Saguaro National Park AQRV's
Most surface waters in Saguaro NP are likely to be well-buffered and, as a result, insensitive to acidic atmospheric deposition because of an abundance of base cations in underlying park soils and rocks. However, studies currently underway have identified certain soils in the park that appear to be very sensitive to acidification; small potholes or other waterbodies on these soils may also be vulnerable to acidification. Small potholes may also be sensitive to nutrient enrichment from nitrogen deposition. Nitrogen enrichment may result in algae blooms and oxygen depletion, but no studies have been done to study these potential effects in the park.
While there have been no systematic studies, there is currently no information indicating that wildlife in Saguaro NP are being affected by air pollutants.
Dark night skies are considered an important air quality related value at Saguaro NP, possessing value as a cultural, scenic, natural, and scientific resource. Air pollution and poor quality outdoor lighting degrade night skies, lessening a viewer's ability to see stars and other astronomical objects, and altering the nocturnal scene. Use of high quality lighting that produces very little scattered light can greatly improve the night sky. Reduction of haze from air pollution can also improve the night sky.
Soils in Saguaro NP may be sensitive to atmospheric deposition of nitrogen compounds. In some areas of the country, elevated nitrogen deposition has been shown to alter soil nutrient cycling.
Several species of vegetation in Saguaro NP are known to be sensitive to ozone, including Pinus ponderosa (ponderosa pine), Populus tremuloides (quaking aspen), and Rhus trilobata (skunkbush). Ozone concentrations and cumulative ozone doses are high enough to induce foliar injury to sensitive vegetation under certain conditions. Surveys done in the late 1980s found symptoms of ozone injury on ponderosa pine.
Vegetation in Saguaro NP may also be sensitive to nitrogen deposition. In some parts of the country, excess nitrogen deposition has resulted in changes in species composition and abundance; native plants adapted to nitrogen-poor conditions have been replaced by invasive and exotic species that are able to take advantage of increased nitrogen levels.
- Ozone Sensitive Plant Species Listed by Park
- Ozone Sensitive Plant Species on NPS and U.S. FWS Lands
- Ozone Bioindicators on NPS and U.S. FWS Lands
Visibility is a sensitive AQRV at Saguaro NP. Visibility monitoring in the park has documented frequent visibility impairment (haze) due to fine particle pollution in the area.