Assessment of reduction of air pollutant emissions from road transportation in the Bangkok metropolitan region during the Coronavirus disease 2019 (Covid-19) lockdown

Abstract

This study aimed to assess air pollution emissions from road transport in the Bangkok Metropolitan Region (BMR) from 2018 to 2021 and estimated the effectiveness of PM2.5 reduction during the COVID-19 lockdown. The emissions were calculated by using the specific-area data and the related on-road activity data together with the emission factors from EMEP/EEA and GAINS-Asia. The results showed different trends in the amount of emission of each air pollutant from 2018 to 2021. This study found the number of emissions over the BMR area in the year 2018-2021 (and the trend during the period from 2018-2021) is approximately 22.6-22.2Mt of CO2(-1.7%), 210.4-197.2kt of CO(-6.3%), 31.4-27.7kt of NMVOC(-11.6%), 0.8-0.7kt of NH3(-21.5%), 14.6-9.6kt of CH4(-34.6%), 135.4-142.5kt of NOx(+5.3%), 0.9-1.0kt of N2O(+12.9%), 14.6-16.6kt of SO2(+14.2%), 7.1-8.4kt of PM2.5(+17.8%), 7.3-8.7kt of PM10(+18.8%), 4.7-5.6kt of BC(+19.3%), and 2.0-2.4kt of OC(+21.9%). In addition, the amount of PM2.5 during the COVID-19 lockdown was less than the normal situation. In 2020, there was about 0.72kt of the normal situation and 0.68kt of the lockdown period (5.17% of the PM2.5 decreased from the usual situation), and there was around 0.73kt of the normal situation and 0.61kt of the lockdown period in 2021 (16.70% of the PM2.5 decreased from the normal condition). These results indicate that the PM2.5 level can be reduced by the lockdown measurement significantly. Furthermore, the LDT and HDT diesel vehicles with low-emission control standards are the vehicle groups that released high PM2.5 emissions in this study; it should be a measure or policy related to handling these vehicle groups to reduce the PM2.5 levels from road transport in BMR. The study's findings indicate that removing LDT and HDT diesel vehicles off BMR roads that have no emission control technology will also reduce PM2.5 levels by about 30% of all PM2.5 emissions produced by the road transportation industry in BMR. Implication of the Thesis: This research provides the calculation results of air pollution emissions from road transport in BMR in the form of quantitative data by showing trends in the emissions of various air pollutants during the COVID-19 pandemic, which can be linked to the measures used during the epidemic and applied to manage air pollution problems in BMR. In addition, considering both quantitative and qualitative data on air pollutant emissions will lead to more efficient policies and measures to reduce emissions by road transport.