air pollution

Air Pollution



Contents of entire course

Smog
Control of Air Pollution
Air Inversion
Global Warming
Greenhouse Gases

adapted to HTML from lecture notes of Prof. Stephen A. Nelson Tulane University


Smog

Smoke plus Fog (based on Britain's experience) (Grey smog). Control of Air Pollution Automobiles

  • Catlytic converter converts carbon monoxide, nitrous oxides and hydrocarbons into carbon dioxide, nitrogen and water.
  • Recirculating exhaust gas along with a catlytic converter greatly reduces emissions.
    • Coal Main problem is the sulfur dioxide it produces upon burning. Solutions:
  • Burn only low sulfur coal.
  • Wash coal to remove pyrite.
  • Convert coal to gas (called Gasification)
  • Fluidized Bed Combustion (or Limestone Injection): Mix coal with limestone, to form calcium sulfides or sulfates, which are prevent sulfur from forming sulfur dioxide.
  • Scrubbing - slurries of lime or limestone.

    • Air Inversion

     In valleys or on the lee side of mountains, air inversion may occur. A warmer air mass moves above cooler air, trapping the cooler, denser air underneath and increasing the severity of air pollution. Los Angeles is a good example of this, where warm desert air from the east comes over the mountains to the east of Los Angeles and lies over the cooler Pacific Ocean air. The cooler air is trapped because it cannot rise through the less dense warm air above it, and the pollution in the cold air accumulates.
     


    A similar situation arises in mountain valleys where warm air overlies the colder air which accumulates in the valleys.

    Also, cities tend to form featuers known as heat islands or dust domes, which tend to collect warm air filled with pollutants, and help spread it out over nearby suburbs.




    Global Warming


    solar-radiation.gif (5318 bytes)

  • If there were no greenhouse effect, the average temperature on the earth would be 0°F with huge fluctuations in a 24 hour period.
  • When visible light from the sun hits the earth some is absorbed, heating the earth.   The heated earth gives off infrared radiation characteristic of the 60o F temperature. This longer wavelength infrared radiation  is then reradiated back into space. Some of the  infrared radiation, however, is  trapped (absorbed) by greenhouse gases. This is known as The Greenhouse Effect. See Blatt pg. 491 for a more detailed explanation.
  • There are several gases which cause the greenhouse effect, and whose concentrations determine the amount of heat retained by the earth. Primary among these are water vapor, carbon-dioxide and methane. The chart below shows how the concentration of CO2 in the atmosphere has changed in the last 40 years:



  • The increase in CO2 is anthropogenic (related to human activities). It is mostly due to the burning of fossil fuels and deforestation.


    • Gases contributing to Anthropogenic Greenhouse Effect
    Gas  Rate of Increase 
    (% per year)      		Relative Contribution(%) 
    CO2  0.5  60 
    CH4  1  15 
    N2O  0.2  5 
    O3  0.5  8 
    CFC-11  4  4 
    CFC-12  4  8 
         
    They are listed below:


    Scientific Consensus on Global Warming
    Statement  Consensus 
    Fundamental Physics  90+% 
    Added greenhouse gases add heat  90+% 
    Added gases are anthropogenic  90+% 
    Reduction of uncertainty will require a decade  90+% 
    Full recovery will require many centuries  90+% 
    Large stratospheric cooling  90+% 
    Precipitation will increase  90% 
    Reduction of sea ice  90% 
    Warming in arctic  90% 
    Rise in sea level  90% 
    Local details of global change  ? 
    Tropical storms increase  ? 
    Details of next 25 years  ? 
       

    Greenhouse Gases

    Links


  • Air Pollution
  • A collection of Links on Air Pollution: http://www.deb.uminho.pt/fontes/enviroinfo/air.htm

    • Global Warming

  • NASA Climate News page: http://www.climatenews.com/
  • The Union of Concerned Scientists have a global warming page: http://www.ucsusa.org/warming/index.html
  • The Sierra Club page: http://www.toowarm.org/home.html
  • The Environmental Protection Agency site on Global Warming: http://www.epa.gov/globalwarming/
  • This is a page arguing against global warming: http://www.webaxs.net/~noel/gwarming.htm
  • This page details the myths and misarguments by both sides of the global warming debate: http://members.aol.com/jimn469897/warming.htm

    • A Collection of sites that NASA put together about global warming: http://gcmd.gsfc.nasa.gov/faq/globwarm.html

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