AP ENVIRONMENTAL SCIENCE
AIR POLLUTION
ATMOSPHERE
The atmosphere is a gaseous envelope composed of Nitrogen (78.08%),
Oxygen(20.95%), argon (0.93%), and carbon dioxide (0.04%). Other gases and
particles, including those we call pollutants occur in much smaller
concentrations.
The two atmospheric gases most important to humans and other organisms are
carbon dioxide and oxygen. During plants use carbon dioxide to manufacture
sugars and other organic molecules and this process produces oxygen. During
cellular respiration, most organisms use oxygen to break down food molecules
and supply themselves with energy and this process produces carbon dioxide.
Nitrogen gas is an important component of the nitrogen cycle.
The atmosphere also performs ecosystem services, namely blocking Earth’s
surface from much of the ultraviolet radiation coming from the sun, moderating
the climate, and redistributing water in the hydrologic cycle.
Types and sources of Air Pollution
Air pollution consists of gases, liquids, or solids present in the atmosphere in
high enough levels to harm humans, and other organisms or materials.
Natural sources of air pollution - fires, volcanic eruption.
Human activities release many kinds of substances into the atmosphere and
make a major contribution to air pollution. Much of the air pollution released by
humans is concentrated in densely populated urban areas.
Important pollutants are: particulate matter, nitrogen oxides, sulfur oxides,
carbon dioxides, hydro carbons, ozone, and air toxics. Air pollutants are divided
into two categories
 Primary air pollutants are harmful chemicals that enter directly into the
atmosphere like carbon dioxides, nitrogen oxides, sulfur oxides, and
particulate matter.
 Secondary air pollutants are harmful chemicals that form from other
substances released into the atmosphere. Ozone and sulfur trioxide are
secondary air pollutants because they are formed by chemical reactions
that take place in the atmosphere.
Refer to the table in your text book Table 20.1 on Major air pollutants.
Major classes of air pollutants
Table 20-1 Major Classes of Air Pollutants
Particulate matter consists of different solid and liquid particles
suspended in the atmosphere.
Solid particulate matter is generally referred to as dust.
Liquid suspensions are commonly called mists.
Particulate matter includes a variety of pollutants such as soil particles,
soot, lead, asbestos, sea salt, sulfuric acid droplets. Of these dust, lead are
primary pollutant whereas sulfuric acid is an example of a secondary pollutant.
 Major human sources: Burning coal in power and industrial plants
(40%), burning diesel and other fuels in vehicles (17%), agriculture
(plowing, burning off fields), unpaved roads, construction.
Effect of particulate matter
 Reduces visibility by scattering and absorbing sunlight. Urban areas
receive less sunlight than rural areas, partly as a result of greater
quantities of particulate matter in the air.
 It corrodes metals, erodes buildings and works of sculpture when
the air is humid.
 Soils clothing and draperies.
 Heavy metals present in the particulate matter such as asbestos can
have carcinogenic effects.
 Being extremely small particles, even if not toxic, can get lodged
deep in the lungs.
 Health effects: Nose and throat irritation, lung damage, and
bronchitis; aggravates bronchitis and asthma; shortens life; toxic
particulates (such as lead, cadmium, PCBs, and dioxins) can cause
mutations, reproductive problems, cancer.
 Environmental effects: Reduces visibility; acid deposition of H2SO4
droplets can
 damage trees, soils, and aquatic life in lakes.
 Property damage: Corrodes metal; soils and discolors buildings,
clothes, fabrics, and paints.
NITROGEN OXIDES
Collectively known as NOx, nitrogen oxides consist mainly of nitric oxide (NO),
nitrogen dioxide (NO2), and nitrous oxide (N2O).
Cause : Produced by the chemical interactions between atmospheric nitrogen
and oxygen when a source of energy, such s combustion of fuels, produces high
temperature.
Effects
 Nitrogen oxides inhibits plant growth
 When breathed aggravate health problems such as asthma, in which
breathing is wheezy and labored because of airway constriction
 They are involved in the production of photochemical smog and acid
deposition
 Nitrous oxide is associated with global warming as it traps heat in the
atmosphere and is therefore a greenhouse gas and depletes ozone in the
stratosphere
 Nitrogen oxides cause metals to corrode and textiles to fade and
deteriorate.
 NITROGEN DIOXIDE (NO2)
 Description: Reddish-brown irritating gas that gives photochemical smog
its brownish color; in the atmosphere can be converted to nitric acid
(HNO3), a major component of acid deposition.
 Major human sources: Fossil fuel burning in motor vehicles (49%) and
power and industrial plants (49%).
 Health effects: Lung irritation and damage; aggravates asthma and
chronic bronchitis; increases susceptibility to respiratory infections such
as the
 flu and common colds (especially in young children and older adults).
 Environmental effects: Reduces visibility; acid deposition of HNO3 can
damage trees, soils, and aquatic life in lakes.
 Property damage: HNO3 can corrode metals and eat away stone on
buildings, statues, and monuments; NO2 can damage fabrics.
SULFUR OXIDES
CAUSES
 Produced by the chemical interactions between sulfur and oxygen.
 It is a colorless, nonflammable gs with a strong, irritating dor, emitted as a
primary air pollutant.
 SO3, a secondary air pollutant that forms when sulfur dioxide react with
oxygen in air. Sulfur trioxide, in turn reacts with water to form another
secondary air pollutant, sulfuric acid.
