Assessment of the Impact of COVID-19 Lockdown on the Spatio-Temporal Distribution of PM_2.5 in Thailand

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 PM_2.5 pollution in Thailand was examined. Inverse Distance Weighted interpolation was used to generate a more accurate visual representation of the PM_2.5 pollution through a spatial distribution of atmospheric pollutants across the provinces of Thailand. PM_2.5 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 PM_2.5 concentrations in all selected provinces were gradually increased from December 2019 to March 2020. During the lockdown period, the concentration of PM_2.5 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 PM_2.5 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.