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Studies and Monitoring

Voyageurs National Park

Voyageurs National Park (NP), Minnesota, has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring programs at Voyageurs NP focus on the deposition and effects of mercury and other air toxics, as well as wet and dry deposition of nitrogen and sulfur, ozone, and visibility. Click on the tabs below to review air quality studies and key scientific references at Voyageurs NP, as well as to access information on air quality monitoring in or near the park.

  • Studies & Projects
  • Monitoring & Data
  • Key References

Ongoing research in Voyageurs NP, Minnesota:

Addressing Mercury at Voyageurs NP: A Case Study on Dams

Lake levels in the park’s large lakes have been controlled by dams since the early 1900s (Kallemeyn et al. 2003 [pdf, 11.3 KB]). The resultant water level fluctuations create a favorable environment for mercury methylation by elevating activity of sulfate-reducing bacteria. High levels of mercury in fish are correlated to frequent water level fluctuations in lakes (Sorensen et al. 2005). Because of mercury bioavailability, and other concerns, the park worked with U.S. and Canadian representatives to develop a consensus approach to managing the waters. As a result, the International Joint Commission (IJC) began a new water management regime that considered ecosystem health (Kallemeyn et al. 2003 [pdf, 11.3 KB]). Results are positive. In the case of bald eagle nestlings, mercury levels in feathers declined from the mid-1980s to the late 1990s/2000, a trend attributed to the stabilization of water levels in large lakes in the park (Rowe 2001).

This kind of cooperation and other tactics—including appropriate regulatory and voluntary action— have helped reduce the mercury problem (Cain et al. 2011). However, mercury pollution remains a major concern in the Great Lakes region (Evers et al. 2011a [pdf, 8.3 MB]; Weiner et al. 2011). Some observations, including that of mercury levels in feathers of bald eagle nestlings at the park (Pittman et al. 2011), indicate recent increases. Further controlling air emission sources would likely lead to lower mercury concentrations in aquatic food webs yielding multiple benefits to fish, wildlife, and people in the region.

Airborne Toxic Impacts

Over three decades of scientific studies at Voyageurs NP indicate elevated concentrations of many contaminants, specifically mercury, in numerous ecosystem components at the park (Kallemeyn et al. 2003 [pdf, 11.3 KB]; Swackhamer and Hornbuckle 2004 [pdf, 4.5 MB]). Bald eagle feathers, blood, and eggs have been monitored for contaminants since 1973 (Pittman et al. 2011 [pdf, 1.8 MB]). Concentrations of mercury in fish and loons are at levels known to cause reproductive impairment (NPS 2010 [pdf, 337 KB]; Sorensen et al. 2001; Sandheinrich et al. 2011; Evers et al. 2011b; Evers et al. 1998; Scheuhammer and Blancher 1994). While the park is in a remote location on the Minnesota-Canada border, nearby and distant sources contribute to the deposition of toxics at the park. The abundance of wetlands, low pH lakes, complex food webs, and predatory fish create an environment susceptible to bioaccumulation of these contaminants. Concentrations of mercury in fish exceed thresholds established for human health (MN-DNR 2011), a concern as many park visitors fish in Voyageurs NP.

A variety of projects monitor air toxics and impacts in or near Voyageurs NP. The University of Wisconsin-La Crosse assesses contaminants (especially mercury) in fish, larval dragonflies, zooplankton, water, and sediment in the park’s Brown, Peary, Ryan, and Sand Point lakes to better understand the transfer of contaminants through aquatic food webs and to identify where concentrations of measured contaminants may be harmful to fish, wildlife, or fish-eating humans (Issue Brief [pdf, 211 KB]; NPS 2010 [pdf, 337 KB]). In collaboration with the U.S. Geological Survey, the NPS Inventory & Monitoring Network also assesses mercury in water samples from Brown, Ek, Peary, Ryan, and Shoepack lakes (Elias and Damstra 2011 [pdf, 2.1 MB]). Additionally, the Minnesota Department of Natural Resources and the Minnesota Pollution Control Agency monitor fish at the park and issue statewide fish consumption guidance (pdf, 1.3 MB). There are many ongoing multi-agency, binational efforts, including: The Great Lakes Binational Toxics Strategy, Great Lakes Air Deposition Program (GLAD), Regional Air Pollutant Inventory Development System (RAPIDS), and Great Lakes Mercury Connections (Biodiversity Research Institute, the Great Lakes Commission, and the University of Wisconsin-La Crosse): four-page summary (pdf, 3.9 MB) or the full report (pdf, 8.3 MB). These efforts are all improving understanding of contaminant pollution in the Great Lakes region and using partnerships to address the problem.

