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Washington, Apr 23: Air pollution over northern India has plummeted to a 20-year-low for this time of the year, according to satellite data published by US space agency National Aeronautics and Space Administration (NASA).
The US space agency's satellite sensors observed aerosol levels at a 20-year low post the countrywide lockdown, implemented to slow the spread of the novel coronavirus.

"We knew we would see changes in atmospheric composition in many places during the lockdown," said Pawan Gupta, a Universities Space Research Association (USRA) scientist at NASA''s Marshall Space Flight Center. "But I have never seen aerosol values so low in the Indo-Gangetic Plain at this time of year," added Mr Gupta.

Acting Assistant Secretary of State for South and Central Asia Alice G Wells tweeted, "These images from NASA were taken each spring starting in 2016 and show a 20-year low in airborne particle levels over India. When India and the world are ready to work and travel again, let's not forget that collaborative action can result in cleaner air."

The data published with maps show aerosol optical depth (AOD) in 2020 compared to the average for 2016-2019. 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, an optical depth of 1 or above indicates very hazy conditions. An optical depth, or thickness, of less than 0.1 over the entire atmospheric vertical column is considered "clean." The data were retrieved by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite.

In the first few days of the lockdown, it was difficult to observe a change in the pollution signature. "We saw an aerosol decrease in the first week of the shutdown, but that was due to a combination of rain and the lockdown," said Mr Gupta.

Around March 27, heavy rain poured over vast areas of northern India and helped clear the air of aerosols. Aerosol concentrations usually increase again after such heavy precipitation.

"After the rainfall, I was really impressed that aerosol levels did not go up and return to normal. We saw a gradual decrease and things have been staying at the level we might expect without anthropogenic emissions," Mr Gupta said.

On March 25, the Indian government placed its 1.3 billion citizens under a strict lockdown to reduce the spread of COVID-19. The countrywide mandate decreased activity at factories and severely reduced car, bus, truck and airplane traffic. Every year, aerosols from anthropogenic (human-made) sources contribute to unhealthy levels of air pollution in many Indian cities.

Aerosols are tiny solid and liquid particles suspended in the air that reduce visibility and can damage the human lungs and heart.

In southern India though, the story is a little hazier. Satellite data show aerosol levels have not yet decreased to the same extent. In fact, levels seem to be slightly higher than in the past four years. The reasons are unclear but could be related to recent weather patterns, agricultural fires, winds or other factors.

"This a model scientific experiment," Robert Levy, program leader for NASA's MODIS aerosol products, said about the lockdown and its effects on pollution.

"We have a unique opportunity to learn how the atmosphere reacts to sharp and sudden reductions in emissions from certain sectors. This can help us separate how natural and human sources of aerosols affect the atmosphere," Mr Levy added.

New Delhi, Mar 9: Petrol and diesel prices registered a drop across the country on Monday as global oil prices plummeted around 30 per cent after Saudi Arabia slashed prices and set plans for a dramatic increase in crude production in April.

In New Delhi, petrol price fell by 24 paise intra-day and stood at Rs 70.59 per litre. Diesel in the national capital was retailed at Rs 63.26 per litre on Monday as against Rs 63.51 on Sunday.

The retail price of petrol in Kolkata saw a drop of 23 paise to Rs 73.28 per litre. The diesel price fell by 25 paise in the eastern metropolitan city to retail at Rs 65.59 per litre.

In Mumbai, petrol price was Rs 76.29 per litre as against Rs 76.53 a day earlier. Diesel was retailed at Rs 66.24 per litre, 26 paise lower than on Sunday.

In Chennai, petrol was retailed at Rs 73.33 per litre, 25 paise lower than a day earlier. Diesel price saw a fall of 26 paise to retail at Rs 66.75 per litre in the southern metropolitan.

Global crude oil prices fell by as much as a third following Saudi Arabia's move to start a price war with Russia amid worries over the spread of coronavirus.

Brent crude futures were down 13.29 dollars or 29 per cent at 31.98 dollars a barrel by 04:33 hrs GMT after earlier dropping to 31.02 dollars, their lowest since February 12, 2016.

Brent futures were on track for their biggest daily decline since January 17, 1991 at the start of the first Gulf War.

Jaipur, Mar 26: Two new COVID-19 positive cases were registered in Rajasthan taking the total number of coronavirus cases to 38 in the state.
The Union Health Ministry had on Wednesday reported 606 positive COVID-19 cases in India including 43 foreign nationals.