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Studies and Monitoring

Yellowstone National Park

Yellowstone National Park (NP), Wyoming/Montana/Idaho, has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring programs at Yellowstone NP focus on visibility; the deposition of nitrogen, sulfur, and mercury; and the impact of snowmobile use in the park. Click on the tabs below to review air quality studies and key scientific references at Yellowstone NP, as well as to access information on air quality monitoring in the park.

  • Studies & Projects
  • Monitoring & Data
  • Key References

Ongoing research in Yellowstone NP, Wyoming/Montana/Idaho:

Winter Air Quality at Yellowstone NP

Since the mid 1970’s, snowmachine use been an increasingly popular winter tourist activity at Yellowstone NP (Yochim 1999 [pdf, 116 KB]). Although park visitation is far lower in the winter than in the summer, over-snow vehicles (OSVs) produce more emissions than cars (NPS 2000 [pdf, 281 KB]). Air pollution related to winter OSVs at the park has primarily been problematic at congested locations such as park entrance stations, rest areas, thermal feature parking lots, and at Old Faithful. find data »    see live webcam »

At times, elevated levels of carbon monoxide (CO), fine particulate matter (< 2.5 micrometers), and hydrocarbons have reached harmful levels at these sites, posing a health risk to visitors and park employees. OSV management changes have been effective in reducing air pollutant levels in the park. Such changes include: lowering numbers of OSVs allowed, requiring OSVs to use best available technology (BAT) to reduce emissions, and modifying entrance station procedures that reduce OSV numbers concentrated in one spot (YELL 2011).

For more information, refer to the following links:

Nitrogen and Sulfur Impacts

Nitrogen and sulfur deposition can be particularly harmful to sensitive ecosystems at the park. Recent analyses indicate that certain high elevation lakes and vegetation communities are at risk from atmospheric deposition (Nanus et al. 2009; Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 12 MB]). Concentrations of ammonium in wet deposition, from regional agricultural activities, are elevated and increasing in the park (NPS 2010 [pdf, 2.8 MB]; Ingersoll et al. 2007). Excess nitrogen can induce fertilization effects, including changes to the species composition of sensitive aquatic and terrestrial communities. find data »

Airborne Toxic, including Mercury, Impacts

Air currents transport toxic contaminants such as mercury from their sources, and deposit these pollutants in rain, snow, and dry deposition (e.g., dust) at Yellowstone NP. Research findings from such studies as the Rocky Mountain Regional Snowpack Chemistry Monitoring Study found mercury in park air, snow, and water (Hall et al. 2006; Ingersoll et al. 2007; Krabbenhoft et al. 2002). Over-snow motor vehicles also emit air toxics including benzene, toluene, and polycyclic aromatic hydrocarbons (PAHs; NPS 2000 [pdf, 281 KB]). Mercury and other heavy metals and air toxics are also emitted naturally from the park’s geothermal features. find data »

Air quality monitoring information and data access:

Air Pollutant/Impact

Monitoring Program

Sites and Data Access

Nitrogen & Sulfur Wet deposition NADP/NTN
Dry deposition CASTNet
Mercury MDN
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
    MDN: Mercury Deposition Network
    NADP: National Atmospheric Deposition Program
    NPS: National Park Service
    NTN: National Trends Network
    VIEWS: Visibility Information Exchange Web System

See current air pollutant and weather data at Old Faithful, Yellowstone NP.

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 Yellowstone NP.

Key air quality related references from Yellowstone NP, Wyoming:

Fenn, M. E., Haeuber, G. S., Tonnesen, J. S., Baron, J. S., Grossman-Clarke, S., Hope, D., Jaffe, D. A., Copeland, S., Geiser, L., Rueth, H. M., and Sickman, J. O. 2003. Nitrogen emissions, deposition and monitoring in the western United States. Bioscience 53: 391–403.

Hall, B. D., Olson, M. L., Rutter, A. P., Frontiera, R. R., Krabbenhoft, D. P., Gross, D. S., Yuen, M., Rudolph, T. M., Schauer, J. J. 2006. Atmospheric mercury speciation in Yellowstone National Park. Science of the Total Environment 367 (1): 354–366.