EFFECTS
 Sulfur oxides cause acid deposition, and they corrode metals and
damage stone and other materials.
 Sulfuric acid and sulfate salts produced in the atmosphere from sulfur
oxides damage plants and irritate the respiratory tracts of humans and
other animals.
SULFUR DIOXIDE
 Description: Colorless, irritating; forms mostly from the combustion of
sulfur containing fossil fuels such as coal and oil (S + O2
SO2); in the
atmosphere
 can be converted to sulfuric acid (H2SO4), a major component of acid
deposition.
 Major human sources: Coal burning in power plants (88%) and
industrial processes
 (10%).
 Health effects: Breathing problems for healthy people; restriction of
airways in people with asthma; chronic exposure can cause a
permanent condition similar to bronchitis. According to the WHO, at
least 625 million people are exposed to unsafe levels of sulfur dioxide
from fossil fuel burning.
 Environmental effects: Reduces visibility; acid deposition of H2SO4 can
damage trees, soils, and aquatic life in lakes.
 Property damage: SO2 and H2SO4 can corrode metals and eat away
stone on buildings, statues, and monuments; SO2 can damage paint,
paper, and leather.

CARBON OXIDES
Carbon monoxide (CO)
Description: Colorless, odorless gas that is poisonous to air-breathing animals;
forms during the incomplete combustion of carbon-containing fuels (2 C + O2
2 CO).
Major human sources: Cigarette smoking ,incomplete burning of fossil fuels.
About 77% (95% in cities)comes from motor vehicle exhaust.
Health effects: Reacts with hemoglobin in red blood cells and reduces the ability
of blood to bring oxygen to body cells and tissues. This impairs perception and
thinking; slows reflexes; causes headaches, drowsiness, dizziness, and nausea;
can trigger heart attacks and angina; damages the development of fetuses and
young children; and aggravates chronic bronchitis, emphysema, and anemia. At
high levels it causes collapse, coma, irreversible brain cell damage, and death.
HYDROCARBONS
Hydrocarbons are a diverse group of organic compounds that contain only
carbon and hydrogen. Methane is a colorless, odorless gas that is the principal
component of natural gas. Medium size hydrocarbons are liquid at room
temperature like benzene. The largest hydrocarbons, such as the waxy
substance paraffin are solids at room temperature.
 Some hydrocarbons injure the respiratory tract, and still others cause
cancer.
 All except methane are important in the production of photochemical
smog.
 Methane is a potent greenhouse gas linked to global climate change.
.
EFFECTS OF AIR POLLUTION
Air pollution and human health
Health effects of several major air pollutants
Pollutant
Particulate
Source
Effects
Industries, electric power Aggravates respiratory
plants, motor vehicles,
illness; long-term
construction, agriculture
exposure may cause
increased incidence of
chronic conditions such
as bronchitis; heart
disease; suppresses
immune system; some
particles such as heavy
metals may cause cancer
or other tissue damage.
Nitrogen oxides
Motor vehicles,
Irritate respiratory tract;
industries, heavily
asthma and chronic
fertilized farmland
bronchitis
Sulfur oxides
Electric power plants and Irritate respiratory tract;
other industries
same effects as
particulates
Carbon monoxides
Motor vehicles,
Reduces blood’s ability
industries, fireplaces
to transport oxygen;
headache and fatigue at
lower levels; mental
impairment or death at
high levels. People at
greatest risk from carbon
monoxide include
pregnant women,
infants, and those with
heart or respiratory
disease.
ozone
Formed in the
Irritate eyes; irritates
atmosphere as a
respiratory tract;
secondary pollutant
coughing; produces chest
discomfort; aggravates
respiratory conditions
such as asthma and
chronic conditions
CHILDREN AND AIR POLLUTION
Air pollution is a greater health threat to children than it is to adults.
 The lungs continue to develop throughout childhood, and air pollution
can restrict lung development, making children vulnerable to health
problems later in life.
 A child has a higher metabolic rate than an adult and needs more oxygen.
To obtain this oxygen, a child breathes more air-about two times as much
air per pound of body weight as an adult. This means that a child
breathes more air pollutants into the lungs.
 Results from the study of children exposed to air pollution in southern
California in 2001, indicate that children who live in high-ozone areas and
participate in sports are more likely to develop asthma than children who
live there but do not participate in sports.
 Results also indicate that children who breathe the most polluted air
(higher concentration of nitrogen dioxide, particulate matter, and acid
vapor) have less lung growth than children who breathe cleaner air. If
children moved to areas with less particulate air pollution, their lung
development increased, but if they moved to areas with worse
particulate air pollution their lung development decreased.
Controlling air pollutants
 Many measures followed for energy efficiency and energy
conservation also reduce air pollution.
 Hybrid cars and natural-gas powered buses, for example, produce
much lower emissions than do their predecessors.
 Historically “command and control” technologies have been used to
reduce emissions. This means equipment that limits the emissions
after they have been generated. This technological process can be
more expensive than alternatives such as changing industrial
processes to reduce emissions.
 Smokestacks fitted with electrostatic precipitators, fabric filters,
scrubbers, or other technologies remove particulate matter.
Particulate matter is also controlled by careful land-excavating




activities, such as sprinkling water on dry soil being moved during
road construction.
Several methods exist for removing sulfur oxides from flue (chimney)
gases, but it is often less expensive to switch to a low-sulfur fuel such
as natural gas or even to a non-fossil fuel energy source such as solar
energy. Sulfur can be removed from fuels before they are burned, as
in coal gasification.
