Measurements of ozone fluxes using the eddy-correlation (EC) technique were carried out for the first time at the Mace Head atmospheric research station, on the west coast of Ireland between August-October 2009. Vertical exchange of ozone was measured from a tower platform at 22？m above mean sea level to study fluxes over coastal waters excluding the tidal region. The results were averaged over 30？min and exhibited predominantly downward but also upward transport of ozone in the boundary layer. Data quality was found to be high based on inspection of cospectra and micrometeorological measurements. During the study period, a major physical influence on fluxes was found to be wind speed. Measured fluxes were of the same magnitude as reported in previous open ocean studies ranging from approximately to ？ g ( ？ g on average, corresponding to a deposition velocity of 0.25？mm or a surface resistance of 4.13？s ). These results are considered to represent ozone fluxes over shallow coastal waters west of Ireland for conditions during summer and fall not affected by phytoplankton blooms. 1. Introduction Tropospheric ozone has potential negative impacts on human health and vegetation, and also acts as an important greenhouse gas. Background ozone levels at Mace Head Research Station in western Ireland, currently at an annual average of 35？ppbv, have shown a steady increase over the past two decades at an overall rate of 0.31？ppbv/year between 1987 and 2007 [1]. During the same period the relative contribution to these increasing ozone levels from air advected over the North Atlantic has also significantly grown. Deposition of ozone to surface ocean waters via physical uptake (solubility, turbulent mixing) and chemical reactions in the surface layer [2–4] likely constitute a significant, albeit highly variable “buffer” curtailing the rate of ozone increase in this region. It has been proposed that ozone can be rapidly degraded by chemical reactions with biogenically produced compounds such as iodide in surface seawater [5–7] leading to the release of iodine compounds followed by rapid particle nucleation [8]. Recent measurements over the northern coast of France by Whitehead et al. [9] appear to confirm the link between ozone deposition fluxes to exposed tidal flats and the reactions of ozone with volatilized iodine compounds producing new particles and contributing to particle growth and formation of cloud condensation nuclei. This study was primarily aimed at understanding particle production involving ozone deposition over tidal regions whereas very little is
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