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Elucidation of the origins of stratospheric sulfate aerosols by isotopic methods

Citation

Leung, Fok-Yan Thomas (2003) Elucidation of the origins of stratospheric sulfate aerosols by isotopic methods. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05292003-144531

Abstract

Stratospheric sulfate aerosols (SSA) play an important part in regulating the climate of the earth and in the maintenance of important stratospheric species, including stratospheric ozone. The sources of stratospheric sulfate aerosol sulfur remain an unresolved issue because of uncertainties in the global sulfur budget and model limitations. The origins of SSA particles should be reflected in their isotopic composition. In this thesis project, the sulfur isotopic fractionation factors of processes that produce stratospheric sulfate aerosols (SSA) were quantified using a variety of theoretical and experimental techniques. RRKM (unimolecular dissociation) theory was applied to compute the isotopic fractionation of the homogeneous oxidation of SO2 via OH radicals. The overall isotopic enrichment associated with the total OCS loss pathways in the stratosphere was determined by analyzing high resolution FT-IR data from balloon flights. The isotopic fractionation of the photolytic decomposition of OCS was estimated by measuring the absorption spectra of OCS sulfur isotopologues. We also measured the isotopic composition of stratospheric aerosols sampled during the period 1973-1974, in the course of the Department of Energy?s AIRSTREAM campaign. Combining our results with literature values of the sulfur isotopic composition of SSA precursors, we modeled the steady-state isotopic composition of sulfur compounds in the atmosphere using the JPL/Caltech 1-D chemical transport model. Our data supports the view that OCS and SO2 are both important in the maintenance of the background stratospheric sulfate aerosol layer.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:; 34S; composition of stratosphere; COS; H2SO4; isotopic methods; OCS; SO2; stratospheric sulfate aerosols
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Environmental Science and Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hoffmann, Michael R. (advisor)
  • Yung, Yuk L. (co-advisor)
Thesis Committee:
  • Hoffmann, Michael R. (chair)
  • Randerson, James T.
  • Wennberg, Paul O.
  • Yung, Yuk L.
Defense Date:6 March 2003
Author Email:fok-yan (AT) its.caltech.edu
Record Number:CaltechETD:etd-05292003-144531
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05292003-144531
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2233
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:06 Jun 2003
Last Modified:26 Dec 2012 02:48

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