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Identifier |
000365613 |
Title |
Χημικές διεργασίες ατμοσφαιρικού ενδιαφέροντος σε συσσωματώματα νερού |
Alternative Title |
Chemical processes of atmospheric interest in water clusters |
Author
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Ζάρας, Αριστοτέλης Ματ.
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Thesis advisor
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Παπαγιαννακόπουλος, Πάνος
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Abstract |
Two of the most contemporary issues facing humanity, are the enhancement of the greenhouse effect and the depletion of the ozone layer in the stratosphere. The
rapid industrial development and excessive use of chemical contaminants in a variety of technological applications are main causes of air pollution. Therefore, the design of
environmentally friendly compounds and control emissions is imperative to protect the environment. Besides the photolysis and gas-phase chemical degradation by the active components (OH, Cl, NO3) and O3), lies the suggestion that water in the
Atmosphere, can form complexes through strong hydrogen bonds with atmospheric pollutants, which may alter the kinetics of their chemical conversion processes. The possible change in the gas phase reaction rates was the springboard for the focus of
interest in chemical processes during the presence of water clusters.
This study investigated the effect of the presence of water clusters [(H2) O)n
where n: 1,2,3], in the rate coefficients of reactions OH radicals and Cl atoms with the simplest air pollutants: CH4 , CH3 OH, CH3 F, CH2 F2 and CHF3 , using theoretical calculations, with the computational chemistry package Gaussian 03. Main concern
was to determine the change in the reaction rate coefficient when water is involved as a substrate, in comparison with the reaction that occurs in the gas phase. The geometry optimization as well as the vibrational frequencies of the structures was carried out at two levels: a) MP2/cc-pVDZ and b) BH&HLYP/cc-pVDZ. The
optimized geometries of the components were further refined by extra single point calculations using the method G3, in order to obtain even more reliable energetic
results.The results of this study showed that the presence of water clusters, introduces a change in the kinetics of Cl atoms and the OH radicals reactions, with most frequent effect their acceleration. As OH radicals and Cl atoms are considered as main
tropospheric detergents and given the notable atmospheric abundance of water, its tendency to form water clusters as well as their considerable concentrations, it appears
that the acceleration may modify the atmospheric lifetimes of the investigated
molecules. These molecules are expected to exhibit shorter lifetimes and hence smaller global warming potentials (GWP).
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Language |
Greek |
Subject |
atmospheric lifetime |
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chemical degradation |
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chlorine atoms |
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hydroxyl radicals |
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reaction rate coefficient |
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theoretical calculations |
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άτομα χλωρίου |
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ατμοσφαιρικός χρόνος ζωής |
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θεωρητικοί υπολογισμοί |
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ρίζες υδροξυλίου |
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συντελεστής ταχύτητας αντίδρασης |
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χημική αποικοδόμηση |
Issue date |
2011-02-25 |
Collection
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School/Department--School of Sciences and Engineering--Department of Chemistry--Doctoral theses
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Type of Work--Doctoral theses
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Permanent Link |
https://elocus.lib.uoc.gr//dlib/f/f/d/metadata-dlib-69050071ef59ef0d8c89d627e3d63c40_1302862856.tkl
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Views |
823 |