10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
The Role of Iodine Emission in the Atmospheric Aerosol Formation
RAVI KUMAR, Multanimal Modi College, Modinagar-201204 (U.P.), India
Abstract Number: 65 Working Group: Aerosol Chemistry
Abstract Recent studies have shown that new particle formation via a secondary gas-to-particle process at coastal regions (see review articles of Kolb, 2002 and von Glasow, 2005) originates from biogenic emissions (Carpenter, 2003) of iodine-containing vapours such as CH2I2 and I2. These species undergo rapid photo-chemical reactions to produce condensable iodine oxides which, in turn lead to the nucleation and growth of new particles (O’Dowd and Hoffmann, 2005).
These particles may be ubiquitous in the Earth’s atmosphere if open ocean sources are also significant. They may influence the global radiation budget directly i.e. they can scatter and absorb solar radiation to some extent and may therefore affect climate. In terms of an indirect effect, a significant fraction of these particles have the potential to grow into cloud condensation nuclei (CCN). Changes in the number concentration of CCN may affect the number concentration and size of cloud droplets, and therefore the optical properties and the lifetime of clouds (Curtius, 2006).
Despite the recent studies, uncertainty still remains regarding the composition of newly formed particles from photo-oxidation of iodine-containing species. According to Saunders & Plane (2005), the most likely composition of particles is I2O5 while studies of particle formation from photolysis of CH2I2 (Jimenez et al., 2002; O’Dowd and Hoffmann, 2005) have suggested the I2O4 form. However, a thorough knowledge of atmospheric particle composition and properties requires a description of how they interact with other gases (H2O and H2SO4 in particular) in the marine boundary layer (MBL).
This study will report laboratory studies, including: the formation and growth kinetics of iodine oxide nano-particles, and their uptake of water and sulphuric acid; the redox kinetics of iodate/iodide ions in aerosols; and the action of O3 in releasing I2 from aqueous iodide.
References 1. Saunders, R. W., Kumar, R., Martin, J. C. G., Mahajan, A. S., Murray, B. J., and Plane, J. M. C.: Studies of the Formation and Growth of Aerosol from Molecular Iodine Precursor, Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics, 224, 1095-1117, 2010 2. Kumar, R., Saunders, R. W., Mahajan, A. S., Plane, J. M. C., and Murray, B. J.: Physical properties of iodate solutions and the deliquescence of crystalline I2O5 and HIO3, Atmospheric Chemistry and Physics, 10, 12251-12260, 2010. 3. Kolb, C.E. (2002), Iodine’s air of importance, Nature, 417, 597-598. 4. von Glasow, R.(2005), Seaweed, iodine and atmospheric chemistry – the current state of play, Environmental Chemistry, 2 (4), 243-244. 5. O’Dowd, C.D. & Hoffmann, T. (2005), Coastal new particle formation: a review of the current state-of-the-art, Environmental Chemistry, 2 (4), 245-255. 6. Saunders, R.W.and Plane, J.M.C.(2005), Formation pathways and composition of iodine oxide ultra-fine particles, Environmental Chemistry, 2 (4), 299-303 7. Carpenter, L. J., MacDonald, S. M., Shaw, M. D., Kumar, R., Saunders, R. W., Parthipan, R., Wilson, J., and Plane, J. M. C.: Atmospheric iodine levels influenced by sea surface emissions of inorganic iodine, Nature Geoscience, 6, 108-111, 2013 8. Jimenez, J.L., Bahreini R., Cocker III D.R., Zhuang H., Varutbangkul V., Flagan R.C., Seinfeld J.H., O’Dowd C.D., and Hoffmann T. (2003), New particle formation from photooxidation of diiodomethane (CH2I2), Journal of Geophysical Research, 108D(10), 4318. 9. Curtius, J. (2006), Nucleation of atmospheric aerosol particles, Comptes Rendus Physique, 7, 1027-1045