Transcript Understanding Our Environment

Air Pollution
Chapter 18
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Outline:
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Natural Sources
Human-Caused Air Pollution
 Conventional Pollutants
 Unconventional Pollutants
 Indoor Air Pollution
Climate and Topography
Effects of Air Pollution
Air Pollution Control
Clean Air Legislation
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
THE AIR AROUND US
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Approximately 14 million metric tons of air
pollution are released annually into the
atmosphere in the US by human activities.
 Worldwide emissions total around 2 billion
metric tons.
Developed countries have been improving air
quality, while air quality in developing world is
getting worse.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
NATURAL SOURCES OF AIR POLLUTION
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Natural Fires - Smoke
Volcanoes - Ash and Acid components
Sea Spray - Sulfur
Vegetation - Volatile organic compounds
Bacterial Metabolism - Methane
Dust
 Pollen
Viruses and Bacteria
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
HUMAN-CAUSED AIR POLLUTION
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Primary Pollutants - Released directly from
the source.
Secondary Pollutants - Modified to a
hazardous form after entering the air and
mixing with other environmental components.
 Fugitive Emissions - Do not go through
smokestack.
- Dust from human-activities.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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US Clean Air Act designated seven major
(conventional or criteria) pollutants for which
maximum ambient air levels are mandated.
 Sulfur Dioxide
 Carbon Monoxide
 Particulates
 Hydrocarbons
 Nitrogen Oxides
 Photochemical Oxidants
 Lead
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Sulfur Compounds
 Natural sources of sulfur in the atmosphere
include evaporation from sea spray, volcanic
fumes, and organic compounds.
 Predominant form of anthropogenic sulfur is
sulfur-dioxide from fossil-fuel combustion.
- Annual Emissions: 114 million metric tons
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Compounds
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Nitrogen Compounds
 Nitrogen oxides are reactive gases formed
when nitrogen is heated above 650o C in the
presence of oxygen, or when nitrogen
compounds are oxidized.
- Annual Emissions: 230 million metric tons
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Nitrogen Compounds
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Carbon Oxides
 Predominant form of carbon in the air is
carbon dioxide.
- Increasing levels due to human activities.
- Annual Emissions: 8-10 billion metric tons
 Carbon monoxide is a colorless, odorless,
toxic gas produced by incomplete fuel
combustion.
- Annual Emissions: 1 billion metric tons
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Metals
 Many toxic metals occur as trace elements
in fuel.
- Lead Emissions: 2 million metric tons.
 Mercury
- Bioaccumulation in aquatic ecosystems.
 Nickel, beryllium, cadmiuym, arsenic…
Halogens (Fluorine, Chlorine, Bromine)
 CFC’s
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Particulate Matter
 Atmospheric aerosols (solid or liquid)
- Respirable particles smaller than 2.5
micrometers are among most dangerous.
Volatile Organic Compounds
 Organic chemicals
- Generally oxidized to CO and CO2.
 Of 188 air toxics listed in Clean Air Act,
two-thirds are VOC’s.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Conventional Pollutants
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Photochemical Oxidants
 Products of secondary atmospheric
reactions driven by solar energy.
- Ozone formed by splitting nitrogen
dioxide.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Unconventional Pollutants
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EPA sets emissions standards for
unconventional or non-criteria pollutants that
are considered especially hazardous.
 Asbestos, benzene, beryllium, etc.
- Most have no natural source in the
environment.
 Aesthetic Degradation
- Noise, odor, light pollution.
 Reduce quality of life.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Indoor Air Pollution
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EPA found indoor concentrations of toxic air
pollutants are often higher than outdoor.
 People generally spend more time indoors.
 Smoking is the most important air pollutant
in the US.
- 400,000 die annually from a disease
related to smoking.
 Associated costs are estimated at
$100 billion annually.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Indoor Air Pollution
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Less Developed Countries also suffer from
indoor air pollution.
 Organic fuels make up majority of
household energy.
- Often burned in smoky, poorly ventilated
heating and cooking fires.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CLIMATE AND TOPOGRAPHY
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Inversions
 Temperature inversions occur when a
stable layer of warm air overlays cooler air,
reversing the normal temperature decline
with increasing height, and preventing
convection currents from dispersing
pollutants.
- Cold front slides under warm air mass.
- Cool air subsides down slope.
 Rapid nighttime cooling in a basin.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Inversions
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Dust Domes and Heat Islands
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Sparse vegetation and large amounts of
concrete and glass create warm, stable air
masses, heat islands, over large cities.
 Concentrates pollutants in a “dust dome”.
- Rural areas downwind from major
industrial areas often have significantly
decreased visibility and increased
rainfall.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Long-Range Transport
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Fine aerosols can be carried great distances
by the wind.
 Increasingly, sensitive monitoring
equipment has begun to reveal industrial
contaminants in places usually considered
among the cleanest in the world.
