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The most stable form of iodine in seawater (iodate) is reduced to iodide in the surface waters of the oceans. We are not certain how this process occurs, although it seems to be linked in some way to biological activity. |
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| Some macroalgae (seaweed) and phytoplankton release iodine-containing organic gases into the sea. There may also be some formation of these substances through reactions brought about by sunlight. |
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The iodine-containing gases cross the sea - air interface and enter the atmosphere where their iodine is released into the "Reactive Iodine Pool" by the action of sunlight. |
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| The chemistry of iodine in the atmosphere is extremely complex, and plays a part in the destruction of ozone. More information on this interesting chemistry can be found on Jochen Stutz's and the ACSOE home pages. |
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There are several different chemical forms of iodine in aerosol: the inorganic forms iodide (I-) and iodate (IO3-), soluble organic iodine compounds (RI), an insoluble iodine fraction (I'), which may be organic or inorganic, as well as several other forms which are only present for short periods, either because they are volatile or reactive. |
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| Iodine is deposited on land or back into the sea by rain-out or dry deposition of aerosol. The amount of iodine deposited on land decreases rapidly with increasing distance from the ocean, hence the higher prevalence of iodine deficiency disorders in continental interiors. |
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Dead organic matter becomes buried in marine sediments, where it decomposes and releases iodide into the pore waters. |
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