Chamber investigations of atmospheric mercury oxidation chemistry

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dc.check.embargoformatE-thesis on CORA onlyen
dc.check.entireThesisEntire Thesis Restricted
dc.check.opt-outNot applicableen
dc.check.reasonThis thesis is due for publication or the author is actively seeking to publish this materialen
dc.contributor.advisorVenables, Dean S.en
dc.contributor.authorDarby, Steven B.en
dc.contributor.funderScience Foundation Irelanden
dc.date.accessioned2015-11-19T10:25:36Z
dc.date.issued2015
dc.date.submitted2015
dc.description.abstractMercury is a potent neurotoxin even at low concentrations. The unoxidised metal has a high vapour pressure and can circulate through the atmosphere, but when oxidised can deposit and be accumulated through the food chain. This work aims to investigate the oxidation processes of atmospheric Hg0(g). The first part describes efforts to make a portable Hg sensor based on Cavity Enhanced Absorption Spectroscopy (CEAS). The detection limit achieved was 66 ngm−3 for a 10 second averaging time. The second part of this work describes experiments carried out in a temperature controlled atmospheric simulation chamber in the Desert Research Institute, Reno, Nevada, USA. The chamber was built around an existing Hg CRDS system that could measure Hg concentrations in the chamber of<100 ngm−3 at 1 Hz enabling reactions to be followed. The main oxidant studied was bromine, which was quantified with a LED based CEAS system across the chamber. Hg oxidation in the chamber was found to be mostly too slow for current models to explain. A seven reaction model was developed and tested to find which parameters were capable of explaining the deviation. The model was overdetermined and no unique solution could be found. The most likely possibility was that the first oxidation step Hg + Br →HgBr was slower than the preferred literature value by a factor of two. However, if the more uncertain data at low [Br2] was included then the only parameter that could explain the experiments was a fast, temperature independent dissociation of HgBr some hundreds of times faster than predicted thermolysis or photolysis rates. Overall this work concluded that to quantitatively understand the reaction of Hg with Br2, the intermediates HgBr and Br must be measured. This conclusion will help to guide the planning of future studies of atmospheric Hg chemistry.en
dc.description.sponsorshipScience Foundation Ireland (SFI Grant 09/RFP/CAP-2509)en
dc.description.statusNot peer revieweden
dc.description.versionAccepted Version
dc.format.mimetypeapplication/pdfen
dc.identifier.citationDarby, S. B. 2015. Chamber investigations of atmospheric mercury oxidation chemistry. PhD Thesis, University College Cork.en
dc.identifier.endpage171
dc.identifier.urihttps://hdl.handle.net/10468/2076
dc.language.isoenen
dc.publisherUniversity College Corken
dc.rights© 2015, Steven B. Darbyen
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/3.0/en
dc.subjectAtmospheric mercuryen
dc.subjectBromineen
dc.subjectChamberen
dc.subjectCavity enhanced absorption spectroscopyen
dc.thesis.opt-outfalse
dc.titleChamber investigations of atmospheric mercury oxidation chemistryen
dc.typeDoctoral thesisen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD (Science)en
ucc.workflow.supervisord.venables@ucc.ie
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