Hydroxymethanesulphonate

Table of Contents☰

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