Hydroxymethanesulphonate

Key Findings of the Study:

• Hydroxymethanesulphonate Formation: Hydroxymethanesulphonate, a secondary aerosol, forms when formaldehyde reacts with sulphur dioxide in the presence of liquid water.
  • Traditionally thought to occur only in clouds and fog, but found to occur in aerosol particles in Fairbanks winters.
• Role of Temperature: Extremely low temperatures (around -35ºC) cause supercooling of aerosol particles, where liquid water remains unfrozen below its freezing point.
  • Supercooled aerosols allow hydroxymethanesulphonate to form within them.
• Aerosol acidity dynamics: Aerosol acidity depends on the relative concentration of:
  • Sulphate ions (SO₄²⁻) → Increase acidity.
  • Ammonium ions (NH₄⁺) → Neutralize acidity.
• Post-2022 sulphur fuel ban in Fairbanks:
  • Sulphate ion concentrations dropped.
  • Ammonium ion levels increased, reducing aerosol acidity.
• Ammonium dynamics in cold weather: In low temperatures, ammonium ions are less likely to evaporate into ammonia gas. This buildup of ammonium ions further reduces acidity, creating favourable conditions for hydroxymethanesulphonate formation.

Key Concepts

• What are Aerosols?
  • Aerosols: Tiny solid or liquid particles suspended in the air.
  • Examples: Dust, smoke, fog, or chemical particles like sulphates and ammonium.
• What is PM2.5?
  • PM2.5: Fine particulate matter with a diameter less than 2.5 micrometres (µm).
  • Significance:
    • Penetrates the lungs and bloodstream.
    • Causes reduced lung function, asthma aggravation, and premature deaths.
• Supercooling: Process where liquid water remains unfrozen even at temperatures below 0°C.
  • Allows formation of hydroxymethanesulphonate in aerosol particles at very low temperatures.

Q.1. What are the main contributors to Delhi’s air pollution?

Vehicular emissions (51.5%), crop stubble burning (8.19%), dust (3.7%), and industrial pollutants are key contributors. Winter weather worsens the pollution.

News: New chemical pathway found to worsen air quality in harsh winters - The Hindu