Seawater Species Model

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Navigation: Models ➔ Seawater Species Model

Latest SysCAD Version: 31 May 2024 - SysCAD 9.3 Build 139.35544

The Seawater model, is based on thermophysical properties depending on temperature and salinity, which is the mass fraction of a single Brine Species. The brine species may be

  • NaCl(aq): Required Species. You must have both NaCl(aq) present; it can be added from the default database.
  • An accurate chemical representation of standard seawater: Brine1
  • A "synthetic" seawater: Brine2
  • A brine pseudospecies: Brine3

These Brine species are available in the distributed Default DataBase, you should add the appropriate one to your project database.

If none of the brine species are present in the project configuration, then the model will default to using NaCl(aq) as the brine species.

Accurate Brine Representation

Based on the IAPSO Standard Seawater representation [1], we have Brine1 composition in parts per billion.

 Cl    4874839
 Na    4188071
 Mg    471678
 SO4   252152
 Ca    91823
 K     91159
 HCO3  15340
 Br    7520
 BO3H3 2807
 CO3   2134
 BO4H4 900
 Sr    810
 F     610
 CO2   86
 OH    71

we introduce a chemically accurate Seasalt/Brine species Brine1(aq) or (s)

 Mg0.047168 B0.000371 Cl0.487484 Na0.418807 Ca0.009182 F0.000061 C0.001756 O0.106498 S0.025215 
 Br0.000752 H0.002743 K0.009116  Sr0.000081

Note that this is still a single species, having the previous chemical composition.

Synthetic Brine Representation

Brine2 contains only the major components; sodium, potassium, and magnesium, together with chloride and sulphate.

Na0.4189 Cl0.4904 S.0252 O.1008 Mg0.0472 K0.0091

In building models where ongoing chemistry is important, then these representations can be used.

Brine Pseudospeices

Brine3 has no chemical composition; it is effectively a single "element" with the correct molecular weight and can be used when chemistry is unimportant.

Note that the actual thermophysical calculations are the same in all cases. The Salinity of the brine is defined as

Mass of Brine Species/Total mass of liquid. 

and for example, the density is given as a function

[math]\displaystyle{ \rho(T, S) }[/math]


  1. Culkin, F., and P. S. Ridout, J. Atm. Ocean. Technol. 15 1072 (1998)</ref>
  2. The International Association for the Properties of Water and Steam, Berlin Germany. Release on the IAPWS Formulation 2008 for the Thermodynamic Properties of Seawater