Atmospheric sink of styrene, α-methylstyrene, trans-β-methylstyrene and indene: Rate constants and mechanisms of the Cl atoms initiated degradation

The kinetics and products of the oxidation of four aromatic compounds, i.e. styrene, α-methylstyrene, trans-β-methylstyrene and indene, with Cl atoms were determined at atmospheric pressure and room temperature. Kinetic experiments were carried out in a 400 L Teflon reaction chamber using GC-FID for the analysis of reactants and products were determined using a 56 L quartz-glass reactor coupled to FTIR spectrophotometer. The rate constants at 298 K, using different reference compounds, were (in units of cm3 molecule−1 s−1): kstyrene = (1.29 ± 0.52)×10−10, kα-methylstyrene = (1.55 ± 0.27)×10−10, ktrans-β-methylstyrene = (1.09 ± 0.23)×10−10 and kindene = (1.01 ± 0.30)×10−10. Observations with FTIR suggest that the main reaction is the addition of the Cl to the aliphatic chain of the aromatic molecules. We found benzaldehyde, benzoyl chloride, formaldehyde and formyl chloride from styrene; acetophenone, formaldehyde and formyl chloride from α-methylstyrene; and benzaldehyde, formaldehyde and acetyl chloride from trans-β-methylstyrene as the main oxidation products. DFT theoretical calculations were performed in order to shed light on the identification of the reaction products. To the best of our knowledge, this work represents the first determination of the rate coefficients and products for the reaction of the Cl atoms with these compounds, except for the rate constant of styrene which has been studied previously. The loss processes of the title compounds in the atmosphere are mostly controlled by reactions with OH radicals during the day and with NO3 at night, but in coastal areas and some polluted environments, Cl reactions became comparable with OH and NO3 radicals, with lifetimes of 2.2 h for styrene, 1.8 h for AMS, 2.5 h for TBMS and 2.8 h for indene

Secondary organic aerosol formation from styrene photolysis and photooxidation with hydroxyl radicals

The formation of secondary organic aerosol (SOA) generated by irradiating styrene in the presence and/or absence of OH, NOx, H2O vapour and seed aerosol has been investigated for the first time. Experiments were conducted in a smog chamber at 298 K and atmospheric pressure. Styrene decay was measured by gas chromatography with a mass spectrometric detector (GC-MS), and the temporal evolution of the aerosol was monitored using a fast mobility particle sizer (FMPS). The SOA yield increases as the initial styrene concentration increases, leading to yields ranging from 1.8% to 3.5% for styrene photolysis, and from 2.4% to 5.0% for its photooxidation. In both cases, the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model. The particle number concentration, mass and yield decrease in the presence of NOx and seed aerosol but increase at higher relative humidity (RH). The gas phase and SOA composition were analysed offline using a filter/denuder sampling system simultaneously collecting gas- and particle-phase products. Benzaldehyde was confirmed as the main gas-phase product of the reaction. However, although products in the particle phase were detected, they could not be identified. Moreover, the aqueous filter extracts were analysed using UV–Visible spectrophotometry to determine differences in the optical properties of SOA produced in the presence and absence of NOx. The results from this work may be used to discuss the implications of atmospheric SOA generation from styrene degradation

Secondary organic aerosol formation from α-methylstyrene atmospheric degradation: Role of NOx level, relative humidity and inorganic seed aerosol

Secondary Organic Aerosol (SOA) formation during the photolysis and OH-photooxidation of α-methylstyrene was investigated using a simulation chamber at atmospheric pressure and room temperature (296 ± 1) K. α-Methylstyrene concentration was followed by gas chromatography with a mass spectrometric detector (GC–MS) and the aerosol production was monitored using a Fast Mobility Particle Sizer (FMPS). The effect of varying α-methylstyrene (0.5 ppm - 2 ppm) and NOx (0.5 ppm - 1.0 ppm) concentrations on SOA formation was explored, as was the effect of the relative humidity (RH) (5–50%) and the presence of inorganic seed particles. Results indicate that SOA yields increase at higher α-methylstyrene concentrations; low NOx and high RH conditions favour more rapid aerosol formation and a higher aerosol yield; SOA formation is independent of seed surface area, within the studied range, for both inorganic seed particles ((NH4)2SO4 and CaCl2). An off-line chemical analysis using a filter/denuder sampling system and GC–MS confirms acetophenone as the main gas phase product in both processes, photolysis and photooxidation. For the first time, SOA composition in α-methylstyrene degradation was analysed, observing acetophenone and acetol as products present in the formed aerosol in presence and absence of NOx

Impact of SARS-CoV-2 lockdown and de-escalation on air-quality parameters.