Gasoline is extremely volatile, and gasoline vapors can be a major
source of VOCs. In order to reduce these emissions, gasoline sellers in
most urban parts of the world require some form of vapor recovery.
Phase I vapor recovery involves underground storage tanks at gas
stations. As one hose from a delivery truck fills the underground tank,
another returns the vapor in the tank- which otherwise would be
vented to the atmosphere – to the truck. The truck then returns to the
gasoline depot, where the vapor are either combusted, or condensed
into gasoline. Phase II vapor recovery involves removing vapor from
the gas tank in cars as the gas is pumped in. these vapors are usually
returned to the underground tank for removal in the Phase I process.
Lower combustion temperature in automobile engines reduces the
formation of nitrogen oxides.
Mass transit reduces automobile use, thereby decreasing nitrogen
oxide emissions.
http://www.youtube.com/watch?v=PXV6ppONgUk
Ozone depletion
OZONE DEPLETION IN THE STRATOSPHERE
In the stratosphere, ozone extends from 10 to 45 km above Earth’s surface,
oxygen reacts with UV radiation coming from the sun to form ozone.
STRATOSPHERIC OZONE PREVENTS MUCH OF THE SOLAR UV radiation from
penetrating to Earth’s surface. Unfortunately, certain human made pollutants
(chloroflurocarbons, or CFCs react with stratospheric ozone breaking it down
into molecular oxygen. Most ozone is formed over the tropics. However, slow
circulation currents carry the majority of it to the poles, resulting in the thickest
layers over the poles and the thinnest layer above the tropics. It also varies
somewhat due to season, being somewhat thicker in the spring and thinner
during the autumn. The increase in temperature with height in the stratosphere
occurs because of absorption of ultraviolet radiation by ozone.
Ozone is formed in the stratosphere by the reaction of ultraviolet radiation
striking an oxygen molecule. This results in the oxygen molecule splitting apart
and forming atomic oxygen: O2-- O + O. atomic oxygen can now react with
molecular oxygen to form ozone: O + O2- O3. The reverse reaction also occurs
when ultraviolet radiation strikes an ozone molecule, causing it to form atomic
oxygen and molecular oxygen.
Atomic oxygen can also react with ozone to produce oxygen gas. Generally
these reactions balance each other so that concentrations of ozone remains
fairly constant, which keeps the amount of UV radiation reaching Earth also
constant.
Ultraviolet Radiation
The sun emits a wide variety of electromagnetic radiation, including infrared,
visible, and ultraviolet. Ultraviolet can be subdivided into three forms: UVA,
UVB, and UVC.
UVA
320 to 400 nm wavelength. Closer to blue light in the visible spectrum. The form
that causes skin tanning. UVA radiation is 1,000 times less effective than UVB in
producing skin redness, but more of it reaches Earth surface than UVB. Birds,
reptiles, and bees can see UVA. Many birds have patterns in their plumage that
are not visible in the normal spectrum but become visible in the ultraviolet.
UVB
290 to 320 nm in wavelength. Causes blistering sunburns and is associated with
skin cancer.
UVC
10 to 290 nm. Found only in the stratosphere and largely responsible for the
formation of ozone.
CAUSES OF OZONE DEPLETION
THINNING OF THE OZONE LAYER WS FIRST DISCOVERED IN 1985. IT OCCURS
SEASONALLY AND IS DUE TO THE PRESENCE OF HUMAN-MADE COMPOUNDS
CONTAINING HALOGENS (CHLORINE, BROMINE, FLUORINE OR IODINE)
The ozone over the Antarctic has decreased as much s 60% since the late 1970s
with an average net loss of about 3% pr year worldwide.
Halocarbons/halons




Fire retardant (fire extinguishers)
Soil-fumigant/pesticide (e.g.methyl bromide)
Solvents
Foam-blowing insulation
Chloroflurocarbons (CFCs)




Coolant/refrigerant/air conditioners/refrigerators
Aerosol or propellant
Foam-blowing plastics/insulation (Styrofoam)
Solvents/cleaners (e.g. methyl chloroform, carbon tetrachloride
Chlorofluorocarbons are responsible for the depletion of the ozone layer. First
manufactured during the 1920s, they are used as refrigerants (for example
Freon), aerosol propellants, electrical part cleaning solvents, and in the
manufacture of foam products and insulation. The largest single source of CFCs
to the atmosphere is leakage from air conditioners. The average residence time
of CFCs in the environment is 200 years.
When a CFC molecule enters the stratosphere, UV radiation causes it to
decompose and produce atomic chlorine.
This atomic chlorine then reacts with ozone in the atmosphere to produce
chlorine monoxide. (ClO). The chlorine monoxide then reacts with more ozone
to produce even more atomic chlorine in what becomes a essentially a chain
reaction.
Cl + O3 -- ClO + O2
ClO + O3---Cl + 2O2
Thus one chlorine atom released from a CFC can ultimately destroy over 100,000
ozone molecules.
Bromine found in much smaller quantities than chlorine, is about 50 times more
effective than chlorine in its effect in stratospheric ozone depletion and is
responsible for 20% of the problem. Bromine is found in halons, which are used
in fire extinguishers. Methyl bromide is used in fumigation and agriculture. It is
naturally released from phytoplankton and biomass burning.
