Fig. 5. Distribution of Fe in aquifer solids incubated with soluble donors at 1000 mg C L^–1 for 42 d compared with aquifer solids before incubation. Columns with the same letter within an extraction type are not significantly different by the Bonferroni–Dunn procedure. There was no measurable Fe(II) in the solution phase or extracted with HCl for the original aquifer solids before treatment.