IB Environmental Systems and Societies SL

Topic 6: Atmospheric Systems and Societies

6.1. Introduction to the Atmosphere

• Earth's Atmosphere:

  • Unique for sustaining life; composed of nitrogen (78%), oxygen (20%), carbon dioxide (0.03%), argon (0.93%), water vapour, and trace gases.
  • Dynamic system with inputs, outputs, storages, and flows that have evolved over geological time.
  • The atmosphere's condition is influenced by the sun's energy, creating atmospheric currents.

• Importance of Carbon Dioxide:

  • Small increases significantly impact climate change due to its low atmospheric concentration.

• Atmospheric Layers:

  • Troposphere: Contains most water vapour and CO2, weather occurs here.
  • Stratosphere: High ozone concentration, absorbs UV radiation, prevents weather from entering.

• Greenhouse Effect:

  • Natural phenomenon essential for maintaining life-sustaining temperatures.
  • Gases like CO2, water vapour, and methane trap heat near the Earth's surface.

6.2. Stratospheric Ozone

• Ozone Types:

  • Good Ozone (Stratospheric): Forms naturally, absorbs UV radiation.
  • Bad Ozone (Tropospheric): Forms from pollutants, contributes to smog.

• Formation of Ozone:

  • Good ozone: Formed by UV breaking down O2 into atoms, which recombine to form O3.
  • Bad ozone: Results from chemical reactions involving pollutants like car emissions in sunlight.

• Ozone Layer:

  • Protects Earth from UV rays.
  • Ozone depletion monitored since the 1950s, significant decrease observed over Antarctica.

• Ozone Depleting Substances (ODSs):

  • Include CFCs, HCFCs, halons, methyl bromide, and nitrogen oxides.
  • Release chlorine/bromine that break down ozone.

• Montreal Protocol:

  • International treaty to phase out ODSs, successful example of global cooperation.

6.3. Photochemical Smog

• Air Pollution Sources:

  • Primary pollutants: Direct emissions (e.g., CO, NOx, SO2).
  • Secondary pollutants: Result from reactions between primary pollutants (e.g., ozone).

• Formation and Effects of Tropospheric Ozone:

  • Formed from car exhausts, reacts with NOx and sunlight.
  • Toxic, damages plants, respiratory health, and materials.

• Particulates:

  • Released from burning organic material, diesel engines.
  • Cause respiratory issues and decrease plant productivity.

• Photochemical Smog:

  • Requires sunlight, involves VOCs, PAN, ozone, CO, NOx.
  • Contributed to by vehicle emissions, worsened by climate and geography.

6.4. Acid Deposition

• Types of Acid Deposition:

  • Wet deposition (rain, snow) and dry deposition (dust, smoke).
  • Acid rain has pH below 5.6.

• Sources:

  • Primary pollutants: Sulphur dioxide, nitrogen oxides.
  • Secondary pollutants: Sulphuric and nitric acids.

• Effects:

  • Direct: Damage to forests, aquatic life.
  • Indirect: Soil nutrient loss, toxic metal release, building erosion.

• Management Strategies:

  • Alter human activity: Use cleaner fuels, reduce electricity demand.
  • Regulate emissions: Scrubbing technologies, catalytic converters.
  • Clean-up: Liming lakes, afforestation.

Summary

Efforts to manage atmospheric pollutants and protect the ozone layer highlight the importance of international cooperation and sustainable practices to mitigate environmental impacts.