Hafnium (Hf)

Atomic number: 72
Atomic weight: 178.49
Average concentration in ocean: 710 fmol/kg
Residence time: 1300 years

Distribution in ocean
Hafnium has a modified, nutrient-like vertical concentration profile that increases continuously with depth, similar to copper.  There is an interesting offset between the Atlantic and Pacific data that is unusual for a nutrient-like element (data).

Speciation
Hafnium is present in seawater in the +IV oxidation state as the Hf(OH)5- ion.

Residence time
The hafnium residence time is from Sohrin et al. (1998).   It was calculated from the global average river input.

Analysis
Hafnium is determined by inductively coupled plasma mass spectrometry after preconcentration.

References