Sulphur Dioxide

About Sulphur Dioxide

• Sulphur dioxide (SO2) is a heavy, colourless, toxic gas. 
• Source: Its largest source in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities.
  • Other sources: Industrial processes such as extracting metal from ore; natural sources such as volcanoes; and locomotives, ships and other vehicles and heavy equipment that burn fuel with a high sulfur content.
• Properties:
  • Physical State and Appearance: At room temperature, sulfur dioxide is a colourless gas with a pungent and suffocating smell.
  • Solubility: It is easily soluble in water and many organic solvents. In water, it forms sulphurous acid (H₂SO₃).
  • Molecular Weight: Its molecular weight is approximately 64.07 g/mol.
  • Boiling and Melting Points: The boiling point of SO₂ is -10 degrees Celsius, and the melting point is -72 degrees Celsius.
  • Chemical Stability: It is a stable compound but can be oxidised to sulfur trioxide (SO₃), which can react with water to form sulfuric acid (H₂SO₄).
  • Density: Its density at room temperature and pressure is approximately 2.926 g/L.
  • It reacts with other substances in the atmosphere to form sulfur oxides (SOₓ) and fine particulate matter (PM).
• Harmful Effects of Sulfur Dioxide (SO₂)
  • Health Effects: Short-term exposure to SO₂ can irritate the respiratory system and make breathing difficult.
  • Environmental Effects: High concentrations of SO₂ and other sulfur oxides can damage vegetation by injuring leaves and reducing plant growth.
    • It also contributes to the formation of acid rain, which acidifies soil and water bodies, damages forests, and harms aquatic ecosystems.
  • Effects on Visibility: SO₂ reacts with atmospheric compounds to produce fine particles that cause haze and reduce visibility.
  • Damage to Buildings and Cultural Heritage: Sulfur-containing particles settle on surfaces and can stain or corrode buildings, monuments, statues, and other stone materials.

About Findings of the CREA reports

• Nearly 81 per cent of the estimated sulphur dioxide (SO₂) emissions from coal-fired power plants within a 300-kilometre radius of Delhi-NCR originate from plants exempted from mandatory installation of Flue Gas Desulphurisation (FGD) systems.
• The findings indicate that 78 per cent of India’s coal-fired power plants are exempt from mandatory FGD installation following the July 2025 revision of emission norms, despite FGD technology being capable of reducing SO₂ emissions by up to 95 per cent.
• It notes that higher coal-based electricity generation under a strong El Niño scenario, driven by increasing electricity demand and reduced hydropower generation, could further increase SO₂ emissions in the Delhi-NCR region.
• SO₂ is identified as a major precursor to PM2.5, which is associated with respiratory diseases, cardiovascular illnesses, stroke, and premature deaths.