Air Pollution

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Air Pollution
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Outline

• 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
• Current Conditions and Future Prospects

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THE AIR AROUND US

• Approximately 147 million metric tons of air
  pollution are released annually into the
  atmosphere in the U.S. 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.

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NATURAL SOURCES OF AIR POLLUTION

• Natural Fires - Smoke
• Volcanoes - Ash and acidic components
• Sea Spray - Sulfur
• Vegetation - Volatile organic compounds
• Bacterial Metabolism - Methane
• Dust
• Pollen
• Viruses and Bacteria

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HUMAN-CAUSED AIR POLLUTION

• 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.

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Conventional Pollutants

• U.S. Clean Air Act designated seven major
  (conventional or criteria) pollutants for which
  maximum ambient air levels are mandated.
• Sulfur Dioxide
• Nitrogen Oxides
• Carbon Oxides
• Particulate Matter
• Metals and Halogens
• Volatile Organic Compounds

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Conventional Pollutants

• 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

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Conventional Pollutants

• 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

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Conventional Pollutants

• Carbon Oxides
• Predominant form of carbon in the air is carbon
  dioxide.
• Increasing levels due to human activities.
• Annual Emissions 7-8 billion metric tons
• Carbon monoxide is a colorless, odorless, toxic
  gas produced by incomplete fuel combustion.
• Annual Emissions 1 billion metric tons

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Conventional Pollutants

• Particulate Matter
• Atmospheric aerosols (solid or liquid)
• Respirable particles smaller than 2.5 micrometers
  are among most dangerous.
• Anthropogenic particulate emissions amount to
  about 362 million metric tons annually.

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Conventional Pollutants

• Metals
• Many toxic metals occur as trace elements in
  fuel.
• Lead Emissions 2 million metric tons.
• Mercury
• Bioaccumulation in aquatic ecosystems.
• Nickel, beryllium, cadmium, arsenic
• Halogens (Fluorine, Chlorine, Bromine)
• CFCs

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Conventional Pollutants

• Volatile Organic Compounds
• Organic chemicals
• Generally oxidized to CO and CO2.
• Plants are largest source.
• Photochemical Oxidants
• Products of secondary atmospheric reactions
  driven by solar energy.
• Ozone formed by splitting nitrogen dioxide.

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Air Toxins

• Hazardous Air Pollutants
• Require special reporting and management as they
  remain in ecosystems for a long period of time,
  and tend to accumulate in animal tissues.
• Toxic Release Inventory
• Established 1986

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Unconventional Pollutants

• Aesthetic Degradation
• Noise, odor, light pollution.
• Reduce quality of life.

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Indoor Air Pollution

• 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 U.S..
• 400,000 die annually from a disease related to
  smoking.
• Associated costs are estimated at 100 billion
  annually.

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Indoor Air Pollution

• 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.

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CLIMATE AND TOPOGRAPHY

• 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.

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Dust Domes and Heat Islands

• 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.

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Long-Range Transport

• 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.

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Long-Range Transport
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Stratospheric Ozone

• 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.

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Stratospheric Ozone

• 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.
• CFCs believed to be main culprit.
• Persist for decades.
• Production eliminated in 1996.

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Destruction of Stratospheric Ozone
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EFFECTS OF AIR POLLUTION

• 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.

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Human Health

• Bronchitis
• Persistent inflammation of airways in the lung
  that causes mucus build-up and muscle spasms
  constricting airways.
• Can lead to emphysema - irreversible chronic
  obstructive lung disease in which airways become
  permanently constricted and alveoli are damaged
  or destroyed.

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Plant Pathology

• 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.

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Acid Deposition

• pH and Atmospheric Acidity
• pH scale ranges from 0-14.
• 7 Neutral lt7 Acidic gt7 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.

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Acid Precipitation
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Acid Deposition

• 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 1970s, evidence began to accumulate
  suggesting air pollutants are acidifying many
  N.A. lakes.

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Acid Deposition

• 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.

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AIR POLLUTION CONTROL

• Reducing Production
• 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.

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AIR POLLUTION CONTROL

• Reducing Production
• Particulate Removal
• Remove particles physically by trapping them in a
  porous mesh which allows air to pass through but
  holds back solids.
• Sulfur Removal
• Switch from soft coal with a high sulfur content
  to low sulfur coal.
• Change to another fuel (natural gas).

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Air Pollution Control

• Nitrogen Oxides
• Best method is to prevent creation.
• Staged Burners
• Selective Catalysts
• Hydrocarbon Control
• Use closed systems to prevent escape of fugitive
  emissions.

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Modern Automobile Emission-Control System
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CLEAN AIR LEGISLATION

• Clean Air Act (1963) - First national air
  pollution control.
• Clean Air Act (1970) rewrote original.
• Identified critical pollutants.
• Established ambient air quality standards.
• Primary Standards - Human health
• Secondary Standards - Materials, environment,
  aesthetic and comfort.

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Clean Air Act

• Revision (1990) - Included provision for
• Acid Rain
• Urban Smog
• Toxic Air Pollutants
• Ozone Protection
• Marketing Pollution Rights
• Volatile Organic Compounds
• Ambient Ozone
• Nox Emissions
• Revision (1997) - Stricter standards

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CURRENT CONDITIONS AND FUTURE PROSPECTS

• 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.

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Air Pollution in Developing Countries

• Many metropolitan areas of developing countries
  are growing at explosive rates.
• Mexico City
• Pollution levels exceed WHO health standards 350
  days per year.
• Chinas 400,000 factories have no air pollution
  controls.

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Signs of Hope

• Sweden and West Germany cut their sulfur emission
  by two-thirds between 1970 and 1985.
• Australia and Switzerland even regulate
  motorcycle emissions.
• South Coast Air Quality Management District in
  California has adopted rules to clean the air in
  the Los Angeles Basin.

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Summary

• 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
• Current Conditions and Future Prospects

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