Diesel Exhaust System Influences on Transient Particulate Emissions and Particle Size Distribution

The behaviour of particulate matter emissions from a Ford XLD 4T, passengercar diesel engine through a practical exhaust system in place was investigated during transient conditions, namely cold start and fast acceleration. Particulate emissions were measured at four sampling points through the exhaust system and the changes in particulate total mass concentration, total number concentration, particle size distribution and Carbon/SOF fractions were determined for various engine operating conditions. Each cold start test consisted of a step-change cold-start with fast acceleration, reaching one of the following target operation conditions: Idle, 1500rpm - 15kW, 2250rpm - 15kW, 2250rpm-35kW and 3500rpm - 15kW. Two preconditioning procedures were designed to provide repeatable cold start tests. These consisted of a) Idle operation for 4 hours the day before the test, followed by overnight soak; and b)10 minutes at high engine speed operation. Fast acceleration tests consisted of idle preconditioning followed by a step change to the target operation conditions. The particulate matter changes through the exhaust system were shown to be dependent on the previous operational history of the engine, idle conditions being effective at forming particle deposits. The amount of particulate deposited or blown out from the exhaust system constituted a significant fraction of the total engine exhaust emissions in a significant number of cold start and acceleration tests. The changes in particle concentration did not occur throughout the system in the same fashion. The catalyst produced predominantly particle number and mass reduction and the second silencer was a more efficient particle collector than the first silencer. From the first silencer, particles were resuspended more easily and in many more cases. Regarding the chemical composition, high-load conditions produced lower Solvent Organic Fraction (SOF) than their low load counterpart. However, the SOF did not change significantly through the exhaust system. Part of this work consisted of examining the use of the Electrical Low Pressure Impactor (ELP1) to estimate particulate mass emissions. It was observed that the ELP1 tended to overestimate the number of particles in the large (>0.1 (im) size range. This greatly affected the conversion from total particle number concentration to particle mass concentration. A correction based on comparison between the electrical and gravimetric methods (ELPI vs. Andersen Impactors) in the common size range for both techniques was proposed. Transient and steady-state tailpipe emission factors, expressed as grams of particulate per unit of engine work in kWh, were calculated from the test results and used to estimate the effect of transients on total cycle emissions in cycles with a different design from those followed in this work. The ELPI proved to be useful, yet limited for particle collection on Transmission Electron Microscope (TEM) grids in several size ranges. TEM images of particles were analysed and their fractal dimension determined

Metodología para la determinación de un Factor de Emisión de Material Particulado (FEPM) en Chircales de la Sabana de Bogotá

Se realizaron diferentes mediciones de material particulado, durante el periodo decocción de un chircal de la vereda de Patio Bonito en el municipio de Nemocón,Cundinamarca. Con las diferentes muestras se obtuvo un estimado de la emisión total delhorno, y también se calculó el factor de emisión correspondiente. A partir de la exploracióny las observaciones pertinentes de este tipo de hornos, se propuso una metodología másprecisa para la medición y la determinación de un factor de emisión de material particuladopara chircales. Los resultados del análisis muestran que la emisión calculada del horno seencuentra dentro del rango de valores obtenido en otros estudios, sin embargo estosresultados se podrían perfeccionar aplicando una metodología más precisa

Relación entre PM2,5 y PM10 en la ciudad de Bogotá

Se realizaron mediciones simultáneas de material particulado menor a 2,5 micras(PM2,5) y menor a 10 micras (PM10), durante periodos de hasta dos meses, en cincoestaciones de la red de monitoreo de calidad del aire de la ciudad de Bogotá y seanalizaron los resultados con herramientas estadísticas en busca de correlacionesentre PM2,5 y PM10. Los resultados del análisis muestran una correlación positiva ylineal entre los dos parámetros

