22 April 2020

Introduction:

At present Air pollution in India is at its lowest in two decades, says a study published by US space agency National Aeronautics and Space Administration (NASA).

Highlights of the Study:

• Study was conducted by   Pawan Gupta of Universities Space Research Association’s(USRA’s) along with NASA team at Marshall Space Flight Centre.
• The study reveals an all time low aerosol levels in Northern India and over the Indo-Gangetic plains.
• This is due to the low anthropogenic activities because of the lockdown prevailing in the wake of COVID-19.
• Normally during this time of the year there is a rise in the aerosol levels due to increased human activities- motor vehicles, coal fed power plants, industrial sources around urban areas producing sulphates, nitrates, coal combustion producing soot and other carbon rich particles.
• Rural areas add smoke rich in black carbon and organic carbon from cooking and heating.

What are aerosols?

• Aerosols are tiny solid and liquid particles suspended in the air that reduce visibility and can damage human lungs and heart.
• Some aerosols arise from natural sources like dust storms, volcanic eruptions and forest fires. Others come from human activities such as burning of fossil fuels and crop lands.
• Man made aerosols tend to contribute most of the smaller particles that have greater penetration for damaging human health.

What is Aerosol Optical Depth?

• Aerosol optical depth is a measure of how light is absorbed or reflected by airborne particles as it travels through the atmosphere.
• If aerosols are concentrated near the surface at an optical depth of 1 or above –this indicates very hazy conditions.
• An optical depth of less than 0.1 over the entire atmospheric vertical column is considered “clean’’.
• The AOD (aerosol optical depth) patterns were studied by MODIS model. MODIS- Moderate Resolution Imaging Spectroradiometer.
• A comparative study  of aerosols  in the Northern part of India over the years from 2016 is depicted in the self- explanatory pictures above.