Concentrations and species of iodine isotopes (127 I and 129 I) provide vital information about iodine geochemistry, environmental conditions and water masses exchange in oceans. Despite extensive investigations of anthropogenic 129 I in the Arctic Ocean and the Nordic Seas, concentrations of the isotope in the Atlantic Ocean are, however, still unknown. We here present first data on 129 I and 127 I, and their species (iodide and iodate) in surface water transect along the northeastern Atlantic between 30and 50 N. The results show iodate as the predominant species in the analyzed marine waters for both 127 I and 129 I. Despite the rather constant ratios of 127 I - /127 IO 3 -, the 129 I - /129 IO 3 - values reveal variations that apparently response to sources, environmental conditions and residence time. These findings provide a new tracer approach that will strongly enhance the application of anthropogenic 129 I in ocean environments and impact on climate at the ocean boundary layer.
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