The Input Panel

aqion main input panel

Program Start

Just after program start, aqion opens with the main input panel for chemical data – as shown on the right.

There are two possibilities to enter an aqueous solution:

In the following we describe the first option.

Input Data

The input window enable you to enter the following parameters (from top to bottom):1

Filename.  The default filename of the empty input panel is “new”. You can change this name before you save the input solution. Example: water_A3 will be saved as file water_A3.sol (in the user directory aqion/INP)23

pH and T [°C].  pH value (default: 7.0) and water temperature (default: 25).

mol.  This checkbox switches the concentration units from mg/L to mmol/L (and vice versa); it acts for all elements at once. (Also, you can change the concentration unit for each element separately by clicking on the light gray drop-down list next to the respective element.) Fields with molar units are highlighted in pale yellow.

Minerals.  This checkbox opens the mineral table to enter:

These data are stored together with the element concentrations in the same input-water file.

Element Concentrations.  The major elements are arranged in two columns:

The light gray drop-down list on the right side of each element selects the concentration unit: g/L, mg/L, µg/L, mol/L, mmol/L or µmol/L.

DIC – Dissolved Inorganic Carbon.  DIC plays a key role in hydrochemistry and natural waters at all. It is a (non-trivial) topic of its own and will be discussed here.

Fe(2) / Fe(3).  Iron forms compounds and species in the +2 (ferrous) and +3 (ferric) oxidation states. You can enter the iron concentrations in two ways:

Given Fe_total, aqion converts the total concentration into Fe(2) and Fe(3) in accordance with the redox potential.

More Elements.  This checkbox opens a panel with additional elements:

Redox Potential.  This checkbox enables the input of the redox potential:

Once this option is checked the aqueous system is forced to attain the chosen redox potential or pe value by exchange of O2 (“Open System”).

In most cases, it is not necessary to specify the redox potential explicitly. The calculations are then performed at the state of redox equilibrium (or at 240 mV, i.e. pe value 4, as default). In any case, you’ll find the information about pe or Eh for every reaction step in the output tables.

Comments.  Optionally, comments can be entered in two lines; they are then stored together with the data.

Evaluation Temperature.  The evaluation temperature can be entered when the corresponding checkbox is checked. This optional parameter is used in calculations of calcite saturation only.4 If no evaluation temperature is entered the program uses the water temperature from the input field above.

Top Menu Bar






Bottom Menu Bar

Open Opens the standard dialog to select an existing solution (input water) which are stored in directory INP. Alt-O
Save Saves the input water (by storing the data file in directory INP). Note: Saving is not required to run the hydrochemical calculations. Alt-V
H2O Clears the entire panel. The empty window represents pure water with pH 7 and 25.1 Alt-H
Mix Mixing of two waters. Alt-M
Reac Opens the reaction panel to add chemicals (acids, bases, salts) and/or to perform titration calculations.6 Alt-R
Start Starts the hydrochemical calculations (chemical equilibrium and speciation, charge balance, calcite saturation etc.)6 Alt-S
End Closes the program.  

Remarks / Footnotes

  1. The “empty” template represents the simplest of all aqueous solutions: pure water (H2O) with pH 7 at 25. This is often the starting point for pH calculations of acids, bases and salts with the reaction module (via button Reac).  2

  2. All input solutions of aqion have the file extension sol

  3. The input solutions can be used in PhreeqC as input files as well (the syntax is the same). 

  4. For example: The water sample has 20, but we are interested in the calcite saturation parameters at the evaluation temperature 60

  5. only for aqion PRO 

  6. Start vs. Reac – see here  2

[last modified: 2020-12-30]