Effects of Coronavirus Induced City Lockdown on PM2.5 and Gaseous Pollutant Concentrations in Bangkok

Abstract

Partial lockdown measures took effect in Thailand from March 22, 2020 to prevent the spread of the coronavirus. People widely believed that the air quality in Bangkok would improve during the lockdown. This study aims to understand the effects of the traffic on Bangkok PM 2.5 and gas concentrations, by comparing the air quality before and during the lockdown. Some pollutant concentrations in pre-lockdown period were higher, but the differences were not significant, except for O3. When results in the full lockdown month, April 2020, were compared to the same period in 2019, the average PM2.5 concentrations at the road sites decreased by 11.1%. On the other hand, it increased by 16.7% at the business area sites. No clear relation of the PM2.5 change to the reduction of traffic and diesel fuel consumption was observed. The reduction of NO2 was clear, caused by the significant drop in traffic and fuel consumption: in turn, it contributed to an increase of O3. The increment of PM2.5 levels during the lockdown was an external effect, even though significant change of local sources occurred. The values of OC/EC ratios in fine particles and the backward trajectory simulation confirmed that the peaks of PM2.5 levels were affected by both transboundary and local aerosol transport from open biomass burning. Hence, it is clear that road traffic, as well as industries or other human activities, were not the most influential factors on high PM2.5 levels in Bangkok in normal conditions. Possible solutions to reduce sources of Bangkok air pollutants include introduction of small-scale machinery for sugarcane harvesting to reduce biomass burning, adoption of higher standards to control diesel engine emission, and mutual agreement and action among ASEAN members in transboundary haze reduction.

Influence of Meteorological Conditions and Fire Hotspots on PM0.1 in Northern Thailand during Strong Haze Episodes and Carbonaceous Aerosol Characterization

“…Southeast Asia (SEA) is strongly affected by atmospheric haze pollution (Wiriya et al, 2013;(Li and Shao, 2009;Pongpiachan et al, 2014a;Pongpiachan et al, 2015;Chuang et al, 2016;Li et al, 2016;Chomanee et al, 2020;Dejchanchaiwong et al, 2020;ChooChuay et al, 2020a;ChooChuay et al, 2020b;ChooChuay et al, 2020c;Dejchanchaiwong and Tekasakul, 2021). In the upper SEA, the haze is observed during a quarter of every year and studied, mostly in Thailand (Wiriya et al, 2013;Wiriya et al, 2016;Thepnuan et al, 2019;Pani et al, 2019), but recently, air quality affected by PM10 and PM2.5 was studied in Laos (Nguyen et al, 2019), Myanmar (Sricharoenvech et al, 2020) and Vietnam (Le, 2020).…”

Assessing the Impact of Traffic Emissions on Fine Particulate Matter and Carbon Monoxide Levels in Hanoi through COVID-19 Social Distancing Periods

“…Long-range transport plays a crucial role in enhancing the fasting of the particular nitrate formation, the main factor contributing to the high atmospheric particle concentration in Shanghai (Chang et al, 2020). Otherwise, in Thailand, Dejchanchaiwong and Tekasakul (2021) explained the increase of PM2.5 under business areas in the lockdown period by identifying sources via calculating the ratio of organic carbon and elemental carbon (OC/EC) and backward trajectory simulation. The finding shows that the significant effects of local aerosol transport from open biomass burning in Thailand, Myanmar, Cambodia, Laos, and Vietnam affected the PM2.5 increase in Bangkok.…”

Air pollution and COVID-19 lockdown

“…That is, a synergy must be found between three key points; community health, environmental protection, and economic benefits. [47][48][49][50][51][52][53]…”

“…Figure16 The conflict behaviors of ozone pre-and during the lockdown period with reduction of NO 2 emission 47. …”

“…Figure 17Comparison of ozone levels during the lockdown and its level in pre-lockdown 2019 in Bangkok (Source: 47. …”