Air is a mixture of invisible and odorless gases, mostly nitrogen and oxygen. Water droplets, fine particles, and small amounts of other gases such as carbon dioxide, methane, helium, hydrogen, ozone, and others are also part of the mix. Clean air can not be tasted or smelled. If humidity is very high, a person can 'see the air' - actually they see water vapor surrounding particles.
The atmosphere or air resources found in a park, while less tangible than other natural resources and highly transportable, is nevertheless, an extremely important component of park ecosystems. Many organisms depend on air for respiration. The atmosphere also provides the means for various other vital ecological functions such as transpiration, or the loss of water vapor from the internal spaces of a plant through pores, and evaporation, the change of water from a liquid to a gas, to occur. Atmospheric components and conditions influence plant growth, leaf fall, flight of birds and insects, and distribution of seeds. Clearly air, in its own right, is an important natural resource.
The degradation of air quality by air pollutants is a key concern to park managers at Shenandoah National Park.
One useful reference related to the atmosphere is:
Schaefer, V.J. and J.A.Day. 1981. A field guide to the atmosphere. Houghton Mifflin Company,