Studies of heterogeneous ice chemistry relevant to the atmosphere

(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.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• McNeill, Vivian Faye, 1978-

Advisor dc:contributor.advisor

• Mario J. Molina.

• Chemical Engineering.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/28841

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/28841