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Black Canyon of the Gunnison National Park Air Quality Information


Black Canyon of the Gunnison National Park, Colorado
Black Canyon of the Gunnison National Park (NP), located in west-central Colorado, was first established as a national monument in 1933 to protect the natural wonders of a canyon that has the “greatest combination of depth, narrowness, sheerness of any canyon in North America.” The park now encompasses 12,159 hectares (30,045 acres). In 1976, a portion of the monument was designated wilderness; the wilderness now includes 6,313 hectares (15,599 acres). Under the Clean Air Act Amendments of 1977, the Black Canyon of the Gunnison Wilderness was named a Class I air quality area, receiving the highest protection under that Act. In 1999 the monument was given national park status. The canyon averages 600 meters (1,969 feet) deep with a maximum depth of 740 meters (2,428 feet), resulting in significant gradients in temperature and vegetation from the canyon rim to the Gunnison River. Rim vegetation is dominated by pinyon/juniper communities and Gambel oak/shrubland. The inner canyon supports Douglas fir, aspen, and numerous shrub species. Along the river, vegetation includes chokecherry, boxelder, and narrowleaf cottonwood.

Both local and distant air pollutant sources affect air quality in Black Canyon of the Gunnison NP. Power plants in Mesa and Montrose counties in Colorado are the largest nearby point sources of sulfur dioxide and nitrogen oxides. Other large power plants in the Four Corners area, and urban areas throughout the Southwest contribute to pollution in the park.

The air quality related values (AQRVs) of Black Canyon of the Gunnison NP are those resources that are potentially sensitive to air pollution, and include vegetation, wildlife, water quality, soils, historic and prehistoric structures and objects, and visibility. There has been no systematic assessment of AQRVs in the park. Visibility is a very sensitive AQRV, and in many parks on the Colorado Plateau visibility is often impaired by light-scattering pollutants (haze). Other AQRVs may also be very sensitive and at risk from air pollution.

Visibility was monitored with an automatic 35mm camera from 1985-1993. At present, data from IMPROVE monitors located throughout the region (e.g., Mesa Verde NP, Canyonlands NP, White River National Forest) are used to characterize conditions at Black Canyon of the Gunnison NP. The U.S. Environmental Protection Agency's Regional Haze regulations require States to establish goals for each Class I air quality area to improve visibility on the haziest days and ensure no degradation occurs on the clearest days. An analysis of 1990-1999 data indicates that visibility in several Colorado Plateau parks, including Mesa Verde NP, Bryce Canyon NP, Petrified Forest NP, and Grand Canyon NP is degrading on the haziest days; in Canyonlands NP, visibility is improving on both the clearest and the haziest days.

Surface waters in Black Canyon of the Gunnison NP are generally well-buffered and, therefore, not likely to be acidified by atmospheric deposition. Most soils are also likely to be well-buffered from acidification. However, there may be areas in the park where rock is resistant to weathering, and soils and water (e.g., in potholes) may be sensitive to inputs of acidic deposition.

Throughout the Southwest there is concern that soils and vegetation may be affected by increasing loads of nitrogen from atmospheric deposition. In some parts of the country, nitrogen deposition has altered soil nutrient cycling and vegetation species composition; native plants that have evolved under nitrogen-poor conditions have been replaced by invasive species better able to utilize nitrogen. Studies that may have applicability to other parks on the Plateau are underway in Canyonlands NP to investigate nitrogen effects on soil dynamics, exotic plant invasiveness, and biological soil crusts.

The NPS Air Resources Division has estimated deposition of sulfur and nitrogen in Black Canyon of the Gunnison NP, using interpolation techniques on data from deposition monitors throughout the Southwest. Although estimates of deposition are relatively low, they are significantly elevated above natural conditions. In many areas of the Southwest, sulfur deposition is decreasing somewhat while nitrogen deposition is increasing.

Several plant species known to be very sensitive to ozone pollution occur in Black Canyon of the Gunnison NP, including Amelanchier alnifolia (serviceberry), Pinus ponderosa (ponderosa pine), and Populus tremuloides (quaking aspen). Because of concerns about high concentrations of ozone throughout the Colorado Plateau and trends of increasing ozone in the area, a portable ozone monitor has been installed in the park (June 2003). Monitoring throughout the region indicates that ozone concentrations and cumulative annual ozone doses fall within a range that may produce visible effects or growth effects on sensitive plant species.

Additional information relative to air quality and air quality related values at Black Canyon of the Gunnison NP is available in D. Binkley et al. 1997. Status of Air Quality and Related Values in Class I National Parks and Monuments of the Colorado Plateau. National Park Service. Denver, CO.

updated on 02/21/2006  I   http://nature.nps.gov/air/permits/aris/BLCA/index.cfm   I  Email: Webmaster