air pollution i -...

Chapter

Air Pollution

I t is difficult to see the buildings in this photo ofVancouver, British Columbia. Sometimes, the buildingsand the hills around this Canadian city cannot be seen at

a l l . This is due to a haxe called smog. Smog is caused by airpollution that results from human activities. Air pollution canalso cause health problems in people, as well as environmentalproblems. In Chapter 9, you will learn about the causes andeffects of air pollution. You will find out how heat, noise, andlight can be forms of pollution. You will read about howEarth's climate is changing. Finally, you will learn about waysto reduce air pollution.

Organize Your Thoughts

Industrial smogPhotochemical smog

Urban heat island effect

Goals for Learning

To explain what air pollutants are and where theycome from

To describe four major forms of urban air pollution

To explain how acid ratn forms and what effect it has

To describe global warming and climate change

To explain some of the ways to reduce air pollution

327

Lesson Air Pollution and Living Things

Objectives

After reading thislesson, you shouldhe able to+ define air

pollution

+ give examplesof natural andhuman sources ofair pollution

+ describe how airpollutants getinto and out ofthe atmosphere

ParticulatematterLiquid or solid particlesin the air

Air pollutantA material in the airthai harms living thingsand nonliving materials

Air pollutionPollution in the air

What Is in the Air?Stand outside of your school and take a deep breath. Thatbreath of air is made up mostly of oxygen and nitrogen.Without those elements, you could not survive.

The air you breathe contains small amounts of other things,too. It contains carbon dioxide, argon, and other gases. Can youfeel any humidity in the air? Tiny droplets of water are part ofevery breath you take. Have you ever noticed the wind stirringup dirt on a road or baseball field? The air contains particles ofdust and other solids, too.

The air picks up these and other materials as it moves over theearth. A spring wind blows pollen out from a tree. Warm airabsorbs water from a stream. Air over a busy street becomesfilled with car exhaust. These chemicals will be most dense inthe air near their source. Then, as the air circulates, it will carrythem vertically and horizontally through the atmosphere.

Bits of solids and liquids in the air are called paniculate matter.Eventually, all paniculate matter will fall to the ground. It canbe pulled down by gravity. It can also be washed down from theair by precipitation. How long particulate matter stays in the airdepends on its size and on the climate. The largest particles maysettle in minutes or hours. The smallest particles can stay in thetroposphere for one to two weeks.

Air PollutantsSometimes the materials in the air can harm people, wildlife,plants, and even nonliving materials. These damagingsubstances are known as air pollutants. They cause differenttypes of air pollution.

Air pollutants can come from natural sources, such as volcanoesand forest fires. Ash, pollen, and wind-blown dirt are allnatural air pollutants. Natural air pollutants are not usuallyconcentrated enough to harm living things.

328 Chapter 9 Air Pollution

Primary airpollutantA harmful chemical that

enters the air directly

Secondary airpollutantA harmful chemicalthat forms as a reactionbetween other chemicals

in the air

Outdoor airpollutionPollution that is foundami measured inoutdoor air

Indoor airpollutionPollution that is foundand measured indoors

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PhysicsAir a mile up inthe atmosphere isless dense than airat sea level. Thiscauses baseballshit in Denverto travel fartherthan baseballshit in other cities.The thinner airof Denver hasfewer air particles.Therefore, amoving objectencounters less airresistance.

Most damaging air pollutants come from human activities.Paint fumes, for example, spread harmful chemicals into theair. The use of pesticide sprays does, too. Smoke from wood-burning stoves, cement dust, and mining dust are other humansources of air pollution. Most air pollution, though, comesfrom just one activity: burning fossil fuels. Factories, powerplants, and motor vehicles create 90 percent of the air pollutionin the United States.

Scientists group air pollutants into two categories. The firstcategory is primary air pollutants. These pollutants arereleased directly by human or natural sources. Other pollutantsform from a chemical reaction between substances in the air.These are called secondary air pollutants.

When people talk about air pollution, they usually meanoutdoor air pollution. Outdoor air pollution is found andmeasured outdoors. Yet air quality indoors can often be worsethan air quality outdoors. That is because additional pollutantstend to be added to the air inside buildings. Indoor airpollution includes chemicals released from carpets, cleaningproducts, insect spray, and tobacco smoke. Because they arecontained in a small space, indoor air pollutants can reachdangerous levels. Also, people in industrialized countries spendabout 90 percent of their time indoors. Babies, older adults, andsick people often spend even more time indoors. For all thesereasons, indoor air pollution can be a very serious health issue.

Technology and Society

Research labs and medical labs depend on having clean air.Pollutants or microbes can ruin laboratory tests. High EfficiencyPaniculate Air (HEPA) filters are regularly used in such places thatrequire clean, sterile air. These high-tech filters remove even thesmallest particles, including viruses, from the air.

Air Pollution Chapter 9 329

RespiratoryRelated to

EmissionA release of a substanceinto she environment

Impacts and SolutionsAir pollution affects human health in many ways. It can makepeople's eyes and throats burn. It can cause heart problemsand lung cancer. Asthma and emphysema are two types ofrespiratory, or breathing, illnesses. Both are made worse bybreathing polluted air. Each year, more than 600,000 peopleworldwide die earlier than they normally would have becauseof air pollution.

Air pollution affects other kinds of living things, too. Forexample, air pollutants can wash into waterways and harmaquatic wildlife. They can make it harder for plants to grow. Airpollution can even damage statues and buildings.

