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Studies and Monitoring

Shenandoah National Park

Shenandoah National Park (NP) in Virginia has its own unique environmental concerns based on its particular ecology. Air quality studies and monitoring at Shenandoah NP focus on acidic deposition, ozone, mercury, visibility, and atmospheric transport. Click on the tabs below to review air quality studies and key scientific references at Shenandoah NP, as well as to access information on air quality monitoring in the park.

  • Studies & Projects
  • Monitoring & Data
  • Key References

Ongoing research in Shenandoah NP, Virginia:

Science Assessments at Shenandoah NP

In 1990, the Assistant Secretary for Fish, Wildlife, and Parks published a notice in the Federal Register, the U.S. government’s official newspaper, that emissions from proposed new or modified power plants, along with existing emissions, would adversely affect visibility, aquatic, and terrestrial resources at Shenandoah NP (more »). 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 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 Shenandoah NP, and follow up work suggesting that the percent of potentially acid-sensitive streams having chemistry that is chronically unsuitable for brook trout would increase slightly between 1995 and 2040 under all except the most restrictive emissions control strategy (Sullivan et al. 2004). Conclusions from “The Shenandoah Assessment,” (pdf, 10.3 MB) a comprehensive report regarding the effect of various emission reduction scenarios on visibility, aquatic and terrestrial resources at Shenandoah NP (overview summary [pdf, 1.8 MB]), are consistent with the SAMI findings that significant emission reductions will be required to reverse existing adverse impacts on park resources.

Sulfur & Nitrogen Impacts

Shenandoah NP is a leader among the national parks with respect to park-specific knowledge of acidic deposition effects and watershed ecosystem conditions in general due to extensive monitoring, research and assessment activity pertaining to acidic deposition effects on sensitive surface waters in the park. The park has the longest continuous record of streamwater composition in a national park, dating back to 1979 (Shenandoah Watershed Study—Virginia Trout Stream Sensitivity Study).

Sulfur deposition, and to a lesser degree nitrogen deposition, has been high enough to cause the acidification of many streams within Shenandoah NP, with associated harmful impacts on fish, aquatic insects, and other life forms. Research on park waters found that, in some areas, deposition exceeds the “critical load” for acidification (from sulfur), and deposition would have to be decreased substantially in order to improve and maintain acid-sensitive streams, expected to protect against ecological harm (Sullivan et al. 2003 [pdf, 10.3 MB]).

Given the established concern, current research efforts regarding sulfur and nitrogen include the Appalachian Trail Atmospheric Deposition Effects Study to assess ecosystem response to acid deposition in sensitive ridgetop areas and determine critical loads for Trail resources, including forests, soils, and streams, with research conducted at numerous sites within Shenandoah NP and other sites along the Trail. A separate but related project will analyze existing data from Shenandoah NP’s monitoring programs in an effort to better link water chemistry and effects on biota.

Ground-Level Ozone Impacts

Ground-level ozone at Shenandoah NP sometimes exceed standards set by the U.S. Environmental Protection Agency to protect public health and vegetation. Because elevated levels of ozone and the resultant damage to plants has been documented at the Shenandoah NP, park managers are concerned and continue to work on a variety of programs related to monitoring, research, and emissions reductions.

Mercury Monitoring Projects

Toxic airborne mercury deposits into ecosystems at Shenandoah NP and may affect fish and wildlife in the park. Recent research reported that a population of tree swallows at the headwaters of the Shenandoah River had elevated mercury levels (Brasso and Cristal 2008), with possible reduced reproductive success. Most anthropogenic airborne mercury is a result of burning coal for power production. While wet mercury deposition is monitored at the park, research is needed to evaluate the effects of mercury on fish, birds, and other organisms at the park.

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
Mercury NADP/MDN

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 Shenandoah NP.

Key air quality related references from Shenandoah NP, Virginia:

Brasso, R. L. and Cristol, D. A. 2008. Effects of mercury exposure on the reproductive success of tree swallows (Tachycineta bicolor). Ecotoxicology 17:133–141.

