Chapter 15 Review

chapter 15Review

Key Terms

Learning Objectives Revisited

• Identify and describe the major air pollutants.

  Sulfur oxides, nitrogen oxides, carbon monoxide, carbon dioxide, particulates, and ozone are some of the major ground-level air pollutants. Carbon dioxide was not originally considered one of the major pollutants but, because it alters ecosystems, it is now considered an air pollutant.

• Describe the sources of air pollution.

  Air pollution comes from both natural and human sources. Human activities that release these pollutants or their precursors include transportation, generation of electricity, space heating, and industrial processes.

• Explain how photochemical smog forms and why it is still a problem in the United States.

  Smog forms when sunlight, nitrogen oxides, and volatile organic compounds are present. The secondary pollutant ozone is a major component of photochemical smog. Sulfur is the dominant ingredient in sulfurous smog. Smog impairs respiratory function in human beings. Because of an abundance of both nitrogen oxides and volatile organic compounds, smog occurs during daylight hours in many parts of the world, including the United States.

• Describe how acid deposition forms and why it has improved in the United States and become worse elsewhere.

  Acidic deposition, which is composed of hydrogen, sulfate, and nitrate ions, forms from both sulfur dioxide and nitrogen oxides. Acid deposition is harmful to aquatic organisms and can reduce forest productivity in sensitive ecosystems. Due to reductions in sulfur emissions in the United States, acidic deposition is much less of a problem than it used to be. Asia is a location today where acidic deposition is an environmental problem.

• Explain strategies and techniques for controlling sulfur dioxide, nitrogen oxides, and particulate matter.

  Air pollution is best controlled by increasing the efficiency of processes that cause pollution, thereby reducing emissions, or by removing pollutants from fuel before combustion. After combustion occurs, filters and scrubbers remove pollutants from the exhaust stream before they can be released into the environment. The use of filters and scrubbers is preferable to trying to remove pollutants after they have been distributed throughout the environment.

• Describe innovative pollution control measures.

  Some innovative approaches to pollution control include targeting specific sources of certain kinds of pollution. Allowing for the buying and selling of permits to emit sulfur has been an effective means of reducing sulfur dioxide emissions and subsequent acidic deposition.

• Explain the benefits of stratospheric ozone and how it forms.

  Although ozone is the same gas that is a component of photochemical smog in the troposphere, in the stratosphere it is an important gas that absorbs harmful ultraviolet radiation. Its presence allows for plant and animal life to exist on the surface of Earth.

• Describe the depletion of stratospheric ozone.

  Chlorine-containing compounds such as CFCs that were part of refrigeration and air-conditioning systems lead to a reduction in stratospheric ozone. This reduction drew attention from scientists and the media around the world.

• Explain efforts to reduce ozone depletion.

  International efforts to reduce CFC emissions have helped stratospheric ozone levels to recover. The Montreal Protocol on Substances That Deplete the Ozone Layer is regarded as one of the most successful international agreements of modern times.

• Explain how indoor air pollution differs in developing and developed countries.

  Indoor air pollution is a different kind of problem in developing than in developed countries. Cooking over open fires with inadequate ventilation exposes occupants to carbon monoxide in the developing world. Relatively well-insulated living spaces in the developed world expose occupants to higher concentrations of carbon monoxide, radon, and certain volatile organic compounds.

  549

• Describe the major indoor air pollutants and the risks associated with them.

  Carbon monoxide and particulates are the most harmful aspects of indoor air pollution and account for 4 million deaths annually worldwide. Fifty-six percent of those deaths occur among children less than 5 years of age. Cooking over open fires in the developing world exposes women and children to particulate matter and carbon monoxide pollution.