It can be very difficult to clean polluted air. For this reason,most experts try to tackle air pollution at the source. They try toreduce emissions of pollutants from factories, vehicles, and othersources. They research and support new products and alternativeforms of energy that produce less pollution. They try to educatethe public about how to reduce their contribution to air pollution.

Science in Your Life

Technology: ^^^^^_Radon Gas

^^^^^^B K ffBBit_J n G sourco or ^^^^^^indoor air pollution \-%T^His radon gas. Radon ^$$

is a radioactive i i ^ ngas that seeps k / H^up through the L / ^ isoil. Radon gas is ^L \y a problem ^^

indoors because it builds up and becomesconcentrated. It is second only to smokingas a cause of lung cancer.

Radon is produced by the breakdown ofsmall amounts of uranium in the soil. Thegas seeps up into a home through pores

and cracks in the foundation. It has nosmell or taste, so it is not noticeable. Kits areavailable to test for radon, however. Thesekits are inexpensive and easy to use. Youcan find them at a local hardware store.

If radon is detected in a home, a removalsystem can be installed. It vents the radongas outside where it disperses harmlessly.Newer homes are built with technologythat keeps radon out. All homes shouldbe tested for radon, regardless of whetherthey are old or new.

1 . How does radon gas get into homes?

2. What can you do to make sure there isno radon gas in your home?


Addressing air pollution is complicated because air moves.Communities affected by air pollution are often far from thosethat create it. For this reason, communities, states, and evennations must work together to address air pollution.

The U.S. government addresses air pollution through the CleanAir Act. The Clean Air Act is a law that sets national standardsfor air quality. This act is sometimes changed to address new airpollution problems.

Through laws and new technologies, people have already madeimprovements in air quality. For example, gasoline in the UnitedStates used lo have lead in it. This helped engines run. However,burning leaded gasoline released lead into the air. Lead in theenvironment can poison people and cause developmentalproblems in children. In 1970, the ("lean Air Act requiredgasoline to be lead-free by the mid-1980s. Even by 1980, thelevel of lead in people's blood had dropped by 50 percent.

In the following lessons, you will learn more about the majorforms of air pollution. You will also learn more about howpeople are working to control them.

Express Lab 9

Materials

* air freshener or perfume spray

Procedure1. Remain seated as your

teacher sprays the airfreshener or perfume.

2. Raise your hand as soon asyou can smell the spray.

3. Compare the smell eachperson experienced.

Analysis1. How far away was the

spray smelled?

2. How does the spray movethrough the air?


Lesson 1 R E V I E W

Word Bankair pollutants

emissions

indoor

On a sheet of paper, write the word or words from the WordBank that complete each sentence correctly.

1. Materials in the air that can harm living things arecalled _ _.

2. Pollution found inside a huilding is called airpollution.

3. Releases of pollutants into the environment arecalled .

On a sheet of paper, write the letter of the answer thatcompletes each sentence correctly.

4. Two or more substances in the air can react to form aair pollutant.

A particle B primary C secondary D particulate

5. Air pollution causes difficulties for many people.

A eating B sleeping C walking D breathing

6. Most air pollution comes from .

A natural sources C firesB burning fossil fuels D paint

Critical ThinkingOn a sheet of paper, write the answers to the followingquestions. Use complete sentences.

7. How has the Clean Air Act improved people's health?

8. What is the biggest difference between indoor and outdoorair pollution?

9. Why is controlling emissions important for the reductionof air pollution?

10. What are two examples of air pollution that do not comefrom humans?


I N V E S T I G A T I O N 9

Materials

cardboard

scissors

aluminum foil

masking tape

string

petroleum jelly

paper towel

magnifying glass or

microscope

What Is in the Air?Although you usually cannot feel or see air, it is asubstance. Air has mass. Air is filled with many differentparticles, most of which you do not notice. How canyou tell what particles are in the air? Is there a way tocapture them and find out? This lab will show you oneway to do exactly that.

Procedure1. Cut a 4 cm x 4 cm square from the cardboard.

2. Completely cover the cardboard square withaluminum foil. Make sure that the foil is flatand smooth.

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3. Use tape to attach one end of apiece of string to your square.

4. Using a paper towel, cover bothsides of the square with a thin, evenlayer of petroleum jelly. Wipe yourhands immediately after using thepetroleum jelly. Safety Alert: Keepthe petroleum jelly away fromyour eyes, nose, and mouth.

5. Use the string to hang your squarein an indoor or outdoor location.Record the specific location. Makenotes about the surroundings. Forexample, is it near a lot of traffic orother source of pollution?

6. Collect your square after 24 hoursand examine it with a magnifyingglass or microscope.

Cleanup/DisposalReturn the materials and make sureyour area is clean before you leave thelab. Wash your hands thoroughly.

Analysis1. What did you find on your square?

Make a list of the things youobserved.

2. Where do you think these particlescome from? Add these notes toyour list.

Conclusions1. Compare the types of things

found on the squares that werehung outside with the squares thatwere hung inside. How were theydifferent?

2. What do you think you would findin the air of the house of someonewho smokes?

3. How do air particles affect you?

Explore FurtherWork with a partner to prepare apresentation of the investigationresults. Gather data from all indoorand outdoor squares. Create a visualpresentation of the combined results.


