chemistry of the atmosphere

• • about 4/5 (80%) nitrogen
• • small proportion of other gases eg carbon dioxide, water vapour and noble gases
• evidence for the early atmosphere is limited because of the time scale of 4.6 billion years
• one theory suggests that the first billion years:

  • intense volcanic activity that released gases formed the early atmosphere
  • water vapour condensed to form oceans
• the start of the earths atmosphere was like of mars and venus today (mainly co2 and oxygen )
• volcanoes produced nitrogen which gradually built up in the atmosphere and a small proportion of methane and ammonia
• when oceans formed, CO2 was dissolved in water

  • other carbonates were precipitated producing sediment and reducing the amount of c02 in the atmosphere
• algae and plants produced the oxygen that is in the atmosphere by photosynthesis
• algae first produced oxygen about 2.7 billion years ago and soon after the first oxygen was produced in the atmosphere.
• over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve
• algea and plants decreased the percentage of c02 in the atmosphere
• co2 decreased by the formation of sedimentary rock and fossil fuels that contain carbon
• formation of crude oil and natural gas:

  1. deposits of plankton/animals and plants living in oceans and lakes died and remains sank to the bottom
  2. lack of oxygen prevented oxidation
  3. lack of factors for decay prevents decomposition
  4. heat and pressure turns organisms into crude oil
  5. natural gas is found on top of crude oil, trapped under sedimentary rock
• formation of coal:

  • sedimentary rock made from thick plants deposits
• formation of limestone:

  • sedimentary rock made from calcium carbonate deposits from its shells and skeletons of marine organisms
• greenhouse gases maintain temperature on earth high enough to support life eg: carbon dioxide, methane, water vapour
• the greenhouse gas effect:

  • electromagnetic radiation from the sun passes through the earth's atmosphere
  • Earth absorbs electromagnetic radiation with short wavelength
  • heat is radiated from the earth as longer wavelength in infrared radiation
  • some infrared radiation is absorbed by greenhouse gases in the atmosphere
  • atmosphere warms up
• some human activities increase the amount of greenhouse gases in the atmosphere eg carbon dioxide, methane
• human activities :

  • farming cattle release methane
  • farming rice in paddy field releases methane
  • burning fossil fuel in vehicles and power stations release CO2
  • deforestation releases co2 and reduces the absorption of co2 through photosynthesis
• it is difficult to model such complex systems as global climate change.

  • leads simplified models,
  • speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased
• four factors for evaluating the quality of evidence of global climate change:

  • who did the research
  • who funded the research
  • methods to collect and to analysis the data
  • organisation reporting and publishing the evidence
• an increase in average global temperature is a major cause of climate change
• four potential effects of global climate change:

  • glaciers and polar ice melting
  • sea levels rising
  • patterns of rainfall changing (flooding/ droughts)
  • habitats changing
• carbon footprint is the amount of co2 and other greenhouse gases emitted over the full life cycle of a product services or events
• carbon footprint can be reduced by:

  • solar panels on their roof (reducing electricity use)
  • commute to work by bicycle instead of driving
  • improve home insulation (reduce the amount of gases burnt)
• why people cant limit carbon footprint:

  • too expensive
  • work too far from home
• the combustion of fuels is a major source of atmospheric pollutants most fuels, including coal, contain carbon and or hydrogen and may contain sulfur
• • gases released into the atmosphere when a fuel is burned may include CO2, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen
  • solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere
• carbon monoxide is a toxic gas it is colourless and odourless and so it is not easily detected
• sulfur dioxide and oxides of nirogen cause respiratory problems in humans and can cause acid rain
• particulates cause global dimming and health problems for humans