AMS 14C and Chemical Composition of Atmospheric Aerosols from Mexico City

Radiocarbon ◽  
2017 ◽  
Vol 59 (2) ◽  
pp. 321-332 ◽  
Author(s):  
C Solís ◽  
V Gómez ◽  
E Ortíz ◽  
E Chávez ◽  
J Miranda ◽  
...  
Keyword(s):  
Mexico City ◽  
Atmospheric Aerosols ◽  
Material Balance ◽  
Total Carbon ◽  
Crustal Material ◽  
Carbonaceous Matter ◽  
Mineral Salts ◽  
Fossil Carbon ◽  
Biogenic Carbon ◽  
The City

AbstractAir pollution in Mexico City, which has more than 22 million inhabitants, continues to be one of the main environmental issues. Aerosol samples (PM10) collected in Mexico City and the city of Cuernavaca (a clean reference site) have been characterized using different techniques. This multifaceted approach addresses the source apportionment of the carbonaceous matter in PM10, as well as the airborne elements and ions. Accelerator mass spectrometry (AMS) radiocarbon analysis of total carbon, X-ray fluorescence (XRF), and ion chromatography were performed on aerosols collected at three sites in Mexico City and one site in Cuernavaca, during 2 months of the cold-dry season (November–December) in 2012. New results obtained for Mexico City are compared with previous reports. Average levels of PM10 were higher in Mexico City sites (43.3–60.8 μg/m3) than in Cuernavaca (32.2 μg/m3). According to the material balance, PM10 collected in Mexico City had a lower contribution of crustal material (31.2–36.8%) than Cuernavaca (46.9%). Average contributions of particulate carbonaceous matter to PM10 were similar in both cities, but much higher contributions of mineral salts, trace elements, and ions were observed in Mexico City in comparison to Cuernavaca. Total organic carbon (OC) and elemental carbon (EC) contents were higher in aerosols from Mexico City than those from Cuernavaca. The temporal variation results showed that within all locations studied the OC concentration was high compared to the EC. Results from a theoretical calculation of fossil carbon (FC) and biogenic carbon (BC) concentrations showed that FC and BC levels depend on the site: at Mexico City sites, FC was equal or higher than BC. At Cuernavaca, BC was always higher than FC.

scholarly journals Can 3-D models explain the observed fractions of fossil and non-fossil carbon in and near Mexico City?

2010 ◽  
Vol 10 (6) ◽  
pp. 14513-14556 ◽  
Author(s):  
A. Hodzic ◽  
J. L. Jimenez ◽  
A. S. H. Prévôt ◽  
S. Szidat ◽  
J. D. Fast ◽  
...  
Keyword(s):  
Mexico City ◽  
Transport Model ◽  
Measurement Techniques ◽  
Independent Set ◽  
Temporal Variations ◽  
Total Carbon ◽  
High Time Resolution ◽  
Carbonaceous Aerosols ◽  
Source Information ◽  
Fossil Carbon

