Hydroxymethanesulphonate

According to a recent study, hydroxymethanesulphonate, a secondary aerosol forming in cold urban areas like Fairbanks, Alaska, is reshaping our understanding of aerosol chemistry in extreme conditions and its impact on air quality.

About Hydroxymethanesulphonate

It is a secondary aerosol, formed 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. Supercooled aerosols allow hydroxymethanesulphonate to form within them.
Aerosol acidity depends on the relative concentration of:
- Sulphate ions (SO₄²⁻) – Increase acidity.
- Ammonium ions (NH₄⁺) – Neutralize acidity.
Behaviour of Ammonium in low temperatures: In low temperatures, ammonium ions are less likely to evaporate into ammonia gas. This buildup of ammonium ions further reduces acidity. This creates favourable conditions for hydroxymethanesulphonate formation.
Impact on environment:
- Contributes to 5 pollution, worsening air quality.
- Also influences cloud formation and radiative properties which further affect climate.

Related Concepts

Aerosols: Tiny solid or liquid particles suspended in the air.
- E.g. Dust, smoke, fog, chemical particles like sulphates and ammonium etc.
Particulate Matter (PM): A mix of solid particles and liquid droplets suspended in air.
- PM 2.5: Ultrafine particles (<2.5 micrometres), harmful due to their ability to enter lungs and cause health problems like asthma, reduced lung function, and premature death.
Supercooling: It is a process where liquid water remains unfrozen even at temperatures below 0°C.