Predict pore water concentrations using other geochem data?

[FClBrI]

Hi all,

Is it possible/what is the best way to predict the pore water concentration of an element, and maybe even the chemical species it would be present as, from other geochemical data that I already have (bulk geochem, mineralogy, and 24-hour water solubility dissolution data of tailings)?

Sorry if this is obvious, I'm a PHREEQC newbie.

Thanks in advance!

[dlparkhurst]

No, not obvious, and actually a difficult question.

You could look at the results of the 24-hour dissolution and try to use INVERSE_MODELING to determine the amounts of minerals that dissolved. This exercise tends to be more difficult than it seems, so I would not spend much time on it if you do try it. Probably the most useful part of the process is that it makes you consider sources and sinks for the elements in your system.

Otherwise, you must rely on the mineralogy and geochemical insights into what minerals (and gases) are likely to react in your system. There is a whole literature on tailings weathering and pit-lake evolution that you can consider.

I don't know what kind of tailings you are studying, but one of the most important reactions is oxidation of pyrite/marcasite, precipitation of iron oxyhdroxides, and creation of acidic water, if carbonates are not present, or dissolution of carbonates if they are present.