Abstract. A 3-D chemistry-transport model has been applied to the Mexico City metropolitan area to investigate the origin of elevated levels of non-fossil (NF) carbonaceous aerosols observed in this highly urbanized region. High time resolution measurements of the fine aerosol concentration and composition, and 12 or 24 h integrated 14C measurements of aerosol modern carbon have been performed in and near Mexico City during the March 2006 MILAGRO field experiment. The non-fossil carbon fraction (fCNF), which is lower than the measured modern fraction (fCM) due to the elevated 14C in the atmosphere caused by nuclear bomb testing, is estimated from the measured fCM and the available source information. The fCNF contained in PM1 total carbon (fCNFTC) ranged from 0.37 to 0.67 at the downtown location (T0), and from 0.50 to 0.86 at the suburban site T1. Substantially lower values (i.e. 0.24–0.49) were found for PM10 filters at T0 by an independent set of measurements, which are inconsistent with the modeled and known differences between the size ranges, suggesting higher than expected uncertainties in the measurement techniques of 14C. An increase in the non-fossil organic carbon (OC) fraction (fCNFOC) by 0.10–0.15 was observed for both sets of filters during periods with enhanced wildfire activity in comparison to periods when fires were suppressed by rain, which is consistent with the wildfire impacts estimated with other methods. Model results show that the relatively high fraction of non-fossil carbon found in Mexico City seems to arise from the combination of regional biogenic SOA, biomass burning OA, as well as non-fossil urban OA. Similar spatial and temporal variations for fCNFOC are predicted between the urban vs. suburban sites, and high-fire vs. low-fire periods. The absolute modeled values of fCNFOC are consistent with the PM10 dataset but lower than the PM1 filters. Resolving the 14C measurement discrepancies is necessary for further progress in model evaluation. The model simulations that included secondary organic aerosol (SOA) formation from semi-volatile and intermediate volatility (S/IVOC) vapors showed better skill in explaining both total OA mass and fCNFOC compared to simulations which only included SOA from VOCs. Urban sources of modern carbon are important in reducing or closing the gap between model and measurements, even though they are often neglected on the interpretation of 14C datasets. The fCNF of urban POA and SOA precursors is an important parameter that needs to be better constrained by measurements. Performing faster (≤3 h) 14C measurements in future campaigns is critical to further progress in this area. To our knowledge this is the first time that radiocarbon measurements are used together with aerosol mass spectrometer (AMS) organic components to assess the performance of a regional model for organic aerosols.

scholarly journals Source Apportionment of Aerosols by 14C Measurements in Different Carbonaceous Particle Fractions

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 475-484 ◽  
Author(s):  
S Szidat ◽  
T M Jenk ◽  
H W Gäggeler ◽  
H-A Synal ◽  
R Fisseha ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Source Apportionment ◽  
Atmospheric Aerosols ◽  
Elemental Carbon ◽  
Water Soluble ◽  
Total Carbon ◽  
Anthropogenic Sources ◽  
Ambient Aerosols ◽  
Carbonaceous Particle ◽  
Fossil Carbon

Radiocarbon enables a distinction between contemporary and fossil carbon, which can be used for the apportionment of biogenic and anthropogenic sources in environmental studies. In order to apply this approach to carbonaceous atmospheric aerosols, it is necessary to adapt pretreatment procedures to the requirements of 14C measurements. In this work, we followed an approach in which total carbon (TC) is subdivided into fractions of different chemical and physical properties. 14C data of ambient aerosols from Zürich (Switzerland) are presented for the 2 sub-fractions of TC, organic carbon (OC) and elemental carbon (EC). Furthermore, OC is separated into water-insoluble OC (WINSOC) and water-soluble OC (WSOC). Results demonstrate the importance to differentiate between these fractions for 14C-deduced source apportionment, as the contributions can range between both extremes, nearly exclusively biogenic and anthropogenic.

scholarly journals Mexico city aerosol analysis during MILAGRO using high resolution aerosol mass spectrometry at the urban supersite (T0) – Part 2: Analysis of the biomass burning contribution and the non-fossil carbon fraction

2010 ◽  
Vol 10 (12) ◽  
pp. 5315-5341 ◽  
Author(s):  
A. C. Aiken ◽  
B. de Foy ◽  
C. Wiedinmyer ◽  
P. F. DeCarlo ◽  
I. M. Ulbrich ◽  
...  
Keyword(s):  
High Resolution ◽  
Mexico City ◽  
Biomass Burning ◽  
Forest Fires ◽  
Organic Aerosol ◽  
Total Carbon ◽  
Fire Emissions ◽  
Fossil Carbon ◽  
Aerosol Mass ◽  
The Impact

