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20
Global Air Pollution: Ozone
Depletion, Acid Deposition,
and Global Warming
Chapter Outline
Stratospheric Ozone Depletion
Activities That Deplete the Ozone Layer
Ozone Depletion - The History of a Scientific Discovery
The Many Effects of Ozone Depletion
Banning CFCs and Other Ozone-Depleting Chemicals: A Global Success Story
Substitutes for Ozone-Destroying CFCs
The Good News and Bad News About Ozone
Acid Deposition: Ending the Assault
What Is an Acid?
What Is Acid Deposition?
Where Do Acids Come From?
The Transport of Acid Precursors
The Social, Economic, and Environmental Impacts of Acid Deposition
Solving a Growing Problem - Short-Term Solutions
Long-Term Sustainable Strategies
Global Warming/Global Climate Change
Global Energy Balance and the Greenhouse Effect
Upsetting the Balance: Global Warming and Global Climate Change
Signs of Global Climate Change: Is the Planet Already Warming?
Predicting the Effects of Greenhouse Gases
The Ecological Impacts of Global Climate Change
Uncertainties: What We Don’t Know
Solving a Problem in a Climate of Uncertainty: Weighing Risks and Benefits
Solving the Problem Sustainably
Key Terms
ozone layer chlorofluorocarbons ultraviolet radiation
acid deposition pH acid
wet deposition acid precursors dry deposition
buffers buffering capacity greenhouse gases
water vapor carbon dioxide nitrous oxide
methane greenhouse effect global warming
global climate change
Objectives
1. List the major activities that deplete ozone and discuss the extent, effects, and prevention of ozone depletion.
2. List the substitutes for ozone-destroying chlorofluorocarbons.
3. Discuss the sources and transport of acid precursors.
4. Summarize the major environmental impacts of acid deposition.
5. List the short-term and long-term solutions to acid deposition.
6. List the major greenhouse gases, their relative contribution to the greenhouse effect, and principle sources.
7. Discuss some of the potential ecological impacts of global climate change due to global warming.
8. Discuss how application of the principles of sustainability could reduce the problem of global warming.
Lecture Outline
Stratospheric Ozone Depletion - The ozone layer in the stratosphere protects life on earth from harmful levels of ultraviolet radiation.
Activities That Deplete the Ozone Layer
Freons
Freons, or CFCs, are used as spray propellants, blowing agents, and coolants. They break down ozone at an alarming rate.
High-Altitude Jets
High speed, high altitude air- and spacecraft emit nitric oxides, which destroy ozone.
Ozone Depletion - The History of a Scientific Discovery
Studies of the ozone layer show substantial declines over the globe, with the highest level of depletion in the southern hemisphere and Antarctica.
The Many Effects of Ozone Depletion
Ozone depletion could seriously affect human health, ecosystems, crops, and materials and finishes.
Banning CFCs and Other Ozone Depleting Chemicals: A Global Success Story
Nations of the world have responded to the threat of ozone depletion; three international treaties have already been signed to eliminate the production of ozone-depleting chemicals.
Substitutes for Ozone-Destroying CFCs
CFCs are being replaced by HCFCs because HCFCs are much less harmful to the ozone layer.
Research continues to find ozone-friendly substitutes.
The Good News and Bad News About Ozone
CFCs take 15 years or so to migrate into the stratosphere after release.
It will take at least 100 years before the ozone levels return to 1985 levels.
Another 100-200 years may be needed to have a complete recovery of the ozone levels in the stratosphere.
Acid Deposition: Ending the Assault - This phenomenon constitutes one of the most serious environmental and economic threats facing us today.
What Is an Acid?
Acids are chemical substances that add hydrogen ions to a solution.
What Is Acid Deposition?
Acid deposition is the deposition of mostly sulfuric and nitric acids from the sky on soils and in bodies of water.
Wet Deposition
Rain, snow, fog, or clouds may deposit acid in wet form.
Dry Deposition
Sulfur and nitrogen oxides may settle directly out of the air or may form particulates that, on surfaces, combine with water to form acids.
Where Do Acids Come From?
Sources for acid precursors are natural and anthropogenic.
