Transcript PowerPoint Presentation - Greater Atlanta Christian Schools

Air Pollution
Chapter 20
Key Concepts
 Structure and composition of the atmosphere
 Types and sources of outdoor air pollution
 Types, formation, and effects of smog
 Sources and effects of acid deposition
 Effects of air pollution
 Prevention and control of air pollution
The Atmosphere
 Troposphere
This layer extends about 11
miles above sea level at the
equator and about 5 miles
above the poles.
This layer is also responsible
for short-term weather and
long-term climate.
 78% N, 21% O
Fig. 20-2 p. 434
 Stratosphere
Extends from 11–30
miles above the
earth’s surface
 Ozone layer
The concentration of ozone in this layer
is much higher than in the
troposphere.
• Ozone is produced when oxygen
molecules interact with ultraviolet
radiation (3 O2 + UV  2 O3).
• This “global sunscreen” keeps
about 95% of the sun’s harmful UV
radiation from reaching the earth’s
surface.
Fig. 20-2 p. 434
 Ozone layer
•
•
This ozone layer protects
us from sunburn, cataracts,
cancer of skin and eye, and
damage to our immune
system.
There is evidence of a
decrease in “good” ozone
in the stratosphere and an
increase in “bad” ozone in
the troposphere.
Fig. 20-2 p. 434
• Air Pollution
• Chemicals in the atmosphere in
concentrations high enough to affect
climate, materials, and health.
• Natural sources of air pollution such as
dust particles, organic chemicals
released by plant decay, forest fires,
etc. rarely reach harmful levels.
Outdoor Air Pollution
 Primary pollutants
 Secondary pollutants
Fig. 20-4 p. 436
Also refer to Tables 20-1 p. 436 and 20-2 p. 438
•Carbon oxides - Carbon monoxide
(CO) and carbon dioxide (C02)
• Sulfur
oxides - Sulfur dioxide (S02)
and sulfur trioxide (S03)
•Nitrogen oxides - Sulfur dioxide
(S02) and sulfur trioxide (S03) Nitric
oxide (NO), nitrogen dioxide (N02), nitrous
oxide (N20)
(NO and N02 often are lumped together and
labeled NOx)
•Volatile organic compounds' (VOCs)
•Methane (CH4), propane (C3Hs),
chlorofluorocarbons (CFCs)
•Suspended particulate matter (SPM)
•Solid particles (dust; soot, asbestos, lead,
nitrate, and sulfate salts), liquid droplets
(sulfuric acid, PCBs, dioxins, and pesticides)
•Photochemical oxidants
•Ozone (03), peroxyacyl nitrates
(PANs); hydrogen peroxide(H202),
aldehydes
• Radioactive substances - Radon-222,
iodine-131 , strontium-90, plutonium-239
(Table 3-1, p. 49)
• Hazardous air pollutants (HAPs), which
cause health effects such as cancer, birth
defects, and nervous system problems Carbon tetrachloride (CCl4), methyl
chloride (CH3Cl), chloroform . (CHCl3),
benzene (C6H6), ethylene dibromide
(C2H2Br2), formaldehyde (CH202)
•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 (p. 409), 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.
NITROGEN DIOXIDE (N02)
•Description: Reddish-brown irritating gas that
gives photochemical smog its brownish color; in
the atmosphere can be converted to nitric acid
(HN03), 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). .
NITROGEN DIOXIDE
•Environmental effects: Reduces visibility;
acid deposition of HN03 can damage trees,
soils, and aquatic life in lakes.
•Property damage: HN03 can corrode
metals and eat away stone on buildings,
statues, and monuments; N02 can damage
fabrics.
SULFUR DIOXIDE (S02)
• Description: Colorless, irritating; forms
mostly from the combustion of sulfurcontaining fossil fuels such as coal and
oil (S + O2
S02); in the atmosphere can
be converted to sulfuric acid (H2S04) a
major component of acid deposition.
•Major human sources: Coal burning in
power plants (88%) and industrial
processes (10%).
SULFUR DIOXIDE (S02)
•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.
SUSPENDED PARTICULATE MATTER
(SPM)
•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 H2S04 droplets can damage trees, soils,
and aquatic life in lakes.
•Property damage: Corrodes metal; soils and
discolors buildings, clothes, fabrics, and paints.
OZONE (03)
•Description: Highly reactive, irritating gas with an
unpleasant odor that forms in the troposphere as a major
component of photochemical smog (Figures 20-3 and 20-5).
