Seawater Technical Papers

Composition of Ocean Standard Seawater

Composition and most important chemical species of some dissolved elements in sea water.

Produced from data supplied in : Summerhayes, C. P., and Thorpe, S. A., 1996 : Oceanography An Illustrated Guide, Chapter 11, 165-181. 

 

Element
Av.Concentration
Range
Units (per kg)
Lithium
174
(a)
ug
Boron
4.5
(a)
mg
Carbon
27.6
24-30
mg
Nitrogen (b)
420
>1 - 630
ug
Fluorine
1.3
(a)
mg
Sodium
10.77
(a)
g
Magnesium
1.29
(a)
g
Aluminium
540
<10 - 1200
ng
Silicon
2.8
<0.02 - 5
mg
Phosphorus
70
<0.1 - 110
ug
Sulphur
0.904
(a)
g
Chlorine
19.354
(a)
g
Potassium
0.399
(a)
g
Calcium
0.412
(a)
g
Manganese
14
5 - 200
ng
Iron
55
5 - 140
ng
Nickel
0.5
0.1 - 0.7
ug
Copper
0.25
0.03 - 0.4
ug
Zinc
0.4
<0.01 - 0.6
ug
Arsenic
1.7
1.1 - 1.9
ug
Bromine
67
(a)
mg
Rubidium
120
(a)
ug
Strontium
7.9
(a)
mg
Cadmium
80
0.1 - 120
ng
Iodine
50
25 - 65
ug
Caesium
0.29
(a)
ug
Barium
14
4 - 20.0
ug
Mercury
1
0.4 - 2
ng
Lead
2
1 - 35 (c)
ng
Uranium
3.3
(a)
ug


a) Variations are determined entirely or largely by those in salinity, i.e., the element is essentially conservative. For these elements, average concentration given is for sea water of salinity 35.

(b) Concentrations refer to combined nitrogen; element occurs also as dissolved nitrogen (N2) gas. Species other than NO3- are often important in the upper ocean (e.g., NO2-, NH4+).

(c) Concentrations are affected by inputs to surface ocean of atmospherically transported lead from combustion of leaded petroleum.

NOTES

Based mainly upon information in Bruland. Usual ranges for oceanic waters are shown; concentrations of certain elements can be higher in some coastal waters.

Chemical oceanographers often employ molar units instead of the mass units shown here. For sodium (atomic weight 22.99) the concentration given above of 10.77 g/kg can alternatively be expressed as 0.449 mol/kg.

Print this Article

            
              All of our marine instruments and systems, meteorological instruments, calibration standards and rental equipment can also be found in our new product catalogue