Sulphur causes acid rain through a chemical reaction that begins when sulphur dioxide (SO₂) is released into the atmosphere. Here's a breakdown of the process:
1. Sulphur Dioxide Emission
- Sulphur dioxide (SO₂) is primarily released through:
- Burning of fossil fuels (coal and oil) in power plants, industrial facilities, and vehicles.
- Industrial processes like smelting of metal ores.
- Natural sources such as volcanic eruptions, but these are less significant compared to human activities.
2. Atmospheric Oxidation
- Once in the atmosphere, SO₂ undergoes oxidation, meaning it reacts with oxygen and other chemicals. This process can occur in two main ways:
- Gas-phase oxidation: SO₂ reacts directly with oxidants like hydroxyl radicals (OH•) in the air.
- Aqueous-phase oxidation: SO₂ dissolves in water droplets (clouds, fog, rain) and then reacts with oxidants such as hydrogen peroxide (H₂O₂) or ozone (O₃).
3. Formation of Sulphuric Acid
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These oxidation reactions ultimately lead to the formation of sulphuric acid (H₂SO₄). The overall reaction can be simplified as:
SO₂ + Oxidants + H₂O → H₂SO₄
4. Acid Deposition
- The sulphuric acid then dissolves in atmospheric moisture. This acidic solution falls to the earth's surface as acid rain (wet deposition). It can also deposit in dry form as acidic particles and gases, which later become acidic when they encounter water (dry deposition).
5. Environmental Impacts
- Acid rain has several harmful effects:
- Acidification of lakes and streams: Harming aquatic life.
- Damage to forests: Affecting plant growth and making them susceptible to diseases.
- Corrosion of buildings and monuments: Especially those made of limestone and marble.
- Impacts on human health: Respiratory problems and irritation.
In summary, sulphur, when burned, releases sulphur dioxide into the atmosphere. This gas reacts with water, oxygen, and other chemicals to form sulphuric acid, which then falls to the earth as acid rain, causing significant environmental damage.