•Major human sources: Chemical reaction with volatile
organic compounds (VOCs, emitted mostly by cars and
industries) and nitrogen oxides to form photochemical
smog (Figure 20-5).
•Health effects: Breathing problems; coughing; eye, nose,
and throat irritation; aggravates chronic diseases
such as asthma, bronchitis, emphysema, and heart disease;
reduces resistance to colds and pneumonia; may
speed up lung tissue aging.
•Environmental effects: Ozone can damage plants and trees;
smog can reduce visibility.
•Property damage: Damages rubber, fabrics, and paints.
LEAD
•Description: Solid toxic metal and its
compounds, emitted into the atmosphere as
particulate matter.
•Major human sources: Paint (old houses),
smelters (metal refineries), lead manufacture,
storage batteries, leaded gasoline (being phased
out in developed countries).
•Health effects: Accumulates in the body; brain
and other nervous system damage and mental
retardation (especially in children); digestive and
other health problems; some lead-containing
chemicals cause cancer in test animals.
•Environmental effects: Can harm wildlife.
• Increased use of fossil fuels has greatly increased the
amount of air pollution, especially in urban areas
where people, cars, and industry are concentrated.
• Outdoor air pollutants are classified into two
categories: primary pollutants that enter directly into
the troposphere (soot, carbon monoxide) and secondary
pollutants that may form when primary pollutants
interact with one another or with the air to form new
pollutants.
• Cities generally have higher pollution levels than rural
areas. Winds can carry these pollutants away from their
source to other areas.
• Indoor air pollutants come from
infiltration of outside air and chemicals
used or produced inside buildings.
• Air pollution is classified as a high-risk
human health problem.
• Most people exposed to poor air live in
developing countries.
• Six conventional air pollutants have
maximum standards of allowable
concentrations set by governments of
developed countries (see Table 20-2).
• Carbon dioxide can be classified as an air
pollutant because it can warm the
atmosphere and contribute to global climate
change.
• There are three reasons for classifying CO2
as an air pollutant.
• 1-In high concentrations any chemical can
become a pollutant
• 2- CO2 concentration in the troposphere has
increased due to fossil fuel burning and
clearing trees that absorb CO2.
• 3- The troposphere is warming.
Photochemical Smog
 Brown-air smog
 Photochemical
reaction
 Photochemical
oxidants
Fig. 20-5 p. 440
•Photochemical smog is formed by the
reaction of nitrogen oxides and volatile
hydrocarbons under the influence of
sunlight.
•A photochemical
reaction is any
chemical reaction
activated by
light.
•Photochemical smog contains more
than 100 primary and secondary
pollutants.
•Nitrogen dioxide
found in
photochemical
smog is a yellowbrown gas with a
noxious odor and
causes a
brownish haze to
form.
•Some NO2 reacts with hydrocarbons to produce
a mixture of ozone, nitric acid, aldehydes,
peroxyacyl nitrates (PANs), and other pollutants.
•These substances are photochemical
oxidants and can irritate the
respiratory tract and damage crops
and trees.
•Photochemical
smog is more
common in cities
in warm, dry,
sunny areas.
Industrial Smog
Industrial smog
Particulates
Sulfur dioxide
Sulfuric acid
Gray-air smog
Fig. 20-6 p. 441
• Industrial smog is a mixture of sulfur
dioxide, droplets of sulfuric acid, and a
variety of suspended solid particles
emitted by burning coal and oil.
• When coal is burned, it is converted to
carbon dioxide, carbon monoxide, and
unburned carbon particles (soot).
• Coal and oil also contain sulfur that is
then converted to sulfur dioxide.
• Reactions with water vapor changes sulfur
dioxide to sulfuric acid in several steps.
• These droplets can then react with ammonia
in the atmosphere to form ammonium
sulfate.
• These various components give the air a gray
color.
• China has a serious gray-smog problem in
many areas, and many people die
prematurely from this.
• Three natural factors help reduce
outdoor air pollution: rain and snow,
salty sea spray, and winds. Each of
these factors helps remove pollutants,
but they are then deposited elsewhere.
• Four factors can increase thhe outdoor
air pollution [Photochemical Smog]:
urban buildings, hills and mountains,
high temperatures, and the grasshopper
effect where volatile compounds are
carried from tropical or temperate areas
to the poles.
Temperature Inversions
Subsidence inversion
Fig. 20-7 p. 443
•A layer of warm air sitting on top of a
layer of cool air near the ground can
prevent outdoor pollutants from rising
and dispersing.
•Turbulence, caused by the mixing of warm
and cold air, disperses air pollutants.
