| Atomic number: | 24 |
| Atomic weight: | 51.996 |
| Average concentration in ocean: | 4.0 nmol/kg |
| Residence time: | 8000 years |
Distribution in ocean
Chromium is slightly depleted at the surface and the vertical concentration
profile increases with
depth (data).
Speciation
Chromium exists in seawater primarily in the +VI oxidation state as the
chromate, CrO42-, ion. Detectable amounts of
chromium in the +III oxidation state are also present as Cr(OH)2+
and Cr(OH)30.
Residence time
The chromium residence time is from Tracers in the Sea (Broecker, W. S. and Peng,
T.-H., 1982. Eldigo Press, Palisades, NY). It was calculated from
the global average river input.
Analysis
Chromium is concentrated by coprecipitation with iron hydroxide and then
determined by graphite furnace atomic absorption spectrophotometry or by isotope
dilution mass spectrometry.