Dissolved and Labile Particulate Zr, Hf, Nb, Ta, Mo and W in the Western North Pacific Ocean

Firdaus, M. Lutfi and KAZUHIRO, NORISUYE and YUSUKE, NAKAGAWA and SEIJI , NAKATSUKA and YOSHIKI, SOHRIN (2008) Dissolved and Labile Particulate Zr, Hf, Nb, Ta, Mo and W in the Western North Pacific Ocean. Journal of Oceanography, 64. pp. 247-257. ISSN 1573-868X

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Abstract

Dissolved and labile particulate Zr, Hf, Nb, Ta, Mo and W were determined at stations K1 (51°N, 165°E), K2 (47°N, 160°E), KNOT (44°N, 155°E) and 35N (35°N, 160°E) in the western North Pacific Ocean. A portion of seawater for dissolved species (D) was passed through a 0.2 μm Nuclepore filter and acidified to pH 2.2 with HCl and HF. A portion of seawater for acid-dissolvable species (AD) was acidified without filtration. Labile particulate (LP) species is defined as AD minus D, which represents a chemically labile fraction of particulate species. D-Zr, Hf and Ta increase with depth, Nb shows a slight depletion in surface water, whereas Mo and W have a conservative vertical profile. The concentration range of D-Zr, Hf, Nb, Ta and W is 31–275, 0.14–0.95, 4.0–7.2, 0.08–0.29 and 40–51 pmol/kg, respectively, whereas that of Mo is 97–105 nmol/kg. LP-species of Zr, Hf and Ta account for 10–14% of AD in average and increase up to 25 % below 4000 m, whereas those for Mo and W are negligible. In contrast, LP-Nb shows maxima (up to 27%) in surface water. We also found that DZr/Hf, Nb/Ta and Mo/W mole ratios generally increase in the order continental crust < river water < coastal sea < open ocean.

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