Chapter 13: Air Pollution

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Chapter 13 Air Pollution

• Dr. R. B. Schultz
• Geography 101 Weather and Climate

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Air Pollution and Weather

• Air pollution and weather are linked in two ways.
  One way concerns the influence that weather
  conditions have on the dilution and dispersal of
  air pollutants.
• The second way is the reverse and deals with the
  effect that air pollution has on weather and
  climate.
• Air is never perfectly clean.
• Examples of natural air pollution include
• Ash,
• salt particles,
• pollen and spores,
• smoke and
• windblown dust

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Air Pollutant Types

• Although some types of air pollution are recent
  creations, others, such as London's infamous
  smoke pollution, have been around for centuries.
  One of the most tragic air pollution episodes
  ever occurred in London in December 1952 when
  more than four- thousand people died.
• Air pollutants are airborne particles and gasses
  that occur in concentrations that endanger the
  heath and well-being of organisms or disrupt the
  orderly functioning of the environment.
• Pollutants can be grouped into two categories
• (1) primary pollutants, which are emitted
  directly from identifiable sources, and
• (2) secondary pollutants, which are produced in
  the atmosphere when certain chemical reactions
  take place among primary pollutants.

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Primary Pollutants

• The major primary pollutants include
• particulate matter (PM),
• sulfur dioxide,
• nitrogen oxides,
• volatile organic compounds (VOCs),
• carbon monoxide, and
• lead.

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Secondary Pollutants

• Atmospheric sulfuric acid is one example of a
  secondary pollutant.
• Air pollution in urban and industrial areas is
  often called smog.
• Photochemical smog, a noxious mixture of gases
  and particles, is produced when strong sunlight
  triggers photochemical reactions in the
  atmosphere.
• The major component of photochemical smog is
  ozone.
• Although considerable progress has been made in
  controlling air pollution, the quality of the air
  we breathe remains a serious public health
  problem.

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Controlling Air Pollution through Regulations

• Economic activity, population growth,
  meteorological conditions, and regulatory efforts
  to control emissions, all influence the trends in
  air pollution.
• The Clean Air Act of 1970 mandated the setting of
  standards for four of the primary pollutants
• particulates,
• sulfur dioxide,
• carbon monoxide, and
• Nitrogen
• as well as the secondary pollutant ozone.

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Have Regulations Helped?

• In 1997, the emissions of the five major primary
  pollutants in the United States were about 31
  percent lower than 1970.
• In 1990, Congress passed the Clean Air Act
  Amendments, which further tightened controls on
  air quality.
• Regulations and standards regarding the
  provisions of the Clean Air Act Amendments of
  1990 are periodically established and revised.

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Air Pollution Occurrences

• The most obvious factor influencing air pollution
  is the quantity of contaminants emitted into the
  atmosphere.
• However, when air pollution episodes take place,
  they are not generally the result of a drastic
  increase in the output of pollutants instead,
  they occur because of changes in certain
  atmospheric conditions.
• Two of the most important atmospheric conditions
  affecting the dispersion of pollutants are
• (1) the strength of the wind and
• (2) the stability of the air.

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Air Mixing

• The direct effect of wind speed is to influence
  the concentration of pollutants.
• Atmospheric stability determines the extent to
  which vertical motions will mix the pollution
  with cleaner air above the surface layers.
• The vertical distance between Earth's surface and
  the height to which convectional movements extend
  is called the mixing depth.
• Generally, the greater the mixing depth, the
  better the air quality.

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Inversions

• Temperature inversions represent a situation in
  which the atmosphere is very stable and the
  mixing depth is significantly restricted.
• When an inversion exists and winds are light,
  diffusion is inhibited and high pollution
  concentrations are to be expected in areas where
  pollution sources exist.
• Surface temperature inversions form because the
  ground is a more effective radiator than the air
  above. Inversions aloft are associated with
  sinking air that characterizes centers of high
  air pressure (anticyclones).

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Inversion
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This is an example of a generalized temperature
profile for a surface inversion.
Temperature-profile changes in bottom diagram
after the sun has heated the surface.
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An Inversion Aloft
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Acid Precipitation

• In most areas within several hundred kilometers
  of large centers of human activity, the pH value
  is much lower than the usual value found in
  unpopulated areas.
• This acidic rain or snow, formed when sulfur and
  nitrogen oxides produced as by-products of
  combustion and industrial activity are converted
  into acids during complex atmospheric reactions,
  is called acid precipitation.

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Acid Precipitation (cont.)

• The atmosphere is both the avenue by which
  offending compounds travel from sources to the
  sites where they are deposited and the medium in
  which the combustion products are transformed
  into acidic substances.
• Beyond possible impacts on health, the damaging
  effects of acid precipitation on the environment
  include the lowering of pH in thousands of lakes
  in Scandinavia and eastern North America.
• Besides producing water that is toxic to fish,
  acid precipitation has also detrimentally altered
  complex ecosystems by many interactions at many
  levels of organization.

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Key Terminology

• Natural air pollution Primary pollutants
• Secondary pollutants Smog
• Photochemical smog Photochemical reactions
• Ozone Clean Air Act (1970)
• Mixing depth Inversion
• Surface inversion Inversion aloft
• Acid Precipitation

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Pertinent Web Sites

• Acid Rain FAQs (Environment Canada))
• Answers to frequently asked questions about acid
  rain.
• Air Pollution - U.S. EPA Office of Air and
  Radiation
• EPA's Office of Air and Radiation (OAR) deals
  with issues that affect the quality of our air
  and protection from exposure to harmful
  radiation. OAR develops national programs,
  technical policies, and regulations for
  controlling air pollution and radiation exposure.
  Areas of concern to OAR include indoor and
  outdoor air quality, stationary and mobile
  sources of air pollution, radon, acid rain,
  stratospheric ozone depletion, radiation
  protection, and pollution prevention.
• Atmospheric Ozone Concentrations
• Ozone concentration maps from the World
  Meteorological Organization (WMO).
• Atmospheric Pollution (EPA)
• Here is the Environmental Protection Agency (EPA)
  atmospheric pollution home page.
• Atmospheric Research Information Centre (ARIC)
• The ARIC is a multidisciplinary centre of
  excellence for the study and resolution of
  atmospheric pollution issues located at
  Manchester University in England.

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• Carbon Dioxide Information Analysis Center
  (CDIAC)
• The Carbon Dioxide Information Analysis Center
  (CDIAC) is the primary global-change data and
  information analysis center of the U.S.
  Department of Energy (DOE).
• Environmental Protection Agency (EPA)
• Here is the Environmental Protection Agency's
  (EPA) home Page.
• EPA Internet Site Search Engine
• The Environmental Protection Agency's (EPA)
  search page can be used to search the extensive
  EPA data base.
• EPA Topics, Browse
• Here is a site with access to a wide variety of
  topics related to the environment hosted by the
  Environmental Protection Agency (EPA).
• Montreal Protocol (AFEAS)
• An international agreement, known as the Montreal
  Protocol on Substances that Deplete the Ozone
  Layer, controls the production and consumption of
  substances that can cause ozone depletion.
• National Air Quality Trends Brochure (1996) - Six
  Principal Pollutants
• This site has an in-depth report on the six
  principal atmospheric pollutants.
• Ozone Depletion