PhreeqcUsers Discussion Forum

Mixing => Mixing Solutions => Topic started by: nspanoudakis on February 06, 2018, 11:44:02 AM

Title: Unmixing
Post by: nspanoudakis on February 06, 2018, 11:44:02 AM
Hi to all and thank you for accepting me to the community.
I am very new to phreeqc and I have problem to solve which i cannot by myself (yet).
I have a water sample, let's say solution 1, from a sub thermal spring that emerges a few meters from the coast. There is a sea water (let's say solution 2) intrusion to the spring water.
So if I know the composition of these two waters, is there any way to find out what is the composition of the water that mixes with solution 2 (sea water) and results to the final solution 1?
Thank you in advance,
Nikos
Title: Re: Unmixing
Post by: dlparkhurst on February 06, 2018, 05:52:35 PM
No promises, but here is a suggestion. You do not know the composition of the other water nor the mixing fractions of the two waters, so I do not think there is a unique solution to the problem.

You can mix negative amounts in the MIX keyword, so if you had

MIX
1 1.0
2 -0.1
END

you would create a water that when 0.9 L of it were mixed with 0.1 L of seawater, you would produce solution 1. You could do this calculation with varying ratios to get a range of solution compositions for your unknown solution.
Title: Re: Unmixing
Post by: nspanoudakis on February 07, 2018, 08:04:06 AM
Thank you Mr Parkhurst.
I really appreciate your help.
One more question from a beginner. From my experience in the area the Na+ concentration in the waters never exceeds 30ppm, while my mix contains ~3500ppm Na+. Could I use this difference or fraction and if yes how, to limit calculations? Considering that Na+ in my mix originates "exclusively" from the sea water...?
Thank you in adnvance
Nikos
Title: Re: Unmixing
Post by: MichaelZ20 on February 07, 2018, 09:20:14 PM
See also http://phreeqcusers.org/index.php/topic,471.msg1443.html#msg1443
Title: Re: Unmixing
Post by: nspanoudakis on February 09, 2018, 08:25:43 AM
Thank you also Michael.
It seems it is the same problem.
Nikos