## 5 Conclusions  
The effect of restricted human activities due to the COVID-19 pandemic in Colombia since mid-March of 2020 was studied by analyzing emissions variations of eleven criteria pollutants, comparing the first half of 2020 with values obtained in the same period of 2018. In general, the air quality improved during the COVID-19 lockdown, and it was apparently caused by reductions in emissions of some human activities, such as in the transportation sector. Lifting the lockdown and the normalization of activities in the productive sectors may reverse the reduction of global air pollution and even increase air pollution levels if researchers, decision makers, productive sectors, and governments do not articulate efforts to maintain the economy with minimum emissions. COVID-19 has allowed us to analyze the positive impacts of the measures adopted during the lockdown, specifically those that have generated reductions in pollution emissions with evident consequences for the air quality. Thus, it is important to identify the impact of low, moderate and high actions on reducing emissions, with emphasis in the agricultural and energy sectors, and especially the contributions of the transport sub-sector. The circumstances under which we have lived, and the measures adopted during the pandemic, taking in consideration changes for improving environmental conditions, can be the subject of dialogue at the next conference of the United Nations for Climate Change, COP26. Additionally, future work may use more detailed methodologies, such as tier 3 [42,88], to achieve high-resolution spatial inventories in Colombia. Conceptualization, Y.C.-C. and T.R.B.-O. ; data curation, Y.C.-C., L.C.M.-R. and T.R.B.-O. ; formal analysis, Y.C.-C., L.C.M.-R. and T.R.B.-O. ; investigation, Y.C.-C., L.C.M.-R. and T.R.B.-O. ; writing--original draft preparation, Y.C.-C., L.C.M.-R and T.R.B.-O. ; project administration, Y.C.-C.; software, L.C.M.-R.; supervision, Y.C.-C. and T.R.B.-O. ; visualization, Y.C.-C., L.C.M.-R. and T.R.B.-O. ; writing--original draft, Y.C.-C., L.C.M.-R. and T.R.B.-O. ; funding acquisition, Y.C.-C. All authors have read and agreed to the published version of the manuscript. The work of T.R.B.-O. was funded in part by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (National Council for Scientific and Technical Investigations), the National Agency of Scientific and Technological Promotion (ANPCyT) (Agencia Nacional de Promocion Cientifica y Tecnologica) under project PICT 2016 1115, and Universidad Tecnologica Nacional (UTN) (National Technological University) in Argentina. T.R.B.-O. also thanks GOREFNDR-V Region in Valparaiso and Programa de Asignacion Rapida de Recursos para Proyectos de Investigacion Sobre el Coronavirus (COVID-19) (project CO-VID0581-2020), ANID, Ministerio de Ciencia, Tecnologia, Conocimiento e Innovacion, both in Chile. Y.C.-C. and L.M.R. thank the grants and fund research (AA N\({}^{\circ}\) 014-2015, AA N\({}^{\circ}\) 031-2016, Res N\({}^{\circ}\) 0388-2017, Res N\({}^{\circ}\) 0709-2017, Res N\({}^{\circ}\) 0119-2018, Res N\({}^{\circ}\) 0305-2018 and Res N\({}^{\circ}\)0347-2020) from Universidad del Magdalena (Santa Marta, Colombia). Not applicable. The data presented in this study are available on request from the corresponding authors. We would like to thank [PERSON] for her help to graph Figure 4. We also would like to thank NASA's Aura Mission scientific teams, and their associated personnel, for the production of the data used in this research effort. The authors declare no conflict of interest. Figure A1: Fuel consumption from March to June 2018 and 2020. GNG sales data was only available at the national level.