Selection of the Program Software

Practically all hydrogeochemical programs include their own bases of thermodynamical parameters represented in certain format. Parameter sets and list of components in them are rather individual, although many of them may be substituted for one another as they are based mostly on the same sources. 

Databases contain information on properties of components participating in hydrochemical processes, and constants, which do not change in the 

Components on the list are usually separated into basis and secondary. Often are included 30-80 or more basis polar, gas and nonpolar organic components of solutions plus a collection of minerals, from which the user may select necessary for the description of composition for all compounds of water, gas and minerals in the study object. Data for the components and minerals include their major properties charge, ionic radius, molecular mass, elemental composition, etc. If an element, for instance strontium (Sr +), is not included among the basis compounds, the program cannot compute the content of its migration forms or minerals even if strontium is present among the initial data. 

The list of secondary components and minerals is usually accompanied by formulae of their formation reactions from basis components and appropriate equihbrium constants. The list includes stoichiometry of secondary compounds from the position of basis ones and also their stability constants. Besides, all minerals and gases included in the program must be associated with basis compounds by the appropriate reaction and its equilibrium constant. With inclusion of mass transfer kinetics are needed reaction velocities order and constants. 

Databases are not introduced in the computation program but accompany it in an individual file, which allows changing or amending their content without any damage to the modeling process itself. The reason for this is that not even one of these databases is complete and absolutely reliable. Their content reflects the state of knowledge of their parameters as of the moment of program software development. For this reason critical evaluation of the completeness and databank content reliability is necessary. The user has the opportunity to renew or amend it. 

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