Chemistry of the atmosphere

• Proportions of gases in the modern atmosphere


  • Around 80% N2
  • 20% O2
  • Small quantities of CO2, H2O, and noble gases
• Formation of the Earth's early atmosphere

  1. The Earth was hot when it was formed

  2. There was significant volcanic activity

  3. Gases have been released from these volcanoes

  4. These gases included CO2, N2, CH4, NH3, H2O
• Increase in oxygen in the atmosphere

  1. Algae and plants produced the atmospheric O2 by photosynthesis, which can be represented by the equation: 6 CO2+ 6 H2O → C6H12O6+ 6 O2

  2. As the amount of O2 increased, there were more plants that produced more oxygen
• Decrease in carbon dioxide in the atmosphere

  1. Some CO2 was dissolved in the oceans, where it reacted with metal ions to form insoluble carbonates, such as CaCO3, or was taken in by animals to become a part of skeleton. When animal dies, this becomes a sedimentary rock

  2. Some CO2 was used in photosynthesis to make oxygen
• Greenhouse effect

  • Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life
  • They allow short wavelength radiation from the sun to pass through the atmosphere to the Earth's surface, but absorb the outgoing long wavelength radiation from the Earth causing an increase in temperature
• Greenhouse gases

  • Water vapour, carbon dioxide, and methane
• The greenhouse effect is necessary for life
• Increase in greenhouse gases due to human activities

  1. Carbon dioxide – combustion and deforestation

  2. Methane – increased farming and decomposition in landfills
• Potential effects of global climate change

  • Sea level rise, which may cause flooding and increased coastal erosion
  • More frequent and severe storms
  • Changes in the amount, timing and distribution of rainfall
  • Temperature and water stress for humans and wildlife
  • Changes in the food-producing capacity of some regions
  • Changes to the distribution of wildlife species
• Carbon footprint

  The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event
• Actions to reduce carbon footprint

  • Increased use of alternative energy supplies
  • Energy conservation
  • Carbon capture and storage (where CO2 is trapped in solvents and stored underground)
  • Carbon taxes and licences
  • Carbon off-setting including through tree planting
  • Carbon neutrality – zero net release
• Challenges in reducing carbon footprint

  • Scientific disagreement over causes and consequences of global climate change
  • Lack of public information and education
  • Lifestyle changes (people don't want to give up their cars)
  • Economic considerations (it will cost money)
  • Incomplete international cooperation
• Advantages of complete combustion

  • Less soot (carbon particulates) is made
  • More heat per gram of fuel is released
  • Poisonous carbon monoxide is not produced
• Pollution caused by combustion

  1. When a fuel burns, the gases released to the atmosphere include carbon dioxide, water (vapour), carbon monoxide, sulphur dioxide and oxides of nitrogen

  2. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere
• Issues with sulfur dioxide and oxides of nitrogen

  • They cause respiratory problems in humans and cause acid rain
  • Acid rain damages plants and buildings
• Problems caused by particulates

  • They cause global dimming by reducing the amount of sunlight that reaches the Earth's surface
  • They cause health problems for humans because of damage to the lungs