2002 Annual

Tuesday, 15 January 2002: 2:00 PM
Atmospheric Deposition of Nitrogen as a Contributor to Coastal Eutrophication: How Far Away it Comes
Robin L. Dennis, NOAA-ARL / USEPA-ORD NERL, Research Triangle Park, NC
Nitrogen from atmospheric deposition is estimated to contribute 20-30% of new nitrogen to coastal estuaries of the East and Gulf Coasts. The major contributor is inorganic nitrogen, which comes in two forms: oxidized nitrogen (ox-N) (nitrates and nitric acid) and reduced nitrogen (red-N) (ammonia and ammonium). Their relative contribution to wet + dry deposition across the eastern U.S. will be presented. The range of influence of emissions of the two forms on nitrogen will be described and shown to be several hundred km for ox-N and a few hundreds of km for red-N. The red-N results are counter to conventional wisdom. A model budget analysis will be used to explain why conventional wisdom is an incorrect interpretation of observations. The red-N range of influence, while different from ox-N, still involves long-range transport. Several ox-N and red-N Principal Airsheds for several East and Gulf Coast watersheds and their estuaries will be presented. The airsheds are large, many times larger than the watersheds, and they are multi-state in size. Ramifications of the large size of the airsheds for atmospheric nitrogen affecting coastal estuaries will be noted.

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