Assessment of the Impact of COVID-19 Lockdown on the Spatio-Temporal Distribution of PM<inf>2.5</inf> in Thailand

Abstract

During COVID-19 pandemic several countries have implemented quarantines in response to the virus’ spread, which was considered an emergency. Thailand was under a state of emergency from January to December 2020, which has had an impact on the state of environment. Based on real-time data from the Pollution Control Department, the impact of COVID-19 lockdown on PM2.5 pollution in Thailand was examined. Inverse Distance Weighted interpolation was used to generate a more accurate visual representation of the PM2.5 pollution through a spatial distribution of atmospheric pollutants across the provinces of Thailand. PM2.5 levels in all considered areas reduced considerably between 2017 and 2020, with the most significant decrease occurring during the lockdown period of April-July in 2020. As the pre-COVID-19 period occurred during late winter in Thailand, the monthly average PM2.5 concentrations in all selected provinces were gradually increased from December 2019 to March 2020. During the lockdown period, the concentration of PM2.5 was reduced in Pathum Thani (48.9%), Samut Sakhon (35.6%) Samut Prakarn (33.6%), and Bangkok (31.7%) The spatial–temporal distribution of the PM2.5 levels in Samut Sakhon and Samut Prakarn provinces were analyzed for October 2020, during the new normal period. The results showed a significant decrease in concentration of up to 31% compared to previous years where industrial operations were situated. This study showed that the government enforced lockdown during COVID-19 pandemic was beneficial in understanding the impact of reduced human activities on anthropogenic air pollutants’ concentrations.