Source: TOI
Subject: Environment
Context: A new IIT Madras–led study published in Science Advances shows that air pollution aerosols are intensifying and prolonging winter fog over north India.
About Aerosols:
What they are?
Aerosols are tiny solid or liquid particles suspended in the atmosphere, often invisible to the naked eye, that strongly influence air quality, weather and climate.
Origin:
- Natural sources: desert dust, sea spray, volcanic ash, forest fires
- Human sources: vehicle emissions, industrial pollution, biomass burning, coal and diesel use
They can be primary aerosols (emitted directly) or secondary aerosols (formed from gases like sulphur dioxide and nitrogen oxides in the air).
Key features:
- Extremely small in size: Their tiny size allows aerosols to enter deep into lungs and stay suspended easily in the air.
- Stay in air for days to weeks: They travel long distances before settling or being washed out by rain.
- Condensation nuclei: Aerosols provide surfaces for water vapour to condense, forming fog and cloud droplets.
- Scatter or absorb sunlight: Some aerosols reflect sunlight, while others like black carbon absorb heat.
Implications:
- Health: Aerosols worsen asthma, lung infections and heart diseases by penetrating the respiratory system.
- Weather: They make fog thicker and longer-lasting by increasing droplet formation and cooling.
- Climate (cooling): Reflective aerosols send sunlight back to space, lowering surface temperature.
- Climate (warming): Black carbon absorbs solar heat, warming the atmosphere.
- Cloud and rainfall changes: Aerosols make clouds brighter and longer-lived, altering rainfall patterns.
