Download Air Pollution

3/2/2015
The atmosphere

Atmosphere
 Absorbs radiation and
moderates climate
 Transports and recycles
Chapter 13
water and nutrients

Human activity is now
changing the amount
of some gases
 CO2, methane (CH4),
ozone (O3)
The atmosphere is layered

Troposphere
 Bottommost layer
The sun influences weather and
climate

(11 km [7 miles])
 Responsible for Earth’s
 70% is absorbed by water, evaporating the
weather
 The air gets colder with
altitude

Stratosphere
water
 Air near Earth’s surface is warm and moist

 11–50 km (7–31 mi) above

 Creates vertical currents
 Convection influences weather and climate
Circulation systems produce
climate patterns
Thermal inversion

 A layer of cool air forms

Inversions trap
pollutants
in cities surrounded by
mountains
Convective currents contribute to climatic patterns
Hadley cells
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beneath warm air
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Convective circulation
 Less dense, warmer air rises
sea level
 Ozone layer blocks UV
radiation
Inversions affect air quality
An enormous amount of energy from the
sun hits Earth
Convective cells near the equator
Surface air warms, rises, and expands
Causing heavy rainfall near the equator
Giving rise to tropical rainforests

Currents heading north and south are dry

Ferrel cells and polar cells
 Giving rise to deserts at 30 degrees
 Lift air and create precipitation at 60 degrees latitude north
and south
 Conditions at the poles are dry
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Global wind patterns

Coriolis effect: the apparent north–south
deflection of air currents of the
convective cells
Large-scale convective cells
create global patterns of
moisture and wind
 Results in curving global wind patterns
 Global wind patterns helped sailing ships
travel the oceans
Some pollution is from natural
sources

Humans can make impacts worse
We create outdoor air pollution

 Farming, grazing cause erosion, desertification
 Fire suppression leads to worse fires


Fires generate soot and gases
Winds send huge amounts of dust aloft
Point sources
 Specific spots where large quantities of pollutants
are discharged (e.g., power plants)

Non-point sources
 More diffuse, consisting of many small, widely
spread sources (e.g., automobiles)
 Even across oceans

Volcanoes release particulate matter, sulfur
dioxide

Primary pollutants
 Directly harmful or can react to form harmful
substances (e.g., soot and carbon monoxide)

Secondary pollutants
 Form when primary pollutants react with constituents
of the atmosphere
Residence time
 The time a pollutant stays in the atmosphere
The Clean Air Act addresses
pollution

The Clean Air Act (1963, amended in 1970, 1990)

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Funds research for pollution control
Sets standards for air quality, limits on emissions
Allows citizens to sue parties violating the standards
Introduced a cap-and-trade program for sulfur dioxide
The EPA sets standards for emissions and pollutants
States monitor air quality
 Develop, implement, and enforce regulations
 Submit plans to the EPA for approval
 The EPA takes over enforcement if plans are inadequate
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Agencies monitor emissions

State and local agencies monitor and report to
the EPA emissions of six major pollutants
Emissions

 Colorless gas with a strong odor
 Coal emissions from electricity generation, industry
 Carbon monoxide, sulfur dioxide, nitrogen oxides,
 Can form acid deposition
volatile organic compounds, particulate matter, lead

Carbon monoxide (CO)
Sulfur dioxide (SO2)

Nitrogen oxides (NOx)
 Colorless, odorless gas
 Formed when nitrogen and oxygen react at high
 Produced primarily by incomplete combustion of fuel
 From vehicles and engines, industry, waste
 Vehicles, electrical utilities, industrial combustion
combustion, residential wood burning
temperatures in engines

Volatile organic compounds (VOCs)
 Carbon-containing chemicals emitted by vehicles and a
 Prevents blood hemoglobin from binding with
wide range of solvents
oxygen
 Can react to produce a number of secondary pollutants,
as occurs in urban smog
Emissions
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Particulate matter
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Suspended solid or liquid particles
Damages respiratory tissue when inhaled
Primary pollutants: dust and soot
Secondary pollutants: sulfates and nitrates
We have reduced U.S. air
pollution

Total emissions of the six monitored
pollutants have declined 72% since the
Clean Air Act of 1970
○ From dust and combustion processes

Lead
 In gasoline and industrial metal smelting
 Bioaccumulates and damages the nervous
system
 Banned in gasoline in developed countries, but
not in developing countries
Scrubbers

Catalytic converters
Chemically convert or physically remove
pollutants before they leave smokestacks
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Air quality has improved

Criteria pollutants
Air quality has improved (cont’d)

 Especially great threats to humans
 Carbon monoxide, sulfur dioxide, particulate
 A secondary pollutant created from sunlight,
matter, lead, and all nitrogen dioxides and
tropospheric ozone
 EPA compiles data for these pollutants into a
list called the Air Quality Index (AQI)

