Species appear two times in time.out

Hi, I have a problem in reading result file.

Some primary species in <time.out> appear two times; one column with the header of "t_xxx" and the other start with just "xxx" without "t_" ahead.

For example, I have "t_fe+2" column next to the"fe+2" column, and they are a little different (trend is similar).

 t_fe+2       fe+2      
0.2022E-18  0.8529E-03 

I want to know the difference and which Fe+2 is real aqueous ferrous concentration.

Thank you.

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  • Hi Jaeshik,

    The first set of species that are written out as "t_fe+2" are the total concentrations, and the others such as "fe+2" are the actual concentrations of those species. So "fe+2" is the "real aqueous ferrous concentration". So in this case "t_fe+2" would include the concentration of Fe+2 plus other species such as Fe(OH)2, FeOH+, FeCl2, FeS, etc...

    best regards,

    Eric

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  • Oh, thank you Dr. Sonnenthal,

    I got to know the difference clearly now but here is one more question.

    Let's say we sample the groundwater under reducing condition and measure the ferrous ion after filtering particulate (ferric) hydroxides out.

    In this case, what I need to compare with this measured value is it fe+2 or t_fe+2? 

    Again, does the t_fe+2 column contain both aqueous and solid phase fe+2 compounds? (Is FeS you wrote in the above reply is aqueous FeS(aq) that is partitioned from solid FeS(s) mineral?)

    Thank you in advance : )

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  • Hi Jaeshik,

    The total concentrations, such as "t_fe+2" only refer to aqueous species concentrations, not solids. Yes, FeS was meant to be FeS(aq). If you measure the Fe+2 concentration, then what you compare it to depends on the analysis method. If you removed all Fe+3 solids and then measured all dissolved Fe, assuming it is Fe+2, then you would compare it to "t_fe+2". That is likely your case, right? Otherwise, if you  measured actual species concentrations then you would compare them to Fe+2, Fe(OH)2 (aq), etc..

    Eric

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  • Yes, Only if the "t_fe+2" column represent all the aqueous fe2+ species and not solid phase, I can regard the measured value as "t_fe+2". 

    It's clear now. 

    Thank you for the kind lesson.

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  • Hi Jaeshik,

    you could also print out all of your Fe containing secondary species in plot.out and sum up all Fe(II) and Fe(III) species separately. This is a little laborious work, but it gives you a good feeling about the fraction of dissolved Fe(III) contained in t_fe+2.

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