Coastal iodine emissions. 1. Release of I2 by Laminaria digitata in chamber experiments

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Accepted Version
Ashu-Ayem, Enowmbi R.
Nitschke, Udo
Monahan, Ciaran
Chen, Jun
Darby, Steven B.
Smith, Paul D.
O'Dowd, Colin D.
Stengel, Dagmar B.
Venables, Dean S.
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American Chemical Society
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Tidally exposed macroalgae emit large amounts of I2 and iodocarbons that produce hotspots of iodine chemistry and intense particle nucleation events in the coastal marine boundary layer. Current emission rates are poorly characterized, however,with reported emission rates varying by 3 orders of magnitude. In this study, I2 emissions from 25 Laminaria digitata samples were investigated in a simulation chamber using incoherent broadbandcavity-enhanced absorption spectroscopy (IBBCEAS). The chamber design allowed gradual extraction of seawater to simulate tidal emersion of algae. Samples were exposed to air with or without O3 and to varying irradiances. Emission of I2 occurred in four distinct stages: (1) moderate emissions from partially submerged samples;(2) a strong release by fully emerged samples; (3) slowing or stopping of I2 release; and (4) later pulses of I2 evident in some samples. Emission rates were highly variable and ranged from 7to 616 pmol min−1 gFW−1 in ozone-free air, with a median value of 55 pmol min−1 gFW−1 for 20 samples.
Air pollution and industrial hygiene , Iodine release , Marine boundary layer
ASHU-AYEM, E. R., NITSCHKE, U., MONAHAN, C., CHEN, J., DARBY, S. B., SMITH, P. D., O’DOWD, C. D., STENGEL, D. B. & VENABLES, D. S. 2012. Coastal Iodine Emissions. 1. Release of I2 by Laminaria digitata in Chamber Experiments. Environmental Science & Technology, 46, 10413-10421.
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Copyright © 2012 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science and Technology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see