101
Minor Elements in Seawater
of R is used as a measure of the undersaturation of a given element. One would expect
the elements with small values of R to have the longest residence times. Although this is
generally true, many reactive elements have a short residence time and concentration well
below the saturation limits. These results mean that factors other than solubility control
the reactivity of most elements in the oceans.
log τ obs
2
3
4
5
6
7
8
log τ
calc
2
3
4
5
6
7
8
Mg
Rb
Li
Co
Sr
Hg
Cs
Ni V
Ti
Zn
Pb
Mn
Al
Fe
Figure 3.4
Calculated and observed residence times.
Table 3.7
Comparison of Ratio of Saturated Concentration
to Measured Values and Residence Times
Metal
Insoluble Compound
R a
Years
Pb 2+
PbCO 3
10,000–20,000
2,000
Ni 2+
Ni(OH) 2
10,000–225,000
18,000
Co 2+
CoCO 3
50,000–400,000
18,000
Cu 2+
CuCO 3
133–266
50,000
Ba 2+
BaSO 4
3.7
84,000
Zn 2+
ZnCO 3
120–250
180,000
Cd 2+
CdOHCl
40,000–10,000,000
500,000
Ca 2+
CaCO 3
0.25–1.2
8,000,000
Sr 2+
SrCO 3
2.75
190,000,000
Mg 2+
MgCO 3
27
450,000,000
a Measure of degree of undersaturation. R, saturation concentration/
measured concentration.