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Light-absorbing aerosols emitted during open biomass burning (BB) events such as wildfires and agricultural burns have a strong impact on the Earth's radiation budget through both direct and indirect effects. Additionally, BB aerosols and gas-phase emissions can substantially reduce air quality at local, regional, and global scales, negatively affecting human health. South America is one of largest contributors to BB emissions globally. After Amazonia, the BB emissions from wildfires and agricultural burns in the grassland plains of northern South America (NSA) are the most significant in the region. However, few studies have analyzed the potential impact of NSA BB emissions on regional air quality. Recent evidence suggests that seasonal variations in air quality in several major cities in NSA could be associated with open biomass burning emissions, but it is still uncertain to what extent those sources impact air quality in the region. In this work, we report on 3 years of continuous equivalent black carbon (eBC) and brown carbon (BrC) observations at a hilltop site located upwind of the city of Bogotá, and we demonstrate its association with fires detected by the MODerate-resolution Imaging Spectroradiometer (MODIS) in a 3000 km × 2000 km domain. Offline PM2.5 filter samples collected during three field campaigns were analyzed to quantify water-soluble organic carbon (WSOC), organic and elemental carbon (OC∕EC), and biomass burning tracers such as levoglucosan, galactosan, and potassium. MODIS active fire data and HYSPLIT back trajectories were used to identify potential biomass burning plumes transported to the city. We analyzed the relationship between BrC, WSOC, water-soluble potassium, and levoglucosan to identify signals of the regional transport of BB aerosols. Our results confirm that regional biomass burning transport from wildfires occurs annually during the months of January and April. The seasonality of eBC closely followed that of PM2.5 at the city air quality stations; however, the observed seasonality of BrC is distinctly different to that of eBC and strongly associated with regional fire counts. The strong correlation between BrC and regional fire counts was observed at daily, weekly, and monthly timescales. WSOC at the measurement site was observed to increase linearly with levoglucosan during high BB periods and to remain constant at ∼2.5 µgC m−3 during the low BB seasons. Our findings show, for the first time in this region, that aged BB plumes can regularly reach densely populated areas in the Central Andes of northern South America. A source footprint analysis involving BrC observations, back trajectories, and remotely sensed fire activity shows that the eastern savannas in NSA are the main BB source region for the domain analyzed.

BRT (Bus Rapid Transport) vehicles are a frequented microenvironment, it consists of exclusive lines for the transport of passengers in articulated buses. In many large cities of developing countries BRT vehicles are diesel operated buses emitting important amounts of PM2.5, a pollutant related with many health affectations. Evidence of high exposure levels have been reported onboard BRT vehicles, but detailed analysis of self-pollutions has not been developed. In this research, measurements of PM2.5 inside the BRT system of Bogota called TransMilenio were performed. Speed and location data were recorded in real-time. In-situ measurements were performed in 3 lines of the system: Av. El Dorado, Av. Caracas and Calle 80, in different seat locations inside the buses. PM2.5 concentrations above 120 μg/m3 were measured for all the cases studied. Values above the 24 h WHO (World Health Organization) recommendation were registered. Trips were determined to be between 20 to 40 minutes per passenger. A CFD (Computational Fluid Dynamics) model was implemented to simulate the exhaust emissions from the buses, 3 traffic velocities of BRT were evaluated: 20, 32 and 60 km/h. Measurements and simulation results were used to calculate the self-pollution ratios inside the vehicles. The rear of the buses was identified as the most polluted section onboard with a ratio of selfpollution about 35% average.

Objective The present study aimed to determine the association between chronic exposure to fine particulate matter (PM2.5), sociodemographic aspects, and health conditions with COVID-19 mortality in Colombia. Methods We performed an ecological study using data at the municipality level. We used COVID-19 data obtained from government public reports up to and including July 17th, 2020. We defined PM2.5 long-term exposure as the 2014–2018 average of the estimated concentrations at municipalities obtained from the Copernicus Atmospheric Monitoring Service Reanalysis (CAMSRA) model. We fitted a logit-negative binomial hurdle model for the mortality rate adjusting for sociodemographic and health conditions. Results Estimated mortality rate ratios (MRR) for long-term average PM2.5 were not statistically significant in either of the two components of the hurdle model (i.e., the likelihood of reporting at least one death or the count of fatal cases). We found that having 10% or more of the population over 65 years of age (MRR = 3.91 95%CI 2.24–6.81), the poverty index (MRR = 1.03 95%CI 1.01–1.05), and the prevalence of hypertension over 6% (MRR = 1.32 95%CI1.03–1.68) are the main factors associated with death rate at the municipality level. Having higher hospital beds capacity is inversely correlated to mortality. Conclusions There was no evidence of an association between long-term exposure to PM2.5 and COVID-19 mortality rate at the municipality level in Colombia. Demographics, health system capacity, and social conditions did have evidence of an ecological effect on COVID-19 mortality. The use of model-based estimations of long-term PM2.5 exposure includes an undetermined level of uncertainty in the results, and therefore they should be interpreted as preliminary evidence., Graphical abstract Unlabelled Image, Highlights • There was not a significant association between long-term exposure to PM2.5 and COVID-19 mortality in Colombia. • Demographic, health system, and social conditions are related to COVID-19 mortality. • Population over 65 years, poverty index, and prevalence of hypertension are associated to the death rate.