EFFECTS OF OZONE DEPLETION






Increases in skin cancer
Increases in sunburns and damages to the skin
Increases in cataracts of the eye
Reduction in crop production
Deleterious effects to animals
Reduction in growth of phytoplankton and the cumulative effect on food
webs
 Increase in mutations since UV radiation causes change in DNA structure
 Reduction in the body’s immune system
 Climatic change
STRATEGIES FOR REDUCING OZONE DEPLETION
 There are several alternatives to CFC use. First, HCFC replaces chlorine
with hydrogen. Unfortunately it is still capable of destroying ozone less
effectively because it breaks down more readily in the troposphere.
 Second, alternatives to halons can be used in fire extinguishers.
 Third, helium, ammonia, propane, or butane can be used as a coolant.
Helium-cooled refrigerators use 50% less electricity than those using CFCs
or HCFCs.
 Individuals can use pump sprays instead of aerosol spray cans when
possible, comply with disposal requirements of the Clean Air Act for old
refrigerators and air conditioners, and when choices are available, use
ozone friendly products, and support legislation tht reduces ozonedestroying products.
RELEVANT LAWS AND TREATIES
MONTREAL PROTOCOL (1987)
Designed to protect the stratospheric ozone layer. The treaty was originally
signed in 1987 and substantially mended in 1990 and 1992. The Montreal
Protocol stipulated that the production and consumption of compounds that
deplete ozone in the stratosphere – Chloroflurocarbons (CFCs), halons, carbon
tetrachloride, and methyl chloroform – were to be phased out by 2000 (2005 for
methyl chloroform)
London (1990)the countries that signed the Montreal Protocol met again in
London and decided that a total phaseout of CFCs was necessary. They agreed
that this could be achieved by the year 2000. Control measures were also
adopted for carbon tetrachloride and methyl chloroform.
Copenhagen (1992)
The phaseout schedule for CFCs was again accelerated with the industrialized
countries agreeing to stop production by 1996. This goal had already been
prescribed in the United States in the 1990 amendments to the Clean Air Act in
1994, the European Community decided that a phaseout could be achieved in
Europe by 1995.
GLOBAL WARMING
http://www.youtube.com/watch?v=oJAbATJCugs
http://www.youtube.com/watch?v=zQZO0K4m1iQ
Effects of global warming
http://www.youtube.com/watch?v=fxmG5tGYbys
WHEN SUNLIGHT STRIKES Earth’s surface, some of it is reflected back toward
space as infrared radiation (heat). Greenhouse gases absorb this infrared
radiation and trap the het in the atmosphere.
U.S. anthropogenic greenhouse gas emissions 2001
Greenhouse gas
Carbon dioxide
Carbon tetra
chloride
Halons
Average time in
Relative
Troposphere(years) warming
potential
(CO2=1)
100
1
source
45
1,500
65
6,000
Cleaning
solvent
Fire
extinguisher
Air
conditioners,
refrigerators.
Foam
products,
insulation
Air
conditioners,
refrigerators.
Foam
products,
insulation
Air
conditioners,
refrigerators.
Foam
products,
insulation
Rice
cultivation,
enteric
fermentation,
production of
coal, natural
gas leaks
Burning fossil
fuels,
fertilizers,
livestock
chloroflurocarbons 15 (100 in
stratosphere)
1,000-8000
HCFCs
10-400
500-2,000
HFCs
15-400
150-13,000
Methane
15
25
Nitrous oxide
115
300
Fossil-Fuel
Combustion,
deforestation,
cellular
respiration
Approximate
current
concentration
(PPB)
400,000550,00
2,200-2500
330-350
Sulfur
hexafluoride
3200
24,000
wastes,
plastic
manufacturing
Electrical
industry as a
replacement
for PCBs
Levels of several greenhouse gases have increased by about 25%
since large-scale industrialization began around 150 years ago.
During the past 20 years about three-quarters of human made carbon
dioxide emissions were from burning fossil fuels.
In the U.S, greenhouse gas emissions come mostly from energy use.
This is mainly due to fuel used for electricity generation, and weather
pattern affecting heating and cooling needs. Energy related carbon
dioxide emissions, resulting from petroleum and natural gas,
represent 82% of total U.S. anthropogenic greenhouse gas emissions.
Concentrations of carbon dioxide in the atmosphere are naturally
regulated by numerous processes collectively known as the carbon cycle.
The movement of carbon between the atmosphere and the land and
oceans is dominated by natural processes, such as plant photosynthesis.
Earth’s positive imbalance between emissions and absorption results in
the continuing growth in greenhouse gases in the atmosphere.
CONSEQUENCES OF GLOBAL WARMING
ACIDIFICATION
The oceans currently absorb 1 metric ton of carbon dioxide per person
per year. Increased carbon dioxide absorption of ocean will lower the pH
of seawater. This adversely affects corals, plankton, organisms with
shells, and reproduction rates as eggs and sperm are exposed to higher
levels of acid.
CHANGES IN TROPOSPHERIC WEATHER PATTERNS
Air temperatures today average 50F to 90F (30C to 50C) warmer than they
were before the Industrial revolution. Historic increases in air
temperature averaged less than 20F (10C) per 1000 years.
 Higher temperatures result in higher amounts of rainfall due to
higher rates of evaporation.
 Worldwide, hurricanes of category 4 or 5 have risen from 20% of
all hurricanes in the 1970s to 30% in the 1990s.
 More rainfall increases erosion, which then leads to higher rates of
desertification due to deforestation. This then leads to loss of
biodiversity s some species are forced out of their habitat.
