Faster phototransformation of the formate (terrestrial) versus methanesulphonate (marine) markers of airborne particles: implications for modelling climate change

Atmospheric particulate matter is altering climate. For instance marine biogenic particles are cooling climate. Organic markers are major tools to elucidate the sources of atmospheric particulate matter. Formate is commonly used as a marker of continental aerosols, whereas methanesulphonate is used as tracer of biogenic marine aerosols. However, transformation processes during aerosol transport may modify their relative concentrations and, in turn, introduce a bias in the assessment of particle sources. Actually very little is known about the transformation of formate and methanesulphonate in aerosols. Therefore, we irradiated formate and methanesulphonate in the presence of nitrate and haematite. Nitrate and haematite are aerosol photosensitisers, producing reactive species that degrade organic compounds. The time evolution of formate and methanesulphonate was monitored by ion chromatography. Our results show that formate is transformed from 1.6 to 4.1 times faster than methanesulphonate. This trend is partly due to higher reactivity with the hydroxyl radical and partly due to additional reaction with other transients such as nitrogen dioxide. Such results strongly suggest faster formate transformation during particle transport. Therefore, when formate and methanesulphonate are used as particle tracers, an overestimation of marine biogenic versus continental particle sources is expected. This bias has major implications for climate prediction models, because marine biogenic particles have a cooling effect on climate.     

Self-ignition of tetrafluoroethylene induced by rapid valve opening in small diameter pipes

This work investigates the ignition of tetrafluoroethylene induced by the adiabatic compression that can arise by activating a high speed valve separating two portions of a pipeline with a high pressure difference. In the tests performed the high pressure zone contained tetrafluoroethylene at pressures between 15 and 30 bar. For the low pressure zone, experiments with nitrogen, air and tetrafluoroethylene were carried out. The pressure range in the low pressure zone was comprised between 0.05 and 1 bar. The pipe diameters analyzed were 15 and 20 mm. For the analyzed geometries, special conditions were required in order to reach reproducible ignitions, namely air at temperatures of at least 105 °C had to be present in the compression pipe. Furthermore, a minimum length of the compression pipe had to be used. The current work describes the experimental setup employed for the tests and discusses the achieved results. Numerical simulations were performed in order to clarify unexpected findings.     

Gathering new knowledge from existing monitoring dataset of Campania marine coastal area (Southern Italy)

Environmental Science and Pollution Research - In this study we propose, a multi-step strategy of selection and characterization of long-term dataset of contaminant concentrations in different...     

Choice of macroinvertebrate metrics to evaluate stream conditions in Atlantic Forest, Brazil

The development of biomonitoring programs based on the macroinvertebrate community requires the understanding of species distribution patterns, as well as of the responses of the community to anthropogenic stressors. In this study, 49 metrics were tested as potential means of assessing the condition of 29 first- and second-order streams located in areas of differing types of land use in São Paulo State, Brazil. Of the sampled streams, 15 were in well-preserved regions in the Atlantic Forest, 5 were among sugarcane cultivations, 5 were in areas of pasture, and 4 were among eucalyptus plantations. The metrics were assessed against the following criteria: (1) predictable response to the impact of human activity; (2) highest taxonomic resolution, and (3) operational and theoretical simplicity. We found that 18 metrics were correlated with the environmental and spatial predictors used, and seven of these satisfied the selection criteria and are thus candidates for inclusion in a multimetric system to assess low-order streams in São Paulo State. These metrics are family richness; Ephemeroptera, Plecoptera and Trichoptera (EPT) richness; proportion of Megaloptera and Hirudinea; proportion of EPT; Shannon diversity index for genus; and adapted Biological Monitoring Work Party biotic index.     

Exploratory analysis in the evaluation of stress due to aluminum presence in Physalis angulata L. and multielement determination by microwave-induced plasma optical emission spectrometry (MIP OES)

Environmental Science and Pollution Research - The present work aimed to analyze the mineral nutrition of Physalis angulata L. under stress by aluminum in the nutrient solution. The treatments...     

A preliminary investigation on the use of organic ionic liquids as green solvents for acylation and oxidation reactions

Different organic ionic liquids (OILs) have been used as green solvents in Friedel–Crafts acylation and alcohol oxidation reactions. Specifically, three OILs were employed, 1-ethyl-3-methylimidazolium chloride, tetraethylammonium bromide, and 1-butyl-3-methylimidazolium chloride, and four reactions studied, acylation of toluene by acetyl chloride, acylation of benzene by propionyl chloride, oxidation of benzyl alcohol by N-methylmorpholine N-oxide, and oxidation of salicylic alcohol by o-iodoxybenzoic acid. The reactions were carried out, at room temperature, in a well-stirred lab-scale glass batch reactor, under inert atmosphere and for reaction times ranging from 5 to 90 min. Gas chromatography was employed to characterize the reaction products. First of all, the desired products yield as a function of the reaction time was investigated. Moreover, simple kinetic models were built for the interpretation of the experimental results. Additional tests were carried out to assess the possibility of recycling the OILs employed. The results of this preliminary study were satisfactory as the OILs investigated proved to be good media in which to carry out the reactions studied in this work (desired products yield greater than 90% were achieved). Moreover, the reaction rate expressions of the kinetic models were able to satisfactorily predict the experimental results. Finally, the possibility of recycling the OIL (in one of the reactions) was proved to be feasible and this suggests the use of recycled OIL together with a fresh make-up, to match high yield values with economical/ecological advantages.     

Liquid–solid adsorption processes interpreted by fractal-like kinetic models

Environmental Chemistry Letters - The transport of an adsorbate molecule from the bulk of a fluid phase to the active centre of an adsorbent particle involves complex mechanisms. Mechanisms need to...