Chemical composition and mass closure for airborne particulate matter in bogotá

Particulate matter, measured as PM10, is the most concerning airborne pollutant in Bogotá. Determining its chemical com- position is important for understanding its potential effects and to estimate various sources’ contribution to such pollution. This paper gives the results of characterizing the ionic species, carbonaceous material, metals and crustal elements present in airborne PM10 in Bogotá. An ion charge balance and mass reconstruction were done for determining consistency between chemical characterization and gravimetric PM10. The composition was different in each area; however, the fractions contributing most to PM10 were crustal, 37% to 42% was related to fugitive and suspended dust, 12% to 11% was related to carbonaceus fractions, 43% to elemental carbon, 34% for organic matter and 5% to 8% for ionic fractions.El material particulado, medido como PM10, es el contaminante que más afecta la calidad del aire en Bogotá. Conocer la composición del material particulado es crucial para en- tender cuáles son las fracciones químicas que más aportan a ese contaminante e identificar posibles fuentes generadoras de él. En este artículo se presenta el resultado de la caracterización de especies iónicas, fracciones carbonáceas, meta- les y elementos minerales del material particulado en dos puntos de Bogotá. Con base en los resultados de caracterización se realiza un análisis de neutralidad iónica y reconstrucción másica para comparar la consistencia de los resulta- dos obtenidos. La composición es diferente para cada sector, pero en general las fracciones que más aportan al material particulado son la geológica (asociada a polvo fugitivo y re- suspendido), entre el 37 y 42%; las fracciones carbonáceas, que son las que más aportan, entre un 12 y 11% para el car- bono elemental y un 43 y 34% para materia orgánica; la fracción iónica se encontró entre un 5 y 8%

Caracterización del material particulado en dos vías de transporte público colectivo y masivo en Bogotá

Entre septiembre y octubre de 2005, se recolectaron muestras de materialparticulado con un impactador de cascada en tres sitios de la ciudad de Bogotá,conformados por un punto de concentración base de baja contaminación, un punto allado de una vía donde opera el sistema de transporte público colectivo tradicional(buses y busetas), y otro punto ubicado al lado de una vía donde funciona el sistema detransporte masivo Transmilenio. Mediante análisis gravimétrico se determinó laconcentración de PM10 y PM2,5. Se analizó el contenido de metales (Cd, Pb, Fe y Mn)por espectroscopía de absorción atómica, y mediante análisis termogravimétrico sedeterminó el contenido de carbono orgánico y elemental en PM2,5. Las mayoresconcentraciones de PM10 y de PM2,5 se presentaron en la vía de transporte tradicional.Las mayores concentraciones en PM10 de Fe (1175,0 ng. m-3) y de Pb (61,4 ng. m-3) sedieron en la vía donde opera Transmilenio, y la mayor concentración de Cd (0,41 ng.m-3) se presentó en la vía de transporte público colectivo tradicional

Estudio comparativo de la extracción de cafeína con CO2 supercrítico y acetato de etilo

En este trabajo se evalúa el método de extracción con dióxido de carbono (CO2) supercrítico para la obtención de cafeína a partir de granos de café. Se destacan las características operativas que ofrece esta tecnología de extracción y se hace una comparación con el método Soxhlet usando acetato de etilo. Para ello, se desarrolla un diseño de experimentos que incluye variaciones en presión, temperatura y tiempo de extración, y permite determinar la mejor combinación de estas variables. Se emplea un equipo a escala de laboratorio compuesto de una celda de extracción alimentada con CO2 líquido y presurizada con nitrógeno, una chaqueta de calentamiento, y n recipiente de separación en el que se precipita la cafeína. Los resultados indican que la presión y el tiempo son las variables con mayor influencia en la extracción. Se alcanzó un rendimiento de 1.6 gramos de cafeína extraída por cada kilogramo de café verde con CO2 supercrítico y de 3.53 gramos de cafeína extraída por kilogramo de café verde con el método Soxhlet con acetato de etilo

Quantifying polycyclic aromatichydrocarbons in urine samples taken from traffic police working in Bogota’s metropolitan area

