Pollution of the Atmosphere LESSON 2 Guiding Question: What Are the Sources of Air Pollution?

Pollution of the Atmosphere LESSON 2 Guiding Question: What are the sources of air pollution?

• Explain how both natural processes and human Reading Strategy Before you read, make a three-column activities can cause air pollution. KWL chart. In the first column, write what you already know • Describe how air pollutants affect human health. about air pollution. In the second column, write what you want • Explain what causes smog and how temperature to learn. After reading, complete the chart by filling in what inversions affect it and other forms of air pollution. you have learned in the third column. • Explain how acid deposition occurs and describe Vocabulary air pollution, emission, fossil fuel, its effects. primary air pollutant, secondary air pollutant, smog, temperature inversion, acid deposition

CROWDED TOGETHER, the horses in the parade seem to be fight- ing for space. The horse in the forefront is rearing, possibly frightened by the other horses and riders nearby. The rider, in contrast, appears calm as 15.2 LESSON PLAN PREVIEW he looks off into the distance. Thousands of years ago, in ancient Athens, Inquiry Students research the Greek sculptors created this parade in marble to go at the top of the health effects of air pollutants. Parthenon, a temple that honored the goddess Athena. Real World Students predict Today the parade of warriors no longer graces the Parthenon. Instead, how increasing public transpor- the sculptures are inside a museum in Athens. The sculptures were moved tation use might affect a city’s smog levels. to protect them from more damage. One cause of damage was pollutants Differentiated Instruction in the air. If you look carefully at Figure 10, you can see that some of the Less proficient readers organize stone has been worn away. information about the sources and effects of acid deposition.

15.2 RESOURCES Scientific Method Lab, Acid Rain and Seeds • Outdoors Lab, What’s in the Air? • Lesson 15.2 Worksheets • Lesson 15.2 Assessment • Chapter 15 Over- view Presentation

GUIDING QUESTION FOCUS Divide the class into small groups and have each group sit in a circle. Have one student in each circle name a source of air pollution. Then, have the student to his or her right name another source. Have them continue around the circle naming different sources until the group runs out of ideas.

FIGURE 10 Damage From Air Pollution Notice that the warriors’ faces have been worn away. The damage was caused partly by air pollution.

The Atmosphere 461 FIGURE 11 Dust Storm Over a field in Africa, wind blows dust particles into Sources of Air Pollution the air. Air pollution can be caused by natural processes and human activities.

The cars, trucks, and industries of modern Athens have released pollutants that have contributed to the damage to the Parthenon. Both human activities and natural processes cause outdoor air pollution, which is the release of damaging materials into the atmosphere. The substances released are called emissions. Some emissions, such as smoke and soot, consist of tiny particles, or particulate matter. Others are gases such as sulfur dioxide and carbon monoxide.

Natural Processes Natural processes produce a great deal of the world’s air pollution. Winds sweeping over dry land can create huge dust storms, as seen in Figure 11. Winds sometimes blow dust across oceans from one continent to another. Volcanic eruptions release tiny solid particles and gases into the atmosphere. Fires in forests and grasslands also produce smoke, soot, and gases. Human activities can make some natural pollution worse. For example, some farming and grazing practices strip most plants from the soil. When there are few plant roots to hold soil in place, wind erosion may occur. Wind erosion can lead to dust storms. BIG QUESTION Human Sources People’s activities have influenced air quality. The How can we ensure everyone has way we live—for example, our industries, the cars we drive, and the way clean air to breathe? we produce electricity—has introduced many sources of air pollution. Air Perspective After students have read about human sources of air pollu- pollution can come from point sources or nonpoint sources. In London, tion, reread the following sentence: power plants and factories act as point sources of emissions. Millions of Most air pollution comes, directly or cars and trucks together make up a moving nonpoint source. indirectly, from the combustion of Most air pollution comes, directly or indirectly, from the combustion fossil fuels. Have students write a of fossil fuels. Fossil fuels are carbon-containing fuels that formed mil- paragraph or two explaining how this statement affects their answer to lions of years ago from the remains of living things. Motor vehicles, such the Big Question. as cars and trucks, run by burning fossil fuels. Motor vehicles release an enormous amount of pollutants into the air.

