67
Composition of the Major Components of Seawater
the value for Mg 2+ was taken from the work of Carpenter and Manella (1973); the values
for SO 4
2– and Br – were taken from the work of Morris and Riley (1966); the value for F –
was taken from that of Warner (1971); the value of Cl – was determined from the chloride
equivalent by subtracting the equivalent Br – ; and the value of Na + was determined by
difference (i.e., by assuming the cation and anion equivalents were equal). The results for
HCO 3
– , CO 3
2– , B(OH) 3 , and B(OH) 4
– were determined for sea water of pCO 2 = 370 μatm using
B/ Cl(‰) of 0.000232 (Uppström, 1974) and TA = 2296 μmol/ kg (Millero et al., 1993). The
dissociation constants of carbonic and boric acids were, respectively, taken from the work
of Millero et al. (2006) and Millero (2002) and Dickson (1990) using the CO2sys Program
(Pierrot et al., 2006).
It should be pointed out that this is the reference composition of sea water. The composition of sea water in the future will change due to the increasing concentration of CO 2 from
the burning of fossil fuels. The concentration of CO 2 and HCO 3
– will increase, and the
concentration of B(OH) 4
– will decrease.
The composition of sea water in Table 2.3 can be used to develop equations that can estimate the values of molality, equivalents and ionals for the components of sea water as a
function of practical salinity, as well as for sea water. The individual values of the molality
and the like of the components (Ai) can be determined from equations for the values as a
function of S P :
m(ion) = m i (S P /35)
(2.19)
e(ion) = m i (S P /35)
(2.20)
I(ion) = m i (S P /35)
(2.21)
Table 2.3
Composition of Reference Seawater (S P = 35.000, pCO 2 = 337 μatm, and t = 25°C)
g i (g/ kg)
AW
m i
(mol/ kg- H 2 O)
e i
(mol/ kg- H 2 O)
I i
(mol/ kg- H 2 O)
Na +
10.78145
22.9898
0.4860573
0.4860573
0.4860573
Mg 2+
1.28372
24.3050
0.0547419
0.1094837
0.2189674
Ca 2+
0.41208
40.0780
0.0106566
0.0213133
0.0426266
K +
0.3991
39.0983
0.0105796
0.0105796
0.0105796
Sr 2+
0.00795
87.6200
0.0000940
0.0001881
0.0003762
Cl –
19.35271
35.4530
0.5657619
0.5657619
0.5657619
SO 4
2–
2.71235
96.0626
0.0292642
0.0585283
0.1170567
HCO 3
–
0.10481
61.0168
0.0017803
0.0017803
0.0017803
Br–
0.06728
79.9040
0.0008727
0.0008727
0.0008727
CO 3
2–
0.01434
60.0089
0.0002477
0.0004953
0.0009907
B(OH) 4
–
0.00795
78.8404
0.0001045
0.0001045
0.0001045
F –
0.0013
18.9984
0.0000709
0.0000709
0.0000709
OH –
0.00014
17.0073
0.0000085
0.0000085
0.0000085
B(OH) 3
0.01944
61.8330
0.0003259
0.0000000
CO 2
0.00042
44.0095
∑ =
35.16504
1.1605659
1.2552445
1.4452533
H 2 O
964.83496
0.580283
0.627622
0.722627
Source: Millero et al. (2008). With permission.
Composition of the Major Components of Seawater
the value for Mg 2+ was taken from the work of Carpenter and Manella (1973); the values
for SO 4
2– and Br – were taken from the work of Morris and Riley (1966); the value for F –
was taken from that of Warner (1971); the value of Cl – was determined from the chloride
equivalent by subtracting the equivalent Br – ; and the value of Na + was determined by
difference (i.e., by assuming the cation and anion equivalents were equal). The results for
HCO 3
– , CO 3
2– , B(OH) 3 , and B(OH) 4
– were determined for sea water of pCO 2 = 370 μatm using
B/ Cl(‰) of 0.000232 (Uppström, 1974) and TA = 2296 μmol/ kg (Millero et al., 1993). The
dissociation constants of carbonic and boric acids were, respectively, taken from the work
of Millero et al. (2006) and Millero (2002) and Dickson (1990) using the CO2sys Program
(Pierrot et al., 2006).
It should be pointed out that this is the reference composition of sea water. The composition of sea water in the future will change due to the increasing concentration of CO 2 from
the burning of fossil fuels. The concentration of CO 2 and HCO 3
– will increase, and the
concentration of B(OH) 4
– will decrease.
The composition of sea water in Table 2.3 can be used to develop equations that can estimate the values of molality, equivalents and ionals for the components of sea water as a
function of practical salinity, as well as for sea water. The individual values of the molality
and the like of the components (Ai) can be determined from equations for the values as a
function of S P :
m(ion) = m i (S P /35)
(2.19)
e(ion) = m i (S P /35)
(2.20)
I(ion) = m i (S P /35)
(2.21)
Table 2.3
Composition of Reference Seawater (S P = 35.000, pCO 2 = 337 μatm, and t = 25°C)
g i (g/ kg)
AW
m i
(mol/ kg- H 2 O)
e i
(mol/ kg- H 2 O)
I i
(mol/ kg- H 2 O)
Na +
10.78145
22.9898
0.4860573
0.4860573
0.4860573
Mg 2+
1.28372
24.3050
0.0547419
0.1094837
0.2189674
Ca 2+
0.41208
40.0780
0.0106566
0.0213133
0.0426266
K +
0.3991
39.0983
0.0105796
0.0105796
0.0105796
Sr 2+
0.00795
87.6200
0.0000940
0.0001881
0.0003762
Cl –
19.35271
35.4530
0.5657619
0.5657619
0.5657619
SO 4
2–
2.71235
96.0626
0.0292642
0.0585283
0.1170567
HCO 3
–
0.10481
61.0168
0.0017803
0.0017803
0.0017803
Br–
0.06728
79.9040
0.0008727
0.0008727
0.0008727
CO 3
2–
0.01434
60.0089
0.0002477
0.0004953
0.0009907
B(OH) 4
–
0.00795
78.8404
0.0001045
0.0001045
0.0001045
F –
0.0013
18.9984
0.0000709
0.0000709
0.0000709
OH –
0.00014
17.0073
0.0000085
0.0000085
0.0000085
B(OH) 3
0.01944
61.8330
0.0003259
0.0000000
CO 2
0.00042
44.0095
∑ =
35.16504
1.1605659
1.2552445
1.4452533
H 2 O
964.83496
0.580283
0.627622
0.722627
Source: Millero et al. (2008). With permission.