Mediciones continuas de carbono negro, monóxido de carbono y dióxido de carbono, durante la temporada seca caliente 2016, en un sitio periurbano de Querétaro, México

En Juriquilla-Querétaro, se midió la concentración en masa de carbono negro (BC), la relación de mezcla de monóxido de carbono (CO) y el dióxido de carbono (CO2). Las mediciones se realizaron del 01 de marzo al 30 de abril de 2016. En abril, los valores medios del BC (1.23 µg/m3) y CO (0.30 ppm) fueron mayores a sus correspondientes del mes de marzo (1.08 µg/m3 y 0.26 ppm, respetivamente). El CO2 no sufrió variación en estos meses y mantuvo un valor casi constante de alrededor de 406 ppm. Las tendencias diarias del BC, CO y CO2 fueron similares, con un máximo pronunciado por la mañana y un mínimo por la tarde. Estos contaminantes alcanzaron su valor máximo alrededor de las 08:00-09:00 Hora Local (HL). Se presentó una buena correlación en el ajuste lineal de BC-CO, BC-CO2 y CO-CO2, lo que sugiere que estos contaminantes provendrían de las mismas fuentes. Se observó un efecto fin de semana (valores más bajos del BC, CO y CO2 el fin de semana en comparación con los de días laborables), principalmente en las horas de máximo  tráfico.Al no existir estudios de mediciones continuas de BC, CO y CO2; desarrollamos esta investigación para determinar las tendencias diarias de estos contaminantes y sus correlaciones mutuas en una zona periurbana, en Querétaro

PM1 Chemical Characterization during the ACU15 Campaign, South of Mexico City

The “Aerosoles en Ciudad Universitaria 2015” (ACU15) campaign was an intensive experiment measuring chemical and optical properties of aerosols in the winter of 2015, from 19 January to 19 March on a site in the south of Mexico City. The mass concentration and chemical composition of the non-refractory submicron particulate matter (NR-PM1) was determined using an Aerodyne Aerosol Chemical Speciation Monitor (ACSM). The total NR-PM1 mass concentration measured was lower than reported in previous campaigns that took place north and east of the city. This difference might be explained by the natural variability of the atmospheric conditions, as well as the different sources impacting each site. However, the composition of the aerosol indicates that the aerosol is more aged (a larger fraction of the mass corresponds to sulfate and to low-volatility organic aerosol (LV-OOA)) in the south than the north and east areas; this is consistent with the location of the sources of PM and their precursors in the city, as well as the meteorological patterns usually observed in the metropolitan area

Mass Absorption Efficiency of PM₁ in Mexico City during ACU15

From January to March 2015, an atmospheric aerosol measurement campaign, “Aerosoles en Ciudad Universitaria 2015” (ACU15), was carried out in Mexico City to determine the particles’ optical properties and chemical composition. Two photoacoustic spectrometers measured the scattering and absorption coefficient at two different wavelengths. The average absorption coefficient at 532 nm was 12.71 ± 9.48 Mm−1 and at 870 nm was 10.35 ± 7.36 Mm−1. The average scattering coefficient was 65.63 ± 47.12 Mm−1 (532 nm) and 21.12 ± 14.24 Mm−1 (870 nm). The chemical composition was determined via an aerosol chemical speciation monitor. The organic aerosol fraction represented 53% of the total PM1 and was made up of 63% low volatile (4.64 µg m−3), 22% hydrogenated (1.90 µg m−3), and 15% semi-volatile organics (1.54 µg m−3). The correlation coefficient of chemical species (NO3−, NH4+, SO42−, low-volatile, and semi-volatile organics) and optical properties was 0.92. The multilinear regression showed a good agreement among chemical species and optical properties (r > 0.7). The mass absorption coefficient calculated for the measuring site at 870 nm was MAE870 = 5.8 m2 g−1, instead of the default 4.74 m2 g−1. Furthermore, based on the median AAE, the 532 nm MAE532 resulting from the multiple linear regression (MLR) showed the following coefficients: 7.70 m2 g−1 (eBC), 0.22 m2 g−1 (HOA), and 0.16 m2 g−1 (LV–OOA). The coefficients of MLR were: 7.08 m2 g−1 (eBC), 5.83 m2 g−1 (NO3−), 5.69 m2 g−1 (low volatile organic aerosol), 2.78 m2 g−1 (SO42−), 2.40 m2 g−1 (hydrocarbon-like organic aerosol), and 1.04 m2 g−1 (semi volatile organic aerosol)

