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| Titel |
A step-by-step procedure for pH model construction in aquatic systems |
| VerfasserIn |
A. F. Hofmann, F. J. R. Meysman, K. Soetaert, J. J. Middelburg |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 5, no. 1 ; Nr. 5, no. 1 (2008-02-21), S.227-251 |
| Datensatznummer |
250002239
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| Publikation (Nr.) |
 copernicus.org/bg-5-227-2008.pdf |
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| Zusammenfassung |
| We present, by means of a simple example, a comprehensive
step-by-step procedure to consistently derive a pH model of aquatic systems.
As pH modelling is inherently complex, we make every step of the model
generation process explicit, thus ensuring conceptual, mathematical, and
chemical correctness. Summed quantities, such as total inorganic carbon and
total alkalinity, and the influences of modeled processes on them are
consistently derived. The different time scales of processes involved in the pH problem
(biological and physical reactions: days; aquatic chemical reactions: fractions of seconds)
give rise to a stiff equation system. Subsequent reformulations of the system reduce
its stiffness, accepting higher non-linear algebraic complexity.
The model is reformulated until numerically and computationally simple dynamical solutions,
like a variation of the operator splitting approach (OSA) and the direct substitution approach
(DSA), are obtained. As several solution methods are pointed out, connections
between previous pH modelling approaches are established. The final
reformulation of the system according to the DSA allows for quantification of
the influences of kinetic processes on the rate of change of proton
concentration in models containing multiple biogeochemical processes. These
influences are calculated including the effect of re-equilibration of the
system due to a set of acid-base reactions in local equilibrium. This
possibility of quantifying influences of modeled processes on the pH makes
the end-product of the described model generation procedure a powerful tool
for understanding the internal pH dynamics of aquatic systems. |
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