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| Identifier |
000348400 |
| Title |
Μελέτη της ετερογενούς αλληλεπίδρασης αερίου οξικού οξέος με επιφάνειες πάγου |
| Alternative Title |
Heterogeneous interactions of gas phase acetic acid with ice surfaces |
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Author
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Ζόγκα, Αντωνία Γ
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Thesis advisor
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Παπαγιαννακόπουλος, Πάνος
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| Abstract |
In the present study, the heterogeneous interactions of ethanoic acid with pure and doped with nitric acid ice surfaces were investigated. Ethanoic Acid is the most abundant organic acid in the atmosphere, with increased concentrations, globally. Heterogeneous processes are of significant importance in Upper Troposphere/Lower Stratosphere (UTLS) chemistry and hence they play a central role in Air Quality and Climate Change issues. In order to carry out the proposed work, the Continuous Flow Technique of Very Low Pressure Reactor (VLPR) coupled with a quandrupole mass spectrometer (QMS) equipped with a properly modified Knudsen Reactor was employed.
Ice surfaces were formed gradually by water vapors deposition on a cryostatted copper surface. Experiments performed over substrate temperature range Τ: 196-209 Κ, while gas phase concentrations varied over 2x1010 – 1.2x1012 molecule cm-3 . The initial uptake coefficients (γ) and the number of adsorbed molecules (NS), as well as their dependences on substrate temperature and concentration of ethanoic acid on the various ice surfaces studied in this work, were measured under the title temperature and pressure conditions. Subsequently, the coverage (θ), the maximum substrate available sites (Nmax) and the strength of CH3C(O)OH interaction with the different ice surfaces (ΚLang), as well as their dependence on substrate temperature was determined via fitting experimental data with the Langmuir isotherm model, at the different temperatures experiments performed (ΚLang(T)).
Measurements performed using pure ice surfaces as substrates provided with quantitative information about reactivity of acetic acid, while the corresponding experiments using doped ice surfaces with nitric acid instead showed that HNO3 plays a critical role on enhancing their storage efficiency. Finally, both atmospheric lifetime of CH3C(O)OH due to its heterogeneous loss (τhet), and the molecular fraction (a) that interact with cirrus clouds as a function of Surface Area Density (SAD, cm2 cm-3 were determined. The quantitative determination of the interrelation between τhet and a the two last properties is essential in order to systematically evaluate the impact of ethanoic acid in the Atmosphere.
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| Language |
Greek |
| Subject |
Adsorption on Clouds |
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HNO3 Ice-Doped |
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Physics and Structure of Ice |
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Επιφάνειες Πάγου Εμπλουτισμένες σε Νιτρικό Οξύ |
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Προσρόφηση Αερίων σε Επιφάνειες |
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Φυσική και Χημεία του Πάγου |
| Issue date |
2009-07-21 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Chemistry--Post-graduate theses
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Type of Work--Post-graduate theses
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| Views |
171 |
Μελέτη της ετερογενούς αλληλεπίδρασης αερίου οξικού οξέος με επιφάνειες πάγου
