Critical Load Development for

Nitrogen and Sulfur Deposition

Elizabeth Waddell

Air Resources Specialist

Pacific West Region

206 220 4287

Elizabeth_waddell@nps.gov

Critical Load Development for

Nitrogen and Sulfur Deposition

Elizabeth Waddell

Air Resources Specialist

Pacific West Region

206 220 4287

Elizabeth_waddell@nps.gov1

• 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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Science WorkshopScience Workshop

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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ParticipantsParticipants

• NPS Science Staff

• USFS

• NWCAA

• PSCAA

• Ecology

• Tribes

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ParticipantsParticipants

“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.” 5

What is a Critical Load?What is a Critical Load?

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What is a Critical Load?What is a Critical Load?

N Deposition (kg/ ha /yr)

Natural background N deposition

Increased NO3 in lakes

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)

• 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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Critical Loads in ActionCritical Loads in Action

http://www.cdphe.state.co.us/ap/rmnp.html

• 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 – Deposition MonitoringCurrent Knowledge – Deposition Monitoring

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Current Knowledge – NADP N Deposition MonitoringCurrent Knowledge – NADP N Deposition Monitoring

0

0.5

1

1.5

2

2.5

3

pre-1880 ONP MRNP NCNP

Low

2004

High

• 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 – N Deposition Monitoring ResearchCurrent Knowledge – N Deposition Monitoring Research

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Current Knowledge – Deposition Modeling ResearchCurrent Knowledge – Deposition Modeling Research

WSU CMAQ preliminary workbased on 36 km grid

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

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Current Knowledge – Deposition Modeling ResearchCurrent Knowledge – Deposition Modeling Research

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 EffectsCurrent 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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Current Knowledge – Ecological EffectsCurrent Knowledge – Ecological Effects

• 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)15

Research PrioritiesResearch 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 PrioritiesResearch 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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Research PrioritiesResearch Priorities

• Quantifying actual deposition

• Adequate to “index” to NADP or other standard monitor

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Not a Research PriorityNot a Research Priority

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Questions?Questions?