Lesson Smog, Heat, Noise, and Light

Objectives

After reading thislesson, you shouldbe able to

+ describe whatsmog is andwhere it occurs

+ explain what anurban heat island is

^ explain how noisecan be a type ofpollution

+ give examplesof how light canpollute

SmogA haze that forms asa result of vehicle andindustry emissions

Industrial smogA form of smogproduced by burningcoal and oil

In 1970, Chattanooga, Tennessee, had serious air pollutionproblems. Some days were so dark from pollution that peoplehad to drive with headlights on. Pollutants in the air coulddestroy a woman's nylon stockings as she walked down the street.

Chattanooga has much cleaner air now, thanks to lawsand community efforts. Yet urban areas around the worldcontinue to have many air pollution problems. Four formsof air pollution, in particular, occur most often in urbanenvironments.

SmogYou may have noticed a dark haze on the horizon of certaincities. That ha/e is called smog. Some people think of it as acombination of smoke and fog. Yet smog is not quite that simple.

There arc actually two types of smog. Industrial smog is smogcaused by burning coal and oil. It became severe in manybig cities after the start of the Industrial Revolution. That iswhen people began burning huge amounts of coal for power.Burning coal and oil releases sulfur dioxide (SO2) into the air.It also releases liquid and solid particulate matter. Together,these chemicals form a grayish haze. Normally, industrial smogbreaks up from day to day. Certain weather patterns, though,can cause industrial smog to remain for extended periods. In1952, an estimated 12,000 London residents died from fivedays of concentrated smog. This event caused London andother cities to take steps to reduce industrial smog. The mostsignificant change was to make smokestacks taller so pollutantswould blow up and away.

Research and Write

Find the air quality reports for your area and track themthroughout the week. What pollutants are a problem in yourarea? Create a graph to track your data from day to day.


PhotochemicalsmogA mixture of pollutants

produced primarily by

burning gasoline

OzoneA harmful gas found in

photochemical smog

Myth: The ozonelayer is a layer ofpollution.

Fact: There are twotypes of ozone.Atmosphericozone is found inthe ozone layer,which is high in thestratosphere. Thisozone preventshigh levels ofradiation fromreaching Earth.Ground-level ozoneis a secondaryair pollutant andexists in the air thatpeople breathe.Ground-level ozoneis unhealthy.

Today, photochemical smog is more common. Photochemicalsmog produces a brownish haze in the sky. It is most commonin cities with warm, dry, sunny climates, such as Los Angelesand Denver. The source of photochemical smog is primarilycars and other motor vehicles. As they burn gasoline, thesevehicles release nitrogen oxides (NO ) into the air. Thesegases react with sunlight to form several harmful gases. Oneof these is nitrogen dioxide, a brownish gas with a terriblesmell. Another is ozone. Ozone causes breathing difficulties,headaches, and fatigue. A third is called peroxyacetylnitrate, orPAN. PAN can make people's eyes water and sting.

Map Skills: Ozone Levels

Ozone gas can form when pollutants react with sunlight. Ozoneoften builds up in climates that are hot, sunny, and have littlewind. Ozone levels are monitored so that people can be warnedwhen levels are high. You should avoid outdoor activities onhigh ozone days.

This map shows the ozone levels in the Los Angeles area forAugust 28, 2005. In January 2005, this same area map was allgreen. Use the map to answer the questions below.

LEGEND

Healthy air

Moderately rhealthy air I 1

Unhealthy airfor sensitive [~

groups

Dangerous air

1. In what color area is the city of Los Angeles?

2. What times of the year are more likely to have dangerouslevels of ozone?

3. Why do you think the areas along the coast are green?


CatalyticconverterA device designed to

reduce emissions of airpollutants from vehicle

exhaust

Urban heatisltiml effectIncreased temperaturesin urban areas causedby human development

and activity

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Health

Air quality levelsdepend on thephysical features ofland. For example,Los Angeles lies ina large basin, orvalley. Since lessair moves throughthis basin than overflat land, pollutantsare trapped. Thispollution has beenlinked to increasedoccurrences ofasthma, heartattacks, and strokes.

To help reduce photochemical smog, the U.S. governmentrequires car makers to install catalytic converters on allvehicles. Catalytic converters arc devices that reduce emissionsof air pollutants from cars' exhaust systems. These devices havegreatly reduced each car's pollution emissions since the 1970sand 1980s. I lowever, people today drive many more mileseach year than they did then. As a result, automobile emissionsremain high overall and photochemical smog is still common.

Heat IslandsLeaving the city on a hot day, you may notice that thetemperature decreases. Urban areas are usually 1°C to 5.5°Chotter than surrounding areas. Scientists call this the urbanheat island effect.

What causes cities to be hotter than surrounding areas? First,activities that use energy give off waste energy as heat. Moreof these activities are concentrated in urban areas, increasingthis heat load. Also, as cities develop, natural vegetation islost. Before, this vegetation provided shade from the sun anddecreased the air temperature. Finally, urban building materialssuch as asphalt and brick are dark in color. They absorb a lot ofheat and release it slowly into the air.

Heat in the air is not a form of air pollution. However, increasedurban temperatures in summer months can increase energy usefor cooling. More energy use generally means more pollution.Also, heated air above cities tends to trap more pollutants.

There are two main solutions to the heat island effect. One isto plant more trees and other vegetation. Another is to turndark surfaces into light surfaces. When a building's roof is lightcolored, it uses 40 percent less energy for cooling.


Noise pollutionNoise that interruptsdaily life

Light pollutionBothersome brightnessor glare caused by

human-made lights

Physics

A decibel (dB)is a unit used tomeasure loudness.Zero dB is thequietest noise ahuman ear canhear. With eachincrease of 10 dB,the intensity of thesound increasesby 10 times. Forexample, 30 dBis 10 times theintensity of 20 dB,and 100 times theintensity of 10 dB.Long exposure tosounds of 120dBor higher can leadto deafness.