 El Nino and La Nina patterns and their frequencies have changed.
DISPLACEMENT OF PEOPLE
By the year 2050, 150 million people will need to relocate due to the effects of
coastal flooding, shoreline erosion, and agricultural disruption.
Ecological productivity
Satellite photos have shown that productivity in the Northern Hemisphere has
increased since 1982. Biomass increases due to a warmer temperatures reaches
a certain point – the point where limiting factors of water and nutrients curb
future productivity increases. In the tropics, plants increase productivity more
than trees (which are carbon sinks). With higher percentages of plants due to
increased temperatures and carbon dioxide concentrations, the rates of
decomposition increase because plants are shorter lived. As a result more
carbon enters the carbon cycle.
GLACIER MELTING
 Total surface area of glaciers worldwide has decreased by 50% since the
end of 19th century.
 Temperatures f the Antarctic Southern Ocean roe 0.310F (0.170C) between
the 1950s and the 1980s.
 Glacier melting causes landslides, flash floods, glacier lake overflow, and
increased variation in water flows into rivers. Hindu Kush and Himalayan
glacier melts are reliable water sources for many people in China, India,
and much of Asia.
 Global warming initially increases water flow, causing flooding and
disease. Flow will then decrease as the glacier volume dwindles, resulting
in drought.
 Eventual decreases in glacial melt will affect hydroelectric production.
INCREASED HEALTH AND BEHAVIORAL EFFECTS
Higher temperatures result in higher incidences of heart –related deaths. Warm
temperature will be suitable for the spread of vectors carrying diseases like
malaria.
Increase in disease
Rates of malaria ( due to increase in mosquitoes), cholera, and other
waterborne diseases will increase.
INCREASED PROPERTY LOSS
Weather related disasters have increased 3-fold since the 1960s. Insurance
payouts have increased 15 fold during this same period. Much of this can be
attributed to people moving to vulnerable coastal areas.
Money that was designed to increase education, improve health care, reduce
hunger, and improve sanitation and fresh water supplies, will instead be spent
on mitigating the effects of global warming.
LOSS OF BIODIVERSITY
Arctic fauna will be most affected. The food webs of polar bears that depend on
ice flows, birds and marine mammals will be negatively impacted. Grasses have
become established in Antarctica for the first time. Many species of fish and krill
that require cooler waters will be negatively impacted. Decreased glacier melt
will impact migratory fish such as salmon, that need sufficient river flow.
Releases of methane from hydrates
ACID DEPOSITION
Robert Angus Smith, a British chemist, coined the term acid rain in 1872,
after he noticed that buildings in areas with heavy industrial activity were
worn away by rain. Acid precipitation, including acid rain, sleet, snow,
and fog, poses a serious threat to the environment.
Unitil recently, industrialized countries in the Northern Hemisphere had
been hurt the most, especially the Scandinavian countries, Central
Europe, Russia, and North America. More recently, largely due to highsulfur coal, acid rain has become a major concern in china, where sulfur
dioxide releases in 2010 are expected to be three times those of 1990.
A pH of 7 is neither acidic nor basic, whereas a pH less than 7 indicates an
acidic solution. A pH of 6 is 10 times more acidic than a solution with a pH
of 7. Similarly a solution with a pH of 5 is 10 times more acidic than a
solution with a pH of 6 and 100 times more acidic than a solution with a
pH of 7. A solution with a pH of greater than 7 is basic, or alkaline.
Normally rainfall is slightly acidic with a pH from 5 to 6 because carbon
dioxide and other naturally occurring compounds in the air dissolve in
rainwater, forming dilute acids. However, the pH of precipitation in the
northeastern United States averages 4 and is often 3 or even lower.
Cause of acid precipitation
Acid deposition occurs when sulfur dioxide and nitrogen oxides are
released into the atmosphere combines with moisture to form acids, and
are deposited on land through rain, snow, or condense (dew).
Most coal-burning power plants, or smelters, and other industrial plants
in developed countries use tall smokestacks to emit sulfur dioxide,
suspended particles, and nitrogen oxides high into the troposphere
where wind can mix, dilute, and disperse them. These acidic substances
remain in the atmosphere for 2-14 days, depending mostly on prevailing
winds, precipitation, and other weather patterns. During this time they
descent to the earth’s surface in two forms: wet deposition consisting of
acid rain, snow, fog, and cloud vapor with a pH less than 5.6 and dry
deposition consisting of acidic particles. The resulting mixture is called
acid deposition- sometimes called acid rain with a pH below 5.6.
Acid deposition is a regional air pollution problem in areas that lie
downward from coal-burning facilities and from urban areas with large
numbers of cars.
Motor vehicles are a major source of nitrogen oxides. Coal-burning power
plants, large smelters, and industrial boilers are the main sources of
sulfur oxide and nitrogen oxides. During their stay in the atmosphere,
sulfur dioxide and nitrogen oxides react with water to produce dilute
solutions of sulfuric acid, nitric acid and nitrous acid. Acid deposition
returns these acids to the ground, causing the pH of surface waters and
soil to decrease.
In some areas, soils contain basic compounds such as calcium carbonate,
or limestone that can react with and neutralize, or buffer, some inputs of
acids. The areas most sensitive to acid deposition are those with thin
acidic soils, which provide no such natural buffering, and those where the
buffering capacity of soils has been depleted by decades of acid
deposition.
http://www.youtube.com/watch?v=JRvvPOAWMAo
Acid rain animation
EFFECTS OF ACID PRECIPITATION
Acid deposition affects living and non-living things. It can cause or worsen
respiratory disease, attack metallic and stone objects, decrease
atmospheric visibility, kill fish, deplete soil of vital soil nutrients, and
harm crops and plants.
