salinity and composition of seawater

see also: [GRAPH]

 
 

Constituents

 Abundance of Constituents / (g/kg of seawater) 
S = 30 S = 35 S = 40
Cl -
16. 58
19. 33
22. 36
Na+
9. 03
10. 53
12. 13
NaSO4-
0. 98
1. 25
1. 60
Mg2+
0. 974
1. 139
1. 323
SO42-
0. 97
1. 06
1. 14
MgSO4
0. 582
0. 655
0. 717
K +
0. 338
0. 394
0. 455
CaSO4
0. 135
0. 152
0. 166
HCO3-
0. 078
0. 085
0. 059
Br -
0. 057
0. 067
0. 078
Ca2+
0. 051
0. 056
0. 060
MgHCO3+
0. 023
0. 030
0. 037
H3BO3
0. 019
0. 022
0. 025
KSO4-
0. 013
0. 016
0. 020
NaHCO3
0. 012
0. 016
0. 020
Sr2+
0. 007
0. 008
0. 009
F -
0. 001

The physical properties of seawater vary with the concentration of the dissolved constituents. A convenient parameter for describing the composition of seawater is the salinity, S, which is defined in terms of the electrical conductivity of the seawater sample:

where K is the ratio of the conductivity of the seawater sample at 15oC and normal atmospheric pressure to the conductivity of a potassium chloride solution in which the mass fraction of KCl is 0.0324356, at the same temperature and pressure, and the values of the coefficients are:

Thus when K=1, S=35 exactly. Here we see the practical side of the above salinity definition: the value of S is roughly equal with the mass of dissolved compounds, expressed in grams per kilogram of seawater, while the definition in terms of electrical conductivity allows meaningful measurements. Salinity values in the open oceans at mid latitudes typically fall between 34 and 36.
 
 

Source: CRC Handbook of Chemistry and Physics (D.R. Lide, Editor-in-Chief), 83rd edition (2002-2003), CRC Press, Boca Raton, FL, 2002, p.14-15,16.  [N10]

 
 
UPDATED : 2004-12-04 WEBSITE  EDITOR : Krešimir J. Adamić