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[OLD] How to buffer a solution?


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From: Alexander Smirnov

Recently I was trying to model seawater being buffered by various mineral buffers (IW, PPM, HM, QFM) while heated from 25 to 300C. The problem that I have is how to actually model the buffering (or how do I know that the solution is buffered by given redox buffer). My input file looks as below. The input looks fine to me, but I don't know what to do with precipitation. Should it be turned ON or OFF, can I use flow-through or flush models (and still redox-buffer the solution?). My input file looks like this:

temperature initial = 25, final = 300

swap Fayalite for Fe++

swap Magnetite for O2(aq)

swap Quartz for SiO2(aq)

swap N2(aq) for NH3(aq)

1 kg free H2O

free mol Fayalite = 10

free mol Magnetite = 10

free mol Quartz = 10

total mmol N2(aq) = .59

pH = 8.1

total g/kg Cl- = 19.354

total g/kg Na+ = 9.5496

total g/kg Mg++ = 1.29

total g/kg Ca++ = .412

total g/kg K+ = .399

total g/kg HCO3- = .12

total g/kg SO4-- = .2712

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From: Craig Bethke

To check that the system is buffered, you need only go to Plot Minerals in Gtplot and verify that each mineral in the buffer of interest is present over the entire pathway. If one or more of the minerals dissolves completely, try increasing the initial mass to a large value. If the mineral still disappears, or if you want to test the case in which no other minerals are present, set precip = off. And yes, you can use the flow-through or flush option if you wish.

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