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Iron and Arsenic Release from Aquifer Solids in Response to Biostimulation

^a Department of Biological and Irrigation Engineering
^b Department of Civil and Environmental Engineering, Utah Water Research Laboratory, Utah State University, Logan, UT 84322-8200

View larger version (17K): [in a new window]   Fig. 1. Iron(II) release from aquifer solids incubated with soluble carbon donor (1000 mg C L–1) and no carbon addition. Least significant difference (lsd) by the Bonferroni–Dunn procedure.

View larger version (19K): [in a new window]   Fig. 2. Total As release from aquifer solids incubated with soluble carbon donors (1000 mg C L–1) and no carbon addition. Least significant difference (lsd) by the Bonferroni–Dunn procedure.

View larger version (23K): [in a new window]   Fig. 3. Iron(II) and As release from aquifer solids incubated over the first 8 d of the study. Concentrations at each sampling time have been normalized to the maximum Fe(II) or As release to solution during the experiment (Tables 1 and 2). Error bars are standard deviation of triplicate microcosms.

View larger version (10K): [in a new window]   Fig. 4. Distribution of Fe in the original aquifer solids. The fractions removed with these extractants are operationally defined as iron associated with (1) surface exchangeable sites, (2) carbonates, (3) organic matter, (4) Mn oxides, (5) non-crystalline Fe oxides, (6) crystalline Fe oxides, and (7) the residual fraction. Error bars are 95% CI of triplicate extractions.

View larger version (21K): [in a new window]   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.

View larger version (28K): [in a new window]   Fig. 6. Iron(II) release from aquifer solids incubated with no carbon addition and glucose at 200, 2000, and 20 000 mg C L–1. Least significant difference (lsd) by the Bonferroni–Dunn procedure.

View larger version (24K): [in a new window]   Fig. 7. Distribution of Fe in aquifer solids after 21 d of incubation with glucose at 200, 2000, and 20 000 mg C L–1 and acetate at 2000 mg C L–1 compared with aquifer solids before incubation. Columns with the same letter within 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.

View larger version (17K): [in a new window]   Fig. 8. Biogenic Fe(II) produced by different dosing of glucose and acetate. Error bars are 95% confidence intervals on total biogenic Fe(II).

View larger version (21K): [in a new window]   Fig. 9. Biogenic Fe(II) produced by a variety of carbon donors (100–1000 mg C L–1). Error bars are 95% confidence intervals on total biogenic Fe(II).