Jump to content
Geochemist's Workbench Support Forum

Questions about alkalinity calculations

Recommended Posts



I have a few questions regarding alkalinity calculations using both SpecE8 and React:

1) Is the alkalinity calculated as total alkalinity (including species other than carbonate species), or is it only calculated as carbonate alkalinity?

2) If total alkalinity includes other species, which species are included?

3) Can other alkalinity units be used for the calculation (e.g., meq)?


I'm trying to calculate dissolved CO2(aq) concentrations in natural waters based on pH and Alkalinity measurements (have converted the values to mg/kg CaCO3) however the numbers obtained with GWB (v. 7.0 Professional) result in very different values for CO2(aq) compared to Minteq and Phreeqc for some of our samples.




Link to comment
Share on other sites

Hi Ale:


The alkalinity reported by GWB is carbonate alkalinity, computed as follows:


Alk =  50.0445 * 1000 * (m_HCO3 + 2 m_CO3) * (kg_solv/kg_soln)


For computing total alkalinity from the above, refer to Craig Bethke's Geochemical and Biogeochemical Reaction Modeling, page 220 (Chapter 15).


I hope that helps,


Tom Meuzelaar

RockWare, Inc.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...