Download Chapter 12: Air Section 1: What Causes Air Pollution Clean air

Chapter 12: Air
Section 1: What Causes Air Pollution
• Clean air consists mostly of nitrogen and oxygen gas as well as very small amounts of argon, carbon
dioxide, and water vapor.
• When harmful substances build up in the air to unhealthy levels, the result is air pollution.
• Most air pollution is the result of human activity.
• Some does come from natural sources such as volcanic eruptions.
Primary and Secondary Pollutants
• A pollutant that is put directly into the air by human activity is called a primary pollutant. Soot from
smoke is an example.
• Secondary pollutants form when primary pollutants react with other primary pollutants or with
naturally occurring substances such as water vapor. Ground level ozone is an example. This happens
when UV rays cause emissions from vehicles to react with oxygen in the atmosphere.
Sources of Primary Air Pollution
• Household products, power plants, and motor vehicles are sources of primary air pollutants such as
carbon monoxide, nitrogen oxide, sulfur dioxide, and chemicals called volatile organic compounds
(VOCs).
• Carbon monoxide is an important component in the exhaust from vehicles.
• Nitrogen oxides come from vehicles and coal burning power plants.
• Sulfur dioxide forms when coal and oil are burned. Power plants, refineries, and metal smelting are
contributors as well.
• Most VOCs are from vehicles and gas station spillage.
The History of Air Pollution
• The problem is not new :
• 2,000 years ago, Seneca, a Roman philosopher, complained about the foul air in Rome.
• In 1273, King Edward I ordered the burning of sea coal illegal.
• Air quality is worse today because of industrial societies burn large amounts of fossil fuels.
• Most air pollution comes from motor vehicles and industry.
Motor Vehicle Emissions
• Almost 1/3 of our air pollution from gasoline burned by vehicles.
• In 1998 Americans drove over 2.6 trillion miles and 90% of that was passenger vehicles.
Controlling Vehicle Emissions
• The Clean Air Act, passed in 1970, gives the EPA the authority to regulate vehicle emissions in the U.S.
• The EPA called for the gradual elimination of lead in gasoline. As a result, lead pollution has been
reduced by more than 90%.
• Catalytic converters, which are now required, clean exhaust gases of pollutants before the pollutants
are able to escape the tailpipe.
• Cars today burn fuel 35% more efficiently and with 95% fewer emissions.
California Zero Emission Vehicle Program
• In California, vehicle emissions account for more than half of the ozone and particulate matter that
pollutes the air.
• In 1990, the state's Air Resource Board established the Zero Emission Vehicle (ZEV) program.
•
•
Battery powered vehicles are the only true ZEVs at the moment.
There are two types of partial ZEVs. Hybrids which are powered by both battery and gasoline and
methanol fuel cell cars (which are still developmental prototypes).
Industrial Air Pollution
• Many industries and power plants burn fossil fuels to produce energy.
• Burning fossil fuels releases sulfur dioxide and nitrogen oxides into the air.
• Power plants emit at least 2/3 of all sulfur dioxide and more than 1/3 of all nitrogen oxides that pollute
the air.
• Dry cleaning also produces VOCs as do oil refineries, chemical manufacturing plants, furniture
refinished, and automobile repair shops.
Regulating Air Pollution from Industry
• The Clean Air Act requires many industries to use scrubbers to remove some of the more harmful
substances that would otherwise pollute the air.
• A scrubber is a machine that moves gases through a water spray to dissolve many pollutants.
• Electrostatic precipitators are used in cement factories and coal burning power plants. Gas containing
dust particles are blown through an electrically charged chamber causing the particles to stick together
and the sides of the chamber. Clean gas is released and particle can be collected and removed.
• Electrostatic precipitators remove 22 million metric tons of ash every year.
Smog
• When air pollution hangs over urban areas and reduces visibility, it is called smog.
• Smog results from chemical reactions that involve sunlight, air, automobile exhaust, and ozone.
Temperature Inversions
• The circulation of air in the atmosphere usually keeps air pollution from reaching dangerous levels.
• During the day, the sun heats the surface of the Earth and air near the surface. Warm air rises through
the cooler air above it carrying pollutants away from the ground.
