Nickel (Ni)

Atomic number: 28
Atomic weight: 58.6934
Average concentration in ocean: 8.2 nmol/kg
Residence time: 6,000 years

Distribution in ocean
Ni has a nutrient like vertical profile with low concentrations at the surface and values increasing with depth (data).

Speciation
Nickel exists in seawater in the +II oxidation state as Ni2+.

Residence time
The nickel residence time was calculated from the accumulation rate in sediments (Sclater et al., 1976).

Analysis
Nickel has been determined by complexing the metal with an insoluble organic ligand and extracting the complex into an organic phase, followed by graphite furnace atomic absorption spectrometry. 

References