Modelling molecular iodine emissions in a coastal marine environment: the link to new particle formation

[摘要] A model of iodine chemistry in the marine boundary layer (MBL) hasbeen used to investigate the impact of daytime coastal emissions ofmolecular iodine (I₂). The model contains a full treatmentof gas-phase iodine chemistry, combined with a description of thenucleation and growth, by condensation and coagulation, of iodineoxide nano-particles. In-situ measurements of coastalemissions of I₂ made by the broadband cavity ring-downspectroscopy (BBCRDS) and inductively coupled plasma-massspectrometry (ICP/MS) techniques are presented and compared to longpath differential optical absorption spectroscopy (DOAS)observations of I₂ at Mace Head, Ireland. Simultaneousmeasurements of enhanced I₂ emissions and particle burstsshow that I₂ is almost certainly the main precursor of newparticles at this coastal location. The ratio of IO to I₂predicted by the model indicates that the iodine species observed bythe DOAS are concentrated over a short distance (about 8% of the4.2 km light path) consistent with the intertidal zone, bringingthem into good agreement with the I₂ measurements made bythe two in-situ techniques. The model is then used toinvestigate the effect of iodine emission on ozone depletion, andthe production of new particles and their evolution to form stablecloud condensation nuclei (CCN).

[学科分类] 大气科学