2. Air Resources

3. Air contains substances that all organisms need to survive, including nitrogen, carbon dioxide, hydrogen, helium, methane, ozone, neon, and argon. Air Resources Water vapor can make up as much as five percent of air by volume. For animals, the most important component of air is oxygen.

4. Origin of Oxygen Most organisms on Earth require oxygen or carbon dioxide to maintain their life processes. Air Resources –Scientists hypothesize that 4.6 to 4.5 billion years ago, Earth’s atmosphere included primarily carbon dioxide, nitrogen, and water vapor. –Early life-forms in the seas used carbon dioxide during photosynthesis and released oxygen and water vapor. –Over time, oxygen in the atmosphere built up to levels that allowed the evolution of organisms that required oxygen for life processes.

5. Disrupting Earth’s Cycles The geochemical cycles of Earth’s atmosphere are in a delicate balance. Air Resources –Volcanic eruptions release various gases and dust particles into the atmosphere. –Photosynthetic organisms in the oceans and on land take in and use carbon dioxide and release oxygen. –Other organisms take in this oxygen and release carbon dioxide.

6. Disrupting Earth’s Cycles Human activities that release carbon dioxide into the atmosphere, such as burning fossil fuels, can disrupt the geochemical cycles. Air Resources Global warming, which is the gradual rising of Earth’s average surface temperature, may be one result of the human alteration of the carbon cycle. Deforestation has changed precipitation patterns in the tropical rain forests of the Amazon River Basin.

7. Disrupting Earth’s Cycles In the Amazon River Basin, scientists estimate that 1 hectare (ha, about 2.47 acres) of rain forest is cut down each hour. Nearly 20 million ha of rain forest is destroyed each year worldwide. This graph indicates the fate of the world’s tropical rain forests if the current rate of deforestation continues. Air Resources

8. Disrupting Earth’s Cycles Nitrogen oxides released by human activities are converted to nitric acid, which returns to Earth in acid precipitation. Air Resources Sulfur released into the atmosphere is converted to sulfuric acid, which also forms acid precipitation. Pollutants are substances that can adversely affect the survival, health, or activities of organisms. Air pollution results when pollutants in air occur in quantities that become harmful to human health and the health of the environment.

9. Sources of Air Pollution Air pollution has both natural and human origins. Air Resources –Natural sources of air pollution include volcanic eruptions and forest fires. –Human sources of air pollution include gases, smoke, and dust. –The largest human source of air pollution is the burning of fossil fuels in power plants and motor vehicles. –In some large cities, motor vehicles are responsible for 80 to 88 percent of the air pollution.

10. Sources of Air Pollution When humans inhale harmful gases, the gases can be absorbed by the bloodstream and interfere with various body systems. Air Resources Pollution can also cause burning eyes, irritated throats, and breathing difficulties. As clean air in the troposphere moves across Earth’s surface, it collects both naturally occurring and human-made pollutants.

11. Sources of Air Pollution Transport and Dilution Air Resources –Transport of pollutants downwind from their origin depends upon wind direction and speed, topographical features, and the altitude of the pollutants. –If air movement in the troposphere is turbulent, some pollutants are diluted and spread out, which reduces their concentration.

12. Sources of Air Pollution Transformation and Removal Air Resources –Some pollutants undergo chemical changes, called photochemical changes, that are triggered by reactions with ultraviolet (UV) radiation. –Some air pollutants can undergo physical changes and become heavy enough to fall back to Earth’s surface. –Air pollutants are removed from the atmosphere in precipitation, which includes snow, mist, and fog, as well as rain.

13. Indoor Air Pollution About 90 percent of the furniture sold in the United States also contains formaldehyde, which is just one of the many air pollutants that occurs indoors. Air Resources

14. Indoor Air Pollution “Sick” Buildings Air Resources –Indoor air pollutants have been linked to headaches, coughing, sneezing, burning eyes, nausea, chronic fatigue, and flulike symptoms. –A building is said to be “sick” when these symptoms are experienced by 20 percent of its occupants. –Often, these symptoms disappear when the affected people go outside. –New buildings are more likely to be “sick” than older buildings.

15. Indoor Air Pollution Radon Gas Air Resources –Radon-222 is a colorless, odorless, and tasteless naturally occurring gas produced by the radioactive decay of uranium-238. –Outdoors, radon gas seeps from the ground into the atmosphere, where it is diluted to harmless levels. –Radon gas can enter through cracks in a foundation and build up to high levels indoors. –Once indoors, radon gas decays into radioactive elements that can be inhaled, causing an increased risk of lung cancer.

