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| Titel |
Direct evidence for coastal iodine particles from Laminaria macroalgae – linkage to emissions of molecular iodine |
| VerfasserIn |
G. McFiggans, H. Coe, R. Burgess, J. Allan, M. Cubison, M. R. Alfarra, R. Saunders, A. Saiz-Lopez, J. M. C. Plane, D. Wevill, L. Carpenter, A. R. Rickard, P. S. Monks |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 3 ; Nr. 4, no. 3 (2004-05-07), S.701-713 |
| Datensatznummer |
250001710
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| Publikation (Nr.) |
 copernicus.org/acp-4-701-2004.pdf |
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| Zusammenfassung |
| Renewal of ultrafine aerosols in the marine boundary layer may lead to
repopulation of the marine distribution and ultimately determine the
concentration of cloud condensation nuclei (CCN). Thus the formation of
nanometre-scale particles can lead to enhanced scattering of incoming
radiation and a net cooling of the atmosphere. The recent demonstration of
the chamber formation of new particles from the photolytic production of
condensable iodine-containing compounds from diiodomethane
(CH2I2), (O'Dowd et al., 2002; Kolb, 2002; Jimenez et al., 2003a;
Burkholder and Ravishankara, 2003), provides an additional mechanism to the
gas-to-particle conversion of sulphuric acid formed in the photo-oxidation
of dimethylsulphide for marine aerosol repopulation. CH2I2 is
emitted from seaweeds (Carpenter et al., 1999, 2000) and has been suggested
as an initiator of particle formation. We demonstrate here for the first
time that ultrafine iodine-containing particles are produced by intertidal
macroalgae exposed to ambient levels of ozone. The particle composition is
very similar both to those formed in the chamber photo-oxidation of
diiodomethane and in the oxidation of molecular iodine by ozone. The
particles formed in all three systems are similarly aspherical. When small,
those formed in the molecular iodine system swell only moderately when
exposed to increased humidity environments, and swell progressively less
with increasing size; this behaviour occurs whether they are formed in dry
or humid environments, in contrast to those in the CH2I2 system.
Direct coastal boundary layer observations of molecular iodine, ultrafine
particle production and iodocarbons are reported. Using a newly measured
molecular iodine photolysis rate, it is shown that, if atomic iodine is
involved in the observed particle bursts, it is of the order of at least
1000 times more likely to result from molecular iodine photolysis than
diiodomethane photolysis. A hypothesis for molecular iodine release from
intertidal macroalgae is presented and the potential importance of
macroalgal iodine particles in their contribution to CCN and global
radiative forcing are discussed. |
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