This award in the Environmental Geochemistry and Biogeochemistry Program is jointly supported by the Divisions of Atmospheric Science and Chemistry and by the MPS Office of Multidisciplinary Activities. Dr. Scott T. Sandholm of the School of Earth and Atmospheric Sciences, Georgia Institute of Technology, will develop a photofragmentation laser induced fluorescence sensor (PF-LIF) to measure volatile methyl iodide in situ in the marine boundary layer. Current detection methods for organic iodides rely heavily on analysis of stored `grab` samples and can be quite sensitive to preparation and handling of samples and to thermal degradation. The LIF sensor will permit in situ measurements as well as temporal emission profiles of methyl iodide and other simple organic iodides to the atmosphere from oceanic and coastal regions. The method is expected to have the sensitivity and selectivity needed to be effective. The similarities in photofragmentation dynamics of organic iodides enables total iodine emission to be measured by following the cumulative photofragmented production of atomic iodine as I* for all organic iodides known to be emitted from oceanic sources. The role of iodine in tropospheric and stratospheric ozone cycles is not well understood due to lack of quantitative measurements of the source compounds. Organic iodide compounds are thought to evaporate from the ocean and serve as a source. In this research, a new method for direct measurement of iodine will be developed and tested in field deployment off the coast of Georgia.
