Examining Effects of the COVID-19 National Lockdown on Ambient Air Quality Across Urban India

Chimurkar Navinya ； Girish Patidar ； Harish C. Phuleria

《Aerosol and Air Quality Research》 20卷8期 (2020/08) Pp. 1759-1771+ap1-8

https://doi.org/10.4209/aaqr.2020.05.0256

摘要

Lockdown seems the most effective way to prevent the spread of Coronavirus disease (COVID-19) as no vaccine is currently available in the market to cure it. Thus, India has enforced nation-wide lockdown from 25^(th) March to lower the spread of this contagious virus and associated illness. This study aims to quantify the changes in pollution levels as well as meteorology during the 6-weeks 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 air quality monitoring stations during the lockdown and immediate pre-lockdown periods and also corresponding data from the previous year (2019). During the lockdown, PM_(2.5), PM_(10), NO_2, and CO reduced significantly with relatively small changes in meteorological conditions compared to the pre-lockdown period. The highest decline is observed over Ahmedabad (68%), Delhi (71%), Bangalore (87%), and Nagpur (63%) for PM_(2.5), PM_(10), NO_2, and CO, respectively. The Northern region shows the highest decline for all the pollutants with most days below NAAQS during lockdown-86%, 68%, and 100% compared to 18%, 0%, and 38% in 2019 for PM_(2.5), PM_(10), and NO_2, respectively. The smaller cities Dewas and Jorapokhar show lesser improvement with only 3% and 16% improvement in days under NAAQS for PM_(2.5). SO_2 is the least affected pollutant with little improvement. The major decline is observed during 7-10 am and 7-10 pm hours of the day for PM_(2.5), PM_(10), NO_2, and CO with more than 40% reduction. The meteorological changes are very small and heterogeneous over India showing a similar extent of changes compared to the previous year but the pollution levels have reduced significantly. Thus, the sharp decline in pollutant concentration during the ~6 weeks period national lockdown can be attributed to the reduced economic and transport activities.

關鍵字

COVID-19 ； Urban air pollution ； India ； Lockdown ； PM_(2.5)