What is Aerosol

Aerosols are extremely small solid particles, or very small liquid droplets, suspended in the atmosphere. In common language it is dust. Aerosols are also called particle, or TSP (total suspended particles/ SPM/ PM₁₀, PM₄, PM_2.5, PM₁ etc.  Aerosols are omnipresent on our earth. Aerosols consisting of solid particles can be placed in the atmosphere primarily by large dust storms, volcanic eruptions, or the soot particles from large fires.

Relative Size of particles:

Human hair which is quite small but visible to naked eye is of the size 50-180 µm. If we keep going down the scale of small particles, we may come across fine beach sand which would be 90 µm, grain of salt around 60 µm, white blood cells (WBC) around 25 µm, grain of pollen around 15 µm and ultimately coming down to dust particle (PM₁₀) which would be <10 µm. PM_2.5 and PM₁ go even further down the scale.

Source: https://www.visualcapitalist.com/visualizing-relative-size-of-particles/

Definition of Atmospheric aerosol

Solid/ liquid particles suspended in air. They come from different types of natural and human made source

• Natural source: Sea-salts, Dust, Volcano, Biogenic (eg. pollens), forest fire etc.
• Human-made source: Industrial Emissions, Vehicular Emission, Biomass Burning. Thermal Power, Cow dung etc.

The size of aerosol varies from few nm to several micro meter. Sources emit primary particles as well as precursors of secondary particles like Sulphur Dioxide, Carbon Monoxide, Nitrogen Oxide etc. They can be removed via dry and wet deposition.

Lifetime of an aerosol ~ a week in lower troposphere

How do aerosols look under microscope

Why do we study Ambient Aerosols

• Climate Change:
  • Radiation Budget
  • Hydrological Cycle
• Air Quality:
  • Haze & fog/Visibility
  • Human health
• Aquatic Ecosystem:
  • Nutrients Deposition
  • Acid Rain

All particles cannot go inside our body, only <10micron can go to inside our body. But depending on the size they can go deep inside our body. If a particle <100 Nm, it can go to the lungs and if they are further smaller, they can go in the blood stream as well through which they can go to any organ ultimately affecting us in many ways. We may face many types of diseases like Chronic abstractive pulmonary disease (COPD) or even lung cancer.

Atmospheric Aerosols: A Multidisciplinary Research Area

There are lots of fields some of them are mentioned below:

• Environmental Science
• Mining Industry
• Engineering Science
• Social Science
• Pharmacy & Medical Science
• Agricultural Science
• Biology
• Meteorology
• Earth Science
• Architecture Civil Engineering
• Chemistry
• Physics,