Atmospheric Deposition of Nitrogen in Colorado and the Four

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					National Park Service


Atmospheric Deposition of Nitrogen in
 Colorado and the Four Corners Area
                   Ellen Porter
  Air Resources Division – National Park Service
             Ellen Porter@nps gov
             Ellen_Porter@nps.gov


               Air Quality Forum
            Mountain Studies Institute
                  29 May 2008
    Overview


•   Atmospheric Nitrogen (N) Deposition
•   Sources and Transport
•   M it i and Trends
    Monitoring d T d
•   Ecosystem Effects
Sources of airborne nitrogen


 • Combustion sources                                  Misc area sources
                                                              3%
                                                                                 Colorado Nitrogen Emissions

    – NOx from combustion                              Oil and gas
                                                       production
                                                                                                Power plants and
                                                                                                  other point
                                                            5%                                     sources
    – Power plants, vehicles, fires     Agriculture
                                                                                                      26%
                                           25%



 • Agricultural sources
                                              F      fi
                                              Forest fires                                    Motor vehicles
    – NH3 is major nitrogen                      10%
                                                           Biogenic
                                                              6%
                                                                                                  25%

      pollutant
    – Animal waste, fertilizer                                                     Colorado NH3 Emissions

                                                                     Soil and natural
                                                                       vegetation
                                      On-road mobile      Fire             15%
                                           4%             8%                                            Fertilizer
                                      Point sources                                                       22%
                                           1%

                                           Wildlife
                                            7%
                                          Domestic
                                           animals                                Livestock
                                             3%                                      40%


                                 Collettet2008
                                   Aneja al. (2006)
            Particle
            formation, haze,
            ozone formation
                                      NH4   NO3
                               Norg
      NOx



  Norg



NH3
    Air pollutant
    transport

•     Prevailing winds from
      west

•     High and low pressure
      systems can temporarily
      move air east to west
       – Upslope snow storms

•     Mountain-valley winds
      also draw air from eastern
      urban corridor and plains
      up into mountains



    Collett 2008
                                                  Snow sampling: USGS
                                                  Divide-wide Survey


                                                   None of these
                                                   methods measures
Wet deposition sampler: National
                                                   organic N
Atmospheric Deposition Network (NADP)
       Concentration: mg/L or µeq/L
       Deposition: kg/ha/yr

Sampling nitrogen in
atmospheric deposition
           Dry deposition sampler: Clean Air
           Status and Trends Network (CASTNet)*
                    Concentration: µg/m3
                    Deposition: kg/ha/yr
           *Does not measure gaseous NH3
Wet and Dry Deposition Monitors
Relative ammonium ion concentration in   Relative nitrate ion concentration in
snowpack, 2004
         k                               snowpack,
                                         snowpack 2004


                                                          Ingersoll et al. 2007
Change in Nitrate Concentrations in Wet Deposition, 1984-2002




                                                Lehmann et al. 2005
Change in Ammonium Concentrations in Wet Deposition, 1984-2002




                                             Lehmann et al. 2005
Nitrogen deposition may cause
acidification and unwanted enrichment

                                    • Nitrogen enrichment
                                       – alters nutrient cycling
                                       – causes vegetation
                                         species change
                                                 exotics
                                       – Favors exotics,
                                         invasives




  • Acidification (sulfur and
    nitrogen)
     – Reduces buffering capacity
       and pH
     – Leaches nutrients from
         il
       soils
Ecosystem Sensitivity to Nitrogen
Deposition

High sensitivity                  low sensitivity
   •   Short growing season   •   Long growing season
   •   Thin soil              •   Well-developed soils
   •   Sparse vegetation      •   Abundant vegetation
   •   Low productivity       •   High productivity
   •   Examples               •   Examples:
       – Alpine, arid areas       – Lower elevation forests
         (deserts), certain
         g
         grasslands
Nitrogen effects: high-elevation streams
    Nitrate levels increase; productivity increases

                                               Andrews Creek, Loch Vale, RMNP

                      70




                      60



                      50
      trate, μ eq/L




                      40




                      30
    Nit




                      20



                      10
                                       Natural Background Streamwater NO3
                       0
                      Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05
Nitrogen effects: high-elevation lakes
 Increased nitrogen in alpine lakes has caused
• i          in b d          f h t l kt
    increase i abundance of phytoplankton
• species shift in algae indicative of more nutrient-
    rich waters

S di   t        h   lakes have changed more since
Sediment cores show l k h       h    d       i
   1950 than previous 14,000 years

NPS considers this to be a harmful ecosystem
  effect f
    ff t from nitrogen deposition
               it      d      iti                       Critical Load: The amount of
                                                        pollution below which ecosystem
                                                        harm does not occur. (Nilsson and
                                                        Grennfelt 1988)
                                                                      )

