Air pollution
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Air Pollution. 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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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 Monoxide

    • Particulate Matter

    • Hydrocarbons

    • Photochemical Oxidants

    • Lead


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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.

    • Desertification and dust storms

    • Effect of particulates on human health


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Conventional Pollutants

  • Metals

    • Many toxic metals occur as trace elements in fuel.

      • Lead Emissions: 2 million metric tons.

    • Mercury

      • Dangerous neurotoxin

      • Widespread; control is highly contentious.

    • Nickel, beryllium, cadmium, arsenic…

  • Halogens (Fluorine, Chlorine, Bromine)

    • CFC’s


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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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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 could result in a million extra human skin cancers per year worldwide.



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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.

          • Montreal Protocol established deadlines for eliminating CFC’s.


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EFFECTS OF AIR POLLUTION

  • Human Health

    • WHO estimates each year 5-6 million 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

    • 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 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 1970’s, 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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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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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.

    • China’s 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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