Suppress SO4-- from Eh-pH diagram of S species

[Matias Silva]

Tried this on the command prompt in Act 2 but didn't succeed (suppress SO4). Apparently, you cannot suppress the main species of the diagram (SO4--). I'm focusing on the incompletely oxidized S forms, so I need a diagram that only shows those species. Is there a way to suppress SO4--?

[Brian Farrell]

Hi Matias,

The GWB programs are set up so that you cannot suppress basis species, whether they are the original basis species as specified in the thermo dataset, or those that are currently swapped into the basis of an app like Act2. If you're interested in showing only intermediate valence compounds, like thiosulfate or sulfurous acid, you can use the TEdit app to rebalance some of the reactions in the dataset. Looking at thermo_sit.tdat as an example, if you exchange the positions of S2O3-- and SO4--, you can load the modified dataset into Act2, add S2O3-- to the basis, then suppress SO4-- and H(SO4)-- to get a diagram that shows a variety of non-S(VI) species. And by rebalancing just a few more reactions in the dataset, such as the redox coupling reactions for HS- or SO3-- so that they're in terms of S2O3-- instead of SO4--, you can simply decouple SO4-- in Act2. That way, you eliminate SO4-- and all species coupled to it with a single command, rather than suppressing all such species individually.

For more information on the various rebalancing capabilities in TEdit, please see sections 9.2.8, Rebalancing reactions, and 9.2.9, Adjusting redox coupling, in the GWB Essentials Guide.

Hope this helps,

Brian Farrell
Aqueous Solutions