Dr RuJin Huang
Centre for Climate and Air Pollution Studies, National University of Ireland Galway, Galway, Ireland
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Topic: Reaction Cycling of Particulate Iodine in the Marine Boundary Layer-A Chamber Study
(Report)
Host: Thorsten Hoffmann,Institute of Inorganic Chemistry and Analytical Chemistry, Johannes Gutenberg University of Mainz, Mainz, Germany
Date of STSM: 20/01/2011 to 06/05/2011
STSM code: 7680
Motivation and Objectives: Recent studies indicate that iodine oxides, the photochemical products of gaseous iodine species, are the most likely species involved in nucleation and growth of new particles in the marine boundary layer and that iodine is often enriched in the fine marine aerosols by a factor of 100 to 1000 compared to iodine fraction in seawater. However, the chemical reaction cycling and evolution of particulate iodine are still poorly understood, which in turn hinders our knowledge of new particle formation processes. Therefore, laboratory study is essential to reduce the existing uncertainties. The chamber studies proposed here will include reactions between iodine species and organic compounds since submicrometer aerosols consist of 15-63% organic fractions and particulate organic iodine could be the major fraction in marine aerosols. Methods: Iodine oxides-containing aerosols are produced by photolysis of gaseous iodine species in a reaction chamber where organic compounds are injected. The resulting particles are sampled by filters. Speciation of particulate iodine and measurements of organic marker compounds are performed by a recently developed precolumn derivatization and solid phase extraction
preseparation method in combination with liquid chromatographic/mass spectrometric determination. The gaseous iodine species are collected by diffusion denuder samplers, followed by a post-derivatization procedure and gas chromatographic/mass spectrometric determination. Outcomes: This study, togethe with field measurements at Mace Head station, is expected to advance our knowledge of the atmospheric processes of iodine and the mechanisms of new particle formation processes. Publications of the results in major scientific journals are expected.