Differential Effects of the COVID-19 Lockdown and Regional Fire on the Air Quality of Medellín, Colombia

Abstract

Governments’ responses to the COVID-19 pandemic provide a unique opportunity to study the effects of restricted socioeconomic activity on air quality. Here, we study the changes in air pollution levels during the lockdown in Medellín and its metropolitan area, Colombia, for periods with and without enhanced regional fire activity, considering the effects of meteorology using random forest and multiple linear regression methods. The lockdown measures, which reduced mean traffic volume by 70% compared to 2016–2019, resulted in reductions for PM2.5 (50–63%), PM10 (59–64%), NO (75–76%), NO2 (43–47%), and CO (40–47%), while O3 concentration increased by 19–22%. In contrast, when fire activity was high, the effects of the lockdown on air quality were shadowed by the long-range transport of biomass burning emissions, increasing fine particulate matter and ozone. This study shows that healthier levels are achievable through significant efforts from decision-makers and society. The results highlight the need to develop integral measures that do not only consider reductions in the local emissions from transportation and industry, but also the role of fire activity in the region, as well as the difficulties of achieving reductions in ozone from measures that are effective at reducing primary pollutants.

Bayesian dynamic models to estimate the impact of halting vehicle fleets on the air quality: a case study from Medellín, Colombia

“…In Figure 5, for NO x , there is a behavior similar to the one observed with PM 2.5 . The reduction of this pollutant can be explained for similar reasons we highlighted above for PM 2.5 (Henao et al, 2021). For PM 2.5 , a significant reduction is observed from March 31st and for NO x earlier on March 16th.…”

“…These results are consistent with other studies performed in the Aburrrá Valley that showed a reduction in the PM 2.5 concentrations during the lockdown. This reduction can be attributed to the traffic reduction due this particles are mainly formed by particulate matter re-suspension associated to vehicles emissions (Henao et al, 2021;Mendez-Espinosa et al, 2020); industrial activities should contribute far less than transportation, which accounts for the majority of emissions (more than 80% of PM and NO x ) (AMVA & Bolivariana, 2017). Similar reductions were reported worldwide due to the lockdown and restrictions on transportation, economic, and social activities (Chauhan & Singh, 2020;Gkatzelis et al, 2021;Venter, Aunan, Chowdhury, & Lelieveld, 2020).…”

Surface, satellite ozone variations in Northern South America during low anthropogenic emission conditions: a machine learning approach

“…Not only have been carried out a few studies in Latin American countries like the ones in Northern South America but also those studies have not considered the analysis after the lockdown (i.e., post-lockdown, to our knowledge) (Mendez-Espinosa et al 2020 ; Arregocés et al 2021 ; Henao et al 2021 ; Sokhi et al 2021 ). Mendez-Espinosa et al ( 2020 ) found reductions in NO 2 (28–65%), PM 10 (37–66%), and PM 2.5 (45–76%) related to lockdown restrictions.…”

“…Henao et al ( 2021 ) identified that in a single city in Colombia, large average reductions in PM 2.5 (50–63%), PM 10 (59–64%), NO (43–47%), NO 2 (43–47%), and CO (40–47%), and increments in O 3 (19–22%), were presented. Their comparisons of lockdown with pre-lockdown periods used multivariate regression analysis methods, and machine learning (random forest) to untangle the effects of the lockdown on pollution levels.…”