Sonoran Desert Network
The Sonoran Desert Vital Signs Network (SODN) includes 11 national park units in Arizona and New Mexico: Casa Grande Ruins National Monument (NM), Chiricahua NM, Coronado National Memorial (NMEM), Fort Bowie National Historic Site (NHS), Gila Cliff Dwellings NM, Montezuma Castle NM, Organ Pipe Cactus NM, Saguaro National Park, Tonto NM, Tumacacori National Historic Park (NHP), and Tuzigoot NM. SODN has a great diversity of ecosystems, from desert and thornscrub lowlands to high-elevation forests. Its geographical diversity and climate have produced a wide variety of biotic communities.
Chiricahua NM and Saguaro NP are Class I air quality areas, receiving the highest protection under the Clean Air Act. The other park units are Class II air quality areas and receive protection under the Act, but to a lesser degree. Air quality issues of concern in the Sonoran Desert Network include nitrogen deposition effects, ozone injury to vegetation, and visibility impairment from fine particle haze. Nitrogen deposition can cause changes in soil that affect soil microorganisms, plants, and trees. Excess nitrogen deposition can cause changes in plant community structure and diversity, with native species being replaced by invasive and exotic species. Ozone is also a concern for network park units. An ozone injury risk assessment indicates the risk of injury to vegetation is moderate in Montezuma Castle NM, Organ Pipe Cactus NM, and Tonto NM; the remainder of the park units in the network have a low risk rating.
Chiricahua NM, Gila Cliff Dwelling NM, Organ Pipe Cactus NM, and Saguaro NP have on-site air quality monitoring. The other park units have no nearby monitoring.
The Network map below provides information on air quality monitoring. Ozone, sulfur dioxide, dry deposition, and meteorology are collected by the Clean Air Status and Trends (CASTNet) and Gaseous Pollutant Monitoring (GPMN) networks. Ozone is also monitored with passive samplers and portable continuous analyzers. Wet Deposition is monitored through cooperation with National Atmospheric Deposition Program/National Trends Network (NADP/NTN). The Mercury Deposition Network (MDN), part of NADP, collects precipitation samples that are analyzed for mercury. Visibility is monitored as part of the Interagency Monitoring of Protected Visual Environments (IMPROVE). Additional details on these parameters are described in Air Quality Monitoring.
Air quality monitoring in or near the network is indicated on the map by symbols, with the blue line showing the approximate borders of the network. The legend shows the symbols for the type of monitoring present, with NPS park units in green. Class I areas have linkable access to ARIS information.