Juan Felipe Mendez Espinosa

Air pollution in towns adjacent to and downwind of large cities can be similar or even higher than in the city itself. In the case of towns constituting the greater Bogotá area, with more than half a million inhabitants and strong industrial activity, little is known about the factors that affect their poor air quality. This work investigated the incremental excess of the composition and source contribution to PM2.5 in two sites near Bogotá (Soacha: 4°35'4.59" N, 74°13'11.62" W; and Mosquera: 4°42'9.75" N, 74°13'54.94" W), using the Chemical Mass Balance receptor model with organic molecular markers, and back trajectory analysis. Simultaneous sample collection was carried out for two-months. Organic matter was the major component of the PM2.5 mass (66 ± 14% and 61 ± 12%), while secondary inorganic ions (sulfate, nitrate, and ammonium) constituted 13 ± 8 % and 10 ± 2 %. The main anthropogenic sources contributing to PM2.5 at Soacha were wood combus...

La reglamentación en América Latina y el Caribe de la Maquinaria Móvil No de Carretera -MMNC- (también conocida como Maquinaría Fuera de Ruta, Vehículos Fuera de la Ruta, NON-ROAD) supondría una estrategia de lucha frente al cambio climático, la contaminación atmosférica y otros problemas ambientales. La promulgación progresiva de estándares cada vez más estrictos de emisión de contaminantes asociados a esta maquinaria en otras zonas del mundo, como Estados Unidos desde 1994 y la Unión Europea desde 1997 ha permitido que esta categoría reduzca 3% y 2% de CO2e anual, respectivamente, en estas zonas. El presente documento compila información sobre el estado actual de la legislación y avances relativos a los inventarios de emisiones en la región, al tiempo que se analiza el abatimiento de emisiones de contaminantes atmosféricos y climáticos, proyectado a 2030 en Colombia, asociado a la implementación de un estándar de emisiones mínimo (Tier 4 Interim) en MMNC. Las proyecciones a 2030 se realizaron tanto para el escenario business as usual (BAU), en el que el país sigue sin reglamentación ambiental relacionada, como para el escenario de implementación de un estándar de emisiones mínimo para MMNC, mediante una ejecución paulatina, por rango de potencia: mayor a 37 kW desde 2021 y menor a 37 kW desde 2023. Al comparar las proyecciones a 2030 de emisiones respectivas, se obtuvieron reducciones acumuladas de 479 toneladas de BC, 591 toneladas de PM2.5, 610 toneladas de PM10, 3120 toneladas de NOx, 4331 toneladas de CO y 538 toneladas de HC. Asimismo, debido al alto GWP del BC en América Latina, su reducción junto a la del NOx representarían una disminución de 1.68 megatoneladas de CO2e, proyectada a 2030. Entre las principales barreras para generar una política efectiva regional de reducción de emisiones, se encuentran, primero, la ausencia de conceptos y definiciones unificadas para el subcontinente, referente a inventario de emisiones; segundo, un bajo grado de transferencia de información intra- e interinstitucional y sectorial; y, tercero, la ausencia de políticas públicas nacionales contundentes para reducir emisiones de contaminantes climáticos y atmosféricos.

Air pollution in towns adjacent to and downwind of large cities can be similar or even higher than in the city itself. In the case of towns constituting the greater Bogotá area, with more than half a million inhabitants and strong industrial activity, little is known about the factors that affect their poor air quality. This work investigated the incremental excess of the composition and source contribution to PM2.5 in two sites near Bogotá (Soacha: 4°35'4.59" N, 74°13'11.62" W; and Mosquera: 4°42'9.75" N, 74°13'54.94" W), using the Chemical Mass Balance receptor model with organic molecular markers, and back trajectory analysis. Simultaneous sample collection was carried out for two-months. Organic matter was the major component of the PM2.5 mass (66 ± 14% and 61 ± 12%), while secondary inorganic ions (sulfate, nitrate, and ammonium) constituted 13 ± 8 % and 10 ± 2 %. The main anthropogenic sources contributing to PM2.5 at Soacha were wood combustion (23%), diesel vehicles (19%), and coal combustion at small facilities (11%). At Mosquera, they were gasoline vehicles (26%), diesel vehicles (19%), and coal combustion at small inefficient facilities (15%). The contribution of regional Secondary Organic Aerosol to PM2.5 was significant (19% and 15%), arriving mostly from the Orinoco basin but higher with air masses arriving from the Amazon rainforest. The regional contribution to secondary inorganic aerosols was higher with winds from the Magdalena Valley. The methods presented in this manuscript will be useful in other megacities and large cities to better manage impacts of local and regional air pollution sources.

We have read with great interest the paper “Air quality during the COVID-19: PM2.5 analysis in the 50 most polluted capital cities in the world”, published in Environmental Pollution (Rodríguez-Urrego and Rodríguez-Urrego, 2020). We found the paper useful and resourceful, having used available open data at the World Air Quality Index website (World Air Quality Index project, n. d.). However, when we saw the data that the authors used to analyze the impact of the COVID-19 lockdown on air quality, we realized that they have made fundamental mistakes. We illustrate this as follows.

