Nitrogen Dioxide (NO2) Level Changes during the Control of COVID-19 Pandemic in Thailand

The first case of COVID-19 infection was confirmed in Thailand on January 13, 2020; since then, work from home and lockdown measures have slowed the spread of COVID-19. A more stringent, curfew regulation was imposed on April 3, 2020. Under these measures, the activities of businesses, transportation, and industrial sectors were reduced or temporally closed. Therefore, this study aims to investigate the changes in the nitrogen dioxide (NO2) level in the whole of Thailand and specifically in the Bangkok metropolitan area. The concentrations of tropospheric NO2 were extracted from the Sentinel-5P satellite data. The Google Earth Engine JavaScript API was used to retrieve and calculate the NO2 data. Python was also used to extract NO2 values from the output raster data. The results showed that the level of NO2 increased by 47.4% during the COVID-19 pandemic in the whole of Thailand; NO2 declined by 4.8% in the Bangkok metropolitan area, but there was no significant difference compared to before the COVID-19 pandemic. NO2 level during curfew regulation declined by 9.5% in the whole of Thailand and decreased by 20.1% in the Bangkok metropolitan area. After comparing the same time duration in 2019 and 2020 on a monthly basis, the results revealed that NO2 level in 2020 declined by 9.1% and 9.8% for the whole of Thailand and Bangkok metropolitan area, respectively. Our findings support that these measures can temporarily reduce NO2 levels. Once all sectors resume as normal, we concern that the NO2 emissions will rebound. Hence, the challenge after the COVID-19 pandemic is how to improve and protect our environment while restoring the economy, which is a crucial issue that policymakers should fully address.