Effect of Salinity on Seawater

In this section are presented in numerical form the results for numerical similations, on seawater . In each of them only a single parameter is varied (in this case salinity) and the effect of this on the various parameters of seawater is presented in numerical form.

Seawater composition use in all of the simulations is the following:

'**************************************************************
' DOE 1994 Standard mean composition of seawater with borates *
'**************************************************************
[Cl-]  = 0.54586 * S/35  mol/kg(solution)
[Na+]  = 0.46906 * S/35  mol/kg(solution)
[Mg2+] = 0.05282 * S/35  mol/kg(solution)
[Ca2+] = 0.01028 * S/35  mol/kg(solution)
[SO4--]= 0.02824 * S/35  mol/kg(solution)
[K+]   = 0.01021 * S/35  mol/kg(solution)
[Br-]  = 0.00084 * S/35  mol/kg(solution)
[Sr2+] = 0.00009 * S/35  mol/kg(solution)
[F-]   = 0.00007 * S/35  mol/kg(solution)
[Btot] = 0.00042 * S/35  B(OH)3 + B(OH)4- mol/kg(solution)

where S is the salinity in g/(kg-soln).  The standard seawater composition as listed may be supersaturated in respect to calcite or aragonite formation. Calcite is the less soluble form of calcium carbonate, so theoretically should precipitate as first. Coral reef is however constituted by aragonite, a fact that shoul be considered.

The terms 'sat. C' and 'sat. A' in the two colums at the right, refer to the oversaturation of the solution, defined as the ratio between the concentrations product [Ca++] [CO3--] and the solubility product. If greater then 1 , the corresponding form of CaCO3 should start to precipitate. In some of the simulations the precipitation of CaCO3 is simulated to a certain extent (e.g. 10%) or to completion (100%).


Reactions considered in the simulation below are as follows:

H2O <==> H+ + OH- ' pH = pHT
CO2 + H2O <==> H2CO3
H2CO3 <==> H+ + HCO3-
HCO3- <==> H+ + CO3-->
B(OH)3 + H2O <==> H+ + B(OH)4-
HSO4- <==> H+ + SO4--
HF <==> H+ + F-
Ca++ + OH- <==> CaOH+
Mg++ + OH- <==> MgOH+
 

Variable : Salinity (S) from 32 to 37.8 g/(kg-soln)

Constants  : CO2 concentration = 410 ppm ; P = 1 atm; temperature = 17 C

C(Tot) = [H2CO3] + [HCO3-] + [CO3--]

