Search results for "Aerosol"
showing 10 items of 722 documents
Ozone depletion in tropospheric volcanic plumes
2010
Ground based remote sensing techniques are used to measure volcanic SO2 fluxes in efforts to characterise volcanic activity. As these measurements are made several km from source there is the potential for in-plume chemical transformation of SO2 to sulphate aerosol (conversion rates are dependent on meteorological conditions), complicating interpretation of observed SO2 flux trends. In contrast to anthropogenic plumes, SO2 lifetimes are poorly constrained for tropospheric volcanic plumes, where the few previous loss rate estimates vary widely (from 99% per hour). We report experiments conducted on the boundary layer plume of Masaya volcano, Nicaragua during the dry season. We found that SO2…
Towards a representation of halogen chemistry within volcanic plumes in a chemistry transport model
2014
Volcanoes are a known source of halogens to the atmosphere. HBr volcanic emissions lead rapidly to the formation of BrO within volcanic plumes as shown by recent work based on observations and models. BrO, having a longer residence time in the atmosphere than HBr, is expected to have a significant impact on tropospheric chemistry, at least at the local and regional scales. The objective of this paper is to prepare a framework that will allow 3-D modelling of volcanic halogen emissions in order to determine their fate within the volcanic plume and then in the atmosphere at the regional and global scales. This work is based on a 1-D configuration of the chemistry transport model MOCAGE whose …
Degassing of trace volatile metals during the 2001 eruption of Etna
2003
This paper provides new data on sulfur, halogens, and minor and trace metal contents in airborne particulate matter from the Mt. Etna volcanic plume. Aerosol samples were collected by conventional filtration techniques before and during the summer 2001 eruption, in order to investigate relations between plume chemistry and volcano dynamics. Data analysis reveals that abundances of trace metals in the plume result from mixing of erosive and volatile components. The former is responsible for the contents of rare earth elements (REE), Ca, Ba, Sr, Ti, Sc, Y, Hf and Th; the latter contributes significantly to the abundance of Cs, Rb, Na and K, probably transported in the plume as metal halides, …
Sweet chestnut (Castanea sativa) leaves as a bio-indicator of volcanic gas, aerosol and ash deposition onto the flanks of Mt Etna in 2005–2007
2009
Sweet chestnut leaves (Castanea sativa) collected from the flanks of Mt Etna volcano in 2005-2007 were analysed by inductively-coupled plasma mass spectrometry to investigate the spatial and temporal variability of element concentrations. The aim of this work was to determine whether these leaves are a bio-indicator for volcanic gas, aerosol and ash deposition and to gain new insights into the environmental effects of quiescent and eruptive volcanic plumes. Results show a positive correlation between sample variability in the concentration of elements in Castanea sativa and enrichment factors of elements in the plume. The spatial and temporal variability of chalcophilic elements (As, Cd, Cu…
Aqueous-phase reactive species formed by fine particulate matter from remote forests and polluted urban air
2021
In the aqueous phase, fine particulate matter can form reactive species (RS) that influence the aging, properties, and health effects of atmospheric aerosols. In this study, we explore the RS yields of aerosol samples from a remote forest (Hyytiälä, Finland) and polluted urban locations (Mainz, Germany; Beijing, China), and we relate the RS yields to different chemical constituents and reaction mechanisms. Ultra-high-resolution mass spectrometry was used to characterize organic aerosol composition, electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique was applied to determine the concentrations of ⚫OH, O2⚫-, and carbon- or oxygen-centered organic radicals, and a …
The formation, properties and impact of secondary organic aerosol: Current and emerging issues
2009
Hallquist, M. Wenger, J. C. Baltensperger, U. Rudich, Y. Simpson, D. Claeys, M. Dommen, J. Donahue, N. M. George, C. Goldstein, A. H. Hamilton, J. F. Herrmann, H. Hoffmann, T. Iinuma, Y. Jang, M. Jenkin, M. E. Jimenez, J. L. Kiendler-Scharr, A. Maenhaut, W. McFiggans, G. Mentel, Th. F. Monod, A. Prevot, A. S. H. Seinfeld, J. H. Surratt, J. D. Szmigielski, R. Wildt, J.; Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated wit…
Caracterización in-situ de las propiedades espectrales de absorción de los aerosoles atmosféricos en Valencia
2015
Según el último informe del Panel Intergubernamental sobre Cambio Climático (IPCC, 2013) cada una de las tres últimas décadas ha sido más cálida que la anterior a nivel de superficie y, en conjunto, más cálidas que ninguna de las precedentes desde 1850. En la atmósfera, las causas de este aumento de temperatura están relacionadas directamente con la presencia de gases de efecto invernadero y también de aerosoles. En la última década, el estudio de los aerosoles atmosféricos ha cobrado gran interés debido al papel que estos desempeñan en el clima a través del forzamiento radiativo, siendo su interacción mayor que la de algunos gases de efecto invernadero de vida corta (p.e., CO o NOx) Mientr…
Effects of NH3 and alkaline metals on the formation of particulate sulfate and nitrate in wintertime Beijing
2020
Sulfate and nitrate from secondary reactions remain as the most abundant inorganic species in atmospheric particle matter (PM). Their formation is initiated by oxidation (either in gas phase or particle phase), followed by neutralization reaction primarily by NH3, or by other alkaline species such as alkaline metal ions if available. The different roles of NH3 and metal ions in neutralizing H2SO4 or HNO3, however, are seldom investigated. Here we conducted semi-continuous measurements of SO4 2−, NO3 −, NH4 +, and their gaseous precursors, as well as alkaline metal ions (Na+, K+, Ca2+, and Mg2+) in wintertime Beijing. Analysis of aerosol acidity (estimated from a thermodynamic model) indicat…
Marine aerosols and iodine emissions (Reply)
2005
O'Dowd et al. reply - McFiggans raises some interesting, but partly speculative, issues about the possibility of additional condensable-iodine-vapour (CIV) precursors being involved in marine aerosol formation from biogenic iodine emissions, and about the relative roles of iodine oxide and sulphuric acid in the marine new-particle formation process.
Aerosol and droplet generation during intubation and normal breathing: a simulation study
2021
COVID-19 pacientu aprūpē var būt nepieciešama intubācija, kas ir aerosola un pilienu ģenerējoša procedūra, šādi palielinot vīrusa izplatības iespēju. Intubāciju ieteicams veikt pieredzējušam speciālistam labākai balss saišu vizualizācijai un ātrākai procedūras veikšanai, kas tādējādi samazinātu aerosola un pilienu veidošanās laiku. Šī pētījuma mērķis ir izpētīt pilienu un aerosola daudzumu, kas rodas normālas elpošanas laikā, kā arī salīdzināt intubācijas ilgumu, kontakta kontamināciju, pilienu izplatību un aerosolizāciju, kas rodas intubāciju veicot pieredzējušam enesteziologan un anestezioloģijas pirmā gada rezidentam. Metodes Eksperimentā I AMBU elpināšanas maiss tika piestiprināts manek…