Pub. date: 2011 | Online Pub. Date: May 04, 2010 | DOI: 10.4135/9781412973816 | Print ISBN: 9781412996822 | Online ISBN: 9781412973816| Publisher:SAGE Publications, Inc.About this encyclopedia
Petra A. Zimmermann
The standard composition of a well-mixed atmosphere is approximately 78 percent nitrogen, 21 percent oxygen, 0.93 percent argon, and 0.038 percent carbon dioxide, plus water vapor (spatially and temporally variable) and numerous trace constituents. Because of the negative impacts of poor air quality, such as acid precipitation or compromised human health, an understanding of both normal and disturbed atmospheric conditions is necessary. Air quality is an assessment of the state of the atmosphere that uses a combination of various characteristics describing the ambient atmosphere, including concentration of pollutants, visibility, turbidity, and thermal pollution. Air quality problems are often common to urbanized regions, where people engage in industrial activities, vehicular traffic is concentrated, and other conditions that deteriorate the ambient atmosphere exist. Efforts to mitigate compromised air quality range from international treaties and protocols to local regulations and ordinances. Pollutants that compromise the “clean” characteristics of the air may come from ...