E-Locus - Institutional Repository of the University of Crete

Home Search

Results - Details

Search command : Author="Ζάρας" And Author="Αριστοτέλης" And Author="Ματ."

Current Record: 1 of 1

[Add to Basket]

Identifier

000365613

Title

Χημικές διεργασίες ατμοσφαιρικού ενδιαφέροντος σε συσσωματώματα νερού

Alternative Title

Chemical processes of atmospheric interest in water clusters

Author

Ζάρας, Αριστοτέλης Ματ.

Thesis advisor

Παπαγιαννακόπουλος, Πάνος

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).

Language

Greek

Subject

atmospheric lifetime

chemical degradation

chlorine atoms

hydroxyl radicals

reaction rate coefficient

theoretical calculations

άτομα χλωρίου

ατμοσφαιρικός χρόνος ζωής

θεωρητικοί υπολογισμοί