harvard University, 29 Oxford St. Div. Engineering & Applied sciences, Cambridge, MA 02138 United States
AU: Field, B D
EM: bdf@io.harvard.edu
AF: Harvard University, 29 Oxford St. Div. Engineering & Applied sciences, Cambridge, MA 02138 United States
AU: Evans, M J
EM: mje@io.harvard.edu
AF: Harvard University, 29 Oxford St. Div. Engineering & Applied sciences, Cambridge, MA 02138 United States
AU: Yantosca, R M
EM: bmy@io.harvard.edu
AF: Harvard University, 29 Oxford St. Div. Engineering & Applied sciences, Cambridge, MA 02138 United States
AU: Chin, M
EM: chin@rondo.gsfc.nasa.gov
AF: Georgia Institute of Technology, School of Earth and Atmospheric Sciences, Atlanta, GA 30332 United States
AB: We use a global 3-D coupled oxidant-aerosol model (GEOS-CHEM) to quantify natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosol concentrations in the United States. This work is motivated by the EPA Regional Haze Rule, which requires immediate action to improve visibility in U.S. wilderness areas towards an endpoint of ›r­’natural visibility conditions›r­_ by 2064. We present full-year simulations for 1998 and 2001 and evaluate them with nationwide networks of observations in the U.S. and Europe (IMPROVE, CASTNET, NADP, EMEP). Sulfate results are unbiased across all seasons, representing a major improvement over previous models. Ammonia emissions are too high in fall and possible reasons are discussed. Shutting off U.S. anthropogenic emissions in the model defines ›r­’residual›r­_ aerosol concentrations in the U.S. representing contributions from natural and transboundary pollution sources. We find that this residual is dominated by transboundary transport of pollution from Canada, Mexico, and Asia. Transpacific transport of Asian anthropogenic aerosol accounts for 30% of residual ammonium sulfate in both the western and eastern U.S. We find that achievement of natural visibility anywhere in the U.S. is seriously compromised by transboundary transport of anthropogenic sulfate-nitrate-ammonium aerosols. This is in contrast to carbonaceous aerosols, for which we previously found that natural sources dominate over transboundary transport of pollution. Our best estimates of residual aerosol concentrations in the U.S. are 2-4 times higher than the default values recommended by the EPA for natural visibility calculations, with major implications for emission controls to be implemented over the next decade.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting