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| Identifier |
000350390 |
| Title |
Κινητική διερεύνηση της ετερογενούς αλληλεπίδρασης πτητικών ενώσεων ατμοσφαιρικού ενδιαφέροντος με επιφάνειες (H2O, H2O/HNO3), στην περιοχή της ανώτερης τροπόσφαιρας/κατώτερης στρατόσφαιρας (UTLS) |
| Alternative Title |
Heterogeneous Interactions Kinetic Investigation for Volatile Compounds of Atmospheric Interest on Pure and HNO3 Doped Ice Surfaces, in the Region of Upper Troposphere/Lower Stratosphere (UTLS) |
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Author
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Ρωμανιάς, Μανώλης Ν.
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Thesis advisor
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Παπαγιαννακόπουλος, Πάνος
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| Abstract |
The primary goal of the present PhD dissertation, was to investigate The Heterogeneous Interactions of Volatile Organic Acids with Pure (H2O) and Doped with Nitric Acid (HNO3) Ice Surfaces. Heterogeneous processes over ice surfaces are of significant importance in the 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 - Effusive Molecular Beam Technique of Very Low Pressure Reactor (VLPR) equipped with a properly modified Knudsen Reactor was employed. Ice surfaces were formed with gradual water vapors deposition on a cryostatted metal surface.
In the present work the heterogeneous interaction of methanoic (HC(O)OH), propanoic (CH3CH2C(O)OH) and butanoic (CH3CH2CH2C(O)OH) acid with pure and doped with various concentrations (wt %) of nitric acid, ice surfaces was studied. Experiments performed over several substrate temperature range Τ: 209 – 196 Κ, while gas phase concentrations varied over 1x1010 - 1x1012 molecule cm-3. Under these conditions initial uptake coefficients (γ) as well as their dependence on substrate temperature, the coverage (θ), the maximum substrate available sites (Nmax) and the binding probability (Ns) of carboxylic acids on the various ice surfaces were measured. Subsequently, the relative strength of the various acids interactions with the different ice surfaces (ΚLang), as well as its dependence on substrate temperature was determined via fitting experimental data with the Langmuir isotherm model, at the different temperatures experiments performed (ΚLang(T)).
Measurements carried out with pure ice surfaces fingerprint, quantitatively, the relative reactivity for the studied carboxylic acids, while at the same time they provided us with useful information regarding the mechanism of the heterogeneous interaction. The corresponding experiments performed with nitric acid doped ice surfaces showed both that HNO3 plays a critical role on enhancing their storage efficiency, converting them in very strong sinks of volatile organic acids and that heterogeneous processes have a generic and most likely determinative significance in Atmospheric Chemistry. Finally, the atmospheric lifetime of carboxylic acids due to their heterogeneous loss, as well as, the fraction of molecules that interact with cirrus clouds as a function of Surface Area Density (SAD, cm2 cm-3) were determined. The thorough knowledge of the above two parameters is very crucial to the overall assessment of the carboxylic acids Impact in the Atmosphere.
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| Language |
Greek |
| Subject |
Adsorpion Isotherms of Carboxylic Acids |
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Carboxylic Acids- Atmospheric Chemistry |
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Chemical Kinetics |
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Chemistry and Physics of Ice |
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Laboratory Techniques for Studying Heterogeneous Interactions |
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Physisorption-Chemisorption |
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Thermodynamic parameters- Uptake Coefficients |
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upper Troposphere/Lower Stratosphere (UTLS). |
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Ανώτερη Τροπόσφαιρα Κατώτερη Στρατόσφαιρα (UTLS) |
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Θερμοδυναμικές Παράμετροι-Συντελεστές Κατακράτησης |
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Ισόθερμες Προσρόφησης Καρβοξυλικών Οξέων |
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Καρβοξυλικά Οξέα-Ατμοσφαιρική Χημεία |
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Πειραματικές Τεχνικές Ετερογενών Αντιδράσεων |
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Φυσική και Χημεία του Πάγου |
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Φυσιορρόφηση-Χημειορρόφηση |
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Χημική Κινητική |
| Issue date |
2009-06-15 |
| 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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| Views |
251 |
Κινητική διερεύνηση της ετερογενούς αλληλεπίδρασης πτητικών ενώσεων ατμοσφαιρικού ενδιαφέροντος με επιφάνειες (H2O, H2O/HNO3), στην περιοχή της ανώτερης τροπόσφαιρας/κατώτερης στρατόσφαιρας (UTLS)
