Transport

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Air Pollution 1
Omowumi Alabi Department of Geosciences
University of Missouri-Kansas City Kansas City,
MO
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Atmospheric Composition
The primary components of air are nitrogen (N2),
oxygen (O2) and water vapor (H2O). About 99
percent of dry air is nitrogen (78) and oxygen
(21). The remaining percent includes trace
quantities of substances such as carbon dioxide
(CO2), methane (CH4), hydrogen (H2), argon (Ar)
and helium (He).
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What is an Air Pollutant?
A substance that is - not naturally found in the
air - wrongly located or - in high enough
concentrations such that it produces a
detrimental environmental effect.
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Detrimental Environmental Effects

• The two basic physical forms of air pollution are
• Gases
• Particulate Matter
• These can affect
• -the health of humans (primarily the respiratory
  system)
• -the health of plants and animals
• -non-living materials

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Types of Pollutants

• Pollutants can also be classified as either
  primary pollutants or secondary pollutants.
• A primary pollutant is one that is emitted into
  the atmosphere directly from the source of the
  pollutant and retains the same chemical form i.e.
  the ash produced by the burning of solid waste.
• The effect of primary pollutants is most
  pronounced in the immediate vicinity of the
  source.
• A secondary pollutant is one that is formed by
  atmospheric reactions of precursor or primary
  emissions.
• Secondary pollutants are not emitted. Rather,
  they form in the air when primary pollutants
  react or interact. An important example of a
  secondary pollutant is ozone.
• Secondary pollutants take time to form and may
  not affect the immediate vicinity of the
  pollutant source.

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Sources of Air Pollutants
A source of air pollution is any activity that
causes pollutants to be emitted into the air.
Human-generated sources of air pollution are
categorized in two ways mobile and stationary
sources. Mobile sources of air pollution include
most forms of transportation such as automobiles,
trucks, and airplanes. Stationary sources of air
pollution consist of non-moving sources such as
power plants and industrial facilities
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Types Sources of Air Pollutants
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Stationary Sources
Air pollution from stationary sources is produced
by two primary activities - stationary
combustion of fuel such as coal and oil at power
generating facilities -the pollutant losses
from industrial processes such as refineries and
chemical manufacturing facilities.
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Transport Dispersion of Air Pollutants

• On the local level, the primary factors affecting
  transport and dispersion of pollutants are wind
  and atmospheric stability.

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Wind

• the natural horizontal motion of the atmosphere
• caused by differences in pressure in the
  atmosphere.
• air moves from high pressure areas to low
  pressure areas

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Effect of Wind on Dispersion of Pollutant

• Wind speed can greatly affect the pollutant
  concentration in a local area.
• The higher the wind speed, the lower the
  pollutant concentration.
• Wind dilutes pollutants and rapidly disperses
  them throughout the immediate area.

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Atmospheric Stability

• refers to the vertical motion of the atmosphere
• Unstable atmospheric conditions result in a
  vertical mixing, thereby promoting dispersal of
  polluted air

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Unstable Atmosphere Promotes Dispersal of
Polluted Air
Typically, the air near the surface of the earth
is warmer in the day time because of the
absorption of the sun's energy. The warmer and
lighter air from the surface then rises and mixes
with the cooler and heavier air in the upper
atmosphere causing unstable conditions in the
atmosphere. This constant turnover also results
in dispersal of polluted air.
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Stable Atmospheric Condition Discourages
Dispersal of Polluted Air
Stable atmospheric conditions usually occur when
warm air is above cool air and the mixing depth
is significantly restricted. This condition is
called temperature (or thermal) inversion. An
inversion can prevent the rise and dispersal of
pollutants from the lower layers of the
atmosphere and cause localized air pollution
problem.
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• Unstable Atmosphere
• Temperature decreases with height
• Vertical air motion is promoted
• Horizontal air motion is promoted
• Promotes dispersion

• Stable Atmosphere
• Temperature increases with height
• Vertical air motion is restricted
• Horizontal air motion is restricted
• Discourages dispersion