                                                        Hindcasting estimated the critical
      1950                                              load for aquatic ecosystem
                                                        eutrophication (enrichment) in Rocky
                                                        Mountain NP is 1.5 kg/ha/yr wet N
                                                        deposition (Baron 2006)
Nitrogen effects: high-elevation forests



                                 6
                           /d)
Mineralization Rate (ug N/g/




                                 5      R2=0.62                                   LV-E
                                                                                                            Nitrogen in vegetation
                                                                        MP-E
                                                                                                   ML-E
                                                                                                            increases; increased
                                 4
                                                                                                            susceptibility to pathogens
                                 3                                         ER-E
                                                                        LL E
                                                                        LL-E            S
                                                                                      EAST

                                 2                                      BP-E

                                                                               GF-W
                                                  BC-W WR-W
                                 1         BR-W
                                         FC W
                                         FC-W                    WA-W
                                                    WEST
                                 0
                                  0.8     0.9        1    1.1   1.2    1.3        1.4        1.5      1.6
                                                          Organic Soil %N


                                 Soil nutrient cycling accelerates;
                                 more plant-available nitrogen
                                 produced
Nitrogen effects: alpine/tundra plant
  communities



             p               g
Shift from alpine flowers to grasses:
Nitrogen favors sedges and grasses in alpine
ecosystems; forbs are out-competed




                            Critical load
                           “Critical load” for species shift in alpine plant community
                           near Rocky Mountain NP is 2.7 kg/ha/yr wet N deposition
                           (Bowman 2006)
Collaborative process to address air quality
concerns at Rocky Mountain National Park

• Memorandum of Understanding (2005) between NPS,
  EPA Region 8 and State of Colorado to address
  harmful impacts to air quality and other natural
  resources in Rocky Mountain National Park.
               dt       t     k        t    lf    it
   – NPS agreed to set park management goal for nitrogen
     deposition, i.e., critical load
   – NPS, EPA, and State agree to develop nitrogen reduction
     plan
Glide path for Nitrogen Deposition
Reductions in the Park



                                                                              critical target load by
                                         Reduce NOx and NH3 emissions to meet interim load by 2032 2012
                       a/yr




                                    Current Deposition
N Deposition (w in kg/ha




                              3.1
                              31
                                                                                     vegetation): (alpine vegetation)
                                                                Critical Load (alpineCritical Load “Interim Target Load”
                              2.7
              wet)




                              1.5                                Critical Load (aquatic ecosystems)
  D




                                                                                          Natural N Deposition
                              0.2
                                           2008




                                                         2012




                                                                                                        2032
 Additional Nitrogen Effects on Plant
 Biodiversity
• Range of species loss from N fertilization > 60% for
  rare species to 10% for common species (analysis of
               responses,          al.
  900 species responses Suding et al 2005)

• MN grasslands: shift from native to non-native
          (Wedin d Til
  grasses (W di and Tilman 1996)

• CA desert: shift from native shrubs and grasses to
      i    di                     l dh d l i l
  exotic Mediterranean grasses; altered hydrological
  regime (Allen et al. 2006)

• Mojave Desert: decrease in native plants,
  increase in alien annual grasses; increased fuel
  for fires (Brooks 2003)
                         Nitrogen (and sulfur) effects:
                         acidification




                     Stream acidification


                                               Forest acidification




Affects fish, amphibians, invertebrates
Reduces cold tolerance in trees
Leaches nutrients from forest soils
Nitrogen and Climate Change



                    ?
                               plants
  Nitrogen can increase some plants’ capacity to
  sequester carbon, to a certain point……………..
          One of Many Stressors
               Elevated nitrogen deposition
                     Causing altered tree
                          physiology




                         Forest
                        Mortality
 Climate Change                                Insects
Reducing carbohydrate                 Causing tree mortality through
      reserves                    colonization and tree girdling by larval
                                                 feeding
                                              from McNulty 2007
 Current Projects

• Alpine lake sediment analysis/Western
  Critical Loads Pilot Project
   – Rocky Mountain NP, Great Sand Dunes NP,
     Glacier NP
• Tundra plant community nitrogen response
   – Rocky Mountain NP, Glacier NP, Grand Teton
     NP
       g     p                 g
• Nitrogen deposition monitoring
   – NADP, CASTNet, snow, throughfall (Rocky
     Mountain NP)
   – The Rocky Mountain Airborne Nitrogen and
     Sulfur (RoMANS) t d
     S lf (R MANS) study
• Synthesis of information on nitrogen critical
  loads for ecosystems across U.S.