11 research outputs found
Role of iodine oxoacids in atmospheric aerosol nucleation
Get PDFIodic acid (HIO3) is known to form aerosol particles in coastal marine regions, but predicted nucleation and growth rates are lacking. Using the CERN CLOUD (Cosmics Leaving Outdoor Droplets) chamber, we find that the nucleation rates of HIO3 particles are rapid, even exceeding sulfuric acid-ammonia rates under similar conditions. We also find that ion-induced nucleation involves IO3- and the sequential addition of HIO3 and that it proceeds at the kinetic limit below +10 degrees C. In contrast, neutral nucleation involves the repeated sequential addition of iodous acid (HIO2) followed by HIO3, showing that HIO2 plays a key stabilizing role. Freshly formed particles are composed almost entirely of HIO3, which drives rapid particle growth at the kinetic limit. Our measurements indicate that iodine oxoacid particle formation can compete with sulfuric acid in pristine regions of the atmosphere.Peer reviewe
2008 Progress Report on PS215/CLOUD
No full textSummary of progress in 2008 on the PS215/CLOUD experimen
Ion-induced iodic acid nucleation
No full text&lt;p&gt;Aside from capable of influencing atmospheric oxidation capacity, iodine species are known to contribute to particle formation processes. Iodine particle formation was commonly believed to be important in coastal regions only, e.g. Mace Head, but emerging evidence shows that it also plays an important role in Arctic regions.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Although the nucleation mechanisms have been proposed to involve mainly iodine oxides, recent field observations suggest that HIO&lt;sub&gt;3&lt;/sub&gt; plays a key role in the cluster formation processes. Despite these advances, experiments with atmospherically relevant vapor concentrations are lacking and the time evolution of charged cluster formation processes has never been detected at the molecular level to validate the mechanisms observed in the field.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;In this study, we carried out iodine particle formation experiments in the CLOUD chamber at CERN. The precursor vapor (I&lt;sub&gt;2&lt;/sub&gt;) and oxidation products were carefully controlled at concentrations relevant to those in marine boundary layer conditions. Natural galactic cosmic rays were used to produce ions in the chamber which further initiated ion-induced nucleation processes. An atmospheric pressure interface time-of-flight mass spectrometer was used to trace the time evolution of charged iodine clusters which revealed HIO&lt;sub&gt;3&lt;/sub&gt; as the major contributor.&lt;/p&gt;</jats:p
