Date of Award


Document Type

Honors Thesis (Open Access)


Colby College. Chemistry Dept.


D. Whitney King

Second Advisor

Nicholas Boekelheide

Third Advisor

Stephen Archer


The biogeochemical cycles of both iodine and ozone are strongly linked to human health and global climate and are tightly coupled through chemical processes occurring in the surface ocean and troposphere. The concentration and distribution of these compounds have the potential to drive the oxidizing capacity and suite of chemical reactions occurring in the marine boundary layer. However, modeling coupled ocean-atmosphere systems involving them is challenging because of a limited understanding of the magnitude and dominant mechanisms controlling the fluxes of both species, in addition to temporally and spatially heterogeneous distributions of ozone and iodine in the sea surface and lower troposphere. Recent modeling studies have suggested a 30% contribution of halogen chemistry to overall oceanic ozone deposition, which is equivalent to an average annual cooling of 0.1 W m-2, or 30% of the warming effect of tropospheric ozone. This has the potential to appreciably alter the radiative balance of the atmosphere, with broad implications for global climate. A laboratory-based experimental approach was used to explore the role of organic microlayers at the air-water interface in mediating the sea-surface reaction between ozone and iodide. Films of stearic acid, an insoluble fatty acid, were shown to significantly reduce the rate of ozone deposition to both phosphate-buffered solutions and natural seawater. Taken in conjunction with the proportionality between iodide concentration and ozone deposition velocity, regional variability in the concentrations of iodide and insoluble organics have the potential to influence global fluxes of ozone and volatile iodinate compounds, and thus impact tropospheric chemistry and radiative forcing.


Sea Surface Microlayer, Ozone Deposition, Heterogeneous Surface Reactions

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