Volatility of organic aerosol and its components in the megacity of Paris

Using a mass transfer model and the volatility basis set, we estimate the volatility distribution for the organic aerosol (OA) components during summer and winter in Paris, France as part of the collaborative project MEGAPOLI. The concentrations of the OA components as a function of temperature were measured combining data from a thermodenuder and an aerosol mass spectrometer (AMS) with Positive Matrix Factorization (PMF) analysis. The hydrocarbon-like organic aerosol (HOA) had similar volatility distributions for the summer and winter campaigns with half of the material in the saturation concentration bin of 10 µg m⁻³ and another 35–40 % consisting of low and extremely low volatility organic compounds (LVOCs with effective saturation concentrations <i>C</i>* of 10⁻³–0.1 µg m⁻³ and ELVOCs <i>C</i>* less or equal than 10⁻⁴ µg m⁻³, respectively). The winter cooking OA (COA) was more than an order of magnitude less volatile than the summer COA. The low-volatility oxygenated OA (LV-OOA) factor detected in the summer had the lowest volatility of all the derived factors and consisted almost exclusively of ELVOCs. The volatility for the semi-volatile oxygenated OA (SV-OOA) was significantly higher than that of the LV-OOA, containing both semi-volatile organic components (SVOCs with <i>C</i>* in the 1–100 µg m⁻³ range) and LVOCs. The oxygenated OA (OOA) factor in winter consisted of SVOCs (45 %), LVOCs (25 %) and ELVOCs (30 %). The volatility of marine OA (MOA) was higher than that of the other factors containing around 60 % SVOCs. The biomass burning OA (BBOA) factor contained components with a wide range of volatilities with significant contributions from both SVOCs (50 %) and LVOCs (30 %). Finally, combining the bulk average O : C ratios and volatility distributions of the various factors, our results are placed into the two-dimensional volatility basis set (2D-VBS) framework. The OA factors cover a broad spectrum of volatilities with no direct link between the average volatility and average O : C of the OA components

Simulation of atmospheric organic aerosol using its volatility–oxygen-content distribution during the PEGASOS 2012 campaign

A lot of effort has been made to understand and constrain the atmospheric aging of the organic aerosol (OA). Different parameterizations of the organic aerosol formation and evolution in the two-dimensional volatility basis set (2D-VBS) framework are evaluated using ground and airborne measurements collected in the 2012 Pan-European Gas AeroSOls-climate interaction Study (PEGASOS) field campaign in the Po Valley (Italy). A number of chemical aging schemes are examined, taking into account various functionalization and fragmentation pathways for biogenic and anthropogenic OA components. Model predictions and measurements, both at the ground and aloft, indicate a relatively oxidized OA with little average diurnal variation. Total OA concentration and O : C ratios are reproduced within experimental error by a number of chemical aging schemes. Anthropogenic secondary OA (SOA) is predicted to contribute 15&ndash;25&thinsp;% of the total OA, while SOA from intermediate volatility compound oxidation contributes another 20&ndash;35&thinsp;%. Biogenic SOA (bSOA) contributions varied from 15 to 45&thinsp;% depending on the modeling scheme. Primary OA contributed around 5&thinsp;% for all schemes and was comparable to the hydrocarbon-like OA (HOA) concentrations derived from the positive matrix factorization of the aerosol mass spectrometer (PMF-AMS) ground measurements. The average OA and O : C diurnal variation and their vertical profiles showed a surprisingly modest sensitivity to the assumed vaporization enthalpy for all aging schemes. This can be explained by the interplay between the partitioning of the semi-volatile compounds and their gas-phase chemical aging reactions.</p

A Systematic Review of the Treatment of Fears and Phobias Among Children with Autism Spectrum Disorders

Research indicates that fears and phobias are significantly more prevalent and emerge in response to a greater variety of stimuli, among children with autism spectrum disorders (ASD) than among their developmentally disabled or typically developing peers. Such findings are problematic given the difficulty of assessing and identifying fears or phobias among the ASD population and the challenge of identifying effective treatments for those with core diagnostic deficits in comprehension, communication, and attentional skills. The current review aimed to evaluate the literature describing interventions to treat fears, specific phobia, or social phobia among children with ASD and to identify evidence-based practice in this area. The review indicated that a variety of interventions, described as both traditional and novel, were successful in treating fearful or phobic behavioral responses to stimuli. The findings also suggest that behavioral intervention, including reinforcement, modeling, and exposure, may be considered evidence-based practice in the treatment of fears and phobias among children with ASD. However, the current research base is limited by the predominant focus on the behavioral element of the fear response, and the lack of research examining the cognitive or physiological responses during assessment or treatment