C9-Chemistry of the Atmosphere

• The atmosphere today :

  • Approximately 80% of the atmosphere is nitrogen
  • Approximately 20% of the atmosphere is oxygen
  • A small proportions (> 1%) of various other gases, including carbon dioxide, water vapour and noble gases.
• The evolution of the atmosphere :

  • During the first billion years of the earth's existence, the earth was covered with volcanoes which released carbon dioxide, nitrogen and water vapour
  • When the water vapour in the atmosphere condensed, it formed the oceans
  • When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments
  • Around 2.7 billion years ago algae and green plants evolved and started to photosynthesise, increasing the level of oxygen in the atmosphere
• Greenhouse effect :

  1. Shortwave solar radiation travels from the Sun to the Earth. This radiation passes through the atmosphere and is absorbed by the planet’s surface
  2. The warm surface then radiates longwave thermal radiation into the atmosphere. This longwave radiation is absorbed by greenhouse gases in the atmosphere, preventing it from escaping into space.
  3. These greenhouse gases re-radiate the longwave radiation back towards the Earth. This process traps heat from the sun at the surface of the Earth, increasing the Earth's surface temperature
• Human activity affecting greenhouse gases in the atmosphere :

  • Deforestation
  • Burning fossil fuels
  • Agriculture
  • Creating waste (landfills)
• Changes as a result of climate change :

  • Sea levels rising
  • Extreme weather events
  • Changes in the amount and time of rainfall
  • Changes in ecosystems and habitats
  • Polar ice caps melting
• The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
• Ways to reduce carbon footprint :

  • Using renewable energy sources
  • Using public transport
  • Taxing companies based on the amount of greenhouse gases emitted
• Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected.
• Sulfur dioxide and oxides of nitrogen cause respiratory problems in humans and cause acid rain
• Particulates cause global dimming and health problems for humans.