•A temperature inversion, where a layer of
warm air sits over a layer of cold air, prevents
the mixing, and dense, colder air becomes
stagnant and accumulates more pollutants.
•Two areas are particularly susceptible to inversions:
1- a city located in a valley surrounded by mountains that
experiences cloudy, cold weather part of the year and
2- a sunny climate with light winds and mountains on three sides
and several million people and vehicles (Los Angeles basin).
Regional Outdoor Air Pollution from
Acid Deposition
 Acid deposition
 Dry deposition
 Wet deposition
Fig. 20-8 p. 444
• Sulfur dioxide, nitrogen oxides, and
particulates react in the atmosphere to
produce acidic chemicals that travel
long distances before coming back to
the earth.
• Tall smokestacks reduce local
pollution, but can increase regional
pollution.
• Acidic particles remain in the
atmosphere for 2–14 days, depending
on the prevailing winds, precipitation,
and other weather patterns.
The acidic substances return to the earth in one of
two forms:
• 1-wet deposition as acidic rain, snow, fog, and
cold vapor with a pH less than 5.6 and
• 2- dry deposition as acidic particles.
• Acid deposition is a problem in areas
downwind from coal-burning facilities and
urban areas.
• Some areas have basic compounds in the soil
that act to buffer or neutralize some acidic
deposits.
• Many acid-producing chemicals generated in
one country end up in other countries due to
prevailing winds.
Acid Deposition in the US
Fig. 20-9 p. 445
Acid Deposition and Humans
 Respiratory diseases
 Toxic metal leaching
 Damage to structures, especially
containing calcium carbonate
 Decreased visibility
 Decreased productivity and
profitability of fisheries, forests,
and farms
• Acid deposition can cause or worsen respiratory
disease, attack metallic and stone objects,
decrease atmospheric visibility, and kill fish.
• Large amounts of money are spent each year to
clean and repair monuments and statues
damaged by acid deposition.
• Acid deposition also decreases atmospheric
visibility.
• Acidified lakes have fish kill, and aluminum
ions are released into the water by the lower pH
(4.5 or less).
• Many lakes in northern Europe and the eastern
U.S. have few, if any, fish due to decreased pH.
Acid Deposition and Aquatic Systems
Fish declines
Aluminum toxicity
 Acid shock
• Acid deposition can deplete some soil
nutrients, release toxic ions into soil, and
weaken plants that become susceptible to
other stresses.
• Effects of acid deposition on plants is
caused partly by chemical interaction in the
soils.
• There may be an initial growth stimulus
from added nitrogen and sulfur, but
continued deposition leaches essential
magnesium and calcium salts from the soil
and lowers plant productivity.
Acid Deposition, Plants, and Soil
 Nutrient
leaching
 Heavy metal
release
 Weakens trees
Fig. 20-11 p. 447
• Herbivores that eat these plants can
also develop calcium deficiencies.
• Synergistic effects may occur when the
plants are exposed to several
pollutants simultaneously.
• Acid can also dissolve aluminum,
cadmium, and mercury ions from the
soil. These ions are toxic to plants and
animals.
• Acid-loving mosses may be stimulated to
grow and harm trees by holding quantities of
water and killing mycorrhizal fungi needed
by the trees.
• Weakened trees are more susceptible to
diseases.
• The mountaintop trees are those that are most
harmed by acidic rain because they are also
growing in thin soils.
Progress has been made in reducing acid deposition in the
U.S., but there is a long way to go.
• The 1990 amendments to the Clean Air Act have lead to
significant reductions in SO2 and NOx emissions from
coal-fired power and industrial plants.
• Acid deposition has accelerated leaching of ions such
as calcium and magnesium from soils in some areas,
which could lead to a decrease in tree growth.
• Acid deposition has also increased concentrations of
toxic forms of aluminum in some soil and in lakes and
streams.
• It is predicted that an additional 80% reduction in SO2
emissions would be needed to allow northeastern
streams and lakes to recover from the effects of acid
deposition.
Solutions to Acid Deposition
Fig. 20-12 p. 448
• A number of prevention and control methods
can reduce acid deposition, but they are
politically difficult to implement.
• The best approaches are those that reduce or
eliminate emissions of SO2, NOx, and
particulates.
• Use of low sulfur coal is both good and bad;
it lowers the amount of SO2 released, but
because more must be burned to generate the
same amount of electricity, it emits more
mercury, CO2, and radioactive particles.
Controlling acid deposition is a politically
controversial issue.
• Inclusion of environmental and health
costs to the current costs of coal would
give a more realistic picture.
