pH from Biochemistry modules

Can you point to some work on the representation of pH using CROCO’s biogeochemistry modules?

After 10 years simulation using CROCO-PISCES (last release), I saw with roms-gui the PH variable when I lunch the roms-gui in SCRATCH folder, however when lunch roms-gui in COROCO_FILES this variable PH disappears. My questions concerns the PH: Is the model calculate the water PH ?
Many great thanks