The graph shows the iron concentrations in runs 1 and 7 of in-situ iron removal at the groundwater pumping station Schuwacht (NL). In each run, 1440 m3 of oxygenated water are injected in a 10 m thick aquifer in 2 days. Pumping is resumed for 40 days and the cycle repeats. The model lines were calculated assuming equilibrium reactions.
The observed concentrations are more spread out, which suggests that kinetic effects play a role.
The PHREEQC model with kinetic exchange and surface complexation reactions explains the slow increase of
Fe and PO4 in pumped groundwater.
The model shows the effects of a stop-flow experiment, in which pumping is interrupted for
4 days.
This case is discussed in Appelo and De Vet (2002); 203 kB pdf.