Nitrogen and Sulfur Impacts

Nitrogen (N) and sulfur (S) deposition at the park can be particularly harmful to sensitive boreal lakes and soils. The low buffering capabilities of granitic rock and thin soils place the boreal ecosystem at high risk from acidification effects (Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 2.3 MB]). Boreal lakes may also be sensitive to nutrient effects from excess N enrichment (Sullivan et al. 2011c; Sullivan et al. 2011d [pdf, 6.2 MB]). Current water quality monitoring at Voyageurs NP being used to investigate changes to sensitive aquatic communities over time (Elias and Damstra 2011 [pdf, 2.1 MB]). Shifts in community composition may be due to climate change or other stressors like N and S deposition.

Ammonium concentrations in precipitation in the Great Lakes region have increased in recent decades (Lehmann et al. In Prep), increasing the risk of N impacts in the park. Additionally, recent proposals for a new power plant, a copper processing facility, and a combined taconite processing-steel making facility in northern Minnesota also raise concerns about the potentail for additional emissions of N, S, and mercury from future development find data »

Air quality monitoring information and data access:

Air Pollutant/Impact

Monitoring Program

Sites and Data Access

Toxics & Mercury IADN
  • Two sites on Lake Superior: Brule River, WI and Eagle Harbor, MI
Nitrogen & Sulfur Wet deposition NADP/NTN
Dry deposition CASTNet
Visibility IMPROVE

Abbreviations in the above table:

    CASTNet: EPA Clean Air Status and Trends Network
    GPMP: Gaseous Pollutant Monitoring Program
    IADN: Integrated Atmospheric Deposition 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

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 Voyageurs NP.

Key air quality related references from Voyageurs NP, Minnesota:

Bennett, J. P. and Wetmore, C. M. 1997. Chemical element concentrations in four lichens on a transect entering Voyageurs National Park. Environmental and Experimental Botany 37: 259–277.

Caine, A., Morgan, J. T., and Brooks, N. 2011. Mercury policy in the Great Lakes states: past successes and future opportunities. Ecotoxicology 20: 1500–1511.

Elias, J. E. and Damstra, R. A. 2011. Monitoring water quality of inland lakes, Great Lakes Network, 2009 and 2010: Data summary report. Natural Resource Data Series NPS/GLKN/NRDS—2011/163. National Park Service, Fort Collins, Colorado. Available at (pdf, 2.1 MB).

Evers, D. C., Kaplan, J. D., Meyer, M. W., Reaman, P. S., Braselton, W. E., Major, A., and Burgess, N., Scheuhammer, A. M. 1998. Geographic trend in mercury measured in common loon feathers and blood. Environmental Toxicology & Chemistry 17 (2): 173–183.

Evers, D. C., Wiener, J. G., Driscoll, C. T., Gay, D. A., Basu, N., Monson, B. A., Lambert, K. F., Morrison, H. A., Morgan, J. T., Williams, K. A., and Soehl, A. G. 2011a. Great Lakes Mercury Connections: The Extent and Effects of Mercury Pollution in the Great Lakes Region. Biodiversity Research Institute. Gorham, Maine. Report BRI 2011—18. 44 pp. Available at (pdf, 8.3 MB).

Evers, D. C., Williams, K. A., Meyer, M. W., Scheuhammer, A. M., Schoch, N., Gilbert, A., Siegel, L., Taylor, R. J., Poppenga, R., and Perkins, C. R. 2011b. Spatial gradients of methylmercury for breeding common loons in the Laurentian Great Lakes region. Ecotoxicology 20: 1609–1625.

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

Kallemeyn, L. W., Holmberg, K. L., Perry, J. A., and Odde, B. Y. 2003. Aquatic Synthesis for Voyageurs National Park: U.S. Geological Survey, Information and Technology Report 2003—0001. 95 pp. Available at (pdf, 11.3 KB).

Kohut, R. 2004. Assessing the Risk of Foliar Injury from Ozone on Vegetation in Parks in the Great Lakes Network. Available at (pdf, 187 KB).

Lehmann C. M. B. and Gay, D. A. 2011. Monitoring Long-Term Trends of Acidic Wet Deposition in U.S. Precipitation: Results from the National Atmospheric Deposition Program. PowerPlant Chemistry 13 (7): 386–393.

Lehmann, C. M. B., Gay, D. A., and Bowersox, V. C. (in preparation). Trends in NADP/NTN Precipitation Chemistry and Wet Deposition, 1985–2009. Illinois State Water Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign, IL.

