Dissolved iodine in waters overlying and in the Orca Basin,Gulf of Mexico |
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| Authors: | George TF Wong Kazufumi Takayanagi James F Todd |
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| Institution: | Department of Oceanography, Old Dominion University, Norfolk, VA 23508 U.S.A. |
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| Abstract: | The distribution and speciation of iodine, a biophilic redox-sensitive trace element, in waters overlying and in the Orca Basin, Gulf of Mexico, which contains hypersaline, anoxic and yet non-sulfide-bearing brine have been determined. The distribution of iodate and iodide in the oxic waters overlying the anoxic brine are similar to those reported in other oceans. However, in the oxic-anoxic mixing zone, iodate disappears while the concentration of iodide reaches a maximum of 8.1 μM, the highest concentration ever reported in open oceans. There is also a maximum in specific iodine of 30.7 nM‰?1 at this depth. Specific iodine in oxic seawater is only about 10–14 nM ‰?1. These features may be explained by the preferential dissolution of biogenic particles that have accumulated in a strong pycnocline. In the anoxic brine proper, the concentration of iodide is 3.8 μM and can be explained almost entirely by the simultaneous mobilization of chloride and iodide during the dissolution of evaporite beds as the specific iodine of 14.5 nM‰?1 is only slightly higher than those observed in the oxic waters. |
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