ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-6-883-2006 Modelling molecular iodine emissions in a coastal marine environment: the link to new particle formation Saiz-Lopez A. 1 Plane J. M. C. 1 McFiggans G. 2 Williams P. I. 2 Ball S. M. 3 Bitter M. 3 Jones R. L. 3 Hongwei C. 4 Hoffmann T. 4 School of Environmental Sciences, University of East Anglia, Norwich, UK School of Earth, Atmospheric & Environmental Sciences, University of Manchester, Manchester, UK University Chemical Laboratory, Cambridge University, Cambridge, UK Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg-University, Mainz, Germany 20 03 2006 6 4 883 895 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/6/883/2006/acp-6-883-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/6/883/2006/acp-6-883-2006.pdf

A model of iodine chemistry in the marine boundary layer (MBL) has been used to investigate the impact of daytime coastal emissions of molecular iodine (I<sub>2</sub>). The model contains a full treatment of gas-phase iodine chemistry, combined with a description of the nucleation and growth, by condensation and coagulation, of iodine oxide nano-particles. In-situ measurements of coastal emissions of I<sub>2</sub> made by the broadband cavity ring-down spectroscopy (BBCRDS) and inductively coupled plasma-mass spectrometry (ICP/MS) techniques are presented and compared to long path differential optical absorption spectroscopy (DOAS) observations of I<sub>2</sub> at Mace Head, Ireland. Simultaneous measurements of enhanced I<sub>2</sub> emissions and particle bursts show that I<sub>2</sub> is almost certainly the main precursor of new particles at this coastal location. The ratio of IO to I<sub>2</sub> predicted by the model indicates that the iodine species observed by the DOAS are concentrated over a short distance (about 8% of the 4.2 km light path) consistent with the intertidal zone, bringing them into good agreement with the I<sub>2</sub> measurements made by the two in-situ techniques. The model is then used to investigate the effect of iodine emission on ozone depletion, and the production of new particles and their evolution to form stable cloud condensation nuclei (CCN).