- Contaminants trapped by winds at the
north pole, concentrate at high latitudes
and eventually fall out as snow and ice
and enter the food chain.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Long-Range Transport
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Stratospheric Ozone
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Discovered in 1985 that stratospheric ozone
levels were dropping rapidly during
September and October.
 Occurring since at least 1960.
At ground-level, ozone is a pollutant, but in
the stratosphere it screens UV radiation.
 A 1% decrease in ozone results in a 2%
increase in UV rays reaching the earth.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Stratospheric Ozone
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Circumpolar vortex isolates Antarctic air and
allows stratospheric temperatures to drop
and create ice crystals at high altitudes.
 Absorb ozone and chlorine molecules.
- When sun returns in the spring, energy
liberates the chlorine allowing the
depletion process to proceed rapidly.
 CFC’s believed to be main culprit.
 Persist for decades.
 Production eliminated in 1996.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CFC Production
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
EFFECTS OF AIR POLLUTION
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Human Health
 EPA estimates each year 50,000 people
die prematurely from illnesses related to air
pollution.
- Likelihood of suffering ill health is related
to intensity and duration of exposure.
 Inhalation is the most common route,
but absorption through the skin and
consumption via food can also occur.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Human Health
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Bronchitis
 Persistent inflammation of airways in the
lung that causes mucus build-up and
muscle spasms constricting airways.
- Can lead to emphysema - irreversible
obstructive lung disease in which
airways become permanently constricted
and alveoli are damaged or destroyed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Plant Pathology
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Chemical pollutants can directly damage
plants, or can cause indirect damage by
disrupting normal growth and development
patterns.
 Certain environmental factors have
synergistic effects in which the injury
caused by the combination is more than
the sum of the individual exposures.
- Pollutant levels too low to cause visible
effects may still be damaging.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition
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pH and Atmospheric Acidity
 pH scale ranges from 0-14.
- 7 = Neutral; <7 = Acidic; >7 = Basic
 Unpolluted rain generally has ph of 5.6.
- Carbonic acid from atmospheric CO2.
 In industrialized areas, anthropogenic
acids in the air often outweigh natural
sources of acid.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition
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Aquatic Effects
 Thin, acidic soils and oligotrophic lakes of
southern Norway and Sweden have been
severely affected by acid deposition.
- Generally, reproduction is the most
sensitive stage in fish life cycles.
 In early 1970’s, evidence began to
accumulate suggesting air pollutants
are acidifying many NA lakes.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Acid Deposition
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Forest Damage
 Air pollution and depositions of
atmospheric acids are believed to be
important causes of forest destruction in
many areas.
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.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
AIR POLLUTION CONTROL
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Particulate Removal
 Remove particles physically by trapping
them in a porous mesh which allows air to
pass through but holds back solids.
 Electrostatic Precipitators - Fly ash
particles pick up electrostatic charge as
they pass between large electrodes in
waste stream, and accumulate on
collecting plate.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Removal
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Fuel Switching
 Switch from soft coal with a high sulfur
content to low sulfur coal.
 Change to another fuel (natural gas).
Limestone Injection
 Can reduce sulfur emissions by 90% by
mixing crushed limestone with coal before
it is fed into a boiler.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Sulfur Removal
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Flue Gas Desulfurization
 Inject crushed limestone into stack gas
stream to remove sulfur after combustion.
- Dry Alkali Injection
Sulfur Recovery Process
 Use catalytic converters to oxidize or
reduce sulfur and create chemical
compounds that can be collected and sold.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Air Pollution Control
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Nitrogen Oxide Control
 Best method is to prevent creation.
- Staged Burners
- Selective Catalysts
Hydrocarbon Control
 Use closed systems to prevent escape of
fugitive emissions.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CLEAN AIR LEGISLATION
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Clean Air Act (1963) - First national air
pollution control.
Clean Air Act (1970) rewrote original Act.
 Identified critical pollutants.
 Established ambient air quality standards.
- Primary Standards - Human health
- Secondary Standards - Materials,
environment, aesthetic and comfort.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Clean Air Act
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Revision (1990) - Included provision for:
 Acid Rain
 Urban Smog
 Toxic Air Pollutants
 Ozone Protection
 Marketing Pollution Rights
 Volatile Organic Compounds
 Lead
Revision (1997) - Stricter standards
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
CURRENT AND FUTURE CONDITIONS
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In the United States, air quality has improved
dramatically in the last decade in terms of
major large-volume pollutants.
 Cities where pollution is largely from traffic
still have serious air quality problems.
Major metropolitan areas of many developing
countries are growing at explosive rates, and
environmental quality is very poor.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Summary:
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•
•
•
•
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Natural Sources
Human-Caused Air Pollution
 Conventional Pollutants
 Unconventional Pollutants
 Indoor Air Pollution
Climate and Topography
Effects of Air Pollution
Air Pollution Control
Clean Air Legislation
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.