C6.3

• Earth's Atmosphere

  intense volcanic activity that released gases formed the early atmosphere. Volcanoes also released nitrogen which gradually built up the atmosphere (we now have 78%). Water vapour condensed to form oceans and bodies of water. Carbon dioxide in water and carbonates were precipitated producing sediments, reducing the amount of CO2 in the atmosphere.
• Algae

  algae first produced oxygen 2.7 billion years ago and oxygen began to appear in the atmosphere. Over the next billion years evolved and the concentration of oxygen increased, which allowed animals to evolve.
• greenhouse gases

  • they keep temperatures high enough to sustain life
  • carbon dioxide, water vapour / steam, methane
• green house gas effect

  electromagnetic radiation from the sun pass into the Earth's atmosphere. the earth absorbs some radiation and this warm up. but some is radiated as infrared radiation. some of this IR radiation is absorbed by greenhouse gases. the atmosphere warms up leading to the greenhouse effect and global warming.
• life cycle assessment [LCA] - analysis of the overall environmental impact that a product may have through its life time.
• stages of a life cycle assessment

  1. raw materials
  2. manufacture
  3. distribution
  4. use
  5. disposal
• fossil fuels are formed from the remains of animals and plants, formed over millions of years ago.
• atmospheric pollutants


  CO2:

  is released by burning fossil fuels.

  leads to climate change and global warming.

  headache, drowsiness [humans]

  from volcanoes, decays plants and animals
• atmospheric pollutants

  Acid rain:

  caused by sulfur dioxide and various nitrogen oxides, which are released though burning fossil fuels. when these gases mix with clouds, they form dilute sulfuric acid and dilute nitric acid. this then falls as acid rain. power stations and internal combustion engines [cars] are the main cause of acid rain
• atmospheric pollutants

  nitrogen oxides:

  cause photochemical smog - air pollution caused by sunlight acting on nitrogen oxides. these combine with oxygen to produce ozone. ground level ozone can cause breathing difficulties, head aches and tiredness
• reasons for the change in the earth's atmosphere

  • water vapour condensed
  • photosynthesis reduced carbon dioxide concentration through algae, and increasec oxygen concentration
  • less carbon dioxide produced from volcanoes
  • carbon dioxide trapped in sedimentary rocks and fossil fuels.
  • carbon dioxide from air dissolved in oceans.
  • nitrogen builds up because it's unreactive
• Phase 1 -

  the earth's surface was originally molten for millions of year - there was no atmosphere. eventually the surface cooled and a thin crust formed but volcanoes kept erupting, releasing gases from inside the volcano. the 'degassing' released a lot of carbon dioxide, but also steam, methane and ammonia
• Phase 2

  a lot of early carbon dioxide was dissolved into oceans. Nitrogen was the put in the atmosphere through ammonia reacting with oxygen and denitrifying bacteria. nitrogen isn't very reactive, so it was only being made but not broken down [increased].
• Phase 3 - ozone layer

  the build up of oxygen killed the early organisms that couldn't tolerate it. but it allowed the evolution of more complex organisms that used the oxygen. the oxygen also created an ozone layer - which blocked harmful rays from the sun and enabled more complex organisms to evolve.
• Water Treatment

  1. filtration - a sheet of mesh filters out any big solids such as twigs and sticks. and sand beds filter out any other solid bits
  2. sedimentation - iron sulfate or aluminium sulfate is dissolved in the water which causes all fine particles to clump at the bottom.
  3. chlorination - chlorine gas is bubbled through to kill harmful bacteria and other microbes
• filtered tap water can still contain impurities and residue

  nitrate residue - run off from fertilisers into lakes and rivers

  lead compounds - from old lead pipes, very poisonous

  pesticide residue
• Phase 2

  green plants evolved over the earth - which photosynthesised, and removed carbon dioxide and released oxygen. much of the carbon dioxide was locked into sedimentary rocks and fossil fuels