title: Spatial variation of atmospheric nitrogen deposition and critical loads for aquatic ecosystems in the Greater Yellowstone Area.
abstract: Current and historic atmospheric nitrogen (N) deposition has impacted aquatic ecosystems in the Greater Yellowstone Area (GYA). Understanding the spatial variation in total atmospheric deposition (wet + dry) of N is needed to estimate air pollution deposition critical loads for sensitive aquatic ecosystems. This is particularly important for areas that have an increasing contribution of ammonia dry deposition to total N (TN), such as the GYA. High resolution geostatistical models and maps of TN deposition (wet + dry) were developed using a variety of techniques including ordinary kriging in a geographic information system, to evaluate spatial variability and identify areas of elevated loading of pollutants for the GYA. TN deposition estimates in the GYA range from <1.4 to 7.5 kg N ha-1yr-1and show greater variability than wet inorganic N deposition. Critical loads of TN deposition (CLTNdep) for nutrient enrichment in aquatic ecosystems range from less than 1.5 ± 1.0 kg N ha-1yr-1to over 4.0 ± 1.0 kg N ha-1yr-1and variability is controlled by differences in basin characteristics. The lowest CLTNdepestimates occurred in high elevation basins within GYA Wilderness boundaries. TN deposition maps were used to identify critical load exceedances for aquatic ecosystems. Estimated CLTNdepexceedances for the GYA range from 17% to 48% depending on the surface water nitrate (NO3-) threshold. Based on a NO3-threshold of 1.0 μmol L-1, TN deposition exceeds CLTNdepin approximately 30% of the GYA. These predictive models and maps can be used to help identify and protect sensitive ecosystems that may be impacted by excess atmospheric N deposition.
authors.affiliation: San Francisco State University, San Francisco, CA 94132, USA. Electronic address: lnanus@sfsu.edu.
authors.forename: L
authors.initials: L
authors.lastname: Nanus
authors.affiliation: US Forest Service, Air Resources Management Program, Bozeman, MT 59711, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: McMurray
authors.affiliation: US Geological Survey, Denver Federal Center, Denver, CO 80225, USA.
authors.forename: D W
authors.initials: DW
authors.lastname: Clow
authors.affiliation: University of Maine, Orono, ME 04469, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Saros
authors.affiliation: National Park Service, Air Resources Division, Denver, CO 80225, USA.
authors.forename: T
authors.initials: T
authors.lastname: Blett
authors.affiliation: San Francisco State University, San Francisco, CA 94132, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Gurdak
mesh_terms: D000397:Air Pollution / Q000009:adverse effects / Q000032:analysis; D000641:Ammonia / Q000009:adverse effects / Q000032:analysis; D001272:Atmosphere / Q000737:chemistry*; D017753:Ecosystem; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000009:adverse effects* / Q000032:analysis*; D005618:Fresh Water / Q000737:chemistry*; D040362:Geographic Information Systems; D006801:Humans; D009584:Nitrogen / Q000009:adverse effects* / Q000032:analysis*; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000009:adverse effects / Q000032:analysis; D014877:Water Pollution, Chemical / Q000009:adverse effects / Q000706:statistics & numerical data; D014959:Wyoming
chemical_list: D004785:Environmental Pollutants; D014874:Water Pollutants, Chemical; D000641:Ammonia; D009584:Nitrogen
keywords: Atmospheric deposition; Critical loads; GIS; Nitrogen; Rocky Mountains