Volcanoes, forest fires, and bacterial decay are natural sources of sulfur oxides.
Anthropogenic sources include fossil fuel-fired power plants, motor vehicles, and ore smelters.
The Transport of Acid Precursors
Acid precursors generated in industrial regions may travel hundreds or thousands of kilometers downwind.
The Social, Economic, and Environmental Impacts of Acid Precipitation
Acidification of Lakes
Thousands of lakes and streams in the eastern United States, Canada, and Scandinavia are alarmingly acidified; fish and other aquatic organisms are severely impacted.
Widening the Circle of Destruction
Acid deposition affects aquatic species and all species that depend on the aquatic ecosystem for food.
Forest and Crop Damage
Acid deposition damages forests and crops in many parts of the world. Plants are damaged directly by acids but also indirectly through changes in soil chemistry and soil-dwelling organisms.
Acids: Fertilizing Effect
The sulfur and nitrogen released by the acids in the soil can promote plant growth. Damaging effects of the acid conditions usually outweigh the benefits resulting from their fertilizing effect.
Damage to Materials
Many manmade materials, including culturally valuable artifacts, suffer irreparable or costly damage as a result of acid deposition.
Solving a Growing Problem - Short-Term Solutions
Many stopgap measures have been used to reduce the threat of acid deposition. These include the use of smokestack scrubbers, combustion of low-sulfur or desulfurized coal, and liming lakes to neutralize acidity.
Long-Term Sustainable Strategies
Long-term sustainable strategies include: fuel efficiency, renewable fuels, recycling, population stabilization, and growth management.
Global Warming/Global Climate Change - Scientific evidence suggests that human activities can affect local climate.
Global Energy Balance and the Greenhouse Effect
Ordinarily, the earth's energy input is offset by its energy output, thus, a balance is maintained.
Upsetting the Balance: Global Warming and Global Climate Change
Various natural and anthropogenic gases trap heat in our atmosphere; the accumulation of these greenhouse gases (carbon monoxide, methane, nitrous oxides, and CFCs) is thought to pose a threat of global warming.
The concentrations of greenhouse gases have risen dramatically in the atmosphere in the past 45 years. The increased concentration of these gases is believed to be the cause of the increase in global temperature in the past 30 years.
Signs of Global Climate Change: Is the Planet Already Warming?
Global warming is not science fiction; signs of global warming and climate change have already been observed.
Predicting the Effects of Greenhouse Gases
Global climate models are used by scientists to predict possible climatic effects.
Scientists predict a significant global increase in temperature by the end of the next century.
Global temperature increases could shift rainfall patterns and have a profound effect on food production.
Global warming might also be associated with an increase in the number and severity of storms.
The Ecological Effects of Global Climate Change
Organisms could be profoundly affected by global climate change, particularly if the rate of change exceeds their ability for adaptation.
Uncertainties: What We Don’t Know
Current climate models are not able to predict with accuracy what specific effects global warming will have.
It is possible that warming of the world’s oceans, melting of land-based ice, and the loss of forests may result in a rapid increase in global carbon dioxide and accelerate the warming process. Other factors, however, may offset these changes.
Solving a Problem in a Climate of Uncertainty: Weighing Risks and Benefits
The cost of accepting the greenhouse hypothesis and acting accordingly is far lower than the potential cost of rejecting it.
Solving the Problem Sustainably - Human systems need to be redesigned to foster sustainablility. Applying the principles of sustainability below will reduce the root causes of global warming:
Population Stabilization and Restoration
Recycling, Energy Efficiency, and Renewable Energy
International Cooperation to Halt Global Warming
Suggestions for Presenting the Chapter
Ÿ Instructors should emphasize the global impact of ozone depletion. Students should be aware of their impact concerning this problem.
Ÿ Instructors should examine how unsustainable human systems lead to acid deposition. Students should be encouraged to follow the principles of sustainability outlined in the text.
Ÿ The potential impacts of global warming should be stressed during lecture and class discussions. Students should be encouraged to locate the latest information about global climate change.
Ÿ Students might start monitoring your local air quality as a class project. There may already be a monitoring program in your area that you could participate in.
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