Objetivos: Cuantificar niveles urinarios de 1-hidroxipireno (1-OHP) y 3-hidroxibenzo [a] pireno (3-BAP) metabolitos de hidrocarburos policíclicos aromáticos (HAP) de interés toxicológico y relacionar su detección con el grado de exposición a material particulado de tamaño menor a 10 micras (PM10) u otros factores, en una población de Policías de Tránsito ocupacionalmente expuestos en el área metropolitana de Bogotá D.C. Métodos Se realizó un estudio de corte transversal en 524 Policías de Tránsito de los cuales 413 desarrollaban funciones operativas y 111 administrativas. Se tomaron muestras de orina de todos los individuos incluidos, para la determinación de metabolitos de HAP mediante cromatografía de gases con detección de masas. Se analizó la presencia de factores asociados con la detección de los metabolitos como tabaquismo, consumo de alimentos asados, lugar de residencia y exposición a PM10. Como medida de asociación se calcularon Odds Ratio (OR). Resultados Se encontraron niveles de 1-OHP y 3-BAP superiores en los individuos expuestos con OR significativos para detección de los metabolitos de 6,3 (IC95 3,6-11,1) y 15,6 (IC95 6,2-39), respectivamente. Se hallaron OR significativos para detección de metabolitos de HAP y exposición a PM10, tabaquismo y consumo de alimentos asados. Discusión Existe una asociación importante y significativa entre la exposición laboral a contaminación ambiental y la detección de metabolitos de HAP de importancia toxicológica en muestras de orina. Factores tales como tabaquismo, consumo de alimentos asados recientemente y exposición a PM10 también se encontraron asociados positivamente con la detección de dichos metabolitos pero en menor proporción.Objective Quantifying polycyclic aromatic hydrocarbon levels in urine samples taken from a population of traffic police working in the metropolitan area of Bogotá who were occupationally exposed to 1-hydroxypyrene (1-OHP) and 3-hydroxybenzo[a]pyrene (3-BaP) metabolites from polycyclic aromatic hydrocarbons (PAH) having toxicological interest, related to their detection, and a degree of exposure to particulate material having a size less than 10 micrometres (PM10) and/or other factors. Methods A cross-sectional study was made of 524 traffic police, 413 of whom were engaged in operational and 111 in administrative functions. Urine samples were taken from all the individuals included in the study for determining PAH metabolites by gas chromatography/mass spectrometry (GC/MS). The presence of factors associated with the detection of metabolites was analysed, such as smoking, consuming roasted/grilled food, place of residence and exposure to PM10. The odds ratio (OR) was calculated as a measure of association. Results Higher 1-OHP and 3-BaP levels were found in exposed individuals, having a significant OR for detecting 6.3 (3.6-11.1 95 % CI) and 15.6 (6.2-39 95 % CI) metabolites, respectively. Significant OR were found for detecting PAH metabolites and exposure to PM10, smoking and consuming roasted/grilled food. Discussion There was an important and significant association between workrelated exposure to environmental contamination and detecting toxicologically important PAH metabolites in urine samples. Factors such as smoking, consuming freshly grilled/roasted food and exposure to PM10 were also found to be positively associated with detecting such metabolites, but to a lesser extent

Photochemical sensitivity to emissions and local meteorology in Bogotá, Santiago, and São Paulo: An analysis of the initial COVID-19 lockdowns

This study delves into the photochemical atmospheric changes reported globally during the pandemic by analyzing the change in emissions from mobile sources and the contribution of local meteorology to ozone (O3) and particle formation in Bogotá (Colombia), Santiago (Chile), and São Paulo (Brazil). The impact of mobility reductions (50%–80%) produced by the early coronavirus-imposed lockdown was assessed through high-resolution vehicular emission inventories, surface measurements, aerosol optical depth and size, and satellite observations of tropospheric nitrogen dioxide (NO2) columns. A generalized additive model (GAM) technique was also used to separate the local meteorology and urban patterns from other drivers relevant for O3 and NO2 formation. Volatile organic compounds, nitrogen oxides (NOx), and fine particulate matter (PM2.5) decreased significantly due to motorized trip reductions. In situ nitrogen oxide median surface mixing ratios declined by 70%, 67%, and 67% in Bogotá, Santiago, and São Paulo, respectively. NO2 column medians from satellite observations decreased by 40%, 35%, and 47%, respectively, which was consistent with the changes in mobility and surface mixing ratio reductions of 34%, 25%, and 34%. However, the ambient NO2 to NOx ratio increased, denoting a shift of the O3 formation regime that led to a 51%, 36%, and 30% increase in the median O3 surface mixing ratios in the 3 respective cities. O3 showed high sensitivity to slight temperature changes during the pandemic lockdown period analyzed. However, the GAM results indicate that O3 increases were mainly caused by emission changes. The lockdown led to an increase in the median of the maximum daily 8-h average O3 of between 56% and 90% in these cities

A global observational analysis to understand changes in air quality during exceptionally low anthropogenic emission

