The levels of various air pollutants, particularly that of nitrogen dioxide and aerosol particles, decreased considerably during the COVID-19 lockdown period in 41 Indian cities1.
Analysing satellite data, an international team of researchers found that nitrogen dioxide levels reduced significantly during the lockdown period (25 March 25 to 3 May 2020), compared with the pre-lockdown period since the beginning of 2020.
The researchers, including scientists from the Utkal University in Odisha and the Tata Energy Research Institute in New Delhi, analysed data recorded by an instrument onboard the European Space Agency’s Sentinel-5 Precursor satellite. The instrument, designed to quantify the levels of various air pollutants, helped measure the atmospheric levels of nitrogen dioxide and aerosol particles over major Indian cities.
Nitrogen dioxide levels, they found, went down by 13 per cent during the lockdown period compared with that of the pre-lockdown period of 2020. They also observed a 19 per cent reduction in nitrogen oxide levels during the lockdown period as compared with those dates in 2019.
The nitrogen dioxide reduction was higher in New Delhi, Bangalore, Ahmedabad, Nagpur, Gandhinagar and Mumbai than in coastal cities. The cities in north-east India showed an increase in nitrogen dioxide levels because of vegetation fires.
The nitrogen dioxide levels, however, decreased exponentially as the distance from the city centre increased, they report.
This study could help decision-makers arrive at efficient air-quality management plans involving local stakeholders, the researchers say.
1. Vadrebu, K. P. et al. Spatial and temporal variations of air pollution over 41 cities of India during the COVID‑19 lockdown period. Sci. Rep. 10, 16574 (2020)