• Approaches to neutralize acid lakes
include adding limestone or lime to the
water or soil or adding a small amount
of phosphate fertilizer; this approach is
being evaluated.
• Indoor air pollution is usually a much
greater threat to human health than outdoor
air pollution.
EPA studies have shown that:
• levels of 11 common pollutants are 2–5
times greater inside homes and commercial
buildings than outside.
• inside cars in traffic-clogged areas, the
pollution may be 18 times higher than
outside.
• health risks are magnified because people
usually spend 70–98% of their time indoors
or in vehicles.
• Sick-building syndrome has been linked to various
air pollutants, and new buildings are apt to be more
prone to this than old buildings due to less air
exchange.
• The EPA lists the four most dangerous indoor air
pollutants in developed countries as cigarette smoke,
formaldehyde, radioactive radon-222 gas, and very
small fine and ultrafine particles.
• In developing countries, as many as 2.8 million people
die prematurely each year from breathing elevated
levels of indoor smoke and particulates.
Indoor Air Pollution
Fig. 20-13 p.450
• Radon-222 gas is found in some soils and rocks and can
seep into some homes and increase the risk of lung
cancer.
• Radon is produced by the radioactive decay of uranium238.
• Radon gas tends to be pulled into homes because of the
slightly lower atmospheric pressure inside most homes.
• Radon is thought to be the second leading cause of lung
cancer deaths each year in the U.S.
• The EPA and the Surgeon General’s Office
recommended that everyone living in a detached home,
a townhouse, or the first three levels of an apartment
building test for radon.
• Remedies include sealing cracks in foundation and
walls, increasing ventilation, and using a fan for cross
ventilation.
Radon
 Radioactive radon-222
 Lung cancer threat
 Occurs in certain
areas based on
geology
 Associated with
uranium and organic
material in rock
Fig. 20-14 p. 451
Effects of Air Pollution on People
Respiratory diseases (see Fig. 20-15 p. 452)
Asthma
Lung cancer
Chronic bronchitis
Emphysema
Premature death
The respiratory system has several ways to help protect
you from air pollution.
• Hairs in the nose filter out large particles. Sticky
mucus lines the respiratory trap to capture smaller
particles and some dissolved gases.
• Sneezing and coughing expel contaminated air and
mucus.
• Prolonged or acute exposure to air pollutants can
overload or break down the natural defenses.
• Several respiratory diseases can develop such as
asthma, lung cancer, chronic bronchitis, and
emphysema.
• People with respiratory diseases, older adults, infants,
pregnant women, and people with heart disease are
especially vulnerable to air pollution
Solutions: Preventing and Reducing
Air Pollution
Clean Air Act
National Ambient Air Quality
Standards (NAAQS)
Primary and secondary standards
Emissions trading
The EPA has established national emission
standards for 188 hazardous air
pollutants (HAPs) that may cause serious
health and ecological effects. These
include neurotoxins, carcinogens,
mutagens, teratogens, and others.
• The good news is that the six criteria air
pollutants decreased 48% between 1983
and 2002 even with increased energy
consumption, miles traveled, and
population.
• Between 1983 and 2002, emissions from the six
major air pollutants decreased: 93% for lead, 41%
for carbon monoxide, 40% for volatile organic
compounds, 34% for suspended particulate matter,
33% for sulfur dioxide, and 15% for NOx.
• Release of two HAPs—mercury and dioxins has
increased in recent years. These are toxic at very
low levels. The EPA estimates that about 100
million Americans live in areas where the risk of
cancer from HAPs is 10 times higher than the
accepted standard.
Smog levels did not drop any between 1993 and 2003
after dropping in the 1980s.
Fig. 20-17
p. 456
Emission
Reduction
Fig. 20-18a p. 457
Fig. 20-18a p. 457
Fig. 20-17 p. 456
Reducing Motor Vehicle Air
Pollution
Fig. 20-19 p. 458
Reducing Indoor
Air Pollution
Fig. 20-20 p. 459
Waste to Energy Recovery
1. Tipping Floor
2. Refuse Holding Pit
3. Grapple Feed Chute
4. Feed Chute
5. MARTIN Stoker
Grate
6. Combustion Air Fan
7. MARTIN Ash
Discharger
8. Combustion
Chamber
9. Radiant Zone
(furnace)
10. Convection Zone
11. Superheater
12. Economizer
13. Dry Gas Scrubber
14. Baghouse
15. Fly Ash Handling
System
16. Induced Draft Air
Fan
17. Stack
Electrostatic Precipitator