Sources of carbonaceous aerosols over the United States and implications for natural visibility

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Sources of carbonaceous aerosols over the United States and implications for natural visibility

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Title: Sources of carbonaceous aerosols over the United States and implications for natural visibility
Author: Park, Rokjin J.; Jacob, Daniel James; Chin, Mian; Martin, Randall

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Citation: Park, Rokjin J., Daniel J. Jacob, Mian Chin, and Randall V. Martin. 2003. “Sources of Carbonaceous Aerosols over the United States and Implications for Natural Visibility.” Journal of Geophysical Research 108 (D12). doi:10.1029/2002jd003190.
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Abstract: We use a global three-dimensional model (GEOS-CHEM) to better quantify the sources of elemental carbon (EC) and organic carbon (OC) aerosols in the United States through simulation of year-round observations for 1998 at a network of 45 sites (Interagency Monitoring of Protected Visual Environments (IMPROVE)). Simulation with our best a priori understanding of sources, including global satellite data to constrain fire emissions, captures most of the variance in the observations (R2 = 0.84 for EC, 0.67 for OC) with a low bias of 15% for EC and 26% for OC. Multiple linear regression to fit the IMPROVE data yields best estimates of 1998 U.S. sources of 0.60 Tg year−1 EC and 0.52 Tg year−1 OC from fossil fuel; 0.07 Tg year−1 EC and 0.89 Tg year−1 OC from biofuel; 0.08 Tg year−1 EC and 0.60 Tg year−1 OC from wildfires; and 1.10 Tg year−1 OC from vegetation. We find that fires in Mexico and Canada contributed 40–70% of annual mean natural EC in the United States for 1998 and 20–30% of annual mean natural OC. Transpacific transport from Asian pollution sources amounted to less than 10% of the natural EC and less than 2% of the natural OC; in contrast to ozone, we find that intercontinental transport of anthropogenic carbonaceous aerosols does not enhance significantly the natural background. IMPROVE observations and model simulations for the summer of 1995 show that Canadian fire emissions can produce large events of elevated EC and OC in the southeastern United States. Our best estimates of mean natural concentrations of EC and OC in the United States, using a model simulation with climatological monthly mean fire emissions, are 2–3 times higher than the default values recommended by the U.S. Environmental Protection Agency for visibility calculations, except for OC in the eastern United States (16% lower).
Published Version: doi:10.1029/2002JD003190
Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA
Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:14121825
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