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Studies and Monitoring

Great Smoky Mountains National Park

Great Smoky Mountains National Park (NP) in North Carolina and Tennessee, has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring at Great Smoky Mountains NP focus on: nitrogen and sulfur deposition, ozone, and mercury. Click on the tabs below to review air quality studies and key scientific references at Great Smoky Mountains NP, as well as to access information on air quality monitoring in the park.

  • Studies & Projects
  • Monitoring & Data
  • Key References

Ongoing research in Great Smoky Mountains NP, North Carolina/Tennessee:

Science Assessments at Great Smoky
Mountains NP

In 1992, a notice was published in the Federal Register, the U.S. government’s official newspaper, stating that existing air pollution levels were causing adverse impacts on terrestrial, aquatic, and visibility resources at Great Smoky Mountains NP and that any increase in emissions from new or expanding power plants, along with existing emissions, would be deemed to contribute to and exacerbate those adverse impacts (Shaver et al. 1994). Partially as a result of the notice, collaborative efforts were undertaken, one of which was the Southern Appalachian Mountains Initiative (SAMI)—a regional, multi-organizational initiative charged to remedy existing impacts and to prevent future adverse effects of air pollution on the Southern Appalachians. The SAMI Final Report (pdf, 9.0 MB) was issued in August 2002 with several key findings relevant to Great Smoky Mountains NP, most notably that significant emission reductions will be required to reverse existing adverse impacts on park resources. VISTAS, the Visibility Improvement State and Tribal Association of the Southeast, is an example of another collaborative effort of state governments, tribal governments, and various federal agencies established to initiate and coordinate activities associated with the management of regional haze, visibility, and other air quality issues in the Southeastern U.S., including Great Smoky Mountains NP.

Nitrogen & Sulfur Impacts

Acidification of high elevation sensitive soils and streams results from the combined impact of nitrogen and sulfur deposition at Great Smoky Mountains NP. A number of streams in the park have been designated as "impaired" by the State of Tennessee because of acidification. Researchers are currently investigating the amount of reduction in acid deposition needed to restore and protect acidified streams (more »). Research on park soils, which are also affected, found that, in some areas, deposition exceeds the "critical load" for both acidification (from nitrogen and sulfur) and excess fertilization (from nitrogen alone) (Pardo and Duarte 2007 [pdf, 1.54 MB]). Besides contributing to acidification, excess nitrogen can cause imbalances in natural ecosystems by stimulating growth of invasive plant species that out compete native species and eventually decrease biodiversity. Given previously identified concerns, other research includes that of the Appalachian Trail Atmospheric Deposition Effects Study, which plans to conduct research at numerous sites within Great Smoky Mountains NP, as well as other sites along the Trail, to assess ecosystem response to acid deposition in sensitive ridge top areas and determine critical loads for forests, soils, and streams.

Ground-Level Ozone Impacts

Ground-level ozone at Great Smoky Mountains NP sometimes exceeds standards set by the U.S. Environmental Protection Agency to protect public health and vegetation. Up to 90% of black cherry trees and tall milkweed plants in the park exhibit symptoms of ozone damage in high ozone years (Chappelka et al. 1997). Both ozone concentrations and plant damage increase with elevation in the park (Chappelka et al. 1999). In controlled studies, leaf injury occurred on over thirty park species exposed to ozone levels similar to those found in the park (Neufeld et al. 1991). In high ozone years, growth declined seasonally by 30–50 percent in many tree species (McLaughlin et al. 2007a). In addition, affected trees used available water less efficiently, resulting in decreased late summer soil moisture and streamflow in areas of the park (McLaughlin et al. 2007b).

Mercury Monitoring Projects

Toxic airborne mercury deposits into ecosystems at Great Smoky Mountains NP and may affect fish and wildlife. Studies show that most mercury in the air comes from burning coal for power production. Effects from mercury in the park can be attributed to both nearby coal-fired plants as well as more distance sources (Valente et al. 2007). While wet mercury deposition is monitored at the park, research is needed to evaluate the effects of mercury upon fish, birds, and other organisms at the park (NPCA 2006 [pdf, 73.7 KB]).

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
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

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 Great Smoky Mountains NP.

Key air quality related references from Great Smoky Mountains NP, North Carolina and Tennessee:

Chappelka, A., Renfro, J., Somers, G., and Nash, B. 1997. Environmental Pollution 95: 13–18.

Chappelka, A., Skelly, J., Somers, G., Renfro, J., and Hildebrand, E. 1999. Mature Black Cherry used as a Bioindicator of Ozone Injury. Water, Air, and Soil Pollution 116: 261–266.

