Critical Load Development for

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• Critical Load Development for
• Nitrogen and Sulfur Deposition
• Elizabeth Waddell
• Air Resources Specialist
• Pacific West Region
• 206 220 4287
• Elizabeth_waddell_at_nps.gov

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Science Workshop

• Funded by NWCAA
• Co-sponsored by NWCAA, NPS, USFS, and USGS
• Focus on NW WA
• but applicability for
• most of R10

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Participants

• Researchers with expertise in nitrogen and
  sulfur effects on
• Lichens
• Soil chemistry
• Vegetation
• Water chemistry
• Mycorrhizae
• Diatoms
• Deposition monitoring
• Deposition modeling
• Setting critical loads

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Participants

• NPS Science Staff
• USFS
• NWCAA
• PSCAA
• Ecology
• Tribes

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What is a Critical Load?

• the quantitative estimate of an exposure to one
  or more pollutants below which significant
  harmful effects on specified sensitive elements
  of the environment do not occur according to
  present knowledge.

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What is a Critical Load?
N Deposition (kg/ ha /yr)
Natural background N deposition
Changes in tree and soil chemistry
Change in alpine plant species
Change in algal species
Effects on aquatic and terrestrial biota
(episodic or chronic acidification)
Increased NO3 in lakes
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Critical Loads in Action

• Critical load work proceeding at Rocky Mountain
  NP
• 1.5 kg N/ha/yr for eutrophication effects of
  alpine lakes
• Current
• deposition
• is 3-4 kg
• N/ha/yr
• Partnering
• with CDPHE
• to identify
• sources and
• reduce
• emissions

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http//www.cdphe.state.co.us/ap/rmnp.html
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Current Knowledge Deposition Monitoring

• NADP Monitoring
• S deposition declining
• N deposition no trend
• Between 1 and 2 kg/ha/yr
• Does not include dry or occult deposition
• All low elevation sites

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Current Knowledge NADP N Deposition Monitoring
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Current Knowledge N Deposition Monitoring
Research

• Throughfall Monitoring
• Low under canopy
• Lichens absorbing N?
• High in bulk
• deposition
• Inconsistent
• with NADP or CG
• Snowfall
• Comparable to NADP

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Current Knowledge Deposition Modeling Research
WSU CMAQ preliminary work based on 36 km grid
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Current Knowledge Deposition Modeling Research

• Modeling
• Overpredicts dry
• Underpredicts wet
• No cloud
• Limited sensitivity
• analysis

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Current Knowledge Ecological Effects

• Lichens
• Sensitive to air pollution
• N sensitive lichens absent in areas of high
  nitrogen deposition
• Preliminary work with Columbia Gorge throughfall
  monitoring data yields a CL of 2.4 kg/ha/yr
• 2.0 dry deposition
• 0.4 wet deposition

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Current Knowledge Ecological Effects

• Acidification effects
• Nutrient effects of N expected to occur at lower
  deposition rates than acidification effects
• MAGIC model yielded an upper bound CL of 10 kg
  S/ha/yr for acidification of Lake Eunice (Mt.
  Rainier)
• (Recent documentation of episodic acidification
  at Lake Eunice due to snowmelt pulse)

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Research Priorities

• Aquatic Ecosystems
• Mine existing water quality databases to
  identify
• Areas which may already be affected by N or S
  deposition
• Areas which may be sensitive to additional N
• Establish CL for eutrophication of aquatic
  ecosystems using RMNP work as a model (diatoms)

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Research Priorities

• Terrestrial Ecosystems
• Lichens
• Collect lichens from NADP and throughfall
  sites
• Refine deposition modeling and/or conduct
  additional monitoring to better establish a
  deposition gradient and/or use PRISM
• Natural Resources Conservation Service (NRCS)
  soils mapping effort
• Identify sensitive areas (N and Al)

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Research Priorities

• Terrestrial Ecosystems
• Alpine meadows
• Fertilization effects research using RMNP as
  model
• Mycorrhizal diversity
• Similar to lichens in terms of PNW ecological
  importance and diversity.

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Not a Research Priority

• Quantifying actual deposition
• Adequate to index to NADP or other standard
  monitor

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Questions?
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