 Acid deposition contributes to chronic respiratory diseases such as
bronchitis and asthma.
 It can leach toxic metal such as lead and mercury from soils and
rocks into acidic lakes used as sources of drinking water. These
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
toxic metals can accumulate in the tissues of fish eaten by people,
mammals, and birds. Currently 45 U.S states have fish advisories
warning people especially pregnant women not to eat fish caught
from some their waters because of mercury contamination.
Acid deposition also damages statues, national monuments,
buildings, metals, and car finishes. For example, Michelangelo’s
statues and the Parthenon in Athens, Greece, the Washington
Monument in Washington D.C., historic sites in Venice and Rome,
and ancient Mayan ruins in Sothern Mexico are dissolving from the
onslaught of acid deposition.
Acidic particles in the air, especially sulfates, decrease atmospheric
visibility.
The link between acid deposition and aquatic animal populations is
well established. Studies conducted by EPA, and various state and
local organizations, show that lakes and ponds having pH values
lower than 5 had no fish populations. Toxic metals such as
aluminum dissolve in acidic lakes and streams and enter food webs
and adversely affected fishes. These ions asphyxiate many kinds of
fish by stimulating excessive mucus formation, which clogs their
gills. Several thousand lakes in Norway and Sweden contain no fish
because of excess acidity. In Ontario, Canada many lakes show
decline in fish population due to acidic lakes. A 2003 study found
that some of these lakes are slowly becoming less acidic, mostly
because of the country’s 1990 Clean Air Act. Some lakes are still
acidic as they are naturally surrounded by acidic soil.
The birds living in areas with pronounced acid deposition were
much more likely to lay eggs with thin fragile shells that break or
dry out before the chicks hatch. The inability to produce strong
eggshells was attributed to reduced calcium in the bird’s diets.
Calcium is unavailable because in acidic soils it becomes soluble
and is washed away, with little left for plant roots to absorb. A
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smaller amount of calcium for plant tissues means a smaller
amount of calcium available to others in the food chain.
Acid deposition can harm forest and crops- especially when the
soil pH is below 5.1 – be leaching essential plant nutrients such as
calcium and magnesium from soils and releasing ions of aluminum,
lead, cadmium, and mercury that are toxic to the trees. This
reduces plant productivity, tree growth, and the ability of soils to
buffer or neutralize acidic inputs. An estimated 30% of china’s
cropland suffers from excess acidity. Acid deposition rarely kills
trees directly, but can weaken them and leave them vulnerable to
stresses such as severe cold, diseases, insect attacks, drought, and
harmful mosses.
Forest surveys in the Black Forest of south western Germany
indicate that upto 50% of trees in the areas surveyed are dead or
severely damaged. More than half of the red spruce trees in the
mountains of the northeastern United States have died since the
mid-1970s, and sugar maples in eastern Canada and the United
States are dying. Beginning in the late 1990s, the Northern
Hardwood Damage Survey has observed and mapped tree death at
higher elevations of the Appalachian Mountains from Georgia to
Maine.
Many living trees exhibit symptoms of forest decline. The general
symptoms are reduced vigor and growth, some plants show
yellowing of needles in conifers. Forest decline is more pronounced
in higher elevations.
Mountaintop forests are the terrestrial areas hardest hit by acid
deposition. These areas tend to have thin soils without much
buffering capacity. And trees on mountaintops especially conifers
such as red spruce and balsam fir that keep their leaves year-round
are bathed almost continuously in very acidic fog and clouds.
Acid deposition has not reduced overall growth in the vast majority
of forests in the United States and Canada, partly because of
significant reduction in sulfur dioxide and nitrogen oxides
emissions from power and industrial plants under 1990
amendments to the Clean Air Act.
 Many factors interact to decrease the health of trees. Forest
decline appears to result from the combination of multiple factors
– acid deposition, tropospheric ozone, UV radiation which is more
intense at higher altitude, insect attack, drought, and so on.
 Acid deposition alters the chemistry of soils, which affects the
development of plant root as well their uptake of dissolved
minerals and water from soil.
THE POLITICS OF ACID PRECIPITATION
One reason acid deposition is so hard to combat is that it does not occur only in
the location where the gases that cause it are emitted. Acid deposition does not
recognize borders between states or countries; it is entirely possible for sulfur
or nitrogen oxides released in one spot to return to the ground hundreds of
kilometers from their sources.
Several states in the Midwest and East-Illinois, Indiana, Missouri, Ohio,
Pennsylvania, Tenessee, and west Virginia- produce between 50 and 75% of the
acid deposition that contaminates New England and southeastern Canada.
When legislation was formulated to deal with the problem, arguments ensued
about who should pay for the installation of expensive air pollution devices to
reduce emissions of sulfur and nitrogen oxides. Should the states emitting the
gases be required to pay all the expenses to clean up the air, or should some of
the cost be absorbed by the areas that stand to benefit most from a reduction in
pollution?
Pollution abatement issues are complex within one country but are magnified
even more in international disputes. England uses its large reserves of coal to
generate electricity. Gases from coal-burning power plants in England move
eastward with prevailing winds and return to the surface as acid deposition in
Sweden and Norway.