• Sometimes pollution is trapped near the Earth's surface. Usually air temperature decreases with
altitude, but sometimes a temperature inversion occurs. When this happens, the warmer air keeps the
cooler air at the surface from moving upward trapping pollutants in the cooler air closer to the surface.
• Cities in valleys have a greater chance of this occurring.
Section 2: Air, Noise, and Light Pollution
• The very young and very old with heart or lung problems are most susceptible.
• Death certificates will list diseases like emphysema and lung cancer instead of air pollution.
• Americans pay tens of billions of dollars annually to treat respiratory diseases caused by air pollution.
Short Term Effects of Air Pollution on Health
• Many effects of air pollution are short-term and reversible IF exposure decreases.
• Short-term effects include headache, nausea, irritation to the eyes, nose, and throat, tightness in the
chest, coughing, and upper respiratory infections like bronchitis and pneumonia.
• People who have asthma and emphysema can have symptoms worsen.
Long Term Health Effects of Air Pollution
• Long term effects include emphysema, lung cancer, and heart disease.
• Long term exposure may worsen symptoms especially in older people
Sick Building Syndrome
• Chemicals used to make carpets, building materials, paints, and furniture are the major sources of
indoor pollutants.
• Buildings that have very poor air quality have a condition called sick-building syndrome.
• This is most common in hot places where buildings are tightly sealed to keep the heat out.
• Identifying and removing the sources of indoor pollutants is the most effective way to maintain good
indoor air quality.
• Ventilation is necessary for good indoor air quality.
Radon Gas
• Radon is a colorless, odorless, tasteless gas that is radioactive. It is produced by the decay of uranium.
• Radon can seep through the cracks and holes in the foundation of homes, offices, schools, etc. where
it sticks to dust particles.
• In the lungs, radon can destroy the genetic material in the cells that line air passages.
• Radon is the second leading cause of lung cancer in the U.S.
Asbestos
• Several minerals that form in long, thin fibers and that are valued for their strength and resistance to
heat are called asbestos.
• Asbestos is primarily used as an insulator and fire retardant that was used extensively in building
materials.
• The U.S. banned the use of asbestos in the early 1970's.
• Asbestos fibers that are inhaled can cut and scar the lungs causing asbestosis. People who have this
have difficulty breathing and can die of heart failure.
Noise Pollution
• Unwanted sound is noise pollution.
• It is irritating, and it damages our hearing. Hearing loss has doubled in the U.S. in the past 30 years.
About 12% of teens have permanent hearing loss likely due to the use of portable listening devices.
The National Institutes of Health say the safe threshold for MP3 players is 85 dB for 8 hours.
• Sound intensity is measured in decibels (dB).
• Noise pollution can be controlled by devices such as mufflers on lawn mowers and vehicles.
Light Pollution
• Light pollution does not present a direct hazard to human health.
• Light pollution in urban areas diminishes our view of the night sky.
• The more important concern of light pollution is wasted energy.
• Solutions include shields to direct light downward, using timers, and low-pressure sodium sources
which are more efficient.
Section 3: Acid Precipitation
What Causes Acid Rain
Acid precipitation is precipitation such as rain, sleet, or snow that contains a high concentration of
acids.
When fossil fuels a burned, they release oxides of sulfur and nitrogen. When these oxides combine
with water vapor, they form sulfuric and nitric acid which fall as acid precipitation.
It can kill living things and cause decline or loss of plant and animal populations.
A pH number is a measure of how acidic or basic a substance is. The lower the pH, the more acidic the
substance is. The higher the pH the more basic a substance is. Pure water has a pH of 7.
Natural rain is slightly acidic because carbon dioxide dissolves into the precipitation forming carbonic
acid. Normal rain has a pH of about 5.6. Acid rain has a pH of less than 5.
How Acid Precipitation Affects Soil and Plants
Acid precipitation can cause a drop in the pH of soil and water. This increase is called acidification.
This changes the balance of a soil's chemistry. This causes some nutrients to dissolve and wash away.
It also causes aluminum and other toxic metals to be released and absorbed by plant roots.
Acid Precipitation and Aquatic Ecosystems
Aquatic animals are adapted to live in an environment with a particular pH range. If the pH of the
water changes, the fish and other organisms can die.