Noise PollutionNoise pollution is defined as noise that interrupts daily life. Itis not a typical form of air pollution. It is caused by sounds, notpollutants, that travel through the air. This noise comes fromair, rail, and car transportation. It comes from construction andindustry. Sometimes it even comes from recreational activities.All of these activities tend to be concentrated in urban areas.High noise levels can make it harder for people to sleep andwork. They can raise stress levels. They can disrupt the activitiesof wildlife. They can even damage hearing over time.

Noise pollution is very hard to control. Yet many cities havetaken steps to reduce noise pollution. For example, some citiesconstruct walls to block highway noise. Others restrict airplanelandings and takeoffs at night.

Light PollutionIn photographs of North America taken at night, major urbanareas glow with light. Some people believe there is too muchlight in developed areas. They call this light pollution. Lightpollution results from three things. The first is having morelights than are necessary for safety. The second is having lightsthat are brighter than necessary. The third is allowing the lightto spread up and out.

Light pollution causes a number of problems. It can preventpeople from seeing the stars or even keep people awake at night.It can also create a glare that makes it hard for some people tosee and drive. Last, light pollution can disrupt the movementof wildlife. For example, newly hatched sea turtles followthe moon's light to get to sea. In some places, though, theyaccidentally crawl toward the lights of nearby towns. Carefulplacement of lights and control of light angles, however, canminimize light pollution.

Smog, the heat island effect, noise pollution, and light pollutionare most common in cities. Still, even small towns can haveproblems such as loud noises and bright lights. The followinglessons describe air pollution problems that affect everythingfrom cities to wilderness.


Word Bankheat island

noise

smog


On a sheet of paper, write the word or words from the WordBank that complete each sentence correctly.

1. A dark haze called _ _ hovers over many cities.

2. A jackhammer and a loud truck can both contribute topollution.

_ effect refers to the higher temperatures3. The urban __found in urban areas.


4. How are the two types of smog different?

5. Why is light considered to be a form of pollution?

** ** •» # »* ** ** ** ** **Achievements in Science

The Discovery of the Hole in theOzone Layer

The ozone layer blocks 95 percent of thesun's harmful ultraviolet radiation. Withoutthis protection, more humans woulddevelop skin cancer. Other harmful resultswould include the destruction of somefarm crops and marine organisms.

Scientists at the British Antarctic Surveybegan measuring the ozone layer in thelate 1970s. In 1985, they reported thatthere was a "hole" in the layer directlyabove Antarctica. This hole is actuallywhere the ozone layer is very thin, allowing

radiation to come through. The scientistsalso concluded that the hole was growing.

Around the same time, chemistsdiscovered that chemicals called CFCswere destroying atmospheric ozone. CFCstands for "chlorofluorocarbon." CFCswere released by using aerosol spraysand fire extinguishers. They were alsoused as a coolant in refrigerators and airconditioners. Since 1987, many countrieshave signed the Montreal Protocol, whichbans the use of CFCs. Scientists think theozone layer will recover if CFCs are keptout of the atmosphere.


DISCOVERY I N V E S T I G A T I O N 9

Materials

colored ceramic tiles or

paint chips

2 clear drinking glasses

or plastic cups

2 thermometers

stopwatch, or clock

with a second hand

heat lamp or strong

sunlight

Colors and HeatThe colors of building materials can contribute to theurban heat island effect. How much docs color affectthe amount of heat that is absorbed? Which colorsabsorb more heat? You will find out in this lab.

Procedure1. In a small group, select two colors of the same

material, such as ceramic tiles or paint chips.Choose a very dark color and a very light color.

2. Write a hypothesis about the amount of heat eachitem will absorb.

3. Write a procedure and Safety Alerts for yourexperiment, using the materials listed.


4. Have your hypothesis, SafetyAlerts, and procedure approved byyour teacher. Then perform yourexperiment.

5. Collect and record data. Use yourdata to create a graph that showsthe temperatures of the differentcolored materials at different timeintervals.

Cleanup/DisposalReturn the materials and make sure yourarea is clean before you leave the lab.

Analysis1. Was your hypothesis correct?

Explain why or why not.

2. What color absorbed the mostheat? Explain.

3. What color absorbed the leastheat? Explain.

Conclusions1. What color would be good to

use on a house in a cold climate?Explain your answer.

2. What color would be good touse on a house in a hot climate?Explain your answer.

3. Contrast how light- and dark-colored materials interact withenergy from the lamp or the sun.

Explore FurtherTake the paint chip that, according toyour data, absorbed the most heat. Cutpieces of another color and glue thesepieces to the paint chip. How do youthink this will affect the original paintchip's ability to absorb heat? Write ahypothesis and test it.


Lesson Acid Rain

Objectives

After reading thislesson, you shouldbe able to+ describe the

major sourcesof acid rain

^ explain whyacid rain affectsplaces far fromits sources

^ describe problemswith and solutionsto acid rain

AcidA sour-tasting substanceihnl reacts with metalsto produce hydrogen

Acid rainPrecipitation with highlevels of acidity

Acid depositionAnother term foracid rain

Dry depositionAcid pollutants thatsc/f/c on tin1 earthas solids

Wet depositionAcid pollutants thatreach the earth inprecipitation

In the 1960s, scientists became concerned about the health ofcertain freshwater lakes and forests. Biodiversity was decliningin the lakes. Many of the trees in the forests were dying. Thescientists studied the conditions in these ecosystems to discoverthe cause. They found that the lakes' water and the forests' soilswere very acidic. This meant they had a high concentration ofacid. This acid was harming plants and animals. But where didthe acid come from?

