The goals of the spreadsheet are:
- Develop a useful tool for characterizing water chemistry;
- Learn the basic relationships between pH, temperature, ionic strength, and redox with mineral phase equilibria;
- Learn the types of calculations used in geochemical reaction models without writing lots of code...
The minimum assignment is to create a spreadsheet that calculates for any input water:
- Ionic strength and charge balance;
- Activity coefficients for the major elements using the Guntelburg approximation;
- Distribution of carbonate species starting with TIC or alkalinity, and pH
- The Eh of the water using the nitrate/ammonia couple.
- The saturation index for:
aragonite, gypsum, calcite, dolomite, and siderite, Fe(OH)3am, amorphous silica and CO2
corrected for ionic strength, Eh, and temperature
Additional elements to include could be:
- Temperature-corrected activity coefficient calculations using the extended Debye-Hukel equation;
- Temperature-corrected carbonate species calculations;
- Incorporation of the CaSO4o neutral complex in the calculation of solubility.
Graduate Students:
- There will be additional species for the graduated students, depending on the final project.
The final assignment is due the last day of class, and consists of a PC-readable disk with your spreadsheet model, hopefully in Excel, but using whatever spreadsheet program you wish. In addition, before each of the Midterm exams, a copy of your spreadsheet must be turned in. The top few lines of the spreadsheet should have your name, any user directions needed to run the model, and the cell addresses for the required output elements listed above. I grade this assignment by inputting an unknown water into your spreadsheet and looking at the output as I change the temperature and pH. Keep in mind that you will be developing your spreadsheet as the semester progresses, and homework assignments will regularly depend on components of your working spreadsheet.