Acid precipitation causes aluminum to leech out of the soil, and aluminum in the gills of fish interferes
with oxygen and salt exchange.
Effects are worst in the spring when snow melts and rushes into lakes and rivers.
The sudden influx of acidic water is called acid shock.
Acid Precipitation and Humans
Toxic metals like aluminum and mercury can be released into the environment when soil acidity
increases. These metals find their way into crops, water, and fish; then they poison humans.
There is a correlation between acid rain and respiratory problems.
A decrease in the number of fish affects commercial fishermen. Forestry is affected when the trees are
damaged.
Calcium carbonate can dissolve which affects many monuments and creates sink holes.
International Conflict and Cooperation
One problem is that pollutants released in one area may fall to the ground hundreds of miles away.
Acid precipitation is an international problem. Canada and the U.S. signed the Canada-U.S. Air Quality
Agreement in 1991. Both countries agreed to reduce emissions that flow across the U.S. Canada
border.
Sulfur dioxide emissions have reduced significantly because agreements like this.
China still burns large amounts of high-sulfur without pollution controls.
Chapter 13: Atmosphere and Climate Change
Section 1: Climate and Climate Change
 Weather is the state of the atmosphere at any given moment.
 Climate is the long-term prevailing weather conditions at a particular place based upon records.
What Factors Determine Climate
 Climate is determined by a variety of factors including latitude, atmospheric circulation patterns,
oceanic circulation patterns, local geography, solar activity, and volcanic activity.
 Latitude, however, is the most important factor.
Latitude
 Latitude is the distance from the equator measured in degrees north or south
 The equator is 0 degrees latitude; the North Pole is 90 degrees north, and the South Pole is 90
degrees south.
Low Latitudes
 Latitude influences climate because the amount of solar energy an area of Earth receives depends
on its latitude.
 More solar energy falls near the equator than the poles.
 Near the equator, night and day are about 12 hours each. Temperatures are constant year round.
There are no summer and winter.
High Latitudes
 In regions close to the pole, the amount of energy arriving at the surface is reduced.
 Sunlight strikes at oblique angles and spreads over a larger surface area than at the equator.
 Average temperatures are lower because of this, and the amounts of daylight vary.
 Some places get 16 hours of daylight in the summer and 8 in the winter. Near the poles, the sun
sets for only a few hours each day in the summer and rises for only a few hours in the winter.
Atmospheric Circulation
 Three important properties of air illustrate how air circulation affects climate.
 First, cold air sinks because it is more dense than hot air.
 Second, warm air rises expanding and cooling as it rises.
 Third, warm air can hold more water vapor than cold air can. When warm air cools, the water
vapor may condense into liquid water forming rain, snow, or fog.
 Solar energy heats the ground which warms the air above it. The warm air rises and cool air
replaces it. This movement of air within the atmosphere is wind.
 Because Earth rotates and different latitudes receive different amounts of solar energy, the
pattern of global atmospheric circulation results.
 This pattern determine Earth's precipitation pattern.
 Air near Earth's surface at the equator becomes very warm and able to hold a lot of water vapor. As
it rises and cools it loses some of its ability to hold the water, so areas near the equator get more
rain.
Global Circulation Patterns
 Cool air normally sinks, but cool air at the equator cannot sink because hot air is rising below the cool
air.







The cool air rises and is forced away from the equator toward the poles.
At about 30 degrees north and south, some of this cool air sinks back down to the Earth's surface.
As it descends, it becomes warmer. This now warm, dry air moves across the surface causing water to
evaporate from the land below creating dry conditions.
Air descending at 30 degrees north or south either move toward the equator or the poles.
At about 60 degrees north or south, this air collide with cold air traveling from the poles.
Warm air rises reaching the top of the troposphere, but a small amount returns back to the circulation
pattern between 60 and 30 degrees.
Most is uplifted toward the poles creating very cold deserts.
Prevailing Winds
 Belts of prevailing winds blow most of the time between 30 degrees north and south and are called
trade winds. They blow from the northeast in the Northern Hemisphere and from the southeast in the
Southern Hemisphere.
 Prevailing winds known as the westerlies are produced between 30 and 60 degrees north and south.