Light-absorbing aerosols emitted during open
biomass burning (BB) events such as wildfires and agricul-
tural burns have a strong impact on the Earth’s radiation bud-
get 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 affect-
ing human health. South America is one of largest contribu-
tors to BB emissions globally. After Amazonia, the BB emis-
sions from wildfires and agricultural burns in the grassland
plains of northern South America (NSA) are the most signif-
icant in the region. However, few studies have analyzed the
potential impact of NSA BB emissions on regional air qual-
ity. 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 uncer-
tain to what extent those sources impact air quality in the re-
gion. In this work, we report on 3 years of continuous equiv-
alent black carbon (eBC) and brown carbon (BrC) observa-
tions 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 sam-
ples collected during three field campaigns were analyzed
to quantify water-soluble organic carbon (WSOC), organic
and elemental carbon (OC/EC), and biomass burning trac-
ers 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 sig-
nals of the regional transport of BB aerosols. Our results con-
firm 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 ob-
served 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 pop-
ulated 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.

Biomass burning emissions have a substantial impact on regional air quality and climate. The region of Amazonia in South America has long been identified as one of the largest contributors to short lived pollutants globally. However, massive natural wildfires and agricultural burns also occur every year in the grassland plains of Northern South America during the dry season (November to April). The regional-scale air quality impact of these biomass burning emissions has not been studied in depth and is analyzed in this study. We used PM 2.5 and PM 10 concentrations from three large urban areas: Bogotá, Medellín, and Bucaramanga, for the period 2006-2016. Carbon monoxide data was only available for the city of Bogotá for the analysis period. These cities are located hundreds of kilometers westward of the emission areas. The spatio-temporal distribution of fires was obtained from MODIS Active Fire Data. The back-trajectories of air masses reaching the receptor sites were computed with two different meteorological datasets. Radiosonde data, available only for Bogotá, was used to account for local meteorological factors impacting pollution dispersion. A novel analysis algorithm was developed to combine active fire data with back-trajectory locations to select those active fires in the vicinity of the air masses arriving at each city. This analysis allows the selection of only those upwind fires that can be related to the air quality in the selected locations. We show that anomalously high PM and CO levels occurred when air masses originated from the Orinoco grasslands during the times when the largest number of fires in the region were active. The correlation between number of fires and PM 10 concentration was found to decrease with increasing distance from the sources, ranging from 0.6 to 0.25. Our results are insensitive to the meteorological dataset used to generate back-trajectories. For Bogotá it was found that mixing height variations can explain an important fraction of the observed seasonal variations in PM 10 , PM 2.5 , and CO concentration. The number of upwind fires can explain 11% ± 5% of the seasonal variability in CO concentrations. Estimates of the seasonal variability of PM 10 and PM 2.5 explained by fires are 45% ± 7% and 39% ± 8% respectively. However, covariance between occurrence of fires and non-combustion local sources of PM imply that the latter estimates are likely an overestimation of the actual contribution. Our findings support the possibility that fires in the Orinoco river basin deteriorate air quality in highly populated urban centers hundreds of kilometers away from the sources.

The Sahara Desert is one of the main sources of particulate matter (PM) in the world. This PM has the ability to affect air quality thousands of miles from the source. The intrusions of this dust in the Caribbean are well documented; however, no intrusions of this pollutant have been reported in large Colombian cities. This article analyses and determines the possible relationship between the emissions of dust from the Sahara, and an episode of high pollution that occurred in Bogotá and Medellín at the end of June 2014. The data recorded by the air quality networks of Bogotá and Medellín, the dust column mass density of the Merra-2 project, and the results of the NMMB/BSC-Dust model were used. The origins and trajectories of air masses were tracked by implementing HYSPLIT. The aerosol subtype was obtained from the CALIOP-CALIPSO sensor.

En Bogotá, estudios previos han mostrado que las emisiones de material resuspendido constituyen una parte sustancial del inventario de emisiones e impactan de manera importante la calidad del aire de la ciudad. Esta investigación estimó los factores de emisión (FE) de material particulado resuspendido antes, durante y después de la pavimentación de la vía principal del barrio Caracolí, en la localidad de Ciudad Bolívar, por parte de la Unidad de Mantenimiento Vial del Distrito (UMV). Conjuntamente, se midió el impacto de la pavimentación en la calidad del aire. La valoración del impacto y estimación experimental de FE de polvo resuspendido se obtuvo a partir de mediciones y un análisis estadístico experimental entre concentraciones de PM10, PM2.5, BC y variables meteorológicas al lado de la vía, junto con la aplicación de los modelos de dispersión SCREEN3 y AERMOD. Los factores de emisión estimados para vía no pavimentada fueron 7,8 ± 0,5 g PM10/VKT y 0,6 ± 0,2 g PM2.5/VKT y para vía en proceso de construcción de 28 ± 0,27 μg PM10/m2*s y 11 ± 0,13 μg PM2.5/m2*s. La modelación de dispersión atmosférica de material particulado resuspendido mostró una reducción del área de impacto en aproximadamente 1km y más de un 95% en concentración.