COVID-19 lockdown: a boon in boosting the air quality of major Indian Metropolitan Cities

Abstract

The COVID-19 lockdown has not only helped in combating the community transmission of SARS-CoV-2 but also improved air quality in a very emphatic manner in most of the countries. In India, the first phase of COVID-19 lockdown came into force on March 25, 2020, which was later continued in the next phases. The purpose of this study was to investigate the result of lockdown on air quality of major metropolitan cities—Delhi, Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Jaipur, and Lucknow—from March 25 to May 3, 2020. For this study, the concentration of six criteria air pollutants (PM 2.5 , PM 10 , CO, NO 2 , SO 2 , and O 3 ) and air quality index during the COVID-19 lockdown period was compared with the same period of the previous year 2019. The results indicate a substantial improvement in air quality with a drastic decrease in the concentration of PM 2.5 , PM 10 , CO, and NO 2 , while there is a moderate reduction in SO 2 and O 3 concentration. During the lockdown period, the maximum reduction in the concentration of PM 2.5 , PM 10 , CO, NO 2 , SO 2 , and O 3 was observed to be − 49% (Lucknow), − 57% (Delhi), − 75% (Mumbai), − 68% (Kolkata), − 48% (Mumbai), and − 29% (Hyderabad), respectively. The value of the air quality index (AQI) also dwindled significantly during the COVID-19 lockdown period. The maximum decline in AQI was observed – 52% in Bengaluru and Lucknow. The order of AQI was satisfactory > moderate > good > poor and the frequency order of prominent pollutants was O 3 > PM 10 > PM 2.5 > CO > NO 2 > SO 2 during the lockdown period in all the aforementioned metropolitan cities. Graphic abstract

Impact of COVID-19 lockdown and meteorology on the air quality of Srinagar city: A temperate climatic region in Kashmir Himalayas

“… This Study Hyderabad 25 March to 3 May 2020 25 March to 03 May 2019 -23 -41 -37 -9 -29 Na The concentration of almost all pollutants have decreased ranging from -9 to -41 percent. Rathore et al, 2021 Kolkata 25 March to 30 April 2020 25 Feb. to 24 March 2020 -50 -51 -69 -40 12 Na PM 10 , PM 2.5 and NO 2 shows >50% decrease. O 3 was slightly increased during lockdown.…”

“…From Table 1 , it is found that the maximum decrease in NO 2 concentration was reported at Mumbai (-75%) followed by Kolkata (-69%) and the minimum decrease was reported at Singrauli (-12.5%). As NO 2 and NH 3 are primarily associated with the combustion of fuel like gasoline and diesel in vehicles and industries ( Mahato et al, 2020 ; Rathore et al, 2021 ). This maximum reduction in NO 2 and NH 3 could be attributed to the sudden shutdown of the transportation sector, except for emergency services, as transport is the major source of NO 2 emissions ( Hakim et al, 2018 ).…”

“…Due to these restrictions once again anthropogenic emissions of air pollutants are believed to have decreased throughout India, including the Jammu and Kashmir ( Wang et al, 2021 ). Several studies have been published on the impacts of COVID-19 on air pollution levels in India ( Kumari and Toshniwal, 2020 ; Gouda et al, 2021 ; Chelani and Gautam, 2021 ; Mor et al, 2021 ; Verma and Kamyotra, 2020; Rathore et al, 2021 ). According to the findings of the review, the COVID-19 pandemic shutdown has led to a reduction in pollution all across India.…”

Air quality assessment of Jaipur city Rajasthan after the COVID-19 lockdown

“…None of them belongs to an industrial site. At SS-01 and SS-02, PM 10 and PM 2.5 were found above the limit and this may be due to dust arising from the foot of travelers and transport [ 30 ] in the area as two sites are marketing hubs of the city as mentioned in the material and method section. Values of PM 10 observed during the study period (82–235 µg/m 3 ) were found above the NAAQ value which is 100 µg/m 3 at all the sites.…”

Seasonal variation in the allergenic potency of airborne grass pollen in Bratislava (Slovakia) urban environment

“…Moreover, it is demonstrated that pollen allergies appear to be more prevalent in polluted areas, especially areas with heavy traffic (Lucas et al 2019). However, in 2020, the air quality substantially improved in numerous countries due to the COVID-19 lockdown accompanied by restricted movement of the public and shut down of industrial establishments (Dantas et al 2020;Rathore et al 2021). In Slovakia, the first phase of COVID-19 lockdown came into force on March 16, 2020, which later continued in the next phases.…”