Lockdown measures led to air pollution decrease in several countries around the world such as China and India, whereas other regions experimented an increase in pollutant concentrations. Northern South America (NSA) was one of those areas where pollution changed during lockdown due to high fire activity. This study aims to analyze, for the first time in NSA, the behavior of selected criteria air pollutants during the implementation of the SARS-CoV-2 lockdown in two high populated cities of the region: Bogotá and Medellín in Colombia. A set of tools including surface measurements, as well as satellite and modeled data were used. 24-hour average concentrations of PM 10 , PM 2.5 , and NO 2 were collected from air quality stations for the lockdown period ranging from February 21 to June 30, 2020. The Copernicus Atmosphere Monitoring Service (CAMS) was used to analyze the fire flux OC as a biomass burning (BB) indicator, and tropospheric NO 2 concentrations were retrieved from TROPOMI. The HYSPLIT model was used to analyze back trajectories and fire data were obtained from MODIS sensor measurements. Our analysis shows short-term background NO 2 , PM 10 , and PM 2.5 concentration reductions of 60%, 44%, and 40%, respectively, for the strict lockdown; and 62%, 58%, and 69% for the relaxed lockdown. Corresponding long-term reductions were of 50%, 32%, and 9% for the strict lockdown; and 37%, 29%, and 19% for the relaxed lockdown. Regional BB increased PM 2.5 concentrations by 20 μg/m 3 during the strict lockdown, and the Saharan dust event increased PM 10 concentrations up to 168 μg/m 3 in Bogotá, and 104 μg/m 3 in Medellín, bringing an additional risk of morbidity and mortality for population. Regional BB has several causes that need to be properly managed to benefit local air quality improvement plans. Future cleaner transport policies equivalent to reduced lockdown mobility could bring pollution close to WHO guidelines.

Road dust has been identified as one of the main sources of outdoor PM10 in Bogota (a Latin American megacity), but there are no studies that have analyzed the physicochemical characteristics and origins of its respirable fraction. A characterization of inorganic compounds (water soluble ions, major and trace elements, organic and elemental carbon) and an analysis of source contributions to the PM10 fraction of road dust were carried out in this study. A total of twenty road dust samples, selected from representative industrial, residential and commercial areas, were swept and resuspended to obtain the thoracic fraction. Size distribution by laser diffraction and individual particle morphology by Scanning Electron Microscopy were also evaluated. The data obtained revealed that the volume (%) of thoracic particles was higher in samples from industrial zones where heavy vehicular traffic, industrial emissions and deteriorated pavements predominated. Crustal elements were the most abundant species, accounting for 49-62% of the thoracic mass, followed by OC (13-29%), water-soluble ions (1.4-3.8%), EC (0.8-1.9%) and trace elements (0.2-0.5%). The Coefficient of Divergence was obtained to identify the spatial variability of the samples. A source apportionment analysis was carried out considering the variability of chemical profiles, enrichment factors and ratios of Fe/

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PM2.5 monitoring campaigns were conducted in 2006, 2010, and 2011 in Tula de Hidalgo, Mexico, a highly industrialized area which includes a refinery, a thermoelectric power plant, five cement plants, limestone mining, and industrial waste combustion. These data establish baselines and trends against which later concentrations can be compared as emission reduction plans are implemented. PM 2.5 mass, chemical composition, and 15 particle-bound polycyclic aromatic hydrocarbons (PAHs) were measured at two sites. PM2.5 masses ranged from 26 to 31 µg m −3 . Carbonaceous aerosols were the largest PM2.5 component, accounting for 47-57% of the mass. Approximately 40-51% of the carbonaceous aerosol was attributed to secondary organic carbon. Ionic species accounted for 40-44% of PM2.5, with sulfate being the dominant ion. The sum of particle-bound PAH concentrations ranged from 14−31 ng m −3 . Six factors derived from Principal Component Analysis (PCA) explained ~ 85% of the PM2.5 variance. The derived factors were associated with sources based on marker species resulting in heavy-oil combustion (22% of variance), vehicle engine exhaust (13-19% of variance), fugitive dust (18% of variance), biomass burning (9-13% of variance), secondary aerosols (14% of variance), and industrial emissions (6-10% of variance). Combustion of solid waste (e.g., tires and industrial waste) of the recycling cement kilns and incinerators resulted in elevated toxic species such as, Cd, and Sb in the range of 0.02-0.3 µg m −3 .A health risk assessment of carcinogenic trace elements was performed showing that the total cancer risk decreased for both children and adults in 2010/2011 (ranging from 3.5×10 −6 to 6.0×10 −5 ) as compared to 2006 (ranging from 8.6×10 −7 to 5.7×10 −6 ). The inhalation life-time cancer risk (ILCR) for particle-bound PAHs ranged from 8.6×10 −5 to 1.2×10 −4 .Air quality can be improved by switching to cleaner fuels and benefit from the use of natural gas instead of fuel oil in the power plant.

Modern microscopy studies are capable of revealing ultra-fine particles (UFPs) and nanoparticles (NPs) that are produced in the processes related to traffic vehicular, industrial, metropolitan, and marine aerosol dry deposition in the coastal zones. Especially, secondary aerosol passages complexes categories of NPs and UFPs, which can be accumulated on construction compounds and by dry deposition, encourages multiples monuments deterioration routes. The advanced electron microscopies method is one of the most utilized in environmental studies. Between the different industrial areas in the world, the Caribbean area is the most relevant symbols of air quality due to climatic conditions with strong winds, but this study shows that regionally the most industrialized region does not have an adequate air quality. In the present work, electron microscopy analyses are used to describe of the extent of ultra-fine particle and nanoparticles in walls in contact to weathering. Numerous phases were recognized by advanced mineralogy methods. Thanks to the new analytical procedure it was feasible to understand NPs and UFPs; the occurrence of potential hazardous elements (PHEs), most of them as minerals but also combined in multiple accumulations with Al-Cr-Fe-K-Mg-Pb-Si-Ti-Zn amorphous; and carbonaceous phases.

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Air quality measurement is a topic of a great interest for any country due to health and environmental reasons. Tis issue is more critical in low-incomes countries since the air quality is generally worse than in developed countries and the governments give fewer budget to lead environmental policy and research. This explains the increasing demand for low-cost dust optical sensors like the Shinyei PPD24NS during the last years. However, those sensors present mixed results in terms of precision and repeatability, especially in case of new applications like the ones in moving context. Moreover, few or confuse information exists on those sensors functioning and conditions of use and the manufacturer does not provide any comprehensive guideline. The present article aims at filling this gap, providing a real study of the internal sensor operating. This includes: a detailed, theoretical and practical, analysis of the electric diagram, a characterization of the airflow through the optical chamber, an output behavior analysis based on particulate matter concentration and some algorithmic issues guideline. The article ends by providing useful tips and recommendations as well as some tracks to improve its precision for new applications.