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| Titel |
Spectroscopic studies of molecular iodine emitted into the gas phase by seaweed |
| VerfasserIn |
S. M. Ball, A. M. Hollingsworth, J. Humbles, C. Leblanc, P. Potin, G. McFiggans |
| 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 ; 10, no. 13 ; Nr. 10, no. 13 (2010-07-09), S.6237-6254 |
| Datensatznummer |
250008614
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| Publikation (Nr.) |
 copernicus.org/acp-10-6237-2010.pdf |
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| Zusammenfassung |
| Time profiles of molecular iodine emissions from seven species of seaweed
have been measured at high time resolution (7.5 s) by direct
spectroscopic quantification of the gas phase I2 using broadband cavity
enhanced absorption spectroscopy. Substantial differences were found between
species, both in the amounts of I2 emitted when the plants were exposed
to air and in the shapes of their emission time profiles. Two species of
kelp, Laminaria digitata and Laminaria hyperborea,
were found to be the most potent emitters, producing an intense
burst of I2 when first exposed to air. I2 was also observed from
Saccharina latissima and Ascophyllum nodosum but in
lower amounts and with broader time profiles. I2 mixing
ratios from two Fucus species and Dictyopteris membranacea
were at or below the detection limit of the
present instrument (25 pptv). A further set of experiments investigated the
time dependence of I2 emissions and aerosol particle formation when
fragments of L. digitata were exposed to desiccation in air, to ozone and to
oligoguluronate stress factors. Particle formation occurred in all L. digitata stress
experiments where ozone and light were present, subject to the I2
mixing ratios being above certain threshold amounts. Moreover, the particle
number concentrations closely tracked variations in the I2 mixing
ratios, confirming the results of previous studies that the condensable
particle-forming gases derive from the photochemical oxidation of the
plant's I2 emissions. This work also supports the theory that particle
nucleation in the coastal atmosphere occurs in "hot-spot" regions of
locally elevated concentrations of condensable gases: the greatest
atmospheric concentrations of I2 and hence of condensable iodine oxides
are likely to be above plants of the most efficiently emitting kelp species
and localised in time to shortly after these seaweeds are
uncovered by a receding tide. |
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