Abstract. Submicron aerosol was analyzed during the MILAGRO field campaign in March 2006 at the T0 urban supersite in Mexico City with a High-Resolution Aerosol Mass Spectrometer (AMS) and complementary instrumentation. Positive Matrix Factorization (PMF) of high resolution AMS spectra identified a biomass burning organic aerosol (BBOA) component, which includes several large plumes that appear to be from forest fires within the region. Here, we show that the AMS BBOA concentration at T0 correlates with fire counts in the vicinity of Mexico City and that most of the BBOA variability is captured when the FLEXPART model is used for the dispersion of fire emissions as estimated from satellite fire counts. The resulting FLEXPART fire impact factor (FIF) correlates well with the observed BBOA, acetonitrile (CH3CN), levoglucosan, and potassium, indicating that wildfires in the region surrounding Mexico City are the dominant source of BBOA at T0 during MILAGRO. The impact of distant BB sources such as the Yucatan is small during this period. All fire tracers are correlated, with BBOA and levoglucosan showing little background, acetonitrile having a well-known tropospheric background of ~100–150 pptv, and PM2.5 potassium having a background of ~160 ng m−3 (two-thirds of its average concentration), which does not appear to be related to BB sources. We define two high fire periods based on satellite fire counts and FLEXPART-predicted FIFs. We then compare these periods with a low fire period when the impact of regional fires is about a factor of 5 smaller. Fire tracers are very elevated in the high fire periods whereas tracers of urban pollution do not change between these periods. Dust is also elevated during the high BB period but this appears to be coincidental due to the drier conditions and not driven by direct dust emission from the fires. The AMS oxygenated organic aerosol (OA) factor (OOA, mostly secondary OA or SOA) does not show an increase during the fire periods or a correlation with fire counts, FLEXPART-predicted FIFs or fire tracers, indicating that it is dominated by urban and/or regional sources and not by the fires near the MCMA. A new 14C aerosol dataset is presented. Both this new and a previously published dataset of 14C analysis suggest a similar BBOA contribution as the AMS and chemical mass balance (CMB), resulting in 13% higher non-fossil carbon during the high vs. low regional fire periods. The new dataset has ~15% more fossil carbon on average than the previously published one, and possible reasons for this discrepancy are discussed. During the low regional fire period, 38% of organic carbon (OC) and 28% total carbon (TC) are from non-fossil sources, suggesting the importance of urban and regional non-fossil carbon sources other than the fires, such as food cooking and regional biogenic SOA. The ambient BBOA/ΔCH3CN ratio is much higher in the afternoon when the wildfires are most intense than during the rest of the day. Also, there are large differences in the contributions of the different OA components to the surface concentrations vs. the integrated column amounts. Both facts may explain some apparent disagreements between BB impacts estimated from afternoon aircraft flights vs. those from 24-h ground measurements. We show that by properly accounting for the non-BB sources of K, all of the BB PM estimates from MILAGRO can be reconciled. Overall, the fires from the region near the MCMA are estimated to contribute 15–23% of the OA and 7–9% of the fine PM at T0 during MILAGRO, and 2–3% of the fine PM as an annual average. The 2006 MCMA emissions inventory contains a substantially lower impact of the forest fire emissions, although a fraction of these emissions occur just outside of the MCMA inventory area.

scholarly journals Can 3-D models explain the observed fractions of fossil and non-fossil carbon in and near Mexico City?

2010 ◽  
Vol 10 (22) ◽  
pp. 10997-11016 ◽  
Author(s):  
A. Hodzic ◽  
J. L. Jimenez ◽  
A. S. H. Prévôt ◽  
S. Szidat ◽  
J. D. Fast ◽  
...  
Keyword(s):  
Mexico City ◽  
Biomass Burning ◽  
Transport Model ◽  
Measurement Techniques ◽  
Independent Set ◽  
Temporal Variations ◽  
Total Carbon ◽  
High Time Resolution ◽  
Carbonaceous Aerosols ◽  
Fossil Carbon

