Changes in air quality during the COVID-19 lockdown in India

Abstract

Lockdown seems the most effective way to prevent the spread of Coronavirus disease (COVID-19) as no vaccine is available in the market to cure it. Thus, India has enforced nation-wide lockdown from 25th March to lower the spread of this contagious virus and associated illness. Thus, the anthropogenic activities have reduced significantly, as a result of which a decline in the air pollution levels is expected. This study aims to quantify the changes in pollution levels during the COVID-19 lockdown over 17 cities of India for 5 major criteria pollutants using publicly available air quality data. Hourly averaged data is accessed from the fixed air quality monitoring stations during the lockdown and immediate pre-lockdown periods and also corresponding data from the previous year (2019) to account for meteorological differences. After four weeks of lockdown, PM2.5, PM10, NO2, and CO reduced significantly with relatively little changes in meteorological condition compared to pre-lockdown period. The major decline is observed at the ~09:00 and ~21:00 hours of the day for PM, NO2, and CO with >40% reduction. The major impact is seen over metropolitan cities, with significant reduction in air pollutants levels (in particular in PM2.5 and PM10) resulting in 100% days during lockdown within the permissible air quality standards. PM2.5 and PM10 show ~70% decline in pollution levels for Delhi which is the highest among all the cities. Overall, the Northern and the Southern regions show more improvement in air quality during lockdown than other regions. The strict lockdown due to COVID-19, resulting in shutdown of many anthropogenic activities, has helped India to improve the air quality across the cities.