PHREEQC Manual

Program http //wwwbrr.cr.usgs.gov/projects/GWC coupled/phreeqc/index.html Windows surface http //www.geo.vu.nl/users/posv/phreeqc.html PHREEQC Manual ftn //brrcrftr).cr.usgs.gov/geochem/unix/phreeqc/nianual.pdf (pdf format (Adobe Acrobat Reader), size 1.1MB)... 

To model balanced reactions, kinetics or reactive transports, more keywords besides TITLE, SOLUTION and END are needed, which will be listed in the following. Furthermore, the individual input parameters are described in detail in the PHREEQC manual. 

A detailed description of the solutions for these examples can be found in the PHREEQC manual (Parkhurst Appelo 1999). In addition, the following exercises for equilibrium reactions (chapter 3.1), kinetics (chapter 3.2) and transport (chapter 3.3) will help the user to become familiar with the possibilities and limitations of the program. The solutions of all exercises are explained in detail in chapter 4. 

One can also use phreeqc to perform inverse mass balance modeling for the same calculations, phreeqc is capable of taking into account the analytical uncertainties. Here, we assume the analyses of snow and groundwater samples carry 6% errors. The input file is listed in Table 9.3. The readers are referred to the phreeqc manual for a detailed explanation of the input file (Parkhurst and Appelo, 1999). 

The question How much gypsum can be dissolved in distilled water shall be answered by manual calculation and then by means of PHREEQC for comparison [pK gypsum = 4.602 (at T = 20 °C)]. 

To avoid looking for the predominant species in 377 output jobs manually after modeling, two means are offered At first, a SELECTEDOUTPUT (see also chapter 2.2.1.4) has to be defined in the PHREEQC master input file. Besides pE and pH, it will output all species of interest, for example all Fe species, in a. csv file. These species have to be specified explicitly under the sub key word molalities , e.g. Fe2+, Fe3+, FeOH+, etc. The BASIC-reproduction program inserts the 377 SOLUTION jobs before the key word SELECTED OUTPUT. Since the SOLUTIONS are not separated by an END, a SELECTED OUTPUT will be created out of all SOLUTIONS displaying for each of the 377 jobs a row with the columns pH, pE, m Fe2+ (concentration of Fe2+ in mol/L), m Fe3+, m FeOH+, etc. 

To open and to view this csv file use GRID in PHREEQC. The species with the highest concentration (predominant species) have to be determined for each row (i.e. for each pE-pH combination). To avoid doing this manually, the data have to be copied into EXCEL and to be treated with a macro, which can also be found on the CD enclosed in this book. The macro can be activated by opening the Excel file macro.xls from the book s CD and by clicking on activate macros . Now, one can either copy data instead of the given test data into table 1 or open the. csv file directly in Excel. The activated macro is available for all open Excel files. The macro itself can be opened under menu Extras / Macro / Macros under the name... 

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