[IMPROVE] Interagency Monitoring of Protected Visual Environments. 2010. Improve Summary Data. Available at

Ingersoll, G. P., Mast, M. A., Nanus, L., Handran, H. H., Manthorne, D. J., and Hultstrand, D. M. 2007. Rocky  Mountain snowpack chemistry at selected sites, 2004: U.S. Geological Survey Open-File Report 2007—1045, 15 p. Available at

Ingersoll, G. P. 1999. Effects of Snowmobile Use on Snowpack Chemistry in Yellowstone National Park, 1998. U.S. Geological Survey Water Resources Investigation Report 99–4148, 23 pp. Available at (pdf, 660 KB).

Inouye, R. S. 2006. Effects of shrub removal and nitrogen addition on soil moisture in sagebrush steppe. Arid Environments 65: 604–618.

Kohut, R. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the Greater Yellowstone Network. Available at (pdf, 120 KB).

Krabbenhoft, D. P., Olson, M. L., Dewild, J. F., Clow, D. W., Striegl, R. G., Dornblaser, M. M., and VanMetre, P. 2002. Mercury loading and methylmercury production and cycling in high-altitude lakes from the western United States. Water, Air, and Soil Pollution, Focus 2: 233–249.

Nanus, L., Williams, M. W., Campbell, D. H., Tonnessen, K. A., Blett, T., and Clow, D. W. 2009. Assessment of lake sensitivity to acidic deposition in national parks of the Rocky Mountains. Ecological Applications 19(4): 961–973.

Nanus, L., Campbell, D. H., Williams, M. W. 2005. Sensitivity of Alpine and Subalpine Lakes to Acidification from Atmospheric Deposition in Grand Teton National Park and Yellowstone National Park, Wyoming. US Department of the Interior, US Geological Survey, Reston, VA. Scientific Investigations Report 2005—5023. Available at (pdf, 4.0 MB).

[NPS] National Park Service. 2010. Air Quality in National Parks: 2009 Annual Performance and Progress Report. Natural Resource Report NPS/NRPC/ARD/NRR—2010/266. National Park Service, Denver, Colorado. Available at Parks_2009_Final_Web.pdf (pdf, 2.8 MB).

[NPS] National Park Service. 2000. Air Quality Concerns Related to Snowmobile Usage in National Parks. National Park Service, Air Resources Division, Denver, Colorado. Available at (pdf, 281 KB).

Peterson, D. L., Sullivan, T. J., Eilers, J. M., Brace, S., Horner, D., Savig, K., and Morse, D. 1998. Assessment of air quality and air pollutant impacts in national parks of the Rocky Mountains and northern Great Plains. Report NPS/CCSOUW/NRTR—98/19. National Park Service, Air Resources Division, Denver, CO. Chapter 4: Grand Teton National Park. Available at (pdf, 694 KB).

Porter, E. and Johnson, S. 2007. Translating science into policy: Using ecosystem thresholds to protect resources in Rocky Mountain National Park. Environmental Pollution 149: 268–280.

Saros, J. E., Clow, D. W., Blett, T., Wolfe, A. P. 2010. Critical nitrogen deposition loads in high-elevation lakes of the western U.S. inferred from paleolimnological records. Water, Air, and Soil Pollution 216 (1–4): 193–202.

Sullivan, T. J., T. C. McDonnell, G. T. McPherson, S. D. Mackey, and D. Moore. 2011.
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., T. C. McDonnell, G. T. McPherson, S. D. Mackey, and D. Moore. 2011b. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: Greater Yellowstone Network (GRYN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/308. National Park Service, Denver, Colorado. Available at (pdf, 12 MB).

[YELL] Yellowstone National Park. 2011. Scientific Assessment of Yellowstone National Park Winter Use, Draft Report. National Park Service, Yellowstone Center for Resources, Yellowstone National Park, Wyo., YCR—2011-xx.

Yochim, M. J. 2009. The Development of Snowmobile Policy in Yellowstone National Park. Yellowstone Science 7(2): 2–10. Available at (pdf, 116 KB).

Featured Content

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Pollutants including nitrogen, sulfur, mercury, ozone, and fine particles affect resources such as forests, streams, wildlife, and scenic vistas. Find out how on our Yellowstone NP Air Pollution Impacts web page.

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Last Updated: January 03, 2017