Output Table: Water Composition


aqion displays the results of the hydrochemical calculations in different ways. One example is shown in the right screenshot. In this table three aqueous solutions are shown and compared:1

  • the input water (raw data)
  • the solution in chemical equilibrium (and after charge-balance adjustment)
  • the same like in Output 1, but with mineral-water interaction

The values in the last two columns differ only if mineral phases precipitate and/or dissolve. [In this example, Fe precipitates as amorphous Ferrihydrite, Fe(OH)3; hence, in the last column the Fe concentration, which remains in the solution, decreases significantly.2]

Physico-Chemical Parameters

The table shown above contains the following physico-chemical parameters (rows from top to bottom):

pH pH value of the solution
pe pe value of the solution
Eh redox potential in mV (related to standard hydrogen electrode)
T temperature of the solution in °C
Ionic strength ionic strength in mmol/L
TDS total dissolved solids in mg/L
EC electrical conductivity in µS/cm (at sampling temperature)3

In addition, the temperature-compensated value EC25 is displayed when the checkbox mol is activated.

Alkalinity total alkalinity (M alkalinity) in meq/L or ppm CaCO34
TH total hardness in meq/L or ppm CaCO35
CH carbonate hardness or temporary hardness in meq/L or ppm CaCO34
C.B.E. charge-balance error (CBE) in percent6

Element Concentrations – The lower section of the table lists the total element concentrations in mg/L (or in mmol/L if the upper checkbox mol is activated).

Upper Menu Bar

mol checkbox to switch between concentration units mg/L and mmol/L
digits specifies the number of digits after the decimal point
Ions opens a table of all ions and aqueous complexes (complete speciation)7
Minerals opens a table of the precipitated or dissolved mineral phases (if any) and the saturation indices
Export writes the table(s) into text files (for Excel or other programs)
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Lower Menu Bar

Save Out 1 stores the calculated solution shown in column ‘Output 1’8
Save Out 2 stores the calculated solution shown in column ‘Output 2’8
Last line jumps to the last table row (relevant only for large tables)
« back returns to the main window
next » displays all relevant data of the carbonate system (buffer capacities, alkalinity, CO2 partial pressure) and of the calcite-carbonate system (SI, LSI)


  1. The idea behind Output 1 and Output 2 is explained here.

  2. A more interesting example of mineral precipitation is given here.

  3. The program provides three calculation methods for EC, which can be selected in Settings in the upper menu bar of the main window.

  4. In order to switch between units “meq/L” and “ppm CaCO3” click on checkbox mol above. 2

  5. Also named “general hardness” GH (reminiscent of the German “Gesamthärte” = total hardness).

  6. The CBE is non-zero only in the first column (input water); after charge-balance adjustment CBE becomes zero – see the last two columns.

  7. Another example for aqueous speciation is presented here.

  8. The calculated solutions in Output 1 and Output 2 can be saved for successive combination of reaction processes. This, however, is only allowed in aqion PRO. 2

[last modified: 2016-05-28]