This global study, which has been coordinated by the World Meteorological Organization Global Atmospheric Watch (WMO/GAW) programme, aims to understand the behaviour of key air pollutant species during the COVID-19 pandemic period of exceptionally low emissions across the globe. We investigated the effects of the differences in both emissions and regional and local meteorology in 2020 compared with the period 2015–2019. By adopting a globally consistent approach, this comprehensive observational analysis focuses on changes in air quality in and around cities across the globe for the following air pollutants PM2.5, PM10, PMC (coarse fraction of PM), NO2, SO2, NOx, CO, O3 and the total gaseous oxidant (OX = NO2 + O3) during the pre-lockdown, partial lockdown, full lockdown and two relaxation periods spanning from January to September 2020. The analysis is based on in situ ground-based air quality observations at over 540 traffic, background and rural stations, from 63 cities and covering 25 countries over seven geographical regions of the world. Anomalies in the air pollutant concentrations (increases or decreases during 2020 periods compared to equivalent 2015–2019 periods) were calculated and the possible effects of meteorological conditions were analysed by computing anomalies from ERA5 reanalyses and local observations for these periods. We observed a positive correlation between the reductions in NO2 and NOx concentrations and peoples’ mobility for most cities. A correlation between PMC and mobility changes was also seen for some Asian and South American cities. A clear signal was not observed for other pollutants, suggesting that sources besides vehicular emissions also substantially contributed to the change in air quality. As a global and regional overview of the changes in ambient concentrations of key air quality species, we observed decreases of up to about 70% in mean NO2 and between 30% and 40% in mean PM2.5 concentrations over 2020 full lockdown compared to the same period in 2015–2019. However, PM2.5 exhibited complex signals, even within the same region, with increases in some Spanish cities, attributed mainly to the long-range transport of African dust and/or biomass burning (corroborated with the analysis of NO2/CO ratio). Some Chinese cities showed similar increases in PM2.5 during the lockdown periods, but in this case, it was likely due to secondary PM formation. Changes in O3 concentrations were highly heterogeneous, with no overall change or small increases (as in the case of Europe), and positive anomalies of 25% and 30% in East Asia and South America, respectively, with Colombia showing the largest positive anomaly of ~70%. The SO2 anomalies were negative for 2020 compared to 2015–2019 (between ~25 to 60%) for all regions. For CO, negative anomalies were observed for all regions with the largest decrease for South America of up to ~40%. The NO2/CO ratio indicated that specific sites (such as those in Spanish cities) were affected by biomass burning plumes, which outweighed the NO2 decrease due to the general reduction in mobility (ratio of ~60%). Analysis of the total oxidant (OX = NO2 + O3) showed that primary NO2 emissions at urban locations were greater than the O3 production, whereas at background sites, OX was mostly driven by the regional contributions rather than local NO2 and O3 concentrations. The present study clearly highlights the importance of meteorology and episodic contributions (e.g., from dust, domestic, agricultural biomass burning and crop fertilizing) when analysing air quality in and around cities even during large emissions reductions. There is still the need to better understand how the chemical responses of secondary pollutants to emission change under complex meteorological conditions, along with climate change and socio-economic drivers may affect future air quality. The implications for regional and global policies are also significant, as our study clearly indicates that PM2.5 concentrations would not likely meet the World Health Organization guidelines in many parts of the world, despite the drastic reductions in mobility. Consequently, revisions of air quality regulation (e.g., the Gothenburg Protocol) with more ambitious targets that are specific to the different regions of the world may well be required.Peer reviewedFinal Published versio

Chemical composition and mass closure for airborne particulate matter in Bogotá

Particulate matter, measured as PM10, is the most concerning airborne pollutant in Bogotá. Determining its chemical com- position is important for understanding its potential effects and to estimate various sources’ contribution to such pollution. This paper gives the results of characterizing the ionic species, carbonaceous material, metals and crustal elements present in airborne PM10 in Bogotá. An ion charge balance and mass reconstruction were done for determining consistency between chemical characterization and gravimetric PM10. The composition was different in each area; however, the fractions contributing most to PM10 were crustal, 37% to 42% was related to fugitive and suspended dust, 12% to 11% was related to carbonaceus fractions, 43% to elemental carbon, 34% for organic matter and 5% to 8% for ionic fractions