In the Northern Hemisphere these are southwest winds, and in the Southern Hemisphere they are
northwest winds.
 Polar easterlies blow from the poles to 60 degrees north and south.
Oceanic Circulation Patterns
 Ocean currents have a great effect on weather because water holds large amounts of heat.
 Movement of surface ocean currents is caused by both winds and the rotation of Earth. This
redistributes warm and cool masses of water around the planet.
El Nino—Southern Oscillation
 El Niño is the name given to the short term (6 - 18 month), periodic change in the location of warm
and cold water masses in the Pacific Ocean.
 During El Niño, winds in the western Pacific, which are usually weak, strengthen and push warm water
eastward.
 Rainfall follows this warm water and produces increased rainfall in the southern half of the U.S. and in
equatorial South America.
 El Niño causes drought in Indonesia and Australia.
La Nina
 During La Niña, the water in the eastern Pacific is cooler than usual.
 El Niño and La Niña are opposite phases of the El Niño--Southern Oscillation cycle.
 El Niño is the warm phase and La Niña is the cold phase.
Pacific Decadal Oscillation
 The Pacific Decadal Oscillation (PDO) is a long term (20 - 30 year) change in the location of warm and
cold water masses in the Pacific Ocean.
 PDO influences the climate in the northern Pacific and North America.
 It affects ocean surface temperatures, air temperatures, and precipitation patterns.
Topography
 Mt. Kilimanjaro, a 5,896 m extinct volcano, is 3 degrees south of the equator, but snow covers its peak
year round.
 Kilimanjaro illustrates the important effect of height above sea level.
 Temperatures fall about 11 degrees for every 1,000 m increase in elevation.
 Mountains and mountain ranges influence the distribution of rainfall.
 Warm air rises and cools as it rises causing rain on the western side of the mountains. By the time it
reaches the eastern side of the mountain, the air is dry. This effect is known as the rain shadow.
Other Influences on Earth’s Climate
 Both the sun and volcanic eruptions influence Earth's climate.
 At a solar maximum, the sun emits an increased amount of UV radiation which produces more ozone,
warming the stratosphere. The increased radiation can also warm the lower atmosphere and surface of
the Earth.
 In large scale volcanic eruptions, sulfur dioxide gas can reach the upper atmosphere which reacts with
water vapor and dust creating a bright layer of haze that reflects sunlight causing the global
temperature to decrease.
Seasonal Changes in Climate
 Seasons result from the tilt of Earth's axis (about 23.5 degrees).
 Because of this tilt, the angle that the sun's rays strike Earth changes as the Earth moves around the
sun.
 During our summer, the Northern Hemisphere tilts toward the sun and receives direct sunlight. During
our winter, the Southern Hemisphere is tilted toward the sun.
Section 2: The Ozone Shield
The Ozone Layer
The ozone layer is an area in the stratosphere where ozone is highly concentrated.
Ozone is a molecule made of 3 oxygen atoms.
The ozone layer absorbs most of the UV radiation from the sun.
Ozone acts like sunscreen for the Earth.
Chemicals that Cause Ozone Depletion
During the 1970's scientists began to worry that chlorofluorocarbons (CFCs) might be damaging the
ozone layer.
People liked CFCs because they are not poisonous, nonflammable, and do not corrode metals.
They were popular as coolants in refrigerators and air conditioners.
They were also used to produce a fizz in plastic foams and as a propellant in spray cans.
At Earth's surface, CFCs are stable, but they break apart in the stratosphere and destroy the ozone
layer in the process.
Over a 10 - 20 year period, CFCs make their way to the stratosphere.
Each CFC molecule has 1 - 4 chlorine atoms, and a single chlorine atom can destroy 100,000 ozone
molecules.
The Ozone Hole
In 1985, Nature reported the studies by scientists in Antarctica.
The studies revealed that the ozone layer above the South Pole had thinned by 50 - 98%.
This was the first news of an ozone hole.
NASA scientists reviewed data collected from the Nimbus 7 satellite launched in 1978. They were able
to see the first signs in 1979.
Data fluctuates during the year, but the hole is growing. The same thing is happening in the Arctic as
well.
