Bryce Canyon National Park Air Quality Information
Both local and distant air pollutant sources affect air quality in Bryce Canyon NP. Nearby large point sources include power plants, refineries, and lime kilns in Coconino County, Arizona, and Clark County, Nevada. Pollutants also travel greater distances to the park from both mobile and point sources throughout the southwest.
The air quality related values (AQRVs) of Bryce Canyon NP are those resources that are potentially sensitive to air pollution, and include vegetation, wildlife, water quality, soils, and visibility. At present, visibility has been identified as the most sensitive AQRV in the park; other AQRVs may also be very sensitive, but have not been sufficiently studied. Although visibility in the park is still superior to that in many parts of the country, visibility in the park is often impaired by light-scattering pollutants (haze).
As part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, visual air quality in Bryce Canyon NP has been monitored using an aerosol sampler (1988-present), and a 35mm camera (1984-present). 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 Bryce Canyon NP is improving on the clearest days, but degrading on the haziest days. Other parks on the Colorado Plateau, including Mesa Verde NP, Petrified Forest NP, and Grand Canyon NP show similar trends of degrading visibility on the haziest days during the 1990-1999 period, while Canyonlands NP shows improvement.
Surface waters in Bryce Canyon NP are expected to be 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.
Soils and vegetation in the park may also be sensitive to nutrient enrichment from nitrogen 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cycling and vegetation species composition; native plants that have evolved under nitrogen-poor conditions have been replaced by invasive species better able to utilize nitrogen.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 are underway in nearby Canyonlands NP to investigate nitrogen effects on soil dynamics, exotic plant invasiveness, and biological soil crusts.
Estimates of total nitrogen and sulfur deposition can be made by adding wet and dry deposition. Wet deposition is monitored in Bryce Canyon NP (1985-present) as part of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). The site ID is UT99. Rates of atmospheric deposition of nitrogen and sulfur in rain are relatively low in Bryce Canyon NP, but elevated above natural conditions. Trend analysis by NADP shows that nitrogen deposition has increased from 1985-present; sulfur deposition has slightly decreased.
Dry deposition is not monitored in Bryce Canyon NP; however, dry deposition rates are monitored in Canyonlands NP and can be used to characterize conditions in Bryce Canyon NP. Dry deposition rates have been estimated for Canyonlands NP (site CAN407), 1995-present, as part of the Clean Air Status and Trends Networks (CASTNet). A CASTNet analysis of site data for 1995-2001 indicates that annual dry deposition rates of nitrogen have remained steady in Canyonlands NP; dry deposition rates of sulfur have decreased slightly.
Several plant species that occur in Bryce Canyon NP are known to be sensitive to ozone, including Sambucus caerulea (blue elderberry), Symphoricarpos oreophilus (snowberry), and Rhus trilobata (skunkbush). Ozone monitoring is not conducted in the park. However, because of concerns about high concentrations of ozone throughout the Colorado Plateau and trends of increasing ozone in the area, an ozone monitor has been installed at nearby Zion NP (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. In 1999, the National Park Service Air Resources Division surveyed vegetation in Bryce Canyon NP and found probable ozone injury on Sambucus caerulea and possible ozone injury on Symphoricarpos oreophilus. Surveys in nearby Cedar Breaks NM and Zion NP also found symptoms of ozone injury on vegetation.
Additional information relative to air quality and air quality related values at Bryce Canyon 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.