“Aqion”的意思、由来-开放百科全书

Aqion is a hydrochemistry software tool. It bridges the gap between scientific software (such like PhreeqC^[1])

and the calculation/handling of "simple" water-related tasks in daily routine practice. The software aqion is free for private users, education and companies.

Motivation & history

First. Most of the hydrochemical software is designed for experts and scientists. In order to flatten the steep learning curve aqion provides an introduction to fundamental water-related topics in form of a "chemical pocket calculator".

Second. The program mediates between two terminological concepts: The calculations are performed in the "scientific realm" of thermodynamics (activities, speciation, log K values, ionic strength, etc.). Then, the output is translated into the "language" of common use: molar and mass concentrations, alkalinity, buffer capacities, water hardness, conductivity and others.

History. Version 1.0 was released in January 2012 (after a half-year test run in 2011). The project is active with 1-2 updates per month.

Features

Fields of application

Limits of application

Basic algorithm & numerical solver

There are two fundamental approaches in hydrochemistry: Law of mass action (LMA) and Gibbs energy minimization (GEM).^[3]

The program aqion belongs to the category LMA approach. In a nutshell: A system of N_B independent basis components j (i.e. primary species), that combines to form N_S secondary species i, is represented by a set of mass-action and mass-balance equations:

where K_i is the equilibrium constant of formation of the secondary species i, and ν_i,j represents the stoichiometric coefficient of basis species j in secondary species i (the values of ν_j,i can be positive or negative). Here, activities a_i are symbolized by curly brackets {i} while concentrations c_i by rectangular brackets [i]. Both quantities are related by the

with γ_i as the activity coefficient calculated by the Debye–Hückel equation and/or Davies equation. Inserting Eq.(1) into Eq.(2) yields a nonlinear polynomial function f_j for the j-th basis species:

To solve Eq.(4) aqion adopts the numerical solver from the open-source software PhreeqC.^[1]^[4]

The equilibrium constants K_i are taken from the thermodynamic database wateq4f.

Examples, test & verification

The software aqion is shipped with a set of example solutions (input waters) and a tutorial how to attack typical water-related problems (online-manual with about 40 examples). More examples and exercises for testing and re-run can be found in classical textbooks of hydrochemistry.^[6]^[7]^[8]

Screenshots

References

1. ^¹Parkhurst, D.L. and C.A.J. Appelo: User's Guide to PHREEQC (version 2), a computer program for speciation, batch-reaction, one-dimensional transport and inverse geochemical calculations. USGS Water-Resources Investigations Report 99-4259, 1999
2. ^Note: The upper limit is sea water.
3. ^http://www.kristall.uni-frankfurt.de/media/handouts/GEM-lecture.PDF{{dead link|date=October 2016 |bot=InternetArchiveBot |fix-attempted=yes }}
4. ^Remark: To keep things apart, the numerical solver of PhreeqC is outsourced from aqion.exe into a separate DLL.
5. ^Ball J. W. and D. K. Nordstrom: WATEQ4F – "User’s manual with revised thermodynamic data base and test cases for calculating speciation of major, trace and redox elements in natural waters", USGS Open-File Report 90-129, 185 p, 1991.
6. ^Stumm, W. and J. J. Morgan: Aquatic Chemistry, Chemical Equilibria and Rates in Natural Waters (3rd ed.), John Wiley & Sons, Inc., New York, 1996, {{ISBN|978-0471511854}}
7. ^Morel, F. M. M. and J. G. Hering: Principles and Applications of Aquatic Chemistry (2nd ed.), John Wiley, New York, 1993, {{ISBN|978-0471548966}}
8. ^Appelo, C. A. J. and D. Postma: Geochemistry, Groundwater, and Pollution. Taylor & Francis, 2005, {{ISBN|978-0415364287}}
9. ^DIN 38404-10: German standard methods for the examination of water, waste water and sludge - Physical and physicochemical parameters (group C) - Determination of calcite saturation of water (C 10)