Studies of heterogeneous ice chemistry relevant to the atmosphere
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.
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| Format: | Thesis |
| Language: | en_US |
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Massachusetts Institute of Technology
2005
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| Online Access: | http://hdl.handle.net/1721.1/28841 |
| _version_ | 1826205000525676544 |
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| author | McNeill, Vivian Faye, 1978- |
| author2 | Mario J. Molina. |
| author_facet | Mario J. Molina. McNeill, Vivian Faye, 1978- |
| author_sort | McNeill, Vivian Faye, 1978- |
| collection | MIT |
| description | Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. |
| first_indexed | 2024-09-23T13:05:29Z |
| format | Thesis |
| id | mit-1721.1/28841 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T13:05:29Z |
| publishDate | 2005 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/288412019-04-10T21:57:38Z Studies of heterogeneous ice chemistry relevant to the atmosphere McNeill, Vivian Faye, 1978- Mario J. Molina. Massachusetts Institute of Technology. Dept. of Chemical Engineering. Massachusetts Institute of Technology. Dept. of Chemical Engineering. Chemical Engineering. Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005. Includes bibliographical references. (cont.) HCl-induced QLL formation at stratospheric conditions. It appears that the real part of the refractive index of the QLL formed via exposure to gas-phase HCl is closer. to that of liquid water or aqueous HCI solution than to that of ice. We estimate the thickness of the QLL in our experiments to be on the order of 100 nm. We found using the flow tube-CIMS technique that the presence of the QLL enhances the chlorine-activation reaction of HC1 with ClONO₂. The presence of the QLL also enhances CH₃COOH adsorption. We find that the solubilities of HC1 and CH₃COOH in the QLL are intermediate between the solubilities of each species in liquid H20 and those in ice. In a flow-tube CIMS study of HCI adsorption on different types of ice surface, we found that HCI adsorption on polycrystalline ice films typically used in laboratory studies consists of two modes: one relatively strong mode leading to irreversible adsorption, and one relatively weak binding mode leading to reversible adsorption. We have indirect experimental evidence that these two modes of adsorption correspond to adsorption to sites at crystal faces and those at grain boundaries, but there is not enough information to enable us to conclusively assign each adsorption mode to a type of site. We also found indirect evidence that HCI hexahydrate formation on ice at conditions relevant to the polar stratosphere is a process involving hydrate nucleation and propagation on the crystal surface, rather than one originating in grain boundaries, as has been suggested for ice formed at lower temperatures. Characterization of the interaction of hydrogen chloride (HCl) with polar stratospheric cloud (PSC) ice particles is essential to understanding the processes responsible for ozone depletion. The interaction of HCI with ice was studied between -87⁰C and -30⁰C using the complementary approach of a) ellipsometry to monitor the ice surface with chemical ionization mass spectrometry (CIMS) detection of the gas phase, and b) flow tube experiments with CIMS detection. The flow tube-CIMS technique was also used to study the chlorine activation reaction of chlorine nitrate (ClONO₂) and HCl on ice, the co-adsorption of acetic acid (CH₃COOH) and HCI on ice, and the adsorption of CFC-12 (CC1₂F₂) on ice. CH₃COOH and CC1₂F₂ were employed as nonreactive probe molecules to provide information about the state of the ice surface in the HCl-ice system. The ellipsometer-CIMS studies were performed on single-crystalline ice samples, and the flow tube-CIMS studies were performed on smooth and vapor-deposited polycrystalline ice films and on zone-refined ice cylinders. A numerical modeling framework is presented for the interpretation of the flow tube-CIMS studies. A disordered surface region, or quasi-liquid layer (QLL), was detected on bare ice using ellipsometry down to -30 ⁰C. We also found using ellipsometry that trace amounts of HCl induce QLL formation on the ice surface in the vicinity of the solid-liquid equilibrium line on the HCl-ice phase diagram, including conditions encountered in the polar stratosphere during PSC events. These results are supported by the results of the flow tube-CIMS studies of the reaction of ClONO₂ and HCl on ice, CH₃COOH/HC1 co-adsorption on ice, and HCl adsorption on ice. This is the first report of direct experimental evidence of by Vivian Faye McNeill. Ph.D. 2005-09-27T18:38:19Z 2005-09-27T18:38:19Z 2005 2005 Thesis http://hdl.handle.net/1721.1/28841 60385782 en_US M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 156 leaves 7474785 bytes 7496075 bytes application/pdf application/pdf application/pdf Massachusetts Institute of Technology |
| spellingShingle | Chemical Engineering. McNeill, Vivian Faye, 1978- Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title | Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title_full | Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title_fullStr | Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title_full_unstemmed | Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title_short | Studies of heterogeneous ice chemistry relevant to the atmosphere |
| title_sort | studies of heterogeneous ice chemistry relevant to the atmosphere |
| topic | Chemical Engineering. |
| url | http://hdl.handle.net/1721.1/28841 |
| work_keys_str_mv | AT mcneillvivianfaye1978 studiesofheterogeneousicechemistryrelevanttotheatmosphere |