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Studies and Monitoring

North Cascades National Park

North Cascades National Park (NP), Washington, has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring programs at North Cascades NP focus on nitrogen and sulfur deposition, toxic air contaminants, and visibility. Click on the tabs below to review air quality studies and key scientific references at North Cascades NP, as well as to access information on air quality monitoring in the park.

  • Studies & Projects
  • Monitoring & Data
  • Key References

Ongoing research in North Cascades NP, Washington:

Centralia: A Source of Nitrogen, Sulfur, and Mercury Pollution at North Cascades NP

Located approximately 225 km from North Cascades NP in Centralia, WA, TransAlta’s Centralia Power Plant is one of the largest stationary sources of atmospheric nitrogen, sulfur, and mercury in the region. These pollutants are emitted through the coal-burning process used to generate electricity at the power plant. Retrofit technologies have been installed to better control sulfur dioxide and nitrogen oxide emissions, and noticeable reductions in sulfate have followed. Control of mercury emissions is currently achieved via existing controls for sulfur dioxide and nitrogen oxides. The National Park Service currently requests better nitrogen oxide emission controls and continues discussions with other agencies and the owners of Centralia Power Plant.

Nitrogen & Sulfur Impacts

Nitrogen emissions in the Pacific Northwest remain a concern for park managers (Fenn et al. 2003 [pdf, 895 KB]). North Cascades NP receives elevated nitrogen deposition as compared to other sites in the region, resulting in increased surface water nitrate concentration. In conjunction with sulfur deposition, resulting effects could include acidification during rain-on-snow events. Anthropogenic nitrogen inputs also have the potential to unnaturally fertilize aquatic and terrestrial ecosystems (Clow and Campbell 2008 [pdf, 2.12 MB]). For instance, nitrogen deposition exceeds the critical load for lichen community composition in some polluted areas of the Pacific Northwest. As a result, in the Columbia River Gorge and the Willamette Valley, sensitive lichen species important to wildlife have declined and been replaced by pollution-tolerant species (Geiser and Neitlich 2007; Geiser et al. 2010). The critical load for lichens is not exceeded in the park and lichen communities remain diverse, containing many pollution-sensitive species. However, nitrogen deposition in the park is approaching levels known to affect alpine lakes and plant communities. A research study will evaluate nitrogen critical loads for alpine vegetation in the park. North Cascades NP continuously monitors nitrogen and sulfur deposition. Find data »

Airborne Toxic Contaminants Impacts

Air currents transport contaminants such as pesticides, industrial pollutants, and heavy metals from their sources, and deposit these toxics in rain, snow, and dryfall at North Cascades NP. The Western Airborne Contaminants Assessment Project found airborne contaminants, and in particular high concentrations of current-use pesticides, in air and vegetation samples from the park. Additional research found changes in metabolic, endocrine, and immune response-related genes in fish from contaminated lakes when compared to fish from uncontaminated lakes (Moran et al. 2007). The Pacific Northwest Contaminants Workshop addressed regional concerns regarding contaminant distribution and effects. Additional research is examining whether contaminants disrupt reproductive organs in park fish.

Ground-Level Ozone Impacts

The Puget Sound urban zone influences ozone concentrations at North Cascades NP (Brace and Peterson 1998; Barna et al. 2000), while trans-Pacific episodes also transport ozone and ozone-forming pollutants to the west coast of North America (Jaffe et al. 2003). The nearby metropolitan areas of Seattle and Vancouver contribute to occasional increased ozone levels recorded at the park (Eilers et al. 1994 [pdf, 520 KB]). However, ozone levels remain relatively low. Potential effects of elevated ozone on sensitive vegetation have not been documented. North Cascades NP continuously monitors ozone. Find data »

Visibility Impacts

The PREVENT (Pacific Northwest Regional Visibility Experiment Using Natural Tracers) study found that sulfur is the largest contributor to reduced visibility at North Cascades NP. Back trajectories indicate that sulfur dioxide emissions from the Centralia Power Plant are a significant contributor to sulfate levels at the park. Urban sources of sulfur are also significant. Nitrates, also contributing to visibility impairment, mostly result from nitrogen oxide emissions from pulp and paper mills, power plants, transportation, and fires (Malm et al. 1994). Better nitrogen oxide emission controls at the Centralia power plant would improve visibility at the park. North Cascades NP continuously monitors fine particles and visibility. find data »

Air quality monitoring information and data access:

Air Pollutant/Impact

Monitoring Program

Sites and Data Access

Nitrogen Wet deposition NADP/NTN
Dry deposition CASTNet
Toxics WACAP
Visibility IMPROVE

Abbreviations in the above table:

    CASTNet: EPA Clean Air Status and Trends Network
    GPMP: Gaseous Pollutant Monitoring Program
    IMPROVE: Interagency Monitoring of Protected Visual Environments
    NADP: National Atmospheric Deposition Program
    NPS: National Park Service
    NTN: National Trends Network
    VIEWS: Visibility Information Exchange Web System
    WACAP: Western Airborne Contaminants Assessment Project

For more information regarding monitoring and data assessments conducted by the National Park Service, link to the NPS Air Quality Monitoring Program or to the NPS Air Quality Monitoring History Database for a history of active and inactive monitoring sites at North Cascades NP.

