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GEOCHEMICAL MODELLING

Objective

TO DEVELOP A VERSTILE AND USERFRIENDLY PROGRAM-PACKAGE FOR GEOCHEMICAL MODELLING. THE PROGRAMS ARE INTENDED FOR PC'S AND SHOULD HAVE A WIDE APPLICABILITY AND TAKE ADVANTAGE OF NEW AND RECENT INSIGHT IN FUNDAMENTAL PROCESSES.
JENSEN is a program for the computation of chemical equilibria in aqueous systems. The structure, function and use of the computer program intended for personal computers (PCs) is described.

The program, which is written in Turbo Pascal, version 4, is fundamentally similar to most other geochemical programs, but combines in 1 program several of the merits these programs have. The intention has been to make an advanced program, which also should be user friendly and fast, and to attain this several new algorithms have been developed and implemented.

The program has a built in database mainly based on the CHEMVAL compilation containing data for 395 soluble species and 149 minerals. The program can find equilibria in the presence of all or some of these soluble species, under conditions of fixed or floating pH and/or pE. In the present version the program can identify which minerals and how much of them there will be formed when equilibrium is established. The program by itself eliminates a bad guess of a candidate for precipitation. Iteration limits and parameters can be changed during a computation, so the program is capable of solving almost any equilibrium problem encountered. To help in these processes the JENSEN program displays several menus, which guide the user to a successful path.

LITTLE JOE is an expert system to support geochemical modelling. The construction of a minor expert system for use in the evaluation of analytical data for the composition of ground waters from limestone formation is described. Although the example given is rather limited in scope, the application of the expert system for the evaluation of the analytical data clearly demonstrates the mature expert knowledge embedded in the system which is contrasted with the uncritical acceptance of analytical or theoretical data.

With the overall neglect of ion exchange and the formation of solid solutions in geochemical calculations, geochemistry is probably not yet advanced to the stage where the development of larger expert systems can be recommended.
1. TO TRANSLATE THE EARLIER WHATIF-PROGRAMS INTO PASCAL. THE PC VERSION TURBO PASCAL 4.0 HAS BEEN FOUND CONVENIENT.
1.1. SIMULTANEOUSLY THE LIMITATIONS OF THE EARLIER VERSION ARE REMOVED TO SECURE THE VERSATILITY AND INCREASED SCOPE FOR APPLICATIONS.
1.2. ALGORITHMS FOR THE CALCULATIONS ON PHENOMENA LIKE MULTIELEMENT ION-EXCHANGE AND COPRECIPITATIONS ARE CONSTRUCTED AND ADDED TO THE MAIN PROGRAM.
2.2. EXPERIMENTAL WORK ON ADSORPTION PHENOMENA ON CALCITE ARE UNDERTAKEN. THE FORMATION OF SOLID SOLUTIONS "IN" SURFACE LAYER IS CONSIDERED A POSSIBILITY.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

RISOE NATIONAL LABORATORY
Address
Frederiksborgvej 399
Roskilde
Denmark