The scientists soon discovered that the acid was coming fromthe air. This form of pollution is known as acid rain or aciddeposition. Acid rain begins with the emission of sulfur dioxide(SO2) and nitrogen oxides (NOX) into the air. Most of thesulfur dioxide emissions come from coal-burning power plants.Most of the nitrogen oxides emissions come from power plantsand motor vehicles.

Once in the atmosphere, sulfur dioxide and nitrogen oxidesreact with water, oxygen, and other chemicals. They formsecondary pollutants, such as sulfuric acid and nitric acid.These pollutants sometimes settle as solids on trees, buildings,water, and land. This is called dry deposition. Other times, theyare carried to the ground by precipitation. This is called wetdeposition. Wet deposition is not just rain, ft can also be snow,sleet, fog, and dew with these acids in it.

Understanding AcidsAcids are sour-tasting substances. They react with metalsto produce hydrogen. A mild acid can be found in orangesand lemons. A much stronger acid helps break down food inyour stomach.


Base

A bitter, slipperysubstance that containsthe hydroxyl radical

RadicalA group of two or moreatoms that acts likeone atom

A number thai tellswhether a substance isan add or a base

NeutralNeither an acid nor abase; having a pH of 7

Math Tip

A pH valueincreases ordecreases as afactor of 10. Forexample, waterwith a pH of 4 is 10times more acidicthan water with apH of 5. It also is100 times moreacidic than waterwith a pH of 6.

The opposite of acids are a group of substances known asbases. These substances taste bitter and feel slippery. Theycontain something called the hydroxyl (OH) radical. A radicalis a group of two or more atoms that acts like one atom. Soap,deodorants, and antacid medications all contain bases.

A substance's pH determines whether something is an acid ora base. The pH scale runs from 0 to 14. Anything below 7 is anacid. Anything above 7 is a base. A pH of exactly 7 means thata substance is neither an acid nor a base. It is neutral. Purewater is neutral. Vinegar is an acid with a pH of about 4. Manyhousehold cleaners are bases with a pH of around 10. Morematerials and their pHs can be seen in Table 9.3.1, below.

Acids in the EnvironmentAcidity levels in ecosystems can vary. Natural precipitation hasa pH of about 5.6. This slight acidity helps dissolve mineralsthat plants and animals need.

When pH levels fall below 5.5, however, the acidity can causemany problems. The acidity can kill fish, microorganisms,and aquatic plants. It can take nutrients out of the soil. Incombination with other pollutants, it can harm trees, crops,and other plants.

Table 9.3.1 The pH Scale of Some Common Substances

Stomach acid

The worst acid rain

Lemon juice

Vinegar

Cabbage

Tap water

Milk

Pure water

Liquid soaps

Household cleaners

Lye

Acids Neutral Bases


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Ar ts

One of China'smost treasuredarchaeologicalartifacts is thearmy of terra-cotta warriors.These statueswere discoverednear the city ofXi'an in 1974.Unfortunately,this work of art isbeing destroyedby air pollution.Features on thelife-size warriorsare turning grayand may eventuallybreak apart.

The impacts of acid rain depend on the ecosystems and speciesinvolved. When rain falls, only a small portion falls directly intolakes and streams. The rest falls on land and flows through thesoil. Then it drains into lakes and streams. The soils in someregions contain a lot of limestone and other substances thatare bases. When acid rain flows through these soils, the basesreact with it and neutralize it. The water that reaches lakes andstreams is no longer acidic.

Some places, though, have thin, acidic soils. As acid rain passesthrough these soils, it becomes even more acidic. It flows intolocal lakes and streams and raises acidity levels even higher.

Ecosystems with high acidity lose biodiversity. Yet not all speciesreact in the same way. For example, snails, crayfish, salmon, andtrout die when water becomes too acidic. Other species, such aswater beetles, bloodworms, and eels, do well in acidic waters.

Acid rain also affects humans and their communities. It candamage buildings and statues. It can create a haze similar tosmog that makes it harder to see. It can also contribute to healthproblems for people with breathing difficulties.

The Geography of Acid RainIn Lesson 2, you learned that burningfossil fuels in power plants can causeindustrial smog. The local impactsof these power plants are no longer sogreat, however. That is because powerplants now use very tall smokestacks,like the ones in Figure 9.3.1. Whenthese smokestacks are tall enough,pollutants are not trapped above a city.Instead, the wind carries them awayfrom their source.

Figure 9.3.1 Using taller smokestackshelps to disperse pollutants.


ScrubberA device that removessulfur from industrialsmokestack emissions

Tall smokestacks have disadvantages, though. Their pollutantsdo not go away completely. Instead, they blow to other places.They also have a chance to react and form secondary pollutants,such as those in acid rain.

Acid rain is a major problem in many parts of the world. Theseinclude parts of Europe, Scandinavia, China, southeasternCanada, and the northeastern United States. The pollutionthat causes acid rain in these regions comes mostly from otherplaces. For example, more than half of Canada's acid raincomes from the United States. Much of the acid rain in thenortheastern United States comes from the upper Midwest.