16. Human Impact on Air Resources Smog is a photochemical haze caused by the action of solar radiation on an atmosphere polluted with hydrocarbons and nitrogen oxides mostly from automobile exhaust systems. Human Impact on Air Resources Ozone (O 3 ), the major chemical in smog, is a gas molecule made up of three oxygen atoms. –Ozone is beneficial in the upper atmosphere because it absorbs and filters out harmful ultraviolet (UV) radiation. –Ground-level ozone irritates the eyes, noses, throats, and lungs of humans, and it also has harmful effects on plants.

17. Human Impact on Air Resources Air pollution also occurs in the form of particulate matter ranging in size from microscopic bits to large grains. Human Impact on Air Resources Particulates can lodge in lung tissues and cause breathing difficulties and lung disease.

18. Global Impacts of Air Pollution Recently, it has become clear that human activities can affect Earth on a global scale. Human Impact on Air Resources The global atmospheric effects of air pollution include global warming, ozone depletion, and acid precipitation.

19. Global Impacts of Air Pollution Global Warming Human Impact on Air Resources –The greenhouse effect is a natural phenomenon in which Earth’s atmosphere traps heat in the troposphere to warm Earth. –Global warming, a phenomenon related to the greenhouse effect, is an increase in Earth’s average surface temperature. –Human activities, especially the burning of fossil fuels, are largely responsible for increased levels of carbon dioxide, which is the main greenhouse gas that causes global warming.

20. Global Impacts of Air Pollution Global Warming Human Impact on Air Resources The amount of atmospheric carbon dioxide has increased greatly since the 1850s. Water vapor: 35% Carbon Dioxide: 51% Methane: 9% Nitrous Oxide: 5%

21. Global Impacts of Air Pollution Global Warming Human Impact on Air Resources –Earth’s mean surface temperature has risen about 0.5°C in the last century. Some scientists predict it may rise by 1 to 3.5°C in the next 100 years as a result of global warming. Other scientists argue that the increase in Earth’s temperature could be part of a natural pattern of climatic change.

22. Global Impacts of Air Pollution Ozone Depletion Human Impact on Air Resources –The ozone layer serves as a protective shield as it absorbs and filters out harmful UV radiation. –Chlorofluorocarbons (CFCs), which were previously used in refrigerators, cleaning agents, and as propellants in aerosol cans, used to contribute to ozone destruction in the upper atmosphere.

23. Global Impacts of Air Pollution Ozone Depletion Human Impact on Air Resources –Since the mid-1980s, atmospheric studies have detected a thinning of the ozone layer, including an “ozone hole” over Antarctica. –Ozone depletion is entirely a result of human activity. –The Montreal Protocol, which 186 countries had signed by 2003, calls for a phase-out in the production and use of most ozone-destroying chemicals by developed countries by the year 2005 and developing countries by the year 2015. –Based on current trends in data, the return to pre-1980 ozone amounts over Antarctica is expected by the middle of this century.

24. Global Impacts of Air Pollution Acid Precipitation Human Impact on Air Resources –Acid precipitation is precipitation with a pH of less than 5.0. –Acid precipitation forms when sulfur dioxide and nitrogen oxides combine with atmospheric moisture to create sulfuric acid and nitric acid. –Although volcanoes and marshes add sulfur gases to the atmosphere, 90 percent of the sulfur emissions in eastern North America are of human origin.

25. Global Impacts of Air Pollution Acid Precipitation Human Impact on Air Resources Automobiles are the greatest source of the nitrogen oxides that cause acid precipitation. Electrical utilities produce most of the sulfur dioxide.

26. Global Impacts of Air Pollution Acid Precipitation Human Impact on Air Resources –Coal-burning power plants in the midwestern United States release large amounts of sulfur dioxide because the coal they burn contains high amounts of sulfur. –When acids are carried into wet weather, they become part of the rain, snow, or fog that falls to the ground in areas far from their source. Acid precipitation causes damage to aquatic ecosystems and affects plants and soil. It also damages stone buildings and statues, and can corrode metal structures.

27. Reducing Air Pollution Solving air pollution problems requires cooperation between multiple governments because pollution travels across borders. Human Impact on Air Resources –There has been an international effort to reduce global air pollution caused by carbon dioxide and CFCs. –In the United States, the 1990 Clean Air Act set specific reduction goals and enforcement policies for many types of air pollution.

28. Reducing Air Pollution The Clean Air Act of 1972 was an attempt to reduce the amount of air pollution in the United States. This graph tracks the emission rates of six major air pollutants over a 30-year period. Human Impact on Air Resources

29. Reducing Air Pollution Many coal-burning power plants have installed a device such as the wet scrubber to reduce emissions of particulate matter and sulfur dioxide. Human Impact on Air Resources

30. Reducing Air Pollution Removing older, highly polluting vehicles from roadways is the most effective way to reduce air pollution. Human Impact on Air Resources –It is estimated that just 10 percent of the motor vehicles in operation produce 50 to 60 percent of the air pollution generated by gasoline-powered engines.