Air Quality

Distant mountain view, Saguaro National Park


Both the Clean Air Act and the National Park Service Organic Act protect air resources in national parks. Air quality affects park scenery and vistas, vegetation, water, and wildlife. Two Sonoran Desert Network parks, Chiricahua National Monument and Saguaro National Park, are designated as Class I areas under the Clean Air Act. Air quality standards are stricter in these parks than in other network parks.

Because air quality conditions occur over broad spatial scales, park managers have little direct control over the atmospheric conditions of the parks they manage. However, knowing about the state of—and changes in—air quality can help park managers to make planning decisions, influence off-site emitters of pollutants, and indirectly stabilize or improve park air resources. It can also help the Sonoran Desert Network to understand changes in other vital signs.

Information on air quality at all Sonoran Desert Network parks can be found by visiting the website of the National Park Service Air Resources Division, which tracks spatial and temporal trends in ozone, nitrogen deposition, sulfur deposition, and visibility-reducing pollutants in all units of the National Park System.

The Sonoran Desert Network uses information provided by the Air Resources Division to provide occasional updates on air quality in network parks. For more information, contact the National Park Service Air Resources Division or Andy Hubbard, Program Manager, Sonoran Desert Network.

Air Quality-Related Values

An air quality-related value (AQRV) is a resource that may be adversely affected by a change in air quality. AQRVs include visibility and specific scenic, cultural, physical, biological, ecological, or recreational resources. Research has identified certain AQRVs as sensitive, such as lakes with low acid-buffering capacity and plant species that display injury symptoms at ambient ozone concentrations.

Visibility is a sensitive AQRV affected by air pollution to some degree in every unit of the National Park System. Air pollution affects how far we can see vistas and landscape features, and how well we can see them. Air pollution and light pollution also affect the dark night sky resource, an integral component of visibility.

Vegetation may be sensitive to a variety of air pollutants, including nitrogen, sulfur, and ozone. Nitrogen and sulfur may affect plant growth and species composition. Ozone may cause leaf injury and growth and reproduction effects. Ozone-sensitive plant species have been identified in many parks and are listed in risk assessments that have been conducted to evaluate the risk to vegetation from ozone at park units.

Surface waters and soils are susceptible to acidification, unnatural enrichment, or eutrophication from atmospheric deposition of hydrogen ions, nitrogen and/or sulfur. Water and soils that have evolved under low nutrient conditions, or those with low buffering capacity, are particularly vulnerable. Fish and wildlife are all potentially sensitive to air pollutants, including airborne toxics like mercury and dioxins.

Air pollutants may have a direct effect to fish and wildlife (e.g., mercury neurotoxicity) or an indirect effect to their habitat (e.g., stream acidification).

Air Quality-Related Values of Sonoran Desert Network Parks
Park Visibility Vegetation Surface Waters Soils Fish & Wildlife
Casa Grande Ruins NM X X Unk Unk X
Chiricahua NM X X X X X
Coronado NMem X X Unk Unk X
Fort Bowie NHS X X Unk Unk X
Gila Cliff Dwellings NM X X Unk Unk X
Montezuma Castle NM X X Unk Unk X
Organ Pipe Cactus NM X X X X X
Saguaro NP X X X X X
Tonto NM X X Unk Unk X
Tumacacori NHP X Unk X X X
Tuzigoot NM X X Unk Unk X

Last updated: November 27, 2017


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