[MN-DOH] Minnesota Dept. of Health. 2012. Fish Consumption Advice.Site-specific meal advice for tested lakes and rivers available at

[NPS] National Park Service. 2010. Monitoring Persistent Contaminants at Voyageurs. Resource Brief, Great Lakes Network. Available at (pdf, 337 KB).

Pittman, H. T. 2010. Using Nestling Bald Eagles to Assess Temporal and Spatial Trends of Environmental Contaminants, Voyageurs National Park, Minnesota. MS Thesis, Clemson University. Available at (pdf, 1.1 MB).

Pittman, H. T., Bowerman, W. W., Grim, L. H., Grubb, T. G., and Bridges, W. C. 2011. Using nestling feathers to assess spatial and temporal concentrations of mercury in bald eagles at Voyageurs National Park, Minnesota, USA. Ecotoxicology 20: 1626–1635. Available at (pdf, 1.8 MB).

Rowe, A.S. 2001. The Development of an Avian Biosentinel Program for Michigan using the Bald Eagle (Haliaeetus leucocephalus). MS Thesis, Clemson University.

Sandheinrich, M. B., Bhavsar, S. P., Bodaly, R. A., Drevnick, P. E., Paul, E. A. 2011. Ecological risk of methylmercury to piscivorous fish of the Great Lakes region. Ecotoxicology 20: 1577–1587.

Scheuhammer, A. M. and Blancher, P. J. 1994. Potential risk to common loons (Gavia immer) from methylmercury exposure in acidified lakes. Hydrobiologia 279/280: 445–455.

Simcik, M. F. and Dorweiler, K. J. 2005. Ratio of Perfluorochemical Concentrations as a Tracer of Atmospheric Deposition to Surface Waters. Environmental Science and Technology. 39(22): 8678–8683.

Sorensen, J. A., Kallemeyn, L. W., Sydor, M. 2005. Relationship between Mercury Accumulations in Young-of-the-Year Yellow Perch and Water-Level Fluctuations. Environmental Science and Technology. Environmental Science & Technology 39 (23): 9237–9243.

Sorenson, J. A., Rapp Jr., G., Glass, G. E. 2001. The effect of exotic rainbow smelt (Osmerus mordax) on nutrient/trophic pathways and mercury contaminant uptake in the aquatic food web of Voyageurs National Park, a benchmark study of stable element isotopes. NPS Final Report. 52 pp.

Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., Moore, D. 2011a. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: main report. Natural Resource Report NPS/NRPC/ARD/NRR—2011/349. National Park Service, Denver, Colorado. Available at

Sullivan, T. J., McPherson, G. T., McDonnell, T. C., Mackey, S. D., and Moore, D. 2011b. Evaluation of the sensitivity of inventory and monitoring national parks to acidification effects from atmospheric sulfur and nitrogen deposition: Great Lakes Network (GLKN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/356. National Park Service, Denver, Colorado. Available at (pdf, 2.3 MB).

Sullivan, T. J., McDonnell, T. C., McPherson, G. T., Mackey, S. D., and Moore, D. 2011c. 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., and Moore, D. 2011d. Evaluation of the sensitivity of inventory and monitoring national parks to nutrient enrichment effects from atmospheric nitrogen deposition: Great Lakes Network (GLKN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/309. National Park Service, Denver, Colorado. Available at (pdf, 7.4 MB).

Swackhamer, D. L. and Hornbuckle, K. C. 2004. Assessment of Air Quality and Air Pollutant Impacts in Isle Royale National Park and Voyageurs National Park. NPS Report. Available at (pdf, 4.5 MB).

Wiener, J. G., Evers, D. C., Gay, D. A., Morrison, H. A., and Williams, K. A. 2012. Mercury contamination in the Laurentian Great Lakes region: introduction and overview. Environmental Pollution 161: 243–251.

Wiener, J. G., Knights, B. C., Sandheinrich, M. B., Jeremiason, J. D., Brigham, M. E., Engstrom, D. R., Woodruff, L. G., Cannon, W. F., and Balogh, S. J. 2006. Mercury in soils, lakes, and fish in Voyageurs National Park (Minnesota): Importance of atmospheric deposition and ecosystem factors. Environmental Science & Technology 40 (20): 6261–6268.

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Pollutants including mercury and other toxics, nitrogen, sulfur, ozone, and fine particles affect resources such as wildlife, lakes, soils, and scenic vistas. Find out how on our Voyageurs NP Air Pollution Impacts web page.

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Last Updated: January 03, 2017