As virus shuts down cities, pollution drops

Sentinel-5P earth-observation satellite has detected a significant reduction in pollutant nitrogen dioxide in northern Italy and China's Hubei province as the advance of the COVID-19 illness led to drastic measures curtailing ordinary life.

Paris:European Space Agency says they have seen a decrease in air pollution as cities shut down amid the coronavirus outbreak.

The space agency says an earth-observation satellite has detected a significant reduction in pollutant nitrogen dioxide in northern Italy and China's Hubei province as the advance of the COVID-19 illness led to drastic measures curtailing ordinary life.

This is the picture, captured by the European Space Agency's (ESA) Sentinel-5P earth-observation satellite as northern Italy goes into lockdown due to the deadly coronavirus outbreak.

From 1 January to 11 March, northern Italy's nitrogen dioxide levels drop.

The trend coincides with a lockdown in Italy causing less traffic and industrial activities, says Simonetta Cheli, directorate of ESA's Earth Observation Programmes, but there are other factors too.

"The NO2 concentration which is been somehow decreasing quite impressively in the last few months. This decrease can be caused, certainly to the coronavirus, but not only," she says.

"In fact, it's impacted by the weather conditions, in general. So, the decrease in NO2 can be impacted by the fact that you do use more or less heating."

Italy has been the hardest-hit country in Europe by the new coronavirus and the government has implemented a wide lockdown encouraging its 62 million people to stay home unless it's necessary to go out.

It's a similar picture in China's Hubei province which includes virus epicenter Wuhan.

From 20 December 2019 to 16 March, Hubei province sees a dramatic reduction in nitrogen dioxide emissions.

"It was certainly because in the Hubei region in China, all activities were reduced dramatically due to the lockdown," says Cheli.

"So, industrial activities certainly were stopped and the streets were clear, but also to the fact that possibly it was coinciding with the New Year's Eve of the Chinese season."

Pollutant nitrogen dioxide is a byproduct of the use of diesel motors and other human activities.

NO2 is a short-lived pollutant, staying in the atmosphere generally less than a day before being deposited or reacting with other gases, meaning it remains fairly close to where it was emitted.

Most emissions are generated by human activities such as traffic, energy production, residential heating and industry.

Launched in October 2017, Sentinel-5P is the first-atmosphere monitoring satellite of the European Space Agency's earth-monitoring Copernicus program.

The spacecraft carries a "Tropomi" instrument which maps a multitude of trace gases including nitrogen dioxide, ozone, formaldehyde, sulphur dioxide, methane, carbon monoxide and aerosols.

Cheli says she has seen similar examples, such as when Beijing hosted the Summer Olympic Games in 2008.

"We have seen similar examples of a strong reduction in dioxide, the nitrogen dioxide, concentrations in the year 2008, at the occasion of the Olympic Games in China," she says.

(With inputs from AP)