title: Mapping critical loads of nitrogen deposition for aquatic ecosystems in the Rocky Mountains, USA.
abstract: Spatially explicit estimates of critical loads of nitrogen (N) deposition (CL(Ndep)) for nutrient enrichment in aquatic ecosystems were developed for the Rocky Mountains, USA, using a geostatistical approach. The lowest CL(Ndep) estimates (<1.5 ± 1 kg N ha(-1) yr(-1)) occurred in high-elevation basins with steep slopes, sparse vegetation, and abundance of exposed bedrock and talus. These areas often correspond with areas of high N deposition (>3 kg N ha(-1) yr(-1)), resulting in CL(Ndep) exceedances ≥ 1.5 ± 1 kg N ha(-1) yr(-1). CL(Ndep) and CL(Ndep) exceedances exhibit substantial spatial variability related to basin characteristics and are highly sensitive to the NO(3)(-) threshold at which ecological effects are thought to occur. Based on an NO(3)(-) threshold of 0.5 μmol L(-1), N deposition exceeds CL(Ndep) in 21 ± 8% of the study area; thus, broad areas of the Rocky Mountains may be impacted by excess N deposition, with greatest impacts at high elevations.
authors.affiliation: US Geological Survey, Denver Federal Center, Denver, CO 80225, USA. lnanus@sfsu.edu
authors.forename: Leora
authors.initials: L
authors.lastname: Nanus
authors.forename: David W
authors.initials: DW
authors.lastname: Clow
authors.forename: Jasmine E
authors.initials: JE
authors.lastname: Saros
authors.forename: Verlin C
authors.initials: VC
authors.lastname: Stephens
authors.forename: Donald H
authors.initials: DH
authors.lastname: Campbell
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D001272:Atmosphere / Q000737:chemistry; D017753:Ecosystem; D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis*; D011891:Rain / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D000393:Air Pollutants; D014874:Water Pollutants, Chemical; D009584:Nitrogen