462 Lesson 2 Primary and Secondary Air Pollutants Pollutants may do harm directly, or they may cause chemical reactions that produce harmful compounds. Primary air pollutants, such as soot and carbon monoxide, are pollutants released directly into the troposphere. Primary air pollutants may cause damage themselves, or they may react with other products to cause damage. Harmful products produced when primary air pollutants react chemically with other substances are called secondary air pollutants. Secondary air pollutants include tropospheric ozone and sulfuric acid. The table in Figure 12 describes some primary and secondary air pollutants.

FIGURE 12 Air Pollutants Primary air pollutants are released directly into the troposphere. Secondary air pollutants, in contrast, are the products of chemical reactions between primary air pollutants and other substances.

Primary Air Pollutants Pollutant Source E ect Carbon monoxide (CO) The incomplete combustion (burning) Binds to hemoglobin, the oxygen- A colorless, odorless gas of fossil fuels by motor vehicles, carrying chemical in blood; deprives industries, and other sources cells of oxygen

Sulfur dioxide (SO2 ) Burning of fossil fuels, especially coal, Produces secondary pollutants that A colorless gas with a strong, unpleasant odor for electricity generation and industry are part of acid precipitation; causes lung irritation

Nitrogen dioxide (NO2 ) A reaction between atmospheric Can cause serious lung irritation; A foul-smelling, reddish-brown gas that belongs nitrogen and oxygen in combustion contributes to smog and acid to a family of compounds called nitrogen oxides engines and during the production of precipitation electricity Volatile organic compounds (VOCs) Many sources, including vehicle engines, Some can cause cancer; some Carbon-containing chemicals that evaporate household cleaning products, some interact with other chemicals to easily, producing fumes. Examples include industrial processes, and natural produce ozone in the troposphere. methane, propane, butane, and benzene. processes Particulate matter Dust blown by wind; soot and chemicals Can aect breathing and damage Solid or liquid particles that are small enough to produced by res and combustion lungs oat in the atmosphere—soot, dust, tiny bits of within engines; particles produced metals during construction and farming Lead Industrial renement of metals; in Can damage body tissues, including A heavy metal that is one type of particulate developing nations, gasoline contains those in the nervous system matter lead

Secondary Air Pollutants Pollutant Source E ect

Tropospheric ozone (O3 ) Results from the interaction of sunlight, Ozone in the stratosphere protects A colorless gas with an unpleasant odor heat, nitrogen oxides, and volatile humans from radiation, but ozone organic compounds in the troposphere can injure living tissues and cause respiratory problems.

Sulfuric acid (H2SO4 ) and nitric acid (HNO3 ) Produced when sulfur dioxide and Components of acid precipitation nitrogen oxides combine with water in the atmosphere

The Atmosphere 463 FIGURE 13 Effects of Air Pollution A runner in the Beijing Olympic Games wears a mask to protect his respiratory system from air pollution. Beijing has severe air pollution. Before the 2008 Olympic Games, the city made a major effort to clean its air.

How Air Pollutants Affect Your Health Air pollutants can damage the respiratory system, interfere with the body’s uptake of oxygen, and cause cancer.

Outdoor air pollution is a big health problem. Air pollutants can do serious harm to the respiratory system, which transports oxygen into your body and removes carbon dioxide. Some air pollutants can cause cancer.

Respiratory System Problems Have you ever inhaled dust and then started coughing? Particles in the dust irritated your respiratory system, making you cough. Similarly, air pollutants irritate people’s air passages and lungs. If people are exposed over and over to air pollution, they may develop harmful respiratory conditions. Asthma, bronchitis, and emphy- sema have all been linked to air pollutants.

The Effect of Carbon Monoxide How do the cells of your body obtain the oxygen they need? The air that you inhale contains oxygen. This oxygen passes from the lungs into the bloodstream. There, oxygen binds to hemoglobin. Hemoglobin is a molecule in red blood cells that combines chemically with oxygen. The red blood cells then carry the oxygen to the cells of the body. However, if there is carbon monoxide in the air, the carbon monoxide will bind to hemoglobin, replacing some of the oxygen that the blood would normally carry. Therefore, carbon monoxide interferes with your body’s ability to deliver oxygen to cells. This can cause headaches, tired- ness, and nausea. Over time, carbon monoxide can damage the heart because the heart muscle has to work harder than normal to deliver oxygen to cells. In high concentrations, carbon monoxide can be fatal.

Cancer Trace amounts of some air pollutants may contribute to cancer. Soot, for example, can cause cancer if it is inhaled frequently. Benzene, which is a volatile organic compound in gasoline, has also been linked to cancer. Exhaust from cars and trucks contains benzene.