Light-absorbing aerosols emitted during open biomass burning (BB) events such as wildfires and agricultural burns have a strong impact on the Earth’s radiation budget through both direct and indirect effects. Additionally, BB aerosols and gas-phase emissions can substantially reduce air quality at local, regional, and global scales, negatively affecting human health. South America is one of largest contributors to BB emissions globally. After Amazonia, the BB emissions from the wildfires and agricultural burns in the grassland plains of Northern South America (NSA) are the most significant in the region. However, few studies have analyzed the potential impact of NSA BB emissions on regional air quality. Recent evidence suggests that seasonal variations in air quality in several major cities in NSA could be associated with open biomass burning emissions, but it is still uncertain to what those sources impact air quality in the region. In this work, we report on 3 years of continuous equivalent Black Carbon (eBC) and Brown Carbon (BrC) observations at a hill-top site located upwind of the city of Bogotá and we demonstrate its association with MODIS detected fires in a 3000 km × 2000 km domain. Off-line PM2.5 filter samples collected during three field campaigns were analyzed to quantify water-soluble organic carbon (WSOC), organic and elemental carbon (OC/EC), and biomass burning tracers such as levoglucosan, galactosan, and potassium. MODIS Active Fire Data and HYSPLIT back-trajectories were used to identify potential biomass burning plumes transported to the city. We analyzed the relationship between BrC, WSOC, water-soluble potassium, and levoglucosan to identify signals of regional transport of BB aerosols. Our results confirm that regional biomass burning transport from wildfires occurs annually during the months of January and April. The seasonality of eBC followed closely that of PM2.5 at the city air quality stations, however, the observed seasonality of BrC is distinctly different to that of eBC and strongly associated to regional fire counts. The strong correlation between BrC and regional fire counts was observed both at daily, weekly, and monthly time-scales. WSOC at the measurement site was observed to increase linearly with levoglucosan during high BB periods, and to remain constant at ∼ 2.5 µgC m−3 during the low BB activity seasons. Our findings show, for the first time in this region, that aged BB plumes can regularly reach densely populated areas in the Central Andes of Northern South America. A source footprint analysis involving BrC observations, back-trajectories, and remotely sensed fire activity shows that the eastern savannas in NSA are the main BB source region for the domain analyzed.

CFD, procesamiEl procesamiento de gas natural requiere la aplicación de nuevas tecnologías en un contexto de aumento de la demanda en todo el mundo. La separación de líquidos de gas natural (LGN) utilizando dispositivos supersónicos, es una novedosa y eficiente manera de reducir el volumen de equipos instalados y costos, utilizando los efectos de los flujos circulares altamente turbulentos. En esta investigación se implementa dinámica computacional de fluidos (CFD) para mejorar la eficiencia del proceso típico de recuperación de LGN utilizando el enfoque supersónico. También se puso en práctica un nuevo enfoque de modelado de la turbulencia con el objetivo de minimizar el tiempo de procesamiento, los resultados obtenidos fueron validados con datos experimentales disponibles. Esta investigación se basa en el modelo llamado k-épsilon RNG modificado para flujo remolino; este modelo no se ha utilizado ni validado antes en sistemas de flujo altamente compresibles, turbulentos y circulares. La eficiencia del proceso fue mejorada en un 11% en comparación con la eficiencia reportada en investigaciones previas, y el tiempo de procesamiento para el modelado redujo 40% con el enfoque turbulencia propuesto y ajustado. Durante la validación del modelo k-épsilon RNG modificado para flujo remolino el factor de remolino, parte del modelo de turbulencia, se ajustó a un valor óptimo para sistemas de flujo compresibles, turbulentos y circulares que participan en procesos de separación de NGL supersónico, lo que permite obtener resultados más precisos y con un menor tiempo de procesamiento en comparación con otros enfoques típicos y comunes como RSM y LES.