Addressing Acid RainThe effects of acid rain arc visible all over the world. Sugarmaples are dying in Vermont. More than 4,000 lakes in Swedencontain no fish. One-quarter of the lakes in New York'sAdirondack Mountains are considered biologically dead. Theselakes were once full of otters, loons, and trout.

In the 1970s, scientists and others began working to reduceacid rain. That required reducing emissions of the pollutantsthat cause it. The Clean Air Act requires power plants toreduce their emissions of sulfur dioxide and nitrogen oxides.In general, they can do this by burning low-sulfur coal or byinstalling scrubbers. Scrubbers are devices that remove sulfurfrom smokestack emissions before they reach the air.

These requirements have been partly successful. Between 1990and 1998, sulfur dioxide emissions decreased by 17 percent.Yet nitrogen oxides continue to be emitted at the same rate.Moreover, acid levels remain dangerously high in many parts ofthe country and the world. Solving these pollution problems isstill a major concern for scientists.



Word Bankdeposition

neutral

scrubbers

d| ^

On a sheet of paper, write the word from the Word Bank thatcompletes each sentence correctly.

1. Another term for acid rain is acid .

2. A _ _ substance is neither an acid nor a base.

3. Devices that clean sulfur from smokestacks arecalled .


4. Substances with a pH higher than 7 are .

A acids B bases C neutral D radicals

5. An ecosystem with high acidity loses .

A water B soil C sunlight D biodiversity

6. Sulfuric acid and nitric acid are examples ofpollutants.

A safe B secondary C stationary D primary


7. What can you guess about the pH of medicine used totreat an acidic stomach? Explain your answer.

8. How does acid rain form?

9. What kind of damage would you expect to find in a citythat receives acid rain?

10. How can acid rain fall in areas where there is no industry?


Lesson Climate Change

Objectives

After reading thislesson, you shouldbe able to

+ define globalwarming andclimate change

^ describe thegreenhouseeffect and howit contributes toglobal warming

+ name severalimpacts of climatechange on peopleand ecosystems

Climate change.\ inclimnic associated withglobal warming

Montana's Glacier National Park is named for its manyenormous glaciers. Today, though, these glaciers are meltingand shrinking. Many scientists believe that by 2030, GlacierNational Park will no longer have glaciers. The reason is thattemperatures are getting warmer each year. Since 1900, averagesummer temperatures at the park have risen by 1°C. This trendis happening all over the world.

Figure 9.4.1 The glaciers of Glacier National Park in Montana areslowly shrinking.

A Changing ClimateGlobal temperatures have been accurately recorded since thelate 1800s. Since that time, average temperatures worldwidehave risen from between 0.4°C and 0.8°C. As you learned inChapter 1, this is called global warming. Current data suggestthat temperatures are still rising. The 10 hottest years of the1900s occurred in that century's last 15 years. The first fiveyears of the 2000s had four of the five hottest years on record.

These increases in Earth's temperature affect the climate inother ways. They affect wind patterns, precipitation patterns,and hurricane intensity. These changes are referred to as globalclimate change. Sometimes "global warming" and "climatechange" are used to mean the same thing. In general, though,climate change refers to more than just rising temperatures.


Greenhouse gasA gas in the atmospherethat helps trap heataround the earth

GreenhouseeffectThe warming of theatmosphere because oftrapped heat energyfrom the sun

ChemistryEarth's earlyatmosphere wasmade up mostly ofmethane. Today,air is made up ofabout 78 percentnitrogen and 21percent oxygen.The remaining 1percent containsa variety of othergases.

The Greenhouse EffectYou may recall that Earth's climate has always been changing.Ice ages have been followed by periods of warming. Short-termchanges in temperature and precipitation have also occurred.Such natural changes in the climate are still going on. Yet mostscientists believe that current climatic changes are largelycaused by human activities.

Over the last 200 years, the makeup of the atmosphere has beenchanging. Since the Industrial Revolution began, the amount ofcarbon dioxide has increased by almost one-third. The amountof methane has more than doubled. Nitrogen oxides have alsoincreased. These gases are referred to as greenhouse gases. Theynormally help trap heat around the Earth. This is known as thegreenhouse effect. Now they are increasing in the atmosphereand trapping even more heat. The result is higher temperaturesat Earth's surface.

Most scientists believe that human activities are causing thisincrease of greenhouse gases. The main cause is the burningof fossil fuels. About 98 percent of U.S. carbon dioxideemissions come from burning fossil fuels. Burning fossil fuelsalso contributes about one-fourth of methane emissions and18 percent of nitrogen oxides emissions. The rest of theseemissions come from cutting down forests, mining, and otheractivities. The United States contributes about one-fifth of allthe greenhouse gases emitted worldwide.

Science Myth

Myth: The greenhouse effect is bad for life on Earth.

Fact: The greenhouse effect is one reason that life can exist onEarth. The gases trap enough heat against the planet for humansand other living things to survive. However, pollution has causedan increase in the greenhouse effect. This increase may lead toglobal warming and other problems.


Researchand Write

Some scientistsbelieve that globalwarming is dueto the buildup ofgreenhouse gases.Other scientistsbelieve that Earthis going througha natural warmingperiod. Researchboth sides of theissue and picka point of view.Write a paper thatexplains why youchose the positionthat you did.

Impacts of Climate ChangeScientists agree that global warming is occurring. Yet someuncertainty surrounds exactly how Earth's climate will change.Past changes in greenhouse gas concentrations have causedbig changes in temperature, rainfall, and sea level. These pastchanges can be used to develop tools to predict future changes.