464 Lesson 2 What Do you think?

Smog and Temperature Inversions Temperature inversions may trap smog close to the surface of What Do Earth, preventing the pollutants from dispersing. you think? If you combine the words smoke and fog, you get the word smog. Smog Should your city, or a city near is an unhealthy mixture of air pollutants that may form over cities and you, start a congestion-charging nearby areas. program like London’s? What are Industrial Smog The smog that covered London in 1952 was indus- some of the pros and cons of such trial smog. Industrial smog is produced when soot combines with sulfur a program? compounds and water droplets in air. Because of government regulation, this type of smog is far less common in developed nations than it was 50–100 years ago. However, the situation is different in developing nations, ANSWERS such as China and the nations of Eastern Europe. Industrial technologies What Do You Think? Answers will in these nations are often older than those in developed nations, and have vary. Students should identify logical less ability to control pollution than do newer technologies. Also, there pros and cons. is less government regulation of air quality in these nations. Therefore, Reading Checkpoint For pho- industrial smog continues to create health problems in many areas. tochemical smog to form, light is necessary. Industrial smog can form Photochemical Smog A photochemical process is one that needs without light. light. Photochemical smog is a thick, brownish haze that forms when Figure 14 Burning coal sunlight acts on certain air pollutants, such as nitrogen oxides and chemicals called hydrocarbons. Tropospheric ozone is often the most abundant pollutant in photochemical smog. Ozone in the troposphere is chemically identical to ozone in the stratosphere. However, unlike ozone in the stratosphere, which protects living things by filtering ultraviolet light, tropospheric ozone can damage living tissue—especially eye and lung tissues and plant leaves—as well as other materials. The main source of the pollutants in photochemical smog is the FIGURE 14 Photochemical exhaust released by cars and trucks. Governments are acting to reduce Smog Smog shrouds the borough of Manhattan in New York City. Relate motor-vehicle emissions, which will reduce photochemical smog. For Cause and Effect What was the main example, vehicle inspection programs make drivers fix cars and trucks source of the pollutants that caused that release high levels of pollutants. London’s “killer smog” in 1952? Reading What is the difference between industrial smog and Checkpoint photochemical smog?

The Atmosphere 465 Temperature Inversions Recall that in the troposphere, air temperature usually decreases as altitude increases. Earth’s surface warms the air at low altitudes. Since warm air rises, any pollutants in the air are car- ried away from the surface and higher into the troposphere. This process removes pollutants from low altitudes and helps them disperse. The situation is different, however, when a temperature inversion occurs. A temperature inversion, or thermal inversion, is the condition in the troposphere in which a layer of cooler air is located beneath a layer of warmer air. Since cold air has a greater density than warm air, the air at Earth’s surface does not rise and mix with the air higher up. Therefore, temperature inversions can keep air pollutants, including those found in smog, from going away. Figure 15 shows how a temperature inversion can worsen air pollution. It was a thermal inversion that caused London’s “killer smog” of 1952. Inversions regularly cause smog buildup in some ANSWERS cities, such as Los Angeles and Mexico City. Reading Checkpoint During a tem- Reading During a temperature inversion, why doesn’t air at Earth’s perature inversion, the air at Earth’s Checkpoint surface rise? surface is colder than the air above it. Cold air has a greater density than warm air, so the cold air does not rise and mix with the air above it. Cool High Figure 15 A temperature inversion can trap pollutants, including those in smog, near the ground. Vertical Surface mixing warmed by sun Altitude Temperature

Low Warm (a) Normal Conditions

Cool High

Warm Inversion layer

FIGURE 15 Temperature Inversion Pollution Normally, tropospheric temperature Altitude trapped decreases with height above the ground (a), and air at the surface mixes with air above it. In a temperature inversion (b), cool air stays Temperature near the ground, under a layer of warmer air, and little mixing occurs. Relate Cause and Effect Why can a temperature inversion, Cool such as the one that occurred in London in Low 1952, make air pollution worse? (b) Thermal Inversion

466 Lesson 2 Primary pollutants Secondary pollutants

Water (H2O), oxygen (O2), and other substances

Sulfur dioxide (SO2) Sulfuric acid (H2SO4)

Nitric oxide (NO) Nitric acid (HNO3)

Acid precipitation

FIGURE 16 Formation of Acid Acid Deposition Precipitation Acid precipitation Acid deposition results when products of combustion combine starts when sulfur dioxide and nitrogen oxides such as nitric oxide with water, oxygen, and other substances in the atmosphere. combine with water, oxygen, and other substances. Acid precipitation When some pollutants combine with water, oxygen, and other chemicals can affect areas a long way from the in the atmosphere, they form compounds called acids. These acids may original source. settle to the surface of Earth as acid deposition. Acid deposition may consist of solid or gaseous particles, or the acids may dissolve in fog or precipitation. Acid precipitation is sometimes called acid rain, but any kind of precipitation, such as snow or sleet, can contain acidic pollutants.

