Air Quality
For many years, Americans have been concerned about air quality because of its effects on human health and the natural environment. Air-quality problems in the southern Appalachians include increases in ozone concentration, acidity of rain, and decreased visibility (SAMAB 1996). Air quality effects forest productivity, aquatic resources, recreation, and human health. Because of these important impacts, air quality was one of the five major research topics of the Southern Appalachian Assessment. SAMABs air quality technical report (1996) resulted from that assessment.
Degradation of air quality is caused by pollutants. Pollutants are produced in several ways: stationary or point sources such as power-generating plants and industrial facilities; area sources such as dust from roads, open burning, and smoke from fires; or mobile sources such as automobiles, trucks, and aircraft. The chemicals that are released from these sources are called "primary pollutants." The primary pollutants of greatest concern in the southern Appalachians are sulfur dioxide, nitrogen oxides, volatile organic compounds, toxic compounds, and particulate matter. Many of these primary pollutants are transformed in the atmosphere into secondary pollutants, such as ozone, sulfates and nitrates. Secondary pollutants reduce visibility, acidify soils and streams, and injure vegetation. Acid deposition is also linked to nitrogen saturation in several high-elevation forests in the southern Appalachians (SAMAB 1996).
The air quality impacts that are likely to be seen today in the southern Appalachians cannot be traced back to one, or even a few sources of pollution. Instead, pollutants are generated both within as well as outside the region at distances hundreds of miles away. Therefore, airborne emissions and the resulting impacts to forested ecosystems are a regional problem requiring regional solutions. Additional research is needed to better understand air quality issues, impacts, and interactions with ecosystem processes (SAMAB 1996).
The Clean Air Act, along with its Amendments of 1977 and 1990, addresses a large variety of air pollution sources and a number of specific pollutants. The U.S. Environmental Protection Agency maintains National Ambient Air Quality Standards for six common air pollutants: particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, ozone, and lead. Air quality standards are designed at two levels, a primary standard that protects public health and a secondary standard for public welfare. In this case, public welfare means forest and agricultural productivity, stability of ecosystems, transportation safety, maintenance of man-made improvements, and enjoyment of recreational opportunities (SAMAB 1996).
- Sulfur Dioxide : Sulfur dioxide is a gas released into the atmosphere during the combustion of fossil fuels that contain sulfur. In the atmosphere, sulfur dioxide is transformed into secondary pollutants called sulfates. Sulfates are the main contributors to visibility re
- Nitrogen Oxides : Nitrogen oxide can affect visibility, acid deposition, and ground-level ozone. The primary form of nitrogen oxide emissions is nitric oxide. This gas is rapidly converted in the atmosphere, in the presence of volatile organic compounds and sunlight, to ni
- Volatile Organic Compounds : Volatile organic compounds represent a wide range of organic chemicals which are emitted into the atmosphere. Combined with nitrogen dioxide, these chemicals contribute to the formation of ground-level ozone.
- Toxic Air Pollutants : Some compounds produced by human activities, such as chemical-manufacturing and paint-spraying operations, are classified as toxic air pollutants. Toxic compounds are important because they can have severe human health impacts, or impact natural resources
- Particulate Matter : Particulate matter is a leading pollutant responsible for declines in visibility throughout the United States. Particulate matter in the atmosphere includes wind-blown soil, soot, smoke, and liquid droplets.
- Ozone : Ozone is potentially the most significant pollutant affecting forests in North America. Ozone is highly damaging to tissues inside of plant leaves, which it enters through small pores called stomates. Once inside the leaf the ozone is either destroyed by
- Visibility : For visitors and residents, spectacular views are major attractions in the southern Appalachians. However, visibility has deteriorated considerably since the 1940s—with the poorest visibility in the summer, the major tourist season.
- Acid Deposition : High-elevation forests in the southern Appalachians have some of the highest levels of acid deposition in the United States. When raindrops fall through air that contains gaseous oxides of sulphur and nitrogen, these gases can dissolve in the droplets an
- Air Quality Research Needs : The Southern Appalachian Assessment identified the several research and monitoring needs for air quality.
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