Dear Dr. Parkhurst: I am Li Yang, a graduate student in the department of Geological Sciences at the University of Alabama.I and My advisor, Dr, Donahoe, are currently working on a project studying the leachability and sequestering mechanisms of heavy metals from power plant ash disposal facilities. We use your geochemical modeling code PHREEQC to set up some simulations for pore water speciation calculation according to our analytical data. In the model output, we get a list of minerals and their saturation indexes (S.I) with respect to the given pore water solution. What puzzles us is that for a series of pore water of very similar chemical composition collected at different depth, we get different list of minerals for each pore water. In the user's manual, it is said that all minerals with their saturation indexes appropriate for the given solution will be listed in the output file. We are interested in what caused such a difference in the simulation output results. How does the program search the database to choose the minerals to be listed for a given solution? Is there a criteria that the program will follow to calculate the S.I of this mineral over another for a given solution? Thanks for your time! We are looking forward to your reply! Li Yang Li Yang Department of Geological Sciences University of Alabama Tel:(205)348-9293 E-mail:yang003@xxxxxxxxxxx
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