Cole, D.W. 1992. Nitrogen Chemistry, Deposition, and Cycling in Forests. In Atmospheric Deposition and Forest Nutrient Cycling. D.W. Johnson and S.E. Lindberg (Eds.). Springer-Verlag, New York: New York.

Copeland, S.A., Pitchford, M., and Ames, R. 2008. Regional Haze Rule Natural Level Estimates Using the Revised IMPROVE Aerosol Reconstructed Light Extinction Algorithm. Final Paper #48. Available at
(pdf, 183 KB).

Eager, C. and Adams, M.B. 1992. Ecology and decline of red spruce in the eastern United States. Springer-Verlag, New York: New York.

[EPA] U.S. Environmental Protection Agency. 2003. Guidance for Tracking Progress Under the Regional Haze Rule. EPA-454/B-03-004. U.S. EPA Office of Air Quality Planning and Standards, Research Triangle Park, NC.

Herlihy, A., Kaufmann, P., Stoddard, J., Eshleman, K., and Bulger, A. 1996. Effects of acid deposition on aquatic resources in the Southern Appalachians with a special focus on Class I Wilderness areas. Report to the Southern Appalachian Mountains Initiative. 92 pp.

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

Johnson, D.W., Van Miegroet, J., Lindberg, S.E., Todd, D.E., and Harrison, R.B. 1991. Nutrient cycling in red spruce forests in Great Smoky Mountains. Canadian Journal of Forest Research 21:769–787.

Li, Z., and Aneja, V.P. 1992. Regional analysis of cloud chemistry at high elevations in the eastern United States. Atmospheric Environment 26A(11): 2001–2017.

Lovett, G.M., Reiners, W.A., and Olson, R.K. 1982. Cloud droplet deposition in subalpine balsam fir forest: Hydrological and chemical inputs. Science 218: 1303–1304.

[MADPro] Mountain Acid Deposition Program. 2007. Cloud deposition monitoring, Clingmans Dome, TN, Great Smoky Mountains National Park. U.S. Environmental Protection Agency, Clean Air Markets Division, Office of Air and Radiation, Washington, D.C.

McLaughlin, S.B., Nosal, M., Wullschleger, S.D., and Sun, G. 2007a. Interactive effects of ozone and climate on tree growth and water use in a southern Appalachian forest in the USA. New Phytologist 174: 109–124.

McLaughlin, S.B., Wullschleger, S.D., Sun, G., and Nosal, M. 2007b. Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Appalachian forest in the USA. New Phytologist 174:125–136.

Neufeld, H.S., Renfro, J.R., Hacker, W.D., and Silsbee, D. 1991. Ozone in Great Smoky Mountains National Park: Dynamics and Effects on Plants. in proc. Trophospheric Ozone and the Environment II. R. L. Berglund ed. A.W.M.A. 594–617.

[NPCA] National Parks Conservation Association. 2006. Recommendations for a Smokies Mercury Study. Letter to the State of Tennessee Department of Environment and Conservation.

[NADP] National Atmospheric Deposition Program. 2000. Annual & Seasonal Data Summary for Site TN11. Available at

Pardo, L. and Duarte, N. 2007. Assessment of Effects of Acidic Deposition on Forested Ecosystems in Great Smoky Mountains National Park using Critical Loads for Sulfur and Nitrogen. NPS Final Report. Available at (pdf, 1.54 MB).

[SAMI] Southern Appalachians Mountains Initiative. 2002. Final Report. 145 pp. Available at (pdf, 9.0 MB).

Shaver, C.L., Tonnessen, K.A., and Maniero, T.G. 1994. Clearing the air at Great Smoky Mountains National Park. Ecological Applications 4: 690–701.

Somers, G.L., Chappelka, A.H., Rosseau, P., and Renfro, J.R. 1998. Empirical evidence of growth decline related to visible ozone injury. Forest Ecology and Management 104:129–137. 

Stoddard, J. 1994. Long-term changes in watershed retention of nitrogen: its causes and aquatic consequences. Pgs 223–284 in Environmental chemistry of lakes and reservoirs. L. A. Baker (ed). American Chemical Society, Washington, D.C.: USA.

Valente, R.J., Shea, C., Humes, K.L. and Tanner, R.L. 2007. Atmospheric mercury in the Great Smoky Mountains compared to regional and global levels. Atmospheric Environment 41:1861–1873.

Featured Content

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Pollutants including sulfur, nitrogen and ozone affect resources such as streams, soils, and scenic vistas. Find out how on our Great Smoky Mountains NP Air Pollution Impacts web page.

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Last Updated: January 03, 2017