Key air quality related references from North Cascades NP, Washington:

Barna, M., Lamb, B., O’Neill, S., Westberg, H., Figueroa-Kaminsky, C. Otterson, S., Bowman, C., and DeMay, J. 2000. Modeling Ozone Formation and Transport in the Cascadia Region of the Pacific Northwest. Journal of Applied Meteorology 39: 349–366.

Basabe, F. A., Edmonds, R. L., Chang, W. L., and Larson, T. V. 1989a. Fog and cloudwater chemistry in Western Washington. In: Olson, R. K. and Lefohn, A. S. (eds.) Symposium on the effects of air pollution on western forests. June 1989. Anaheim, CA. Air and Waste Management Association. pp. 33–49.

Brace, S. and Peterson, D. L. 1998. Spatial Patterns of Tropospheric Ozone in the Mount Rainier Region of the Cascade Mountains, U.S.A. Atmospheric Environment 32(21): 3629–3637.

Clow, D. W. and Campbell, D. H. 2008. Atmospheric deposition and surface-water chemistry in Mount Rainier and North Cascades National Parks, U.S.A., water years 2000 and 2005–2006: U.S. Geological Survey Scientific Investigations Report 2008—5152, 37 pp. Available at (pdf, 2.12 MB).

Eilers, J. M., Rose, C. L., Sullivan, T. J. 1994. Status of Air Quality and Effects of Atmospheric Pollutants on Ecosystems in the Pacific Northwest Region of the National Park Service. NPS Final Report. 255 pp. Available at (pdf, 520 KB).

Fenn, M., Geiser, L., Peterson, J., Waddell, E., and Porter, E. 2003. Why Federal Land Managers in the Northwest are Concerned about Nitrogen Emissions. National Park Service. 18 pp. Available at (pdf, 895 KB).

Geiser, L. H., Jovan, S. E., Glavich, D. A., Porter, M. K. 2010. Lichen-based critical loads for atmospheric nitrogen deposition in Western Oregon and Washington Forests, USA. Environmental Pollution 158: 2412–2421.

Geiser, L. and Neitlich, P. 2007. Air pollution and climate gradients in western Oregon and Washington indicated by epiphytic macrolichens. Environmental Pollution 145: 203–218.

Jaffe, D., McKendry, I., Anderson, T., Price, H. 2003. Six ‘new’ episodes of trans-Pacific transport of air pollutants. Atmos. Envir. 37: 391–404.

Landers, D. H., Simonich, S. M., Jaffe, D., Geiser, L., Campbell, D. H., Schwindt, A., Schreck, C., Kent, M., Hafner, W., Taylor, H. E., Hageman, K., Usenko, S., Ackerman, L., Schrlau, J., Rose, N., Blett, T., Erway, M. M. 2010. The Western Airborne Contaminant Assessment Project (WACAP): An Interdisciplinary Evaluation of the Impacts of Airborne Contaminants in Western U.S. National Parks. Environmental Science and Technology 44: 855–859.

Landers, D. H., S. L. Simonich, D. A. Jaffe, L. H. Geiser, D. H. Campbell, A. R. Schwindt, C. B. Schreck, M. L. Kent, W. D. Hafner, H. E. Taylor, K. J. Hageman, S. Usenko, L. K. Ackerman, J. E. Schrlau, N. L. Rose, T. F. Blett, and M. M. Erway. 2008. The Fate, Transport, and Ecological Impacts of Airborne Contaminants in Western National Parks (USA). EPA/600/R—07/138. U.S. Environmental Protection Agency, Office of Research and Development, NHEERL, Western Ecology Division, Corvallis, Oregon. Available at

Larson, G. L., Lomnicky, G., Hoffman, R., Liss, W. J., and Deimling, E. 1999. Integrating physical and chemical characteristics of lakes into the glacially influenced landscape of the Northern Cascade Mountains, Washington State, U.S.A. Environmental Management 24(2): 219–228.

Malm, W. C., Gebhart, K. A., Molenar, J., Eldred, R., Harrison, H. 1994. Pacific Northwest Regional Visibility Experiment Using Natural Tracers—PREVENT. National Park Service Final Report. Available at

Moran P. W., Aluru, N., Black, R. W., Vijayan, M. M. 2007. Tissue contaminants and associated transcriptional response in trout liver from high elevation lakes of Washington. Environ Sci Technol. 41(18): 6591–6597.

Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011a. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/313. National Park Service, Denver, Colorado. Available at

Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., Moore, D. 2011b. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: North Coast and Cascades Network (NCCN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/330. National Park Service, Denver, Colorado. Available at (pdf, 7.4 MB).

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Pollutants including nitrogen, toxics, ozone, and fine particles affect resources such as streams, soils, and scenic vistas. Find out how on our North Cascades NP Air Pollution Impacts web page.

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Last Updated: January 03, 2017