The SARS-CoV-2 health crisis has temporarily forced the lockdown of entire countries. This work reportsthe short-term effects on air quality of such unprecedented paralysis of industry and transport indifferent continental cities in Spain, one of the countries most affected by the virus and with the hardestconfinement measures. The study takes into account sites with different sizes and diverse emissionsources, such as traffic, residential or industrial emissions. This work reports newfield measurementdata for the studied pandemic period and assesses the air quality parameters within the historic trend ofeach pollutant and site. Thus, 2013e2020 data series from ground-air quality monitoring networks havebeen analysed tofind out statistically significant changes in atmospheric pollutants during MarcheJune2020 due to this sudden paralysis of activity. The results show substantial concentration drops of primarypollutants, including NOx, CO, BTX, NMHC and NH3. Particulate matter changes were smaller due to theexistence of other natural sources. During the lockdown the ozone patterns were different for eachstudied location, depending on the VOCs-NOx ratios, with concentration changes close to those expectedfrom the historical series in each site and not statistically attributable to the health crisis effects. Finally,the gradual de-escalation and progressive increase of traffic density within cities reflects a slow recoveryof primary pollutants. The results and conclusions for these cities, with different sizes and population,and specific emission sources, may serve as a behavioural model for other continental sites and help understand future crises

Secondary organic aerosol formation from the ozonolysis and oh-photooxidation of 2,5-dimethylfuran

In this study, the O3 and OH radical oxidation of 2,5-dimethylfuran (2,5-DMF) were investigated in two different chambers at (296±1) K and atmospheric pressure to examine secondary organic aerosol (SOA) formation. Results for OH-photooxidation indicate that SOA yieldsdecrease (from 6.2 to 0.4) with the rise of 2,5-DMF concentration (from10 to 1000 ppb). In the absence of NOx and under high relative humidity (RH) conditions (60%), higher aerosol yields are favoured. SOA formation is dependent on the initial seed surface for two kinds of inorganic seed particles ((NH4)2SO4 and CaCl2), being the effect slightly greater for CaCl2. The ozonolysis only generates particles in the presence of SO2 and the increase of relative humidity from 0 to 15% lowers the particle number and particle mass concentrations. The water-to-SO2 rate constant ratio of the Criegee intermediate was derived from the SOA yield in experiments with different relative humidity values, with kH2O/kSO2 = (1.6±0.4)x10−5

Educar con arte : un proyecto de acercamiento al mundo del arte en un centro de enseñanzas no artísticas

Mención honorífica en los Premios Nacionales a la Innovación Educativa 2003Este proyecto se ha llevado a cabo en el IES Clara del Rey (Madrid). Los profesores implicados son mayoritariamente los de enseñanza secundaria y los profesores de enseñanzas técnicas y en proporción inferior los profesores de francés inglés . El objetivo general es favorecer la integración de los alumnos en el centro de enseñanza, interesarlos y acercarlos a la expresión artística a través de un proyecto en el que intervengan directa y activamente. Los objetivos específicos son: a) acercar la expresión artística a un centro en el que no existe expresamente; b) Interpretar y aplicar conceptos teóricos impartidos previamente en el aula, relativos a la atención al público asistente al evento; c) Desarrollar una actitud crítica y analítica respecto a las diferentes disciplinas artísticas expuestas; d) Motivar a los alumnos a expresar sus habilidades y destrezas artísticas; e) Utilizar estrategias eficientes de comunicación para recibir y transmitir información y resolver posibles situaciones conflictivas en la atención individualizada a visitantes y e las operaciones de gestión de compras; f) Diseñar, editar e imprimir diferentes modelos de documentos y formularios utilizando herramientas informáticas; g) Cumplimentar, organizar y archivar los distintos documentos y formularios, seleccionando el apropiado a cada tarea; h) Participar como autores de cualquier tipo de expresión artística profesores y alumnos. El proyecto surge de una reunión de profesores del instituto donde se valora la posible repercusión negativa que entraña el hecho de que en las enseñanzas especializadas no se impartiesen materias artísticas. Se planifica montar una exposición y traer la pintura a las aulas y acercar la escultura a las clases. En un primer momento se configuran las actividades: a) Ubicación y diseño de la sala de exposiciones; b) Gestión de compras; c) Organización de la exposición; d) Difusión del evento; e) Elaboración del catálogo; f) formación de alumnos colaboradores, se les da protagonismo y se les asignan las actividades propias de su ciclo formativo. Los resultados han sido muy positivos. La experiencia ha sido enriquecedora tanto para los profesores como para los alumnos, ya que han conseguido que el arte tenga cabida en las enseñanzas profesionales. Se plantean posteriores ediciones. Se han admitido todas las obras artísticas de todo el mundo que ha querido contribuir: padres, alumnos, profesores y allegados.Consejería de Educación de MadridPatrocinios de empresasIES Clara del Rey (Madrid)MadridBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 Planta; 28014 Madrid; Tel. +34917748000; Fax +34917748026; [email protected]