DISSOLVED ZIRCONIUM IN THE NORTH PACIFIC-OCEAN

Picomolar levels of dissolved Zr in seawater were measured using an an alytical technique developed with a Chelex-100 extraction/concentratio n step and subsequent detection by isotope dilution inductively couple d plasma mass spectrometry (ID-ICP-MS). Here we present the first vert ical profile of Zr in the oceans, from the central-North Pacific, and a horizontal surface transect across the western Pacific. Dissolved Zr ranges from 12-95 pmol/kg in the surface waters then increases linear ly with depth to a maximum of 300 pmol/kg in the deep water. The verti cal profile shows a strong correlation with Si in the mid-waters, with higher Zr/Si ratios in the surface and bottom waters. There is eviden ce of both a bottom source and a coastal source of dissolved Zr to the oceans. A comparison with dissolved Ti and Be shows similar depth dep endence, but an enrichment in Zr/Ti and a depletion in Zr/Be ratios in seawater relative to average crustal materials. Zirconium appears to have a reactivity intermediate between these two elements.