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Supply of Os to the oceans via atmospheric transport is assessed by means of aerosol analyses and tracking with 210Pb. Although the inferred continental Os flux at a coastal site (New Haven, Connecticut) was found to be large, this flux is not representative of the global atmospheric flux to the oceans. This conclusion is based on the observed 210Pb atmospheric flux pattern across the Pacific Ocean and the constancy of the 187Os/188Os in the oceans. The 210Pb-based flux of Os to Pacific islands based on a measure of the leachable Os in stream sediments and the measured Al flux to these islands is assessed. By means of this approach, 0.8 mol of Os per year of atmospherically transported Os to the world oceans is obtained. This value is considerably smaller than the value of ∼1500 mol of Os per year assigned to delivery by streams. However, there may be an additional flux of Os to the oceans from the release from coastal aerosols, although the amount is uncertain. |
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