COVID-19: challenges for a new epoch

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Rate coefficient for the reaction of Cl atoms with cis-3-hexene at 296 ± 2 K

The rate coefficient of the cis-3-hexene + Cl atoms reaction at 296 ± 2 K and 750 ± 10 Torr was determined using the relative rate technique. The reaction was investigated using an 80 L Teflon reaction bag and a gas chromatograph coupled with flame-ionization detection. Chlorine atoms were produced by the photolysis of trichloroacetyl chloride. No previous experimental data was available in the literature, to the best of our knowledge. The mean second-order rate coefficient value found was (4.13 ± 0.51) × 10-10 cm3 molecule-1 s-1. The experimental value agrees with the rate coefficient estimated by structure-reactivity analysis, 4.27 × 10-10 cm3 molecule-1 s-1. Moreover, both addition and hydrogen abstraction channels contribute to the global kinetics, with branching ratios 70:30. Effective lifetime with respect to Cl atoms is predicted as 67.2 hours; however, the cis-3-hexene + Cl channel is suggested to be non-negligible at atmospheric conditions. Other atmospheric implications are discussed.Fil: Barbosa, Thaís S.. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Barrera, Javier Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Jara Toro, Rafael Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Bauerfeldt, Glauco F.. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Arbilla, Graciela. Universidade Federal do Rio de Janeiro; BrasilFil: Lane, Silvia Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Uso de uma estação móvel de monitoramento da qualidade do ar para identificar as áreas críticas quanto à qualidade do ar na cidade do Rio de Janeiro

Recent studies have shown that tropospheric ozone, fine particulate matter and nitrogen dioxide are the urban air pollutants of major concern regarding human health effects. Monitoring air quality is a challenge in several cities, such as Rio de Janeiro, where the number of fixed-site air quality monitoring stations and their spatial distribution are insufficient to assess the extent of atmospheric pollutants. However, despite this lack of resources, the data obtained by mobile stations are a valuable means of determining which areas are experiencing critical air quality conditions, and provide key information for an air quality management program. The main purpose of this study was to conduct a critical analysis of data obtained by the Municipal Department of Environment and Climate (SMAC) mobile station in the period 2010–2018. Concentrations determined for particulate matter with a diameter ≤2.5 μm (PM2.5), O3, NO2, SO2 and CO showed that PM2.5 and O3 are the pollutants of major concern, and that the north of the city has higher air quality indices for these compounds. In addition, the south-west district had relatively high ozone levels, probably owing to low concentrations of NO2 in a volatile organic compound (VOC)-limited ozone formation regime. These factors should be considered by the municipal government in future discussions of control strategies for managing the city’s air quality. This study also shows the value of mobile stations in making a preliminary survey of pollutant concentrations, mainly in countries with limited financial investment in air quality management.Estudos recentes têm mostrado que o ozônio troposférico, o material particulado fino e o dióxido de nitrogênio são os poluentes urbanos de maior importância quanto aos efeitos sobre a saúde humana. O monitoramento da qualidade do ar é um desafio, especialmente em cidades como Rio de Janeiro, onde o número e a distribuição das estações de monitoramento fixas é insuficiente para avaliar a distribuição dos poluentes atmosféricos. Contudo, apesar da limitação dos recursos, dados obtidos por estações de monitoramento móveis são de grande utilidade para determinar quais áreas experimentam condições críticas de qualidade do ar e fornecem informações úteis para os programas de gerenciamento da qualidade do ar. O principal objetivo deste estudo foi realizar uma análise crítica dos dados obtidos pela estação móvel da Secretaria Municipal de Ambiente e Clima (SMAC), no período 2010–2018. Os resultados obtidos para material particulado com diâmetro ≤2,5 μm (MP2,5), O3, NO2, SO2 e CO mostram que MP2,5 e O3 são os poluentes que geram maior preocupação, e que a zona norte da cidade tem os piores índices de qualidade do ar para esses compostos. Além disso, a área sudoeste apresenta níveis relativamente altos de ozônio, provavelmente em razão das baixas concentrações de NO2 em um cenário onde a formação de ozônio é controlada pelos compostos orgânicos voláteis (COV). Esses fatores deveriam ser considerados pelo governo municipal em futuras discussões de estratégias para o gerenciamento da qualidade do ar da cidade. Este trabalho mostra, também, a contribuição das estações móveis de qualidade do ar para realizar um estudo preliminar das concentrações de poluentes, especialmente em países com recursos financeiros limitados para o gerenciamento da qualidade do ar

Theoretical calculations of the kinetics of the oh reaction with 2-methyl-2-propen-1-ol and its alkene analogue

