Calcium (Ca)
| Atomic number: |
20 |
| Atomic weight: |
40.078 |
| Average concentration in ocean: |
10.27 mmol/kg |
| Residence time: |
1,100,000 years |
Distribution in ocean
Calcium is the fifth most abundant element in seawater with a nearly
conservative distribution.
High precision measurements made by Horibe et al. (1974) demonstrated a slight
surface depletion in the Pacific that is produced by uptake of calcium and
incorporation into CaCO3 shells that sink from the surface layer. More
recently, high precision measurements of calcium by isotope dilution mass
spectrometry (de Villiers, 1998) have also suggested a maximum concentration
near 2500 m depth, coincident with the depth of the mid-ocean ridge crest
(data). These results
suggest a calcium source from low temperature hydrothermal sources.
Speciation
Calcium is present in seawater as the Ca2+ ion.
Residence time
The calcium 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
Calcium can be determined by a titration with EDTA or by isotope
dilution mass spectrometry.
References