Variations of Black Carbon Concentrations in Two Sites in Mexico: A High-Altitude National Park and a Semi-Urban Site

Black carbon (BC), a component of carbonaceous material, has an important role in the environment, and it is considered a short-lived climate forcer that plays a vital role in the global climate system. BC concentrations were analyzed during 2017 in two sites in Mexico, Juriquilla and Altzomoni, which have different emission sources and atmospheric dynamics. The annual average BC concentrations in 2017 were 0.84 ± 0.70 and 0.58 ± 0.37 µg m−3 for Juriquilla and Altzomoni, respectively. The principal contributors for the highest BC concentration in Juriquilla were anthropogenic sources, while pollutants transport from nearby cities was more important for Altzomoni. Comparison between this analysis and previous reports from 2015 for both sampling sites demonstrated an increase in BC concentration. Results of this study could contribute to a better understanding of BC effects under different emission conditions and provide a scientific reference for developing BC reduction strategies over Mexico

Variations of Black Carbon Concentrations in Two Sites in Mexico: A High-Altitude National Park and a Semi-Urban Site

Black carbon (BC), a component of carbonaceous material, has an important role in the environment, and it is considered a short-lived climate forcer that plays a vital role in the global climate system. BC concentrations were analyzed during 2017 in two sites in Mexico, Juriquilla and Altzomoni, which have different emission sources and atmospheric dynamics. The annual average BC concentrations in 2017 were 0.84 ± 0.70 and 0.58 ± 0.37 µg m−3 for Juriquilla and Altzomoni, respectively. The principal contributors for the highest BC concentration in Juriquilla were anthropogenic sources, while pollutants transport from nearby cities was more important for Altzomoni. Comparison between this analysis and previous reports from 2015 for both sampling sites demonstrated an increase in BC concentration. Results of this study could contribute to a better understanding of BC effects under different emission conditions and provide a scientific reference for developing BC reduction strategies over Mexico

Comparative Analysis of urban atmospheric aerosol by particle-induced X-ray emission (PIXE), proton elastic scattering analysis (PESA), and aerosol mass spectrometry (AMS)

A multifaceted approach to atmospheric aerosol analysis is often desirable infield studies where an understanding of technical comparability among different measurement techniques is essential. Herein, we report quantitative intercomparisons of particle-induced X-ray emission (PIXE) and proton elastic scattering analysis (PESA), performed offline under a vacuum, with analysis by aerosol mass spectrometry (AMS) carried out in real-time during the MCMA-2003 Field Campaign in the Mexico City Metropolitan Area. Good agreement was observed for mass concentrations of PIXE-measured sulfur (assuming it was dominated by SO42-) and AMS-measured sulfate during most of the campaign. PESA-measured hydrogen mass was separated into sulfate H and organic H mass fractions, assuming the only major contributions were (NH4)(2)SO4 and organic compounds. Comparison of the organic H mass with AMS organic aerosol measurements indicates that about 75% of the mass of these species evaporated under a vacuum. However similar to 25% of the organics does remain under a vacuum, which is only possible with low-vapor-pressure compounds, and which supports the presence of high-molecular-weight or highly oxidized organics consistent with atmospheric aging. Approximately 10% of the chloride detected by AMS was measured by PIXE, possibly in the form of metal-chloride complexes, while the majority of Cl was likely present as more volatile species including NH4Cl. This is the first comparison of PIXE/PESA and AMS and, to our knowledge, also the first report of PESA hydrogen measurements for urban organic aerosols

Secondary organic aerosol formation from anthropogenic air pollution

The atmospheric chemistry of volatile organic compounds (VOCs) in urban areas results in the formation of \u27photochemical smog\u27, including secondary organic aerosol (SOA). State-of-the-art SOA models parameterize the results of simulation chamber experiments that bracket the conditions found in the polluted urban atmosphere. Here we show that in the real urban atmosphere reactive anthropogenic VOCs (AVOCs) produce much larger amounts of SOA than these models predict, even shortly after sunrise. Contrary to current belief, a significant fraction of the excess SOA is formed from first-generation AVOC oxidation products. Global models deem AVOCs a very minor contributor to SOA compared to biogenic VOCs (BVOCs). If our results are extrapolated to other urban areas, AVOCs could be responsible for additional 3 - 25 Tg yr(-1) SOA production globally, and cause up to - 0.1 W m(-2) additional top-of-the-atmosphere radiative cooling