Dissolved zirconium in the North Pacific Ocean

Abstract

Picomolar levels of dissolved Zr in seawater were measured using an analytical technique developed with a Chelex-100 extraction/concentration step and subsequent detection by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). Here we present the first vertical 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 linearly with depth to a maximum of 300 pmol/kg in the deep water. The vertical profile shows a strong correlation with Si in the mid-waters, with higher Zr Si ratios in the surface and bottom waters. There is evidence 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 dependence, 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.