Abstract
Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus. It was first identified in December 2019 in Wuhan, Hubei, China, and has resulted in an ongoing pandemic. As of 5 July 2020, more than 11.1 million cases have been reported across 188 countries and territories, resulting in more than 528,000 deaths. More than 6.03 million people have recovered. The entire world population currently faces enormous challenges (i.e., social, environmental, health, and economic) due to the impact of COVID-19. In this regard, the affected countries are now trying to slow down the virus’s transmission through social-distancing, lockdowns, increasing the number of tests and treatment facilities. There have been four lockdowns (25 March 2020–31 May 2020), and two unlock periods (1 June–31 July 2020) in India. Aerosol Optical Depth (AOD) has been analyzed using MODIS satellite data during various phases of lockdowns over India. With the implementation of lockdown steps, AOD values dropped significantly over various regions. A significant reduction in AOD over the North-Central regions (up to −50%) compared to the regions in the South or Northeast India. The AOD over these regions was significantly affected by the lock/unlock phases. It was also observed that there was a considerable buildup of AOD during the pre-lockdown period in the year 2020 as compared to the past two years.
Introduction
The first case of novel coronavirus (COVID-19) was reported in the Wuhan district of China in December 2019 (Gautam and Hens 2020). The virus transmitted rapidly and affected several people within a month (WHO 2020). The first person reported in India was from the State of Kerala in late January 2020 (Gautam 2020b), and according to his travel history, he had returned from China. Since then, there has been a significant rise in the number of COVID-19 patients in India’s various states. As of 5 July 2020, a total of 19,289 deaths have been reported with 6,74,313 infected persons over entire India (https://www.ndtv.com//:5 July 2020). Maharashtra, Tamil Nadu, and Delhi have nearly 50% of all India cases, whereas northeast states have the least number of cases. Considering the seriousness of the disease, initially, a 21-day nationwide lockdown (25 March 2020 to 14 April 2020: LD1.0) was announced by the prime minister of India, “Shri. Narendra Modi” to control the transmission of COVID-19 and due to which many industries, academic institutes, markets, as well as public gatherings were shut down. After the first lockdown (LD 1.0), there have been three more lowdown phases in succession (LD2.0: 15 April to 3 May 2020, LD3.0: 4 May to 17 May 2020, LD4.0: 18 May to 31 May 2020). After that, to restart the Indian economy, two unlock phases (UL) have also been announced (UL1.0: 1 June 2020 to 30 June 2020, and UL1.0: 1 July 2020 to 31 July 2020).these lockdown phases can be taken as an opportunity to identify the hot spots (in terms of anthropogenic air pollution) in India. The present study was carried out with the following objectives:
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To analyze the impacts of various lockdown phases in India.
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To identify anthropogenic pollution hot spots of India.
Study area and data used
According to the World Air Quality Report (WAQR (2019)), 21 of the world’s 30 cities with the worst air pollution are in India, with six in the top ten. Considering the above fact, the present study has been carried out over India. Further, five different regions (covering Delhi, Maharashtra, Uttar Pradesh, Tamil Nadu, and northeast states) were analyzed, as shown in Fig. Fig.1.1. As of 5 July 2020, Maharashtra, Delhi, and Tamil Nadu have nearly 50% of all India COVID-19 cases.
Methodology
The AOD of the year 2020 over entire India and various regions marked in Fig. Fig.11 was analyzed and compared with previous years (2018, 2019) AOD data. For comparison, anomalies of AOD of the year 2020 have been calculated by subtracting it from the AODs of the years 2018 and 2019 at each grid point.
The analysis is carried out for different time intervals, as shown in Table Table1.1. The first period, pre-Lockdown, was the period before any lockdown was imposed in India from 1 January 2020 to 24 March 2020. The second period will be called as the lockdown 1.0 (LD1.0) that existed from 25 March 2020 to 14 April 2020. Subsequently, there were three more lockdowns (LD2.0, LD3.0, and LD4.0) between 15 April 2020 and 31 May 2020. After that, the first unlock period (UL1.0) started from 1 June 2020 to 30 June 2020. At present, the second unlock
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