How Does the Ozone Hole Form?
During the dark, polar winter, strong circulating winds over Antarctica, called the polar vortex, isolate
cold air from surrounding warmer air.
The air in the vortex grows extremely cold.
When the temperature falls below -80 C, polar stratospheric clouds, made of water and nitric acid,
form.
On the surface of polar stratospheric clouds, CFCs are converted into molecular chlorine.
When sunlight returns in the spring, molecular chlorine is split into two chlorine atoms by UV radiation.
Chlorine atoms rapidly destroy ozone. As much as 70% of the ozone layer can be destroyed in the
spring.
Ozone produced by pollution cannot help solve the problem because it combines with other
substances in the troposphere before reaching the stratosphere.
The Effects of Ozone Thinning on Humans
As the amount of ozone in the stratosphere decreases, more UV light is able to pass through the
atmosphere and reach Earth's surface.
UV is dangerous to living things because it can damage DNA.
Exposure to UV light makes the body more susceptible to skin cancer.
The Effects of Ozone Thinning on Animals and Plants
High levels of UV light can kill phytoplankton. This could disrupt ocean food chains and reduce fish
harvests.
Reduction in phytoplankton would also cause an increase in the amount of atmospheric carbon
dioxide.
This would be really devastating for amphibians that lay eggs in shallow water of ponds and streams.
The health of amphibian populations is used as an indicator of environmental change due to the
sensitivity of amphibians.
Plants can be damaged because increased UV exposure interferes with photosynthesis.
Protecting the Ozone Layer
In 1987, a group of nations met in Canada to take action against ozone depletion.
In the agreement made, The Montreal Protocol, these nations greed to sharply limit their production
of CFCs.
A second conference was held in 1992 in Copenhagen, Denmark. Developed countries agreed to
eliminate most CFCs by 1995.
The U.S. pledged to ban all substances that pose a threat to the ozone layer by 2000.
Aerosol cans no longer use propellants, air conditioners are becoming CFC free.
The battle, however, is not over because CFC molecules stay in the stratosphere for 60 - 120 years.
Section 3: Global Warming
The Greenhouse Effect
The Earth is similar to a greenhouse in that the atmosphere acts like a greenhouse.
Sunlight streams through the atmosphere and heats Earth. Heat radiates up from Earth's surface, and
some escapes into space.
The rest of the heat is absorbed in the troposphere and warms the air. The process of absorption is
called the greenhouse effect.
The gases that absorb and radiate heat are called greenhouse gases.
The major greenhouse gases are water vapor, carbon dioxide, chlorofluorocarbons, methane, and
nitrous oxide. Water vapor and carbon dioxide account for most of the absorption.
Measuring Carbon Dioxide in the Atmosphere
In 1958, Charles Keeling, a geochemist, installed an instrument at the top of a tall tower on the volcano
Mauna Loa in Hawaii.
He wanted to measure the amount of carbon dioxide in the air far from forests and cities where levels
vary every day.
The winds that blow over Mauna Loa have travelled thousands of mile across the Pacific Ocean.
Most of the carbon dioxide that is released into the air dissolve in the ocean or is used by plants for
photosynthesis causing levels to vary with the seasons.
During the summer plants are using carbon dioxide for photosynthesis causing the levels to drop in the
summer and increase in the winter when leaves and grass are dying.
Rising Carbon Dioxide Levels
After a few years of measuring carbon dioxide levels, it was clear they were changing in ways other
than seasonal fluctuations.
Levels have increased over 20% in the past 50 years. This is largely due to the carbon dioxide released
when fossil fuels are burned.
Carbon dioxide levels from thousands of years go can be determined by using ice cores drilled from ice
sheets.
Today's levels are higher than they have been in the last 420,000 years.
Greenhouse Gases and the Earth’s Temperature
Many scientists believe that because greenhouse gases trap heat net Earth's surface, more greenhouse
gases will result in an increase in global temperature.
A comparison of carbon dioxide in the atmosphere and average global temperatures for the past
400,000 years supports this view.
Today we are releasing more carbon dioxide than any other greenhouse gas into the atmosphere.
Millions of tons are released each year from power plants that burn coal or oil and from cars that burn
gasoline.