In Havana, transport is blamed as a likely source of pollution issues, which is usually supported on arguments referring to a vehicle fleet mainly made of old cars (i.e., most models are American from the 1950s or Russian from the 1980s) with poor technical conditions. Most of the existing studies are based on measurements from passive samplers collected for 24 h, which may not be representative of conditions where pollutant concentrations (particles or gases) fluctuate or are not homogeneous, such as transport-related pollution. The goal of this paper is to explore the transport-generated pollution by examining short-time correlations between traffic flows, pollutant concentrations and meteorological parameters. To do that, statistical relationships among all variables were analyzed, which revealed that PM 10 , NO 2 and SO 2 concentration levels are influenced by vehicular traffic, mainly with low-speed winds blowing perpendicular to the street axis. Furthermore, southeast and northeast winds force drag pollutionfrom sources other than traffic. These conclusions depend on the specific conditions of the summer season at the measurement area. A more complete analysis could be conducted when more data becomes available for each season.

In the vast majority of Latin American and South American countries, global emission inventories (EIs) are often used for modelling air quality. In particular the Emission Database for Global Atmospheric Research EDGAR is widely deployed but several studies have pointed to some gaps in comparison with national/regional inventories which incur errors in interpreting results. In Cuba, due to scarcity of a spatially distributed national inventory, EDGAR has been used as entry for air quality modelling without verifying their reliability over the region. Our goal in this article is to compare and contrast EDGAR with a local inventory and to evaluate similarities or discrepancies. We use advanced comparison techniques developed by the Forum for Air Quality Modelling in Europe–FAIRMODE. This approach differs from others in the detailed way in which it points out the differences and gets insights in possible explanations. Overall, EDGAR provided spatially smoother results and relatively lower values in hotspot areas. Coarse differences in terms of activities were low for all analyzed sectors. However, EDGAR overestimates emission factors (EFs) of stationary sources for CO by a factor of 3 and SO2 by a factor of 1.5 while underestimates those of PPM10 by a factor of 25. Most of the road transport EFs are overestimated in EDGAR; PM10, CO and NOx are 2 times higher, while CH4 and SO2 are 5 to 20 times higher. Large differences were found on the spatial distribution of energy and industrial sources. EDGAR can be regionally accepted as a reference but it is not recommended for air quality simulation over Cuba. A more complete reporting must be expected when more official national data are due. A review and evaluation of local emission inventories over Cuba can be useful for identifying potential areas for future improvement.

Road traffic emission factors (EFs) are one of the main sources of uncertainties in emission inventories; it is necessary to develop methods to reduce these uncertainties to manage air quality more efficiently. Recently an alternative method has been proposed to estimate the EFs. In that work the emission factors were estimated from a long term tracer study developed in Ho Chi Minh City (HCMC) Vietnam. A passive tracer was continuously emitted from a finite line source placed in one side of an urban street canyon. Simultaneously, the resulting tracer concentrations were monitored at the other side of the street. The results of this experiment were used to calculate the dispersion factors and afterwards, these dispersion factors were used to estimate the EFs. In this paper we use the Computational Fluids Dynamics (CFD) model WinMISKAM to critically evaluate the proposed methodology. In a first step, we use the results of the tracer study to validate the CFD model. Results show that the model is able to simulate quite well the tracer dispersion in most of the cases. The model is then used to evaluate the effect of varying the source configuration and to correct the EFs. A comparison with available studies shows that the corrected EFs are within the range of the EFs reported in other studies. Finally, the CFD model is used to find a source configuration that better represents the vehicle emissions and that may be used in future studies to estimate the EFs more accurately. Results show that a 200 m line placed in the center of the street would represent very well the vehicle emissions. This work shows that it is possible to accurately estimate the EFs from tracer studies.

Road traffic emissions, one of the largest source categories in megacity inventories, are highly uncertain. It is essential to develop methodologies to reduce these uncertainties to manage air quality more effectively. In this paper, we propose a methodology to estimate road traffic emission factors (EFs) from a tracer experiment and from roadside pollutants measurements. We emitted continuously during about 300 non-consecutive hours a passive tracer from a finite line source placed on one site of an urban street. At the same time, we measured continuously the resulting tracer concentrations at the other side of the street with a portable on-line gas chromatograph. We used n-propane contained in commercial liquid petroleum gas (LPG) as a passive tracer. Propane offers several advantages to traditional tracers (SF6, N2O, CFCs): low price, easily available, non-reactive, negligible global warming potential, and easy to detect with commercial on-line gas chromatographs. The tracer experiment was carried out from January to March 2007 in a busy street of Ho Chi Minh City (Vietnam). Traffic volume, weather information and pollutant concentrations were also measured at the measurement site. We used the results of the tracer experiment to calculate the dilution factors and afterwards we used these dilution factors, the traffic counts and the pollutant concentrations to estimate the EFs. The proposed method assumes that the finite emission line represents the emission produced by traffic in the full area of the street and therefore there is an error associated to this assumption. We use the Computational Fluids Dynamics (CFD) model MISKAM to calculate this error and to correct the HCMC EFs. EFs for 15 volatile organic compounds (VOCs) and NO are reported here. A comparison with available studies reveals that most of the EFs estimated here are within the range of EFs reported in other studies.