Outputting H2O?

[Sanskriti]

Hello!

I was wondering if there was a way to output water activity in the .tec files. I tried putting it inside the Output block (also tried with the Chemistry Output block), but it is sadly not working. 

I would appreciate any help anyone could provide! I've attached the input file :)

Best,

Sanskriti

[Hammond, Glenn E]

Sanskriti,

 

I added the ability to output WATER_ACTIVITY_COEFFICIENT in the following branch:

 

https://bitbucket.org/pflotran/pflotran/branch/glenn/add-output-h2o-act-coef

 

Please give it a try. Note that you must add WATER_ACTIVITY to the main CHEMISTRY block for the code to calculate an activity coefficient for water. By default, it is not calculated.

 

CHEMISTRY

  …

  ACTIVITY_WATER

  OUTPUT

    …

    WATER_ACTIVITY_COEFFICIENT

/

 

Also, do you need activity coefficients for the secondary aqueous complexes? The code would need to be updated to output those.

 

Glenn

 

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of Sanskriti <sans...@g.ucla.edu>
Date: Monday, July 28, 2025 at 3:19 PM
To: pflotran-users <pflotra...@googlegroups.com>
Subject: [pflotran-users: 8512] Outputting H2O?

Check twice before you click! This email originated from outside PNNL.

 

--
You received this message because you are subscribed to the Google Groups "pflotran-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to pflotran-user...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/1a678715-6c5d-4fe7-bc87-8b631dab8a85n%40googlegroups.com.

[Sanskriti]

Hi Glenn,

Activity coefficients for the secondary aqueous complexes would be useful! Is this where I would put them in?

CHEMISTRY
  PRIMARY_SPECIES
    H+
    HCO3-
    Ca++
  /
  ACTIVITY_COEFFICIENTS LAG TIMESTEP
  ACTIVITY_H2O
/

Thank you for the PFLOTRAN update - to clarify, I will need to rebuild PFLOTRAN to be able to output water activity?

Best,

Sanskriti

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/SA1PR09MB7838A6FF2295423E8F0983259A25A%40SA1PR09MB7838.namprd09.prod.outlook.com.

[Sanskriti]

Hello everyone,

Update: rebuild was successful, but I don't see water_activity in the output for the .tec files. Attached is my input file, where I added this to Chemistry:

CHEMISTRY
ACTIVITY_WATER
OUTPUT
  WATER_ACTIVITY_COEFFICIENT
/

Would appreciate help in letting me know what I'm missing!

[Hammond, Glenn E]

I see the activity of water when I run your input deck using the latest source code on the master branch. Search on “Gamma H2O”. The symbol \gamma is often use for activity coefficient in the literature.

 

Glenn

 

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/CAENN-c%3D%2BUGvAt%2BTMYt-CJ%2BcA1ccS3L8r%2Bm%2B3mdaJrbjCD5%2B-Cw%40mail.gmail.com.

[Sanskriti]

Hi Glenn,

Thank you! You're right, it is Gamma H2O. Do you know how I would be able to inhibit certain microbial reactions at specific water activities, like we can do for species concentrations? I'm thinking of adding salts to the system to lower the water activity, and I know that some microbial reactions decrease rates as water activity lowers, and then halts at a specific water activity. 

    INHIBITION
      SPECIES_NAME        O2(aq)
      TYPE MONOD
      THRESHOLD_CONCENTRATION 1.00e-05
      INHIBIT_ABOVE_THRESHOLD
    /

Best,

Sanskriti

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/PH0PR09MB7836ADEFEC3BCCBD6E35DDA59A24A%40PH0PR09MB7836.namprd09.prod.outlook.com.

[Hammond, Glenn E]

Sanskriti,

You would need to develop a custom reaction sandbox to inhibit a reaction based on water activity.

https://www.pflotran.org/documentation/theory_guide/reaction_sandbox.html

https://gmd.copernicus.org/articles/15/1659/2022/

Glenn

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/CAENN-ck1ZuLPn4ejhp%3DcuYen%3D1UyvrP66iOarnmCXjoBGXSBqg%40mail.gmail.com.

[Hammond, Glenn E]

Sanskriti,

To output water activity, you need to add ACTIVITY_WATER to the CHEMISTRY block and WATER_ACTIVITY_COEFFICIENT to the CHEMISTRY OUTPUT block. See the following example:

https://bitbucket.org/pflotran/pflotran/src/f79e6e88ad6f7d044ce899f48062d1e2c549541e/regression_tests/ascem/batch/ca-carbonate-debye-huckel-activity.in#lines-66

Glenn

From: pflotra...@googlegroups.com <pflotra...@googlegroups.com> on behalf of Sanskriti <sans...@g.ucla.edu>

Date: Tuesday, July 29, 2025 at 1:43 PM
To: pflotra...@googlegroups.com <pflotra...@googlegroups.com>

To view this discussion visit https://groups.google.com/d/msgid/pflotran-users/CAENN-cm__rPv4Hqi1BGRgxf7keaESZh%2BbG38WDNV8RcuSd4PMQ%40mail.gmail.com.

[Hammond, Glenn E]

And yes, you need to pull the latest source code and recompile the code.

Glenn

[Sanskriti]

Yes, thank you!

We got it working for a few microbial reactions in the sandbox. 

Thank you for your help, and especially thank you for the water activity output functionality you added to PFLOTRAN.

Best,

Sanskriti