Investigation of the Influence of the Sea Surface Microlayer on Ozone Deposition Rates

Ozone deposition to the ocean surface represents a significant loss from the atmosphere with current best estimates, based on chemistry transport model analyses, being about one third of the global annual ozone deposition of 600-1000 Tg O₃ yr^-1. Such deposition likely represents the net flux to the physical ocean surface, chemical interactions in the presence or absence of a surface microlayer, and bidirectional reactions between ozone and reactive iodine dependent on the environmental light regime. A laboratory-based experimental approach is used to further explore controls on the rate of ozone deposition to seawater. We examine the influence of iodide concentration and microlayer composition or absence on ozone deposition velocity as a means to assess the role surface-active organics play in mediating ozone deposition rates. Experimental results are used to discern whether soluble and insoluble model surfactants, micro-algal exudates and natural microlayers act to physically and/or chemically enhance or suppress ozone deposition.