Tc = 17           ' temperature in Celsius (C)
ppmCO2 = 410      ' parts per million (in volume) of CO2 in the atmosphere
P = 0             ' pressure in atm. P=0 means ambient pressure, 1 atm.
S = 30 to 40 step 0.5            ' salinity, in grams of salts in 1 kg of solution
pptF = 0          ' fraction of CaCO3 which actually precipitates 
Cl  = 0.54586     ' Cl-   Mol/kg(solution)
Na  = 0.46906     ' Na+   Mol/kg(solution)
Mg  = 0.05282     ' Mg++  Mol/kg(solution)
Ca  = 0.01028     ' Ca++  Mol/kg(solution)
SO4 = 0.02824     ' SO4-- Mol/kg(solution)
K   = 0.01021     ' K+    Mol/kg(solution)
Br  = 0.00084     ' Br-   Mol/kg(solution)
Sr  = 0.00009     ' Sr++  Mol/kg(solution)
F   = 0.00007     ' F-    Mol/kg(solution)
B   = 0.00042     ' B(OH)3 + B(OH)4- Mol/kg(solution)
save .csv file = 0' (0=no  1 = yes)
---------------------------------------------------------------------------------------------------------------------------------
 *** CO2 SOLUBILITY EQUILIBRIA IN SEAWATER AND CaCO3 FORMATION ***
 Concentrations [..] are in mmol/kg              DIC = [H2CO3] + [HCO3-] + [CO3--]
 Cout>0 means CO2 is outgassed from SeaWater to Atmosphere, the opposite if Cout<0
 +----+------+-----+----+----+------+------+-------+-------+-------+-----+------+-------+------+-------+------+-----+-----+-----+
 |(C)|ppmCO2| pptF|  P |  S |   pH |  pOH |[H2CO3]|[HCO3-]|[CO3--]| DIC |[Ca++]|[CaOH+]|[Mg++]|[MgOH+]| Cout |CaCO3|sat.C|sat.A|
 +----+------+-----+----+----+------+------+-------+-------+-------+-----+------+-------+------+-------+------+-----+-----+-----+
 | 17 |  410 |0.000|   0|30.0| 8.064| 5.514|  0.015|  1.681|0.13097|1.827| 8.811| 0.0005|45.222| 0.0526| 0.000|0.000|  3.2|  2.1|
 | 17 |  410 |0.000|   0|30.5| 8.068| 5.505|  0.015|  1.702|0.13568|1.853| 8.958| 0.0006|45.974| 0.0545|-0.026|0.000|  3.3|  2.1|
 | 17 |  410 |0.000|   0|31.0| 8.073| 5.496|  0.015|  1.723|0.14046|1.878| 9.105| 0.0006|46.727| 0.0565|-0.051|0.000|  3.4|  2.2|
 | 17 |  410 |0.000|   0|31.5| 8.078| 5.487|  0.015|  1.744|0.14532|1.904| 9.251| 0.0006|47.479| 0.0586|-0.077|0.000|  3.5|  2.3|
 | 17 |  410 |0.000|   0|32.0| 8.083| 5.478|  0.015|  1.764|0.15026|1.929| 9.398| 0.0006|48.232| 0.0606|-0.102|0.000|  3.7|  2.3|
 | 17 |  410 |0.000|   0|32.5| 8.088| 5.470|  0.015|  1.784|0.15528|1.954| 9.545| 0.0006|48.984| 0.0627|-0.127|0.000|  3.8|  2.4|
 | 17 |  410 |0.000|   0|33.0| 8.092| 5.461|  0.015|  1.804|0.16037|1.979| 9.692| 0.0007|49.737| 0.0649|-0.152|0.000|  3.9|  2.5|
 | 17 |  410 |0.000|   0|33.5| 8.097| 5.453|  0.015|  1.824|0.16554|2.004| 9.839| 0.0007|50.489| 0.0671|-0.177|0.000|  4.0|  2.6|
 | 17 |  410 |0.000|   0|34.0| 8.101| 5.445|  0.014|  1.843|0.17078|2.029| 9.986| 0.0007|51.242| 0.0693|-0.201|0.000|  4.1|  2.6|
 | 17 |  410 |0.000|   0|34.5| 8.106| 5.437|  0.014|  1.863|0.17610|2.053|10.132| 0.0007|51.994| 0.0716|-0.226|0.000|  4.2|  2.7|
 | 17 |  410 |0.000|   0|35.0| 8.110| 5.429|  0.014|  1.882|0.18148|2.077|10.279| 0.0008|52.746| 0.0739|-0.250|0.000|  4.3|  2.8|
 | 17 |  410 |0.000|   0|35.5| 8.114| 5.421|  0.014|  1.900|0.18694|2.102|10.426| 0.0008|53.498| 0.0763|-0.274|0.000|  4.4|  2.9|
 | 17 |  410 |0.000|   0|36.0| 8.119| 5.414|  0.014|  1.919|0.19247|2.126|10.573| 0.0008|54.250| 0.0787|-0.299|0.000|  4.6|  2.9|
 | 17 |  410 |0.000|   0|36.5| 8.123| 5.406|  0.014|  1.937|0.19806|2.150|10.720| 0.0008|55.003| 0.0812|-0.323|0.000|  4.7|  3.0|
 | 17 |  410 |0.000|   0|37.0| 8.127| 5.398|  0.014|  1.956|0.20373|2.174|10.867| 0.0009|55.755| 0.0837|-0.346|0.000|  4.8|  3.1|
 | 17 |  410 |0.000|   0|37.5| 8.131| 5.391|  0.014|  1.974|0.20946|2.197|11.013| 0.0009|56.507| 0.0862|-0.370|0.000|  4.9|  3.2|
 | 17 |  410 |0.000|   0|38.0| 8.135| 5.384|  0.014|  1.991|0.21525|2.221|11.160| 0.0009|57.259| 0.0888|-0.393|0.000|  5.0|  3.2|
 | 17 |  410 |0.000|   0|38.5| 8.139| 5.376|  0.014|  2.009|0.22111|2.244|11.307| 0.0009|58.011| 0.0915|-0.417|0.000|  5.1|  3.3|
 | 17 |  410 |0.000|   0|39.0| 8.143| 5.369|  0.014|  2.026|0.22704|2.267|11.454| 0.0010|58.762| 0.0942|-0.440|0.000|  5.3|  3.4|
 | 17 |  410 |0.000|   0|39.5| 8.147| 5.362|  0.014|  2.043|0.23303|2.290|11.601| 0.0010|59.514| 0.0970|-0.463|0.000|  5.4|  3.5|
 | 17 |  410 |0.000|   0|40.0| 8.151| 5.355|  0.014|  2.060|0.23907|2.313|11.748| 0.0010|60.266| 0.0998|-0.486|0.000|  5.5|  3.6|
 +----+------+-----+----+----+------+------+-------+-------+-------+-----+------+-------+------+-------+------+-----+-----+-----+
---> END OF PROGRAM !          e-mail and info --> mazzad50@gmail.com