Air quality and climate

This section focuses on the composition of air, the sources and effects of pollutants, and strategies to address environmental issues such as climate change and acid rain. Additionally, the chemistry behind photosynthesis and its importance in mitigating carbon dioxide levels is explained.

Composition of clean, dry air

Clean, dry air consists of:

• 78% nitrogen (N₂): Inert gas, essential for the nitrogen cycle but unreactive in normal conditions.

• 21% oxygen (O₂): Vital for respiration and combustion.

• 1% other gases: Includes noble gases (e.g., argon, helium) and carbon dioxide (CO₂).

Concentration of different gases in the atmosphere

Sources of air pollutants

1. Carbon Dioxide (CO₂):

   • Produced during complete combustion of carbon-based fuels (e.g., in power plants and vehicles).

2. Carbon Monoxide (CO) and Particulates:

   • Formed during incomplete combustion of fuels, particularly in poorly maintained engines or stoves.

3. Methane (CH₄):

   • Released by decomposition of organic matter (e.g., in landfills) and animal digestion (e.g., cattle).

4. Oxides of Nitrogen (NOₓ):

   • Created in car engines due to high temperatures causing nitrogen and oxygen to react.

5. Sulfur Dioxide (SO₂):

   • Emitted during the combustion of fossil fuels containing sulfur compounds (e.g., coal, oil).

Adverse effects of air pollutants

1. Carbon Dioxide (CO₂):

   • Contributes to global warming, leading to climate change (e.g., rising sea levels, extreme weather).

2. Carbon Monoxide (CO):

   • A toxic gas that binds with hemoglobin, reducing oxygen transport in the blood.

3. Particulates:

   • Cause respiratory problems (e.g., asthma) and increase the risk of lung cancer.

4. Methane (CH₄):

   • Potent greenhouse gas, amplifying global warming and climate change.

5. Oxides of Nitrogen (NOₓ):

   • Lead to acid rain, photochemical smog, and respiratory issues.

6. Sulfur Dioxide (SO₂):

   • Causes acid rain, which damages crops, buildings, and aquatic ecosystems.

The greenhouse effect and global warming

• Mechanism:

  • Carbon dioxide (CO₂) and methane (CH₄) absorb and emit thermal energy, trapping heat in the atmosphere.

  • Reduces heat loss to space, leading to global warming.

The greenhouse effect

Strategies to reduce environmental impact

1. Climate Change Mitigation:

   • Planting trees: Increases CO₂ absorption through photosynthesis.

   • Reducing livestock farming: Lowers methane emissions.

   • Using renewable energy: Replaces fossil fuels with wind, solar, and hydrogen energy sources.

2. Acid Rain Reduction:

   • Catalytic converters: Remove NOₓ from vehicle emissions 

     • Reaction: 2CO + 2NO → 2CO₂ + N₂.

   • Low-sulfur fuels: Reduce SO₂ emissions.

   • Flue gas desulfurisation: Uses calcium oxide (CaO) to neutralize SO₂ in power plants.

Photosynthesis