Bulger, A. J., Cosby, B. J. Dolloff, C. A., Eshleman, K. N., Webb, J. R., and Galloway, J. N. 1999. The “Shenandoah National Park: Fish in Sensitive Habitats (SNP: FISH)” An Integrated Assessment of Fish Community Responses to Stream Acidification. National Park Service Final Report. 570 pp. Available at Fish/Shen Fish.htm.

Duchelle, S. F., J. M. Skelly, and B. I. Chevone. 1982. Oxidant effects on forest tree seedling growth in the Appalachian Mountains. Water Air Soil Pollut. 18: 363–373.

Duchelle, S. F., J. M. Skelly, T. L. Sharick, B. I. Chevone, Y-S. Yang, and J. E. Nellessen. 1983. Effects of ozone on the productivity of natural vegetation in a high meadow of the Shenandoah National Park of Virginia. J. Environ. Manage. 17:299–308.

Hildebrand, E., Skelly, J. M., and Fredericksen, T. S. 1996. Foliar response of ozone-sensitive hardwood trees species from 1991 to1993 in Shenandoah National Park, Virginia. Can. J. For. Res. 26: 658–669.

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

Moeykens, M. D. and Voshell, J. R. 2002. Studies of Benthic Macroinvertebrates for the Shenandoah National Park Long-Term Ecological Monitoring System: Statistical Analysis of LTEMS Aquatic Dataset from 1986 to 2000 on Water Chemistry, Habitat and Macroinvertebrates. Report to Shenandoah National Park from the Dept. of Entomology, Virginia Polytechnic and State University, Blacksburg, VA. 49 pp.

[NAPAP] National Acid Precipitation Assessment Program. 1998. Biennial Report to Congress: An Integrated Assessment. National Acid Precipitation Assessment Program: Silver Spring, MD.

Rice, K. C., Deviney, Jr., F. A., Hornberger, G. M., Webb, J. R. 2005. Predicting the Vulnerability of Streams to Episodic Acidification and Potential Effects on Aquatic Biota in Shenandoah National Park, Virginia. U.S. Geological Survey SIR 2005–5259: Reston, VA. Available at (pdf, 5.7 MB).

[SAMI] Southern Appalachian Mountains Initiative. 2002. Final Report. Asheville, NC. Available at (pdf, 9.0 MB).

Sullivan, T. J., Cosby, B. J., Herlihy, A. T., Webb, J. R., Bulger, A. J., Snyder, K. U., Brewer, P. F., Gilbert, E. H., and Moore, D. L. 2004. Regional model projections of future effects of sulfur and nitrogen deposition on streams in the southern Appalachian Mountains. Water Resources Research 40(2): 401–416.

Sullivan, T. J., Cosby, B. J., Laurence, J. A., Dennis, R. L., Savig, K., Webb, J. R., Bulger, A. J., Scruggs, M., Gordon, C., Ray, J., Lee, E. H., Hogsett, W. E., Wayne, H., Miller, D., and Kern, J. S. 2003. Assessment of Air Quality and Related Values in Shenandoah National Park. National Park Service Technical Report NPS/NERCHAL/NRTR—03/090. NPS Northeast Region: Philadelphia, PA. Available at (pdf, 10.3 MB).

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: Mid-Atlantic Network (MIDN). Natural Resource Report NPS/NRPC/ARD/NRR—2011/330. National Park Service, Denver, Colorado. Available at (pdf, 7.4 MB).

Webb, J. R., Cosby, B. J., Deviney, Jr., F. A., Galloway, J. N., Maben, S. W., and Bulger, A. J. 2004. Are brook trout streams in western Virginia and Shenandoah National Park recovering from acidification? Environmental Science and Technology 38: 4091–4096.

Welsch, D. L., Webb, J. R., and Cosby, B. J. 2001. Description of Summer 2000 Field Work: Collection of Soil Samples and Tree Corps in the Shenandoah National Park with Summary Soils Data. Dept. of Environ. Sciences: Univ. of Virginia.

Winner, W. E., Lefohn, A. S., Cotter, I. S., Greitner, C. S., Nellessen, J., McEvoy, Jr., L. R., Olson, R. L., Atkinson, C. J., and Moore, L. D. 1989. Plant responses to elevational gradients of ozone exposures in Virginia. Proceedings National Academy of Sciences 86: 8828–8832.

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

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Last Updated: January 03, 2017