标题：Monitoring the Impact of COVID-19 Lockdown on the Production of Nitrogen Dioxide (NO<sub>2</sub>) Pollutants Using Satellite Imagery: A Case Study of South Asia
摘要：Among the numerous anthropogenic pollutants, nitrogen dioxide (NO<sub>2</sub>) is one of the leading contaminants mainly released by burning fossil fuels in industrial and transport sectors. This study evaluates the impact of COVID-19 lockdown on the growing trend of NO<sub>2</sub> emissions in South Asia. Satellite imagery data of Sentinel-5 Precursor with Tropomi instrument was employed in this study. The analysis was performed using time series data from February–May 2019 and February–May 2020. The time frame from February–May 2020 was further divided into two sub-time-frames, i.e., from 1 February–20 March (pre-lockdown) and from 21 March–May 2020 (lockdown). Results show the concentration of NO<sub>2</sub> pollutants over the region declined by 6.41% from February–May 2019 to February–May 2020. Interestingly, an increasing trend of NO<sub>2</sub> concentration by 6.58% occurred during the pre-lockdown phase in 2020 (1 February–20 March) compared to 2019 (February–May). However, the concentration of NO<sub>2</sub> pollutants reduced considerably by 21.10% during the lockdown phase (21 March–10 May) compared to the pre-lockdown phase in 2020. Furthermore, the country-specific detailed analysis demonstrates the significant impact of COVID-19-attributed lockdown on NO<sub>2</sub> concentration in South Asia.
