Assessing the Immediate Effect of Covid-19 Lockdown on Air Quality: A Case Study of Delhi, India

Abstract

In India, a nationwide lockdown due to COVID-19 has been implemented on 25 March 2020. The lockdown restrictions on more than 1.3 billion people have brought exceptional changes in the air quality all over the country. This study aims to analyze the levels of three major pollutants: particulate matter sized 2.5 μm (PM2.5) and 10 μm (PM10), and nitrogen dioxide (NO2) before and during the lockdown in Delhi, one of the world’s most polluted cities. The data for PM2.5, PM10, and NO2 concentrations are derived from 38 ground stations dispersed within the city. The spatial interpolation maps of pollutants for two times are generated using Inverse Distance Weighting (IDW) model. The results indicate decreasing levels of PM2.5, PM10, and NO2 concentrations in the city by 93%, 83%, and 70% from 25 February 2020 to 21 April 2020 respectively. It is found that one month before the lockdown the levels of air pollution in Delhi were critical and much higher than the guideline values set by the World Health Organization. The levels of air pollution became historically low after the lockdown. Considering the critically degraded air quality for decades and higher morbidity and mortality rate due to unhealthy air in Delhi, the improvement in air quality due to lockdown may result as a boon for the better health of the city’s population.

The Impact of COVID-19 Lockdowns on Air Quality—A Global Review

“…The results indicate the lowering of PM 2.5 , PM 10 , and NO 2 concentrations in the city by 93%, 83%, and 70%, respectively, from 25 February 2020 to 21 April 2020 [17].…”

“…The recent outbreak of COVID-19 has had an immense impact on air quality across the world [11][12][13][14][15]. After the outbreak of COVID-19, a large number of studies were performed on the impact of lockdowns on air quality [16][17][18]. The concentration of major air pollutants, such as PM 2.5 , PM 10 , SO 2 , CO, and NO 2 , were reduced by about 30% because of lockdowns [19].…”

“…According to Muhammad et al [27], there were substantial decreases in fuel demand around the world during lockdown periods due to the cessation of transportation and industrial activities. The reduced demand for fuel resulted in the drastic reduction of carbon emissions and air pollutant concentrations [15][16][17]28,29]. To the best of our knowledge, there have been no review studies performed on the impact of lockdowns on air quality across the globe until now.…”

Effect of COVID-19-induced lockdown on NO2 pollution using TROPOMI and ground-based CPCB observations in Delhi NCR, India

“…Similar results were also presented for Delhi region in several studies for NO 2 and other pollutants like SO 2 , O 3 , PM 2.5 , PM 10 , etc. (Das et al, 2021 ; Dumka et al, 2021 ; Ganguly et al, 2021 ; Jain & Sharma, 2020 ; Mahato et al, 2020 ; Navinya et al, 2020 ; Sharma et al, 2020 ; Sikarwar & Rani, 2020 ; Singh et al, 2020a , b ).…”

“…In Delhi the maximum and average values dropped by 70% followed by Bengaluru (63%), Mumbai (57%), Ahmedabad (56%), Hyderabad (49%), Pune (37%), Kolkata (34%) and Chennai (33%) in maximum NO 2 values as compared to pre-lockdown phase (Siddiqui et al, 2020 ) Delhi, India PM 10 , PM 2.5 , NO 2 Central Pollution Control Board’s (CPCB) ground station data The average PM2.5 concentration in the city has reduced from 122.48 µg/m3 on 25 February 2020 to 17.71 µg/m3 on 21 April 2020. On 21 April, 2020, 29 stations out of the 35 have recorded PM2.5 concentration below the WHO standards (Sikarwar & Rani, 2020 ) India PM 10 , PM 2.5 , NO 2 , CO, SO 2 , O 3 Central Pollution Control Board’s (CPCB) ground station data (134 stations) Studied the temporal and diurnal changes of six criteria air pollutants. PM 10 , PM 2.5 , NO 2 and CO reduced during lockdown, SO 2 and O 3 increased at some sites (IGP) and decreased in other sites (south).…”