Chemistry of the atmosphere

• Phase 1 - Volcanoes gave out gases


  The surface was covered in volcanoes that erupted and released gases; The early atmosphere was mostly CO2 with virtually not oxygen; Volcanic activity released nitrogen, water vapour and small amounts of methane and ammonia
• Phase 2 - oceans, algae and green plants absorbed carbon dioxide

  1. water vapour in the atmosphere condensed and formed oceans
  2. carbon dioxide was removed as it dissolved in oceans; this dissolved carbon dioxide then went through a series of reactions to form carbonate precipitates that formed sediments on the seabed
  3. green plants and algae evolved and absorbed some of the carbon dioxide so that they could carry out photosynthesis
  4. Some carbon are taken in from the atmosphere and oceans became locked up in rocks and fossil fuels after organisms died
• • When plants, plankton and marine animals die, they fall to the seabed and get buried by layers of sediment; Over millions of years, they become compressed and form sedimentary rocks, oil and gas - trapping the carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced
• • crude oil and natural gases are formed from deposits of plankton. These fossil fuels form reservoirs under the seabed when they get trapped in rocks
• • Coal is a sedimentary rock made form thick plant deposits
• • Limestone is a sedimentary rock made from calcium carbonate deposits from shells and skeletons of marine organisms
• Phase 3 - green plants and algae produced oxygen

  1. As well as absorbing carbon dioxide, green plants and algae produced oxygen through photosynthesis
  2. Algae evolved first then green plants
  3. As oxygen levels built up over time, more complex life could evolve
  4. Eventually, the atmosphere reached a composition: 80% nitrogen, 20% oxygen and small amounts of other gases which makes up less than 1% of atmosphere such as carbon dioxide, noble gases and water vapour
• Carbon dioxide is a greenhouse gas

  1. Greenhouses gases like carbon dioxide, methane and water vapour act like an insulating layer in the earth's atmosphere
  2. All particles absorb certain frequencies of radiation. Greenhouse gases absorb long wavelength radiation that gets reflected back off the Earth. Then they re-radiate it in all directions.
  3. The longwave radiation is thermal radiation, so it results in warming of the surface of the earth
  4. This is the greenhouse gas effect
• Deforestation


  fewer trees means less CO2 is removed from the atmosphere via photosynthesis
• Burning fossil fuels


  carbon that was locked up in these fuels are released as CO2
• Agriculture


  more farm animals produce more methane through their digestive processes
• Creating waste


  more landfill sites and more waste from agriculture means more CO2 and methane released by decomposition of waste
• Carbon footprint is the measure of the amount of carbon dioxide and other greenhouse gases released over the full cycle of something
• Problems with particulates in the air

  If they get inhaled it can get stuck in the lungs and lead to respiratory problems; the clouds they help to produce reflect sunlight back into space which causes global dimming
• Carbon monoxide (CO)


  stops blood from doing its job of carrying oxygen around the body, it does this by binding to the haemoglobin in your blood that carries oxygen around your body; lack of oxygen in the blood can lead to fainting, a coma or death - it doesn't have any colour or smell so it is difficult to detect
• Sulfur dioxide

  SO2 is released during combustion of fossil fuels that contain sulfur impurities where the sulfur in the fuel becomes oxidises; can cause respiratory problems
• Nitrogen oxides


  Created from a reaction between nitrogen and oxygen in the air caused by the heat of burning (in the internal combustion engines of cars); when these gases mix with clouds they firm dilute sulfuric acid or dilute nitric acid which falls as acid rain; this kills plants, damages buildings, metal to corrode and causes respiratory problems