Abstract. A 3-D chemistry-transport model has been applied to the Mexico City metropolitan area to investigate the origin of elevated levels of non-fossil (NF) carbonaceous aerosols observed in this highly urbanized region. High time resolution measurements of the fine aerosol concentration and composition, and 12 or 24 h integrated 14C measurements of aerosol modern carbon have been performed in and near Mexico City during the March 2006 MILAGRO field experiment. The non-fossil carbon fraction (fNF), which is lower than the measured modern fraction (fM) due to the elevated 14C in the atmosphere caused by nuclear bomb testing, is estimated from the measured fM and the source-dependent information on modern carbon enrichment. The fNF contained in PM1 total carbon analyzed by a US team (fNFTC) ranged from 0.37 to 0.67 at the downtown location, and from 0.50 to 0.86 at the suburban site. Substantially lower values (i.e. 0.24–0.49) were found for PM10 filters downtown by an independent set of measurements (Swiss team), which are inconsistent with the modeled and known differences between the size ranges, suggesting higher than expected uncertainties in the measurement techniques of 14C. An increase in the non-fossil organic carbon (OC) fraction (fNFOC) by 0.10–0.15 was observed for both sets of filters during periods with enhanced wildfire activity in comparison to periods when fires were suppressed by rain, which is consistent with the wildfire impacts estimated with other methods. Model results show that the relatively high fraction of non-fossil carbon found in Mexico City seems to arise from the combination in about equal proportions of regional biogenic SOA, biomass burning POA and SOA, as well as non-fossil urban POA and SOA. Predicted spatial and temporal variations for fNFOCare similar to those in the measurements between the urban vs. suburban sites, and high-fire vs. low-fire periods. The absolute modeled values of fNFOC are consistent with the Swiss dataset but lower than the US dataset. Resolving the 14C measurement discrepancies is necessary for further progress in model evaluation. The model simulations that included secondary organic aerosol (SOA) formation from semi-volatile and intermediate volatility (S/IVOC) vapors showed improved closure for the total OA mass compared to simulations which only included SOA from VOCs, providing a more realistic basis to evaluate the fNF predictions. fNFOC urban sources of modern carbon are important in reducing or removing the difference in fNF between model and measurements, even though they are often neglected on the interpretation of 14C datasets. An underprediction of biomass burning POA by the model during some mornings also explains a part of the model-measurement differences. The fNF of urban POA and SOA precursors is an important parameter that needs to be better constrained by measurements. Performing faster (≤3 h) 14C measurements in future campaigns is critical to further progress in this area. To our knowledge this is the first time that radiocarbon measurements are used together with aerosol mass spectrometer (AMS) organic components to assess the performance of a regional model for organic aerosols.

Determination of atmospheric aerosol particle size distribution and visibility using a mobile laboratory

1982 ◽  
Vol 60 (8) ◽  
pp. 1101-1107
Author(s):  
C. V. Mathai ◽  
A. W. Harrison
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Atmospheric Aerosols ◽  
Suspended Particle ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Mobile Laboratory ◽  
Mean Values ◽  
The City

As part of an ongoing general research program on the effects of atmospheric aerosols on visibility and its dependence on aerosol size distributions in Calgary, this paper presents the results of a comparative study of particle size distribution and visibility in residential (NW) and industrial (SE) sections of the city using a mobile laboratory. The study was conducted in the period October–December, 1979. An active scattering aerosol spectrometer measured the size distributions and the corresponding visibilities were deduced from scattering coefficients measured with an integrating nephelometer.The results of this transit study show significantly higher suspended particle concentrations and reduced visibilities in the SE than in the NW. The mean values of the visibilities are 44 and 97 km for the SE and the NW respectively. The exponent of R (particle radius) in the power law aerosol size distribution has a mean value of −3.36 ± 0.24 in the SE compared with the corresponding value of −3.89 ± 0.39 for the NW. These results arc in good agreement with the observations of Alberta Environment; however, they are in contradiction with a recent report published by the City of Calgary.

scholarly journals Experiencia urbana e imágenes colectivas de la Ciudad de México / Urban Experience and Collective Images in Mexico City

2006 ◽  
Vol 21 (3) ◽  
pp. 663
Author(s):  
Martha De Alba
Keyword(s):  
Mexico City ◽  
Functional Space ◽  
Cognitive Maps ◽  
Federal District ◽  
The Other ◽  
Urban Experience ◽  
Distrito Federal ◽  
Urban Imagination ◽  
The One ◽  
The City