Also, countries with large supplies of coal (such as China, India, Russia, and the
United States) have a strong incentive to use it as a major energy resource.
Owners of coal-burning power plants also say the costs of adding the latest
pollution control equipment s, using low-sulfur coal, or removing sulfur from
coal are too high and would increase the cost of electricity for consumers.
Solutions: Reducing Acid Deposition
 Reducing emissions of sulfur dioxide and nitrogen oxides curbs acid
deposition.
 Installation of scrubbers in the smokestacks of coal-fired power plants
and use of clean-coal-technologies to burn coal without excessive
emissions effectively diminish acid deposition.
 Large amounts of limestone or lime can be used to neutralize acidified
lake or surrounding soil- the only cleanup approach now being used. This
expensive and temporary remedy must be repeated annually. Also, it can
kill some types of plankton and aquatic plants and can harm wetland
plants that need acidic water. Also it is difficult to know the amount of
lime to be added.
 In 2002, researchers in England found that adding a small amount of
phosphate fertilizer can neutralize excess acidity in a lake.
Reduced emissions have not altered acid deposition and also recovery of
forests. A primary reason for the slow recovery is probably that the past 30 or
more years of aid rain have profoundly altered soil chemistry in many areas.
Essential plant minerals such as calcium and magnesium have leached from
forest and lake soils. Because soils take hundreds or even thousands of years to
develop, it may be decades or centuries before they recover from the effects of
acid rain.
Many scientists are convinced that ecosystems will not recover from acid rain
damage until substantial reduction in nitrogen oxides emissions occur.
Nitrogen oxides are harder to control than sulfur oxides because motor vehicles
produce a substantial portion of nitrogen oxides. Engine improvements may
reduce nitrogen oxide emissions, but as the population continues to grow, the
engineering gains may be offset by an increase in the number of motor vehicles.
Dramatic cut in nitrogen oxide emissions will require a reduction in high
temperature energy generation, especially in gasoline and diesel engines.
INDOOR AIR POLLUTION
The air in enclosed places such s automobiles, homes, schools, and offices may
have significantly higher levels of air pollutants than the air outdoors. Indoor
pollution is of particular concern to urban residents because they may spend as
much s 90% to 95% of their time indoors. The EPA considers indoor pollution as
one of the top five environmental health risks in the United States.
EPA studies have revealed that levels of 11 common pollutants are generally
two to five times higher inside U.S homes and commercial building than
outdoors. Pollution levels inside cars in traffic-clogged urban areas can be upto
18 times higher than outside. Health risks from such chemicals are magnified
because most people in developed countries spend 70-90 % of their time
indoors or inside their vehicles.
At greatest risk are smokers, infants and children under age 5, the old, the sick,
pregnant women, people with respiratory or heart problems and factory
workers.
Illness caused by indoor air pollution includes colds, influenza, or upset
stomachs.
The most common contaminants of indoor air are radon, cigarette smoke,
carbon monoxide, nitrogen dioxide (from gas stoves), formaldehyde (from
carpeting, fabrics, and furniture), household pesticides, lead, cleaning solvents,
ozone (from photocopiers), and asbestos. The reaction of indoor ozone,
generally present in lower levels than outdoors, with volatile chemicals in air
fresheners, aromatherapy candles, and cleaning agents forms secondary air
pollutants such as formaldehyde.
Viruses, bacteria, fungi( yeasts, molds, and mildews), dust mites, pollen, and
other organisms or other toxic parts are important forms of indoor air pollution
often found in heating, air conditioning, and ventilation ducts.
Pesticides residues brought in on shoes can collect in carpets and pesticides are
used in homes at least once a year.
Dust mite is responsible for increase in the number of people suffering from
asthma. It feeds on dead human skin, and household dust, and lives in materials
such as bedding and furniture fabrics.
Excessive indoor dampness induces indoor microbial growth (particularly fungal
growth), dust mite populations, and cockroach rodent infestations.
A 2004 report by the U.S Institute of Medicine said that the presence of mold in
damp indoor environment is linked to upper respiratory tract (nose and throat)
symptoms, including wheezing and coughing, and to asthma symptoms.
There was also suggested evidence of association between molds, a damp
indoor environment, and illness in the lower respiratory tracts in otherwise
healthy children.
Sick building syndrome
Health effects of sick building syndromes includes dizziness, headaches,
coughing, sneezing, shortness of breath, nausea, burning of eyes, sore throat,
chronic fatigue, irritability, skin dryness and irritation, respiratory infection, and
depression. In developing countries, the indoor burning of wood, charcoal,
dung, crop residues, and heating exposes inhabitants to dangerous levels of
particulate air pollutants.
The chemical that causes most people in developed countries difficulty is
formaldehyde. Symptoms are dizziness, rash, headaches, sore throat, sinus and
eye irritation, wheezing and nausea cussed by daily exposure to low levels of
formaldehyde emitted from common household materials. These materials
include building materials such as plywood, paneling, high-gloss wood,
upholstery, adhesive in carpeting and wallpaper, urethane-formaldehyde foam
insulation, wrinkle free coating on permanent-press clothing.
Refer to figure 20.21 in Page number 478
INDOOR AIR POLLUTION AND THE ASTHMA EPIDEMIC
Asthma is far more common in industrialized nations than in developing
countries. Indoor exposure to different air pollutants contributes to the
development and exacerbation of asthma. Exposure to allergens –substances
that stimulate allergic reactions such as dust mites and cockroach feces is a
major cause for asthma.
