There has been a general improvement in the air quality, including in India, amid lockdowns imposed across the world to check the spread of the coronavirus pandemic (Covid-19) with the European Space Agency (ESA) releasing satellite images showing nitrogen dioxide (NO2) levels have plummeted drastically.
The levels of nitrogen dioxide, a pollutant emitted generally by motor vehicles, went down drastically during the lockdown period in parts of China, where the pandemic originated from, and then gradually rose again in the past few days when the restrictions were eased.
In India, several cities otherwise known to record high pollution levels have recorded an improvement in air quality since Friday. A voluntary curfew to check the spread of the disease kept people mostly indoors on Sunday and the lockdown has been extended till the end of March in places like Delhi.
Kanpur’s air quality index (AQI)—193—was in moderate category on Friday. It improved to 77 to reach the satisfactory category on Sunday. AQI of Lucknow, which was 235 on Friday, and in poor category improved to 118 to moderate on Sunday. Kolkata, which had an AQI of 123 in the moderate level, fell to 76 to the satisfactory. Mumbai recorded an AQI of 82 on Friday; it fell further to 54 bordering good air quality on Sunday.
Delhi invoked the Delhi Epidemic Disease Covid-19 Regulations, on March 12 which gives the government powers to take extraordinary steps to combat an outbreak. Before the lockdown, Delhi had shut schools, restricted gathering of over 5 people and closed movie theatres. This led to a reduction in non-essential travel and emissions related to it. The average AQI between March 13 and 22 in Delhi has been 161.4 compared to 190.5 last year. This year Delhi has had only moderate air days during the period but last year there were 4 poor air days.
“The lockdown is catalysing systemic changes, which can be sustained beyond the corona crisis. We are setting up a system to work with less travel. We are now trying to realise the full potential of digitisation. We had not explored this alternative earlier. It’s a big lesson that this is doable. Reduction in emissions will also happen because of shutting down of factories and industries. That will show us the benefit of switching to clean fuel and following emission norms in future,” said Anumita Roychowdhury, executive director, Centre for Science and Environment.
“The time of isolation could be seen as an opportunity to understand nature’s processes and identify what we share our city with. This is a good time to do solitary backyard birding: there are lots of birds that have migrated to India and are still here. You can still see warblers such as Hume’s leaf warblers in the city. And many birds are beginning to nest, like the Purple sunbird and the House Sparrow,” said Neha Sinha, Delhi based conservation biologist.
For China, ESA used data from the Copernicus Sentinel-5P satellite, which shows the NO2 emissions from December 20 to March 16. “The drop in emissions in late-January is visible, coinciding with the nationwide quarantine, and from the beginning of March, the nitrogen dioxide levels have begun to increase,” the analysis released on Thursday said.
The Copernicus Atmosphere Monitoring Service also recorded a decrease of fine particulate matter (PM) concentrations in China in February compared to the previous three years. Studies based on satellite observations and detailed computer models of the atmosphere indicated a reduction of around 20-30% in PM concentrations over large parts of China, the ESA said.
ESA on March 13 released data from the Copernicus Sentinel-5P satellite showing a decline in NO2 emissions over northern Italy, which is among the worst-hit areas by the pandemic.
“We can certainly attribute a part of the nitrogen dioxide emission reduction to the impact of the coronavirus. We currently see around a 40% reduction over Chinese cities, however these are just rough estimates, as weather also has an impact on emissions,” said Claus Zehner, ESA’s Copernicus Sentinel-5P mission manager.
With boat traffic reducing in Venice following orders of stopping all non-essential travel in several cities in Italy, residents posted pictures showing clean water in Venice’s canals. Some images even show fish, swans and dolphins in Venice but they are unverified and may not have been photographed in Venice.
Some from California tweeted on Thursday that Los Angeles seemed to have the freshest air ever with the lockdown. Other residents said because of incredibly clear day, lots of kids were out biking. Modacity, an organisation that promotes cycling in Netherlands, tweeted: “The 1973 oil crisis opened Dutch people’s eyes to the enormous amount of space in their cities reserved for cars. Might the current situation be having a similar effect on places such as Bogota, New York and Melbourne?”
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