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Chesapeake Bay Atmospheric Deposition Estimates

Chesapeake Bay Atmospheric Deposition Estimates. Modeling Subcommittee Quarterly Review April 3, 2007. Lewis Linker and Gary Shenk CBP Modeling Team. Nitrogen Load Indicator. Watershed model indicator of source sector for nitrogen loads to the Bay.

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Chesapeake Bay Atmospheric Deposition Estimates

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  1. Chesapeake Bay Atmospheric Deposition Estimates Modeling Subcommittee Quarterly Review April 3, 2007 Lewis Linker and Gary Shenk CBP Modeling Team

  2. Nitrogen Load Indicator Watershed model indicator of source sector for nitrogen loads to the Bay

  3. Atmospheric Deposition to the Chesapeake Bay Watershed

  4. Response in Loads to the Chesapeake Bay from Changes in Atmospheric Deposition

  5. Before and After Implementation of Title IV of the Clean Air Act Amendments of 1990Mean Annual Wet Deposition of Nitrate Before: 1983-1994 After: 1995-2004 Nitrate ion wet deposition, 2004

  6. Frequency of Occurrence of Nitrate Concentrations at AirMON Stations in the Chesapeake Watershed NO3-≥ 100 microequivalents/liter NO3- ≥ 10 & < 100 microequivalents/liter NO3- < 10 microequivalents/liter

  7. Nitrogen Oxides Emissions from Sources Affected by Title IV of the Clean Air Act Amendments Nitrogen Oxides Emissions from All Point and Area Sources in the United States

  8. The Airshed Model - CMAQ Combining a regression model of wetfall deposition... …with CMAQ estimates of dry deposition for the base… …and using the power of the CMAQ model for scenarios.

  9. Coastal Ocean Boundary Condition The CMAQ Model allows us to estimate atmospheric deposition loads to the coastal ocean. Other assessments (Howarth,1998) are that atmospheric deposition loads are approximately roughly equivalent to watershed loads in the Northeast U.S. Considering the Northeast to include all watersheds from Maine to Virginia draining to the Atlantic, Howarth estimates that the watershed inputs of nitrogen to the Northeast coastal waters to be 0.27 teragrams (1012 grams). Inputs from direct atmospheric deposition to coastal waters are 0.21 teragrams, and inputs from deep ocean upwelling are 1.54 teragrams.

  10. Coastal Ocean Boundary Condition It’s recommended that the ocean boundary condition for nitrogen used in the WQSTM be reduced 7% when running simulations of the 2030 conditions of air controls and tributary strategies. As a point of interest, the loads under pristine conditions for the Northeast coastal waters are estimated to be 0.03, 0.01, and 1.57 teragrams for the watershed, direct deposition, and deep upwelling loads respectively.

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