INDOOR TOBACCO SMOKE
Smoking, causes serious diseases such as lung cancer, emphysema, and heart
disease. Cigarette smoking annually causes about 120,000 of the 140,000 deaths
from lung cancer in the United States. Smoking also contributes to heart
attacks, strokes, male impotence, cancer of the bladder, mouth, throat,
pancreas, kidney, stomach, voice box, and esophagus. It also causes substantial
property damage through fires, burns, and smoke odor.
Cigarette smoke is a mixture of air pollutants that includes hydrocarbons,
carbon dioxide, carbon monoxide, particulate matter, cyanide, and a small
amount of radioactive materials that come from the fertilizer used to grow the
tobacco plants. Passive smokers are also affected by the above said symptoms.
Passive smoking is harmful particularly to infants and young children, pregnant
women, the elderly, the people with chronic lung disease. The children are at a
risk of suffering from pneumonia or bronchitis when exposed to cigarette
smoking. Smoking during pregnancy affects fetal development, leading to a
lower birth weights and smaller head circumferences.
Smoking is more in developing countries than in developed nations. Smoking
has declined in Japan, and most European countries. However more people are
taking up the habit in Brazil, Pakistan, and many other developing countries.
Within the United States, Canada, and other highly developed countries, bans
on smoking in many public places- including government buildings, restaurants
and airplanes- have substantially reduced both smoking and exposure to smoke.
RADON
Radon-222. A radioactive gas found in some soil and rocks, can seep into some
houses and increase the risk of lung cancer. It is a colorless, odorless radioactive
gas that is produced by the natural radioactive decay of Uranium-238 in rocks
and soils.
When radon gas from such deposits seeps upward through the soil and is
released outdoors, it disperses quickly in the air and decays to harmless levels.
However, in buildings above such deposits radon gas can enter through cracks in
foundations and walls, openings around sump pumps and drains, and hollow
concrete blocks. Once inside it can build up to high levels, especially in
unventilated lower levels of homes and buildings.
Radon-222 gas quickly decays into solid particles of other radioactive elements
such as polonium-210 that if inhaled expose lung tissue to a large amount of
ionizing radiation from alpha particles. This exposure can damage lung tissue
and lead to lung cancer. Your chance of getting cancer from radon depends on
how much radon is in your home, how much time you spend in your home.
It is a serious indoor pollutant in many places in highly developed countries.
Radon seeps through the ground and enters buildings, where it sometimes
accumulates to dangerous levels. Although radon is also emitted into the
atmosphere, it gets diluted and dispersed and is of little consequence outdoors.
Radon and its decay products emit alpha particles, a form of ionizing radiation
that is damaging to tissue but cannot penetrate very far into the body. Radon
harms the body only when it is ingested or inhaled. The radioactive particles
lodge in the tiny passages of the lungs and damage surrounding tissue. Studies
based on uranium miners have shown that inhaling large amounts of radon
increases the risk of lung cancer. People who are exposed to low levels of radon
over an extended time are at a risk for lung cancer.
The highest radon levels in the United States occur in homes on a geologic
formation, the Reading Prong, which runs across southeastern Pennsylvania
into northern New Jersey and New York. Iowa has the most pervasive radon
problem, where 71% of the houses tested had radon levels high enough to
warrant corrective action
Radon concentrations in homes are minimized by sealing basement concrete
floors and by ventilating crawl spaces and basements.
OUTDOOR AIR POLLUTION
PHOTOCHEMICAL SMOG
1. Which of the following cities would have the greatest amount of gray-air
smog?
a) New York
b) Beijing, china
c) Los Angeles, California
d) Chicago, Illinois
e) London, England
b. gray air smog is a result of the burning of large volumes of coal to
generate electricity and provide heat to homes. China uses a great deal
of coal to meet the energy needs. The other cities listed have
reasonably effective controls on their generation stations, and people
in those countries do not use much coal to heat their homes.
2. Which of the following is a secondary pollutant?
a) CO
b) Soot
c) VOCs
d) PANs
e) CO2
d. they are produced from the reactions of hydrocarbons, oxygen, and
nitrogen dioxide.
__________ pollutants are emitted directly
from identifiable sources.
Tertiary
Observable
Primary
Secondary
none of the above
2
.
With the passage of the federal
__________ Act, as amended in
1970, major strides were made in
reducing air pollution.
Environmental Protection
Health and Welfare
Clean Air
Ambient Air Quality
Anti-Pollution
Which one of the following is NOT a
primary pollutant?
carbon monoxide
3
.
sulfur dioxide
particulate matter
nitrogen oxides
sulfuric acid
The source of nearly half our pollution
(by weight) is from the __________
category.
stationary source fuel
combustion
4
.
transportation
agricultural
industrial processes
none of the above
A pH of 4 is __________ times more
acidic than a pH of 5.
5
5
.
10
50
75
100
The major component of
photochemical smog is
__________.
nitrogen dioxide
sulfuric acid
particulate matter
carbon monoxide
Ozone this is correct
Two of the most important atmospheric conditions
affecting the dispersion of pollutants are the strength
of the wind and the __________ of the air.
depth
8
.
visibility
temperature
stability
pressure
Which one of the following
pollutants has shown the greatest
percent decrease in
concentration during the past
years?
ozone
sulfur dioxide
nitrogen dioxide
particulate matter
Lead this is correct
10 .
3.