Millions of trees are burned in tropical rain forests to clear the land for farming, thus also increasing
the amount of carbon dioxide being released.
Global Warming
Earth's surface temperature has increased in the 20th century, and this increase is called global
warming.
Because the temperature is rising at a similar rate to greenhouse gases, many scientists have
hypothesized that the increase in greenhouse gases has caused the increase in temperature.
Thousands of experiments and computer models support this hypothesis.
The increase in temperature is predicted to continue throughout the 21st century.
Modeling Global Warming
Predictions about future changes in climate are based on computer models.
Scientists write equations that represent the atmosphere and ocean then enter data about carbon
dioxide levels, prevailing winds, and other variables.
The resulting models can be used to predict how temperature and sea level will be affected.
Computer models are not always accurate, but they are becoming more reliable.
Consequences of a Warmer Earth
In North America, tree swallows, Baltimore orioles, and robins are nesting 11 days earlier than 50 years
ago.
In Britain, at least 200 species of plants are flowering up tom55 days earlier than they did 40 years ago.
This is not proof of global warming; however, we do know when certain birds nest and the time at
which flowers are supposed to bloom and both are strongly influenced by temperature.
The possible effects of global warming include a number of potentially serious environmental problems
such as a change in weather patterns and rising sea levels.
Melting Ice and Rising Sea Levels
Ice melts as global temperatures increase causing the amount of ice near the poles to decrease.
The melting ice from land masses, such as Greenland and Antarctica, causes se levels to rise
worldwide.
Sea levels rising could cause coastal wetlands and other low lying areas to flood.
Enormous numbers of people who live near the coast could lose their homes and source of income.
Beaches could erode. Salinity in bays and estuaries might increase adversely affecting marine fisheries.
Coastal freshwater aquifers could become too salty to use for freshwater.
Global Weather Patterns
If the Earth warms significantly, the oceans will absorb ore heat which may make hurricanes and
typhoons more common.
Some are concerned that there will be a change in ocean current patterns such as cutting off the Gulf
Stream.
Such changes would significantly affect the world's weather. Severe flooding and drought may occur.
Human Health Problems
Greater numbers of heat related deaths would occur. Very young and very old city dwellers are at
greatest risk.
Since trees and flowering plants would bloom earlier and longer, people with allergies would suffer
longer.
Warmer weather would enable mosquitoes (carriers of malaria, dengue fever, and encephalitis) to
establish themselves in areas that are too cold for them currently.
Agriculture
Agriculture would be severely impacted by extreme weather events such as droughts.
Higher temperatures would decrease crop yield.
Demand for irrigation would further deplete aquifers.
Effects on Plants and Animals
Climate change could alter both the range of plant species and the composition of plant communities.
Global warming may cause a shift in the geographical range of some animals. For example, birds may
not have to migrate as far for the winter.
Warming in the ocean might reduce zooplankton which many marine species depend on for food.
Warming in tropical waters may kill algae that nourish coral, thus destroying coral reefs.
Recent Findings
The Intergovernmental Panel on Climate Change (IPCC) is a network of around 2,500 of the world's
leading climatologists from 70 countries.
The Third Assessment Report (TAR) was released in 2001 describing what is currently known as the
global climate system and provides future estimates about the state of the global climate system.
Findings: average global surface temperature increased 0.6 degrees during the 20th century, snow
cover and ice extent have decreased, average global sea level has risen, and atmospheric greenhouse
gases have continued to increase as a result of human activity.
It also predicts that human influences will continue to change the composition of the Earth's
atmosphere throughout the 21st century.
Reducing the Risk
In 1997, representatives from 160 countries met and set time tables for reducing emissions of
greenhouse gases.
This time table will go into effect when a treaty called the Kyoto Protocol is ratified by 55% of the
attending nations.
The Kyoto Protocol requires developed countries to decrease emissions of carbon dioxide and other
greenhouse gases by 5% below 1990 levels by 2012.
In March 2001, the U.S. decided not to ratify the Kyoto Protocol. Most developed nations are going
ahead with the treaty.
Some nations have engaged in reforestation projects to reduce carbon dioxide.
The attempt to slow global warming is made difficult by economic, political, and social factors faced by
different countries.