Barium in the Antarctic Ocean and implications regarding the marine geochemistry of Ba and226Ra

Ba distribution in the ocean correlates linearly with that of ²²⁶Ra, reflecting little fractionation of the two elements in their uptake by marine organisms. The weight ratio of ²²⁶Ra/Ba is estimated to be (0.714 ± 0.08) × 10^?8. A wide range of Ba/Si and Ra/Si values is noted in siliceous plankton collected from different oceans. This corraborates with the observations that, although silica co-varies with Ba and²²⁶Ra, the Ba/Si and²²⁶Ra/Si ratios in seawater vary from one area to another. Sediment pore water contains higher Ba concentrations than the overlying seawater. The resulting diffusive flux of Ba through the sediment-sea interface is estimated to be no more than 20% of the river input. The apparent oversaturation of dissolved Ba in pore fluids with respect to barite supports the idea that complexing of Ba with organic ligands may be important. Box model calculations show that: (1) on a per unit area basis, ²²⁶Ra flux from the continental shelf sediments is higher than that from the deep sea floor; (2) in the deep ocean, the magnitude of diffusive input of ²²⁶Ra from sediments is about equal to the loss due to radioactive decay.