Among the most useful tools for predicting future climatechanges are computer models. These models simulate thebuildup of greenhouse gases in the atmosphere. They calculateaverage temperatures in the air and in the seas. They alsocalculate how climate change will affect the polar ice caps,glaciers, and wildlife habitats. Scientists can get a sense of howaccurate their models are. They enter past data and see howwell their models "predict" what happened next.

Scientists now predict that by 2050, Earth's average temperaturescould rise by another 0.6°C to 2.5°C. They predict a rise of 1.2°Cto 5.6°C by 2100. That may not sound like a major increasein temperature. Yet only a 5°C to 8°C decrease in averagetemperatures caused the last ice age.

Scientists believe that rising temperatures will change manyaspects of life on Earth. Warming seas and melting polar icehave already caused sea levels to rise. These levels could rise by80 cm by 2100. This would flood many coastal communitiesaround the world. Cities near or below sea level, such as NewOrleans, Louisiana, are especially at risk.

Global warming is expected to increase precipitation andextreme weather. Disastrous floods, storms, and droughts arealready becoming common. For example, global warming isbelieved to increase the intensity of hurricanes. The relatedchange in climate is also likely to increase the spread of humandiseases. Warmer, wetter climates encourage disease-carryinginsects. Climate change could also reduce water supplies andthe amount of food grown. This is due to shifts in patterns ofrainfall and changes in temperature. Both of these factors affectwhat crops can be grown where.


Rising temperatures on land and at sea will change and destroywildlife habitat. During past climate changes, some speciesmigrated north and south to find more suitable habitats. Nowhuman development and the speed of climate change mightmake this impossible. Some mountain species are already dyingout as their high-elevation retreats become too warm.

Global warming affects wildlife in other ways, too. For example,Arctic ice has been forming later and melting earlier in recentyears. Polar bears, like the one in Figure 9.4.2, depend on this icefor hunting seals. Now many polar bears are becoming too thinto reproduce, and some are starving and even drowning.

Figure 9.4.2 Polar bears are one of many wild species affected byglobal warming.

Addressing Climate ChangeOne way to combat climate change is to reduce greenhouse gasemissions. However, not all countries have agreed on a plan toreduce emissions of greenhouse gases. Still, some nations, cities,and companies have pledged to reduce their emissions. This canbe achieved in part by reducing fossil fuel use and turning toalternative forms of energy.


CarbonsequestrationThe long-term storageof carbon in forests,soils, oceans, andunderground

Carbon sinkA place where carbonbuilds up and is stored

Some scientists are also researching ways to store excess carbonemitted by human activity. This is called carbon sequestration.Earth is already filled with natural carbon sinks. Carbon sinksare places that absorb and store carbon dioxide. Oceans, forests,and soils are all carbon sinks. Scientists estimate that carbonsinks on U.S. land absorb 300 to 600 million metric tons ofcarbon. Yet the United States emits between 4.5 and 5.5 billionmetric tons each year. Some scientists believe that by maintainingand improving natural processes, they can increase carbonsequestration. This means protecting tropical forests and otherlarge carbon sinks. New methods, such as injecting carbon deepinto the earth, could also help.

No one knows for sure how climate change should beaddressed. Yet most experts agree it is one of the world'sgreatest environmental challenges.

T-* A T - * A T - * A T - * A T - * A T - * A T - * A T* A T - * A T * A T * A T - * A T - * A T - * A T - * A T

Science at Work

Climatologist

Monitoring Earth's climate is an importantjob. This work is done all over the worldby climatologists. Climatologists workmostly with state and federal governmentagencies to determine a climate's impacton humans. A climatologist collectsweather data to create a complete pictureof Earth's climate. This data includesdaily temperature ranges and amounts ofprecipitation. A climatologist also studieshurricanes, blizzards, tornadoes, droughts,heat waves, and other extreme weather.Climatologists also make predictions aboutfuture climate changes.

A climatologist must have a bachelor'sdegree in meteorology or atmosphericscience. A strong background in math andscience is also recommended. Climatologistsmust also have good communication skillsand be able to use databases and computermodeling programs.


Lesson 4 R E

Word Bankclimate change

global warming

greenhouse effect

On a sheet of paper, write the words from the Word Bank thatcomplete each sentence correctly.

1. The rise in average temperatures around the globe isknown as _.

2. The global change in patterns of temperature andprecipitation is known as _ .

3. The way certain gases in the atmosphere trap heat againstthe earth is called the .


4. The buildup of greenhouse gases in the atmosphere isbelieved to be mostly caused by_ .

A burning fossil fuels C volcanic activityB mining D forest clearing

5. Forests and oceans store carbon and are known as .

A storehouses C carbon sinksB greenhouses D carbon copies

6. Climate change is expected to reduce .

A sea levels C extreme weatherB disease D wildlife habitat


7. Does a week of record-breaking cold weather mean globalwarming is not occurring? Explain.

8. How could climate change could affect human life?Give examples.

9. What is carbon sequestration?

10. How are the current changes in climate different from theglobal coolings and warmings that have occurred before?


ENVIRONMENTAL ISSUES IN THE WORLD

Artificial Trees and Carbon PollutionBurning fossil fuels releases carbondioxide into the atmosphere. This createspollution and may contribute to globalwarming. Until now, the only strategyto reduce carbon emissions has beento cut down on fossil fuels and developnew energy sources. But as the planet'spopulation grows and energy needsincrease, it becomes more difficult toreduce the use of fossil fuels. However,scientists are working on other methodsof reducing carbon pollution.