The pH Scale and Precipitation The pH scale is used to measure whether solutions are acidic or alkaline. The values on the scale range from 0 to 14. A pH of 7 is neutral, that is, it is neither acidic nor alkaline. If a solution has a pH that is higher than 7, it is alkaline, or basic. An acid ANSWERS is a solution whose pH is lower than 7. The lower the pH number, the Go Outside higher the acidity. 1. Answers will vary. Students should The pH of precipitation varies. Normal precipitation is slightly acidic, classify rainwater as acidic if its pH with a pH of about 5.6. Acid precipitation has a lower pH. Some areas in is lower than 5.6, the pH of normal the United States have precipitation with a pH as low as 4.3. precipitation. 2. Answers will vary. Go Outside Is the Rainwater Acidic? Analyze and Conclude Analyze Data 1 On2 a rainy3 4 day, 5put a6 clean7 plastic8 9 cup outside 1. Is rainwater in your area more where it will collect rainwater. acidic than normal rainwater? Explain your answer. 1 2 Bring3 4the collected5 6 rainwater7 8 9 indoors. Then use Perform Error Analysis pH paper to measure the pH of the water. 2. If other students obtained different results from yours, try to figure 1 2 3 Compare4 5 your6 results7 8 to9 those of other students. out why.

The Atmosphere 467 Figure 17 Effects of Acid Deposition Notice that many trees no longer have any needles—a result of acid deposition.

Sources of Acid Deposition Acid deposition starts mainly with sulfur dioxide and nitrogen oxides. These pollutants are produced largely through the burning of fossil fuels by automobiles, electric power plants, and industries. In the troposphere, these compounds can react with water, oxygen, and other substances to produce acids such as sulfuric acid and ANSWERS nitric acid. Lesson 2 Assessment Wind can carry pollutants over long distances. Therefore, acid depo- 1. Sulfur dioxide: primary pollutant; sition may fall on areas that are far from where the pollutants were sulfuric acid: secondary pollutant. produced. For example, much of the pollution that is produced in Penn- Sulfuric acid is the product of a sylvania, Ohio, and Illinois falls out in states to the east, including New reaction between sulfur dioxide York, Vermont, and New Hampshire. and water. 2. To protect their respiratory system Effects of Acid Deposition Acid deposition can harm ecosystems 3. In a temperature inversion, cooler, and structures that humans have built. For example, if the pH in lakes dense air is trapped near the becomes too low, neither plants nor fishes can survive. Acid deposition ground. Since the air does not move, the pollutants that the can kill trees and destroy whole forests (Figure 17). When acid gets into air contains cannot mix with air the soil, harmful chemicals can be released. These chemicals can poison higher up. plants growing in the soil. Acid deposition can erode the surfaces of stone 4. No; normal precipitation has a pH buildings and statues, such as the Parthenon sculptures. In addition, acid of about 5.6; acid precipitation has deposition can increase the acidity of the water that comes into your a pH lower than 5.6. home. Water with increased acidity can pick up harmful chemicals from 5. Developing nations are trying to industrialize. By restricting pro- metal pipes and contaminate drinking water. cesses that produce smog, they Acid deposition is a problem, but it can be solved. People and govern- might also slow economic prog- ments have taken steps to eliminate or reduce air pollutants that cause acid ress. deposition. The next lesson describes some of those steps.

1. Interpret Tables Sulfuric acid and sulfur dioxide 3. Relate Cause and Effect Why does a temperature are both air pollutants. Use Figure 12 to determine inversion trap smog and prevent it from dispersing? which is a primary pollutant and which is a sec- 4. Apply Concepts The rain that falls in an area has ondary pollutant. What is the relationship between a pH of 5.8. Is this acid precipitation? Explain your these two types of pollutants? answer. 2. Infer When people work with volatile organic 5. Explore the BIGQUESTION Why might developing compounds, why should they wear special masks nations be more reluctant than developed nations to that cover their noses and mouths? take measures to control industrial smog?

468 Lesson 2