En el presente artículo se estudia el imaginario urbano de la Ciudad de México valiéndose de la comparación de la perspectiva de una muestra de residentes del Distrito Federal con otra muestra de funcionarios encargados de la gestión de la metrópoli. Se parte del supuesto de que las imágenes que esta gran ciudad suscita corresponden a dos registros distintos: por un lado la experiencia urbana captada a través del discurso sobre la ciudad y por el otro las imágenes cartográficas que se materializan en mapas cognitivos del espacio. Se presentan aquí los resultados de estas dos perspectivas complementarias de análisis de las representaciones de la ciudad y se propone una metodología para su estudio. Asimismo se analiza si la vivencia y la representación de la ciudad corresponden a las propuestas teóricas que plantean que la metrópoli contemporánea ya no es más un lugar de convivencia, sociabilidad e identidad, sino que se ha convertido en un espacio únicamente funcional. AbstractThis article studies the urban imagination in Mexico City, using the comparison of the perspective of a sample of residents from the Federal District with another sample of functionaries in charge of managing the metropolis. It begins with the assumption that the images this great city evokes correspond to two different registers: on the one hand, the urban experience recorded through the discourse on the city and on the other, the cartographic images materialized in cognitive maps of space. This article presents the results of these two complementary methods of analyzing the representations of the city and proposes a methodology for studying them. It also analyzes whether the experience and the representation of the city correspond to the theoretical proposals suggesting that the contemporary metropolis is no longer a place of coexistence, sociability and identity but has become a purely functional space.

scholarly journals CDMX Resilient Code: Water Commons in Mexico City

ZARCH ◽  
2021 ◽  
pp. 138-153
Author(s):  
Lorena Bello Gómez
Keyword(s):  
Risk Reduction ◽  
Public Space ◽  
Mexico City ◽  
Environmental Risks ◽  
Social Infrastructure ◽  
Common Goal ◽  
The Social ◽  
Strategic Program ◽  
The Government ◽  
The City

Using Mexico City (CDMX) as a paradigmatic example of seriously unbalanced water regimes, our project Resilient Code helps strengthen and communicate CDMX’s government efforts toward risk reduction and water resilience in marginal communities. Our project does so by bridging otherwise separate agents in the government towards a common goal: equitable resilience. Resilient Code provides design solutions that link the social infrastructure of PILARES (a network of 300 vocational schools distributed throughout the city) to CDMX’s environmental and risk reduction initiatives, including their Risk Atlas. This strategic program of design-based solutions began with “water resilience” as a Pilot to repurpose public space throughout underserviced barrios as a network of “water-commons”. Resilient Code helps partners in CDMX implement projects to reduce environmental risks and complement socio-economic programs, fostering growth of the “water-commons”. Resilient Code is socialized through a participatory game-based workshop, and through an online Atlas of Risk Reduction.

Urban Mobility and Politics in Mexico City

2016 ◽  
Vol 44 (2) ◽  
pp. 184-204 ◽  
Author(s):  
Oscar Sosa López
Keyword(s):  
Social Movement ◽  
Mexico City ◽  
The State ◽  
Urban Mobility ◽  
Infrastructure Projects ◽  
Toll Road ◽  
The City

Study of the struggle of a social movement, the Frente Amplio contra la Supervía, to stop the construction of an urban toll road in the southwestern end of Mexico City reveals that investments in transportation assumed to benefit the larger public are in fact creating new landscapes of infrastructural and democratic exclusion. Examination of the forms of citizen mobilization, alliances among diverse actors, and the role of accountability institutions as spaces for democratic experimentation suggests that struggles against large infrastructure projects allow citizens and the state to redraw the limits of authoritarianism and the meaning of sustainability and democracy in the city. El movimiento social Frente Amplio contra la Supervía se organizó para detener la construcción de una autopista de peaje urbana en el extremo suroeste de la Ciudad de México. El análisis de las luchas del Frente revela que las inversiones en la transportación que se suponía que beneficiarían a un público amplio en realidad están creando nuevos espacios de exclusión infraestructural y democrática. El análisis de las formas de movilización ciudadana, de las alianzas entre diferentes actores y del rol de las instituciones de rendición de cuentas como espacios de experimentación democrática sugiere que las luchas contra los grandes proyectos de infraestructura les permiten a los ciudadanos y al estado volver a trazar los límites del autoritarismo y el significado de la sostenibilidad y la democracia en la ciudad.

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