Tropospheric ozone (O3) is a colorless
gas
heat, nitrogen oxides, volatile carboncontaining chemicals
 A major component of photochemical smog
 Participates in reactions that harm tissues
Nitrogen dioxide (NO2)
and cause respiratory problems
 Foul-smelling red-brown gas
 Contributes to smog and acid deposition
 The pollutant that most frequently
exceeds EPA standards
Air pollution is getting worse in
industrializing nations
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Outdoor pollution is getting worse in
developing nations
Polluting factories and power plants,
increasing numbers of cars
 Nations emphasize economic growth, not pollution
control
 People burn traditional fuels (wood and charcoal)

China has the world’s worst air pollution
 Coal burning, more cars, power plants, factories
 Causes over 300,000 premature deaths/year
 China is reducing pollution (closing factories, using
cleaner fuels, raising efficiency standards, etc.)
Industrial Smog

Burning coal or oil releases CO2, CO,
soot, mercury, sulfur

Regulations in developed countries
reduced smog
Coal-burning industrializing countries
face health risks due to lax pollution
control
 Sulfuric acid is formed
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Photochemical smog

Photochemical smog
 Forms when sunlight drives a chemical reaction
between primary pollutants and atmospheric
compounds
 Ozone, NO2, and many other compounds are
formed
 Appears as a brownish haze

Formed in hot, sunny cities surrounded by
mountains
 Morning traffic releases NO and VOCs
 Irritates eyes, noses, and throats
Ozone depletion

Ozone in the lower stratosphere absorbs
the sun’s ultraviolet (UV) radiation
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Ozone-depleting substances
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Halocarbons
 UV radiation can damage tissues and DNA
 Human-made chemicals that destroy ozone
 Human-made compounds made from
hydrocarbons with added chlorine, bromine,
or fluorine
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We addressed ozone depletion
with the Montreal Protocol
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Montreal Protocol (1987)
 196 nations agreed to cut CFC production in
half by 1998
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The ozone layer has stopped
growing
Industry shifted to safer alternative
chemicals
We stopped the Antarctic ozone hole
from getting worse
It can serve as a model for international
environmental cooperation
Acid deposition

The deposition of acid, or acid-forming,
pollutants from the air onto Earth’s surface
 From automobiles, electric utilities, industrial
facilities
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Acid rain
 Precipitation containing acid
 Includes rain, snow, sleet, hail

Atmospheric deposition
 The wet or dry deposition of pollutants (mercury,
nitrates, organochlorines, etc.)
Burning fossil fuels produces
acid rain
pH of precipitation in the US
 Regions of
greatest acidification are
downwind of heavily industrialized
sources of pollution
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Impacts of acid deposition
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Nutrients are leached from
topsoil
Soil chemistry is changed
Toxic metal ions
(aluminum, zinc, etc.) are
converted into soluble
forms that pollute water
Affects surface water and
kills fish
Damages crops and other
plants
Acid deposition
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Buildings and
monuments
 Limestone and
marble are destroyed
by air pollution at an
alarming rate
 Corroding steel in
reinforced concrete
weakens buildings,
roads, and bridges
The Clear Air Act (1990) established
an emissions trading program for
sulfur dioxide
 Benefits outweighed costs 40:1
Indoor air pollution
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In workplaces, schools, and homes
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 Causes greater health effects than outdoor

pollution
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The most dangerous indoor
pollutants in developed nations
The poor in developing
nations burn wood,
charcoal, dung, and
crop wastes
 In buildings with
Cigarette smoke
Radon
 A radioactive gas resulting from natural
decay of rock, soil, or water that can seep
into buildings
 Kills 21,000 people per year in the U.S.
 New homes are being built to be radon
resistant
little to no ventilation
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Many substances pollute indoor
air

VOCs
 The most diverse group of indoor air pollutants
 Released by everything from plastics and oils to
perfumes and paints; “new car smell”
 Some are released in large amounts when new
 Formaldehyde leaking from pressed wood and
insulation irritates mucous membranes and
induces skin allergies

Sick-building syndrome
 A sickness produced by indoor pollution in which
the specific cause is not identified
We can enhance indoor air
quality
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Keys to alleviating indoor air pollution include:
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Using low-toxicity materials
Monitoring air quality
Keeping rooms clean
Providing adequate ventilation
People in developed nations can:
 Limit use of plastics and treated wood
 Limit exposure to toxic substances (pesticides, etc.)
 Test homes and offices for radon and mold
 Use CO detectors
 Keep rooms and air ducts clean and free of mildew
and other biological pollutants
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