In this work, the first and rate determining steps on the mechanism of the OH addition to 2-methyl-2-propen-1-ol (MPO221) and methylpropene (M2) have been studied at the DFT level, employing the BHandHLYP functional and the cc-pVDZ and aug-cc-pVDZ basis sets. The thermochemical properties of equilibrium (enthalpy, entropy and Gibbs free energies) have been determined within the conventional statistical thermodynamics relations and the rate coefficients have been determined on the basis of the variational transition state theory. The adoption of the microcanonical variational transition state theory was proved to be crucial for the description of the kinetics of OH addition to these unsaturated compounds. The rate coefficients obtained for the OH reactions with MPO221 and M2 at 298.15K deviate, respectively, 27% and 13% from the experimental rate coefficient available in the literature. A non-Arrhenius profile is observed for the rate coefficients. Moreover, the values of the rate coefficients for the MPO221 + OH reaction are greater than those for the M2 + OH reaction, suggesting that the substitution of the hydrogen atom in an alkene by the ?OH functional group, increases the reactivity in respect to the hydroxyl radical.Fil: Da Silva Barbosa, Thais. Departamento de Físico-química, Instituto de Química; BrasilFil: Nieto, Jorge Daniel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Cometto, Pablo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Lane, Silvia Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; ArgentinaFil: Bauerfeldt, Glauco Favilla. Universidade Federal Rural Do Rio de Janeiro; Brasil. Departamento de Química, Instituto de Ciencias Exatas; Brasi

Using mobile air quality station data to identify critical areas in the city of Rio de Janeiro regarding pollutant concentrations

Recent studies have shown that tropospheric ozone, fine particulate matter and nitrogen dioxide are the urban air pollutants of major concern regarding human health effects. Monitoring air quality is a challenge in several cities, such as Rio de Janeiro, where the number of fixed-site air quality monitoring stations and their spatial distribution are insufficient to assess the extent of atmospheric pollutants. However, despite this lack of resources, the data obtained by mobile stations are a valuable means of determining which areas are experiencing critical air quality conditions, and provide key information for an air quality management program. The main purpose of this study was to conduct a critical analysis of data obtained by the Municipal Department of Environment and Climate (SMAC) mobile station in the period 2010–2018. Concentrations determined for particulate matter with a diameter ≤2.5 μm (PM2.5), O3, NO2, SO2 and CO showed that PM2.5 and O3 are the pollutants of major concern, and that the north of the city has higher air quality indices for these compounds. In addition, the south-west district had relatively high ozone levels, probably owing to low concentrations of NO2 in a volatile organic compound (VOC)-limited ozone formation regime. These factors should be considered by the municipal government in future discussions of control strategies for managing the city’s air quality. This study also shows the value of mobile stations in making a preliminary survey of pollutant concentrations, mainly in countries with limited financial investment in air quality management

Particle-associated polycyclic aromatic hydrocarbons in a suburban region of Rio de Janeiro, Brazil, with industrial and traffic emissions

From April 206 to March 2007, total suspended particles (TSP) and PM10 samples were collected at the Campus of FIOCRUZ, situated in a suburban region with intense industrial and commercial activities in Rio de Janeiro (Brazil). The concentrations of 16 selected polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography with mass selective detection. Individual concentrations were between the detection limit (acenaphtylene, acenaphthene, anthracene and fluorene) and 6.16 ng m-3 for benzo[b]fluoranthene. The five most abundant PAHs, in TSP, samples were B[b]F, Ipy, Py, Chry and DB[ah]An, and the mean sum of 16 PAHs was 15.53 ng m-3. The same most abundant compounds were obtained in PM10 samples and a total mean mass of 8.99 ng m-3 was determined. Diagnostic ratios were calculated and vehicular emissions were determined as the potential sources for PAHs in particulate matter. The contribution of both light duty and diesel engines is significant, but the cluster and factorial analysis failed to classify clearly in gasoline or diesel emissions

Clean air for a good start: children are the future of the planet

Abstract In early childhood, air pollution leads to an increased risk of disease, premature death, and development of disruptions. Fine particulate matter (PM2.5) is considered the classical pollutant of major concern. However, in Brazil, fine particulate monitoring is still limited and restricted to a few cities. Particularly, in the city of Rio de Janeiro, only one automatic station obtains PM2.5 concentrations and publishes the air quality indexes daily. This study is part of the project “Clean air for a good start” managed by the Horizon Citizen Foundation, with the goal of obtaining evidence to set a plan to reduce children exposition to air pollution. Data is shared on a global web platform. Results showed that PM2.5 levels are high when compared with WHO guidelines and coordinated actions would be needed to decrease emissions of primary pollutants and secondary aerosol’s precursors