Assessing the immediate impact of COVID-19 lockdown on the air quality of Kolkata and Howrah, West Bengal, India

Abstract

The worldwide spread of COVID-19 caused a nationwide lockdown in India from 24 March 2020 and was further extended up to 3 May 2020 to break off the transmission of novel Coronavirus. The study is designed to assess the changes in air quality from the pre-lockdown period to the during lockdown period in Kolkata and Howrah municipal corporation, West Bengal, India. GIS-based techniques include the spatial and temporal distribution of pollutants using interpolation method, and on the other hand, statistical methods like analysis of variance (ANOVA) was applied to determine the mean differences two phases and correlation matrix helps to understand the changing association of the pollutants in pre- and during lockdown phases. Significant correlations have been found among the pollutants, ANOVA (Two-Way) has shown the significant mean difference of NAQI between the two phases, F (1,611) = 465.723, p < 0.0001; pairwise comparison for Ballygunge has shown the highest mean difference 108.194 at p < 0.0001 significant level between lockdown and pre-lockdown phase. Significant positive correlation has been found between PM 2.5 , PM 10 (0.99*); PM 2.5, NO 2 (0.81*); PM 10 , NO 2 (0.81*); CO, NO 2 (0.77*) and some negative correlations have also been found between O 3 , NO (− 0.15); O 3 and NH 3 (− 0.36) in the pre-lockdown phase. The reduction amount of mean concentration from the pre-lockdown phase to during lockdown of the main pollutants like PM 2.5 , PM 10 and NO 2 are ~ 58.71%, ~ 57.92% and ~ 55.23%. Near Rabindra Bharati University constant emission of PM 2.5 , 10 and NO 2 have been recorded due to the nearby Cossipore thermal power station.

Positive effects of COVID-19 lockdown on air quality of industrial cities (Ankleshwar and Vapi) of Western India

“…The concentration of PM10, PM2.5, NO2 and SO2 reduced by 55%, 49%, 60% and 19%, and 44%, 37%, 78% and 39% for Delhi and Mumbai, respectively, during post-lockdown phase leading to a significant improvement in air quality 47 . The reduction in mean concentration from the pre-lockdown phase to during lockdown of the main air pollutants is observed in Kolkatta City 48 . In a similar study 49 , on 16 cities designated as Hotspot region covering almost two thirds of India, also reported a significant reduction in the observed (mean) levels of PM10, PM2.5 and NO2 concentration during the lockdown period from March 25 to April 25.…”

COVID-19: Has social isolation reduced the emission of pollutants in the megacity of São Paulo—Brazil?

“…For statistical analyses, the initial procedure consisted of verifying the normality of all data, by using as criteria the Asymmetry values ranging from + 3 to − 3, and Kurtosis values between + 8 and − 8, as proposed by Kline ( 2011 ) to accept data as normal. Correlation analyses were used in other studies related to the COVID-19 pandemic to identify, for example, the relationship of the number of cases and deaths with environmental variables (Singh et al 2020 ; Bashir et al 2020 ), and the association among the different pollutants (Sarkar et al 2020 ). Linear regression was used by Prata et al ( 2020 ) to identify the relationship of the number of cases with air temperature and population density.…”

“…Most recent studies related to the emission of pollutants during the COVID-19 pandemic have evaluated changes in air quality compared with a period prior to the lockdown (Aydin et al 2020 ; Bashir et al 2020 ; Collivignarelli et al 2020 ; Dantas et al 2020 ; Mahato et al 2020 ; Muhammad et al 2020 ; Nakada and Urban 2020 ; Otmani et al 2020 ; Rodríguez-Urrego and Rodríguez-Urrego 2020 ; Sarkar et al 2020 ; Sicard et al 2020 ). Some authors sought to correlate other aspects, such as climatic variables and the spread or lethality of COVID-19 (Conticini et al 2020 ; Fattorini and Regoli 2020 ; Guo et al 2020 ; Hendryx and Luo 2020 ; Jahangiri et al 2020 ; Kerimray et al 2020 ; Ogen 2020 ; Prata et al 2020 ; Rehman et al 2020 ; Singh et al 2020 ; Qi et al 2020 ).…”

Evaluation of Air Quality Index by Spatial Analysis Depending on Vehicle Traffic during the COVID-19 Outbreak in Turkey

“…In addition, a study conducted in India in the cities of Kolkata and Howrah Municipal Corporation, West Bengal was designed to assess changes in air quality from the preclosure period to the closure period. This study focused on the application of GIS-based techniques (spatial and temporal distribution of pollutants) using the interpolation method and statistical methods such as analysis of variance (ANOVA) to understand the changing association of pollutants in the pre-and during-closure phases [37].…”