1. Nitrogen Deposition over the US Raluca Ellis, Fabien Paulot Daven Henze, Daniel Jacob Harvard University, U. Colorado Boulder AQAST 3 meeting, June 13, 2012 Funding: AQAST, HUCE Air Quality Management Partner: Bret Schichtel, NPS

2. Nitrogen in the Nation’s Rain, NADP, 2000 Pathways of Reactive Nitrogen NH 3 NO x

3. CL = 1.5 wet kg N ha -1 a -1 alpine lakes CL = 3 - 8 kg N ha -1 a -1 forest/trees CL = 3.0 kg N ha -1 a -1 lichens Pardo et al., Ecol Appl, 2011 Quantify relationship between deposition and ecosystem response = critical load Specific to certain resource and defined harmful effect

4. Total nitrogen deposition to the US (wet + dry) GEOS-Chem total nitrogen deposition (2006-2008 annual mean) Nested North American model 0.5 o x 0.667 o resolution Evaluated using NADP, CASTNetsee Zhang et al., ACP, 2012

5. Total nitrogen deposition to the US (wet + dry) GEOS-Chem total nitrogen deposition (2006-2008 annual mean) Nested North American model 0.5 o x 0.667 o resolution Evaluated using NADP, CASTNetsee Zhang et al., ACP, 2012 Parks exceeding critical load nclude Rocky Mountain, Joshua Tree, Great Smoky Mountains Many western parks near critical load

6. Zhang et al., ACP, 2012 Source Attribution of Reactive Nitrogen Generally less than 10% but up to 30% near borders Higher than average in areas affected by lightning and wildfires

7. NO x emissions are going down but NH 3 is increasing Will N deposition decrease or increase? Will source attribution change? Can critical load goals be met? Total N emissions 2050 – 2005 RCP 2.6 RCP future emission scenarios Total N emissions 2050 – 2005 RCP 8.5 World emissions