Zinc (Zn)

Atomic number:	30
Atomic weight:	65.39
Average concentration in ocean:	5.4 nmol/kg
Residence time:	51,000 yrs

Distribution in ocean
Bruland (1980) found dissolved Zn to have a nutrient like vertical profile in the ocean with low concentrations at the surface and a mid-depth maximum (data). The Zn concentrations are highly correlated with Si concentrations throughout the world ocean.

Speciation
Zinc is found in the +2 oxidation state as Zn²⁺ ion. Electrochemical titrations of Zn in seawater demonstrate that 99% of the dissolved Zn is bound to organic ligands (Bruland, 1989). In the open ocean, most Zn is present in the dissolved phase.

Residence time
The residence time was calculated from the average ocean concentration shown above (from Nozaki) and the average river concentration reported by Shiller and Boyle (1985). Note that they find the average river concentration to be some two orders of magnitude lower than previous estimates. Hence this residence time is much greater than previous estimates.

Analysis
Dissolved Zn is typically measured by an organic extraction to preconcentrate metals and separate them from the seasalt matrix, followed by graphite furnace atomic absorption spectrophotometry to quantify the Zn in the preconcentrated solution. It can also be measured by flow injection analysis with fluorescence detection (see Nowicki et al., 1992)

References