Chapter 12: Air pollution

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Chapter 12 Air pollution

• A brief history of air pollution
• Types and sources of air pollutants
• Factors that affect air pollution
• Air pollution and the urban environment
• Acid deposition

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A brief history of air pollution
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A brief history of air pollution

• Londons historical problems
• disastrous London smog event of 1952
• Donora, Pennsylvania pollution episode, 1948
• U.S. Clean Air Act, 1970, 1990

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Types and sources of air pollutants
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Principal air pollutants

• primary and secondary pollutants
• particulate matter
• PM10, PM2.5
• Carbon monoxide
• Sulfur dioxide

• Globally, a large percentage of air pollution
  sourcesare natural. Within localized areas,
  however, human-caused sources are often the
  largest contributors

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Principal air pollutants

• Volatile organic compounds
• nitrogen oxides

• Along with ozone, VOCs and NOx are major
  componentsof photochemical smog

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Ozone in the troposphere

• photochemical smog
• ozone

• Photochemical smog is a problem on most major
  citiesof the world

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Ozone in the stratosphere

• relationship to ultraviolet radiation
• chlorine compounds
• Montreal Protocol

• When scientists first measured extremely low
  ozonevalues in the Antarctic stratosphere, they
  thought theinstruments were malfunctioning.

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Air pollution trends and patterns

• Primary air quality standards
• secondary air quality standards
• Air Quality Index (AQI)

• Secondary air pollutants are particularly
  difficult to control,because they are not
  emitted directly into the atmosphere

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Factors that affect air pollution
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The role of the wind

• dilution
• turbulence
• mixing

• Dilution is the solution to pollution - in
  the 1950s this motto led to the construction of
  tall smokestacks for large factories. Pollution
  wasreleased higher in the atmosphere where winds
  werestronger. Air quality improved locally but
  suffereddownwind.

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The role of stability and inversions

• temperature lapse rates
• inversions
• mixing depth

• The mixing layer can often be easily seen from
  an airplane.

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The role of topography

• cold air drainage
• air blockage by mountain ranges

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Severe air pollution potential

• sources
• high pressure
• inversions
• stagnation

• Some locations, like Los Angeles and Mexico
  City, havean unfortunate combination of
  surrounding topography,frequent inversions,
  abundant emissions and plentiful sunlight -
  perfect conditions for photochemical smog.

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Air pollution and the urban environment
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Air pollution and the urban environment

• urban heat island
• country breeze

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Acid deposition
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Acid deposition

• pH
• wet deposition
• dry deposition
• acid fog
• acid rain effects

• Strangely enough, an acidified lake looks
  crystal clearand beautiful. But the beauty is
  false its only clearbecause nothing is alive
  in it.