One possible method involves devices thatwill collect and store carbon in the sameway trees and other plants do. Scientistsare trying to develop these synthetic"trees" to absorb carbon from the air.That would greatly improve air quality.

The synthetic trees look like footballgoalposts with rows of flat shutters. Theshutters would hold sodium hydroxideand expose it to the air. Sodiumhydroxide would combine with carbondioxide in the air to create sodiumcarbonate. Sodium carbonate can betreated to remove the carbon in a mineralform. This form of carbon could bestored or buried. The sodium hydroxideis then ready to be used again to capturemore carbon dioxide.

Scientists are currently testing thismethod in hopes of creating an efficientmachine. Someday, we may be ableto reduce carbon pollution two ways:by cutting back on emissions and byremoving some of what is already inthe air.

1.

2.

Describe how a synthetic tree couldbe used to remove carbon from theatmosphere.

What happens to the carbon after itis removed?

3. Where do you think might be agood place to "plant" these artificialforests? Kxplain your answer.


Chapter 9 S U M M A R Y

Most air pollution comes fromhuman activities, especially burningfossil fuels.

Air pollutants can be released directlyinto the air (primary pollutants)or can form as a reaction betweensubstances in the air (secondarypollutants).

The Clean Air Act is a piece oflegislation designed to maintain airquality in the United States.

Certain forms of air pollution aremost common in urban areas: smog,the urban heat island effect, noisepollution, and light pollution.

Smog can come from industrial activity(industrial smog) and from vehicleemissions (photochemical smog).

Acid rain can harm wildlife, people,and nonliving materials.

When the pH of ecosystems falls below5.5, many plants and animals will die.

Global temperatures are rising, whichin turn is causing global climate change.

Most scientists believe that globalwarming is caused by increased levelsof greenhouse gases in the atmosphere.

Rising temperatures will cause avariety of changes on Earth, includingrising sea levels, extreme weather,widespread diseases, and reducedwildlife habitat.

Reducing greenhouse gas emissionsand preserving carbon sinks are twoways people are working to addressclimate change.

Vocabulary

acid, 342,u ill . ! < • [ > . >Miiui i . ;-i;acid rain, 342air pollutant, 328air pollution, 328base, 343carbon sequestration,

351carbon sink, 351catalytic converter,

337

climate change, 347dry deposition, 342emission, 330greenhouse effect,

348greenhouse gas, 348indoor air pollution,

329industrial smog, 335light pollution, 338

neutral, 343noise pollution, 338outdoor air pollution,

329ozone, 336particulate matter, 328pH, 343photochemical smog,

336primary air pollutant,

329

radical, 343respiratory, 330scrubber, 345secondary air

pollutant, 329smog, 335urban heat island

effect, 337wet deposition, 342

354 Chapter1} Air Pollution

Chapter 9 R E V I E W

Word Bankacid rain

acids

air pollutants

carbon sinks

climate change

emissions

greenhouse gases

indoor air pollution

neutral

noise pollution

particulate matter

PH

respiratory

scrubbers

secondary airpollutant

smog

urban heat islandeffect

Vocabulary ReviewOn a sheet of paper, write the word or words from the WordBank that complete each sentence correctly.

1. Materials in the air that can harm living and nonlivingthings are called _ .

2. Bits of solids and liquids in the air are known as .

3. A(n) _____ forms as a reaction between two or moresubstances in the air.

4. Pollution found inside buildings is called .

5. Releases ot chemicals into the environment arecalled .

6. Urban haze caused by traffic or industrial activity iscalled .

7. The is an increase in city temperatures caused byhuman development and activity.

8. Heavy trucks, car alarms, and jackhammers can allcause .

9. Acidic pollution that falls from the air is called _ __.

10. Substances that are sour-tasting and react with metals toproduce hydrogen are called _ .

_ scale measures whether something is an acid11. The___or a base.

12. A(n) substance is neither an acid nor a base.

13. Devices called can remove sulfur dioxide fromsmokestack emissions.

14. Air pollution can cause manychildren and adults.

problems in both

Continued on next page


Chapter 9 R E V I E W - continued

15. A global shift in climate caused by rising temperatures iscalled _ __.

16. Carbon dioxide and other atmospheric gases that trap heatare called .

17. Places that absorb and store carbon dioxide are called .

Concept ReviewOn a sheet of paper, write the letter of the correct answer.

18. What is the primary cause of air pollution worldwide?

A forest fires C paint fumesB mining D fossil fuel burning

19. Which of the following is a secondary air pollutant?

A sulfur dioxide C ozoneB cigarette smoke D ash

20. Which of the following reduced local smog but increasedacid rain?

A tall smokestacks C wind powerB catalytic converters D scrubbers

21. Which of the following is not associated with globalclimate change?

A melting glaciers C volcanic activityB rising sea levels D species decline


Critical ThinkingOn a sheet of paper, write the answer to each of the followingquestions. Use complete sentences,

22. Which members of the population tend to spend the mosttime indoors? How does this increase the harmfulness ofindoor air pollution?

23. Describe some characteristics of air pollutants that makethem easier to stop at the source than clean up later.

24. What are two ways in which burning a tropical forestcontributes to global warming?

25. Some people once doubted that global wanning existed.They pointed out that world temperatures were generallymeasured near cities. Why would this affect the results?

To answer a multiple-choice question, read every choice before youanswer the question. Cross out the choices you know are wrong.Then choose the best answer from the remaining choices.


air pollution i -...

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