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Arches National Park Air Quality Information

Overview

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Arches National Park, Utah
Arches National Park (NP), located in southeastern Utah, Grand County, was first established as a national monument in 1929. In 1971 it was designated a national park and now encompasses 76,519 acres of high desert. In 1977 it was designated a Class I air quality area, receiving the highest protection under the Clean Air Act. Arches NP contains one of the world's largest concentrations of natural rock arches, as well as many spectacular pink and red rock sandstone canyons, fins, slickrock terraces, and pinnacles. The dominant vegetative type is the pinyon/juniper community, followed by blackbrush/shrubland. Biological soil crusts occur widely on undisturbed lands and play an important role as sources of nitrogen for vascular plants and stabilizers of soil surfaces. Ephemeral streams drain into the Colorado River, which forms part of the park's eastern and southern boundaries.

Both local and distant air pollutant sources affect air quality in Arches NP. Power plants in Emery, Uintah, and Carbon counties, Utah, and Mesa County, Colorado, are the largest nearby point sources of both sulfur dioxide and nitrogen oxides. Pollutants also travel greater distances to the park from both mobile and point sources throughout the southwest.

The air quality related values (AQRVs) of Arches NP are those resources that are potentially sensitive to air pollution, and include vegetation, wildlife, water quality, soils, visibility and night skies. 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 Arches NP has been monitored using an aerosol sampler (1988-1992) and 35mm camera (1986-1991). At present, information from visibility monitors in Canyonlands NP (35 km south of Arches NP) is used to characterize conditions in Arches, because of the relative proximity of the two parks. Visual air quality in Canyonlands NP has been monitored using an aerosol sampler (1988-present), a transmissometer (1986-present), and a 35mm camera (1982-1995).

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 Canyonlands NP is improving on both the clearest and the haziest days, suggesting that visibility in Arches NP is also improving. Other parks on the Colorado Plateau, including Mesa Verde NP, Bryce Canyon NP, Petrified Forest NP, and Grand Canyon NP show trends of degrading visibility on the haziest days during the 1990-1999 period.

Surface waters in Arches NP are generally well-buffered and, therefore, not likely to be acidified by atmospheric deposition. Soils are also likely to be well-buffered from acidification. There has been concern that the park’s small pothole aquatic systems, because of their small size, might be sensitive to episodic inputs of acidic rainfall. A 1988 acidification experiment, however, concluded that sediments and suspended particles in the small rock pools tended to buffer introduced acidity rapidly. It was noted that most of the experimental systems were located on sandstone bedrock; rock pools located on bedrock more resistant to weathering could be more susceptible to acid inputs.

Although the small potholes may be insensitive to acidic deposition, they may experience nutrient enrichment from nitrogen deposition, resulting in algae blooms and oxygen depletion. Soils in the park may be similarly affected by nitrogen enrichment. In some parts of the country, nitrogen deposition has degraded water quality and altered soil nutrient cycling and vegetation species composition. There is no information available on the effects of nitrogen deposition on waters or soils in the park. However, studies are underway in nearby Canyonlands NP to investigate nitrogen effects on soil dynamics, exotic plant invasiveness, and biological soil crusts.

Information from wet (i.e., rain, snow) and dry (i.e., dust, dryfall) deposition samplers at Canyonlands NP can be used to characterize conditions in Arches NP. Wet deposition is monitored in Canyonlands NP (1997-present) as part of the National Atmospheric Deposition Program/National Trends Network (NADP/NTN). The site ID is UT09. Rates of atmospheric deposition of nitrogen and sulfur in rain are relatively low in Canyonlands NP, but elevated above natural conditions. The data record is insufficient for a detailed trends analysis. Other Colorado Plateau NADP monitoring sites show decreasing trends in wet sulfur deposition from 1990-1999; for wet nitrogen deposition, some sites show a decreasing trend, while others show an increasing trend. Dry deposition rates are estimated for Canyonlands NP (site CAN407), 1995-present, as part of the Clean Air Status and Trends Networks (CASTNet). Data indicate that, for the period 1999-2001, dry deposition contributed about 60 percent of total inorganic nitrogen deposition and about 50 percent of total sulfur deposition. A CASTNet analysis of site data for 1995-2001 indicates that annual dry deposition rates of nitrogen have remained steady; dry deposition rates of sulfur have decreased slightly.

Several plant species that occur in Arches NP are known to be sensitive to ozone (e.g., Rhus trilobata) although the specific genotypes found in the park have not been tested under controlled conditions for sensitivity. Tropospheric (ground-level) ozone concentrations were monitored in the park from 1987-1992, and are currently monitored in Canyonlands NP, 1992-present. An analysis of the data indicates that ozone concentrations have significantly increased in the park. The observed concentrations in Canyonlands NP fall within a range that may produce visible effects or growth effects on sensitive plant species under certain conditions. It is likely that ozone concentrations in Arches NP are similar. No signs of injury from air pollution have been reported for vegetation in either park; however, systematic surveys for ozone injury have not been conducted. A 1999 survey in Bryce Canyon NP, Cedar Breaks NM, and Zion NP found symptoms of ozone injury on vegetation at all three parks.

Additional information relative to air quality and air quality related values at Arches 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/ARCH/index.cfm   I  Email: Webmaster