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Transport and biogeochemical reaction of metals in a physically and chemically heterogeneous aquifer

¹ Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA
² University of Wisconsin, Department of Geology and Geophysics, 1215 W. Dayton Street, Madison, Wisconsin 53706, USA
³ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, California 94720, USA
⁴ Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA
⁵ Oak Ridge National Laboratory, P.O. Box 2008, MS 6038, Oak Ridge, Tennessee 37831-6038, USA
⁶ Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 90-1116, Berkeley, California 94720, USA

View larger version (109K): [in this window] [in a new window]   Figure 1. Photograph of an excavation face from a borrow pit near the field research site on which the hypothetical model system is based. Dark-reddish bands are fine-grained layers with high proportion of iron-oxide grain coatings.

View larger version (18K): [in this window] [in a new window]   Figure 2. Growth yield of Geobacter metallireducens with Fe(III)-citrate (5–100 mM) as an electron acceptor and excess acetate (20 mM) as a carbon and energy source in batch culture. Each data point represents the average of triplicate culture tubes.

View larger version (17K): [in this window] [in a new window]   Figure 3. Vertical logs of several types of data collected at borehole D1 within the simulated transect.

View larger version (15K): [in this window] [in a new window]   Figure 4. Vertical indicator variogram (symbols—experimental; line—model) of binary sand/mud facies (top), hydraulic conductivity (center), and Fe(III) content (bottom).

View larger version (28K): [in this window] [in a new window]   Figure 5. Ground-penetrating radar (GPR) attenuation (top; units m–1) and probability that sand is present (bottom), where the probability is derived from the calibration shown in Table 3.

View larger version (28K): [in this window] [in a new window]   Figure 6. Three indicator simulations of sand (white) and mud (black) facies distributions, representing 5th percentile (top, 12.4% mud facies), median (center, 14.8%), and 95th percentile (bottom, 17.8%), proportions of mud.

View larger version (114K): [in this window] [in a new window]   Figure 7. Three simulations of hydraulic conductivity corresponding to the three sand/mud facies distributions shown in Figure 6.

View larger version (14K): [in this window] [in a new window]   Figure 8. Box plots showing distribution of measured total Fe(III) for three classes of sediments: (1) sand below the mud/peat zone ("Lower sand"), (2) mud/peat sediments ("Mud"), and (3) sand above the mud/peat zone ("Upper sand"). Total Fe(III) is generally much higher in the lower sand than in the upper sand (note that the vertical scale is logarithmic). The narrowest point in the box plot represents the median; the top and bottom of the box represent the upper and lower quartile, respectively; and the whiskers extend to the maximum and minimum data values, not including outliers. Outliers are defined as any values outside the inter-quartile range by more than 1.5 times the interquartile range and are indicated by asterisks or circles.

View larger version (75K): [in this window] [in a new window]   Figure 9. Three selected realizations of Fe(III) content corresponding to the three realizations of mud/sand distribution shown in Figure 6.

View larger version (111K): [in this window] [in a new window]   Figure 10. Three selected realizations of hydraulic conductivity (K) conditioned to core data only; compare to Figure 7.

View larger version (87K): [in this window] [in a new window]   Figure 11. Three selected realizations of Fe(III) conditioned to core data and hydraulic conductivity simulations shown in Figure 10, but not conditioned to geophysical observations.

View larger version (59K): [in this window] [in a new window]   Figure 12. Simulated distribution of dissolved U(VI) (top panel) and sorbed U(VI) (bottom panel) after the initial 22 yr loading period.

View larger version (49K): [in this window] [in a new window]   Figure 13. Cross-sectional plots of simulated distributions of sodium acetate (upper left), aqueous Fe(II) (upper right), solid-phase Fe(III) (lower left), and sorbed Fe(II) (lower right) at the end of the 200 d simulated biostimulation phase. Note that initial distributions of acetate and Fe(II) (both aqueous and sorbed) were uniform and zero concentration. The initial distribution of Fe(III) is shown in the center panel of Figure 9; for comparison note that 0.1 M approximately equals 40 µmol/cm3 bulk sediment for the model system.

View larger version (52K): [in this window] [in a new window]   Figure 14. Cross-sectional plots of simulated distributions of aqueous and attached biomass (upper-left and lower-left panels, respectively) and aqueous and sorbed U(VI) (upper-right and lower-right panels, respectively) at the end of the 200 d simulated biostimulation phase. Note that the initial distribution of attached biomass was uniform with a cell density of 2.0 x 10-5 M. The initial distribution of U(VI) (sorbed and aqueous) is shown in Figure 12.

View larger version (13K): [in this window] [in a new window]   Figure 15. (Left) Percent of total U(VI) reduced in the simulated transect as a function of time during the 200 d simulated biostimulation period, presented as the mean and range over the 10 and 11 realizations evaluated for the Chen2004 and Geophys2 suites, respectively. (Right) Percent of total U(VI) reduced in the simulated transect as a function of time during the 200 d simulated biostimulation period for each of the 11 realizations evaluated in the Geophys2 suite. The two highlighted realizations have similar total proportion of mud facies, but are at opposite extremes of the range of bioremediation prediction results.

View larger version (13K): [in this window] [in a new window]   Figure 16. Percent of total U(VI) reduced in the simulated transect as a function of time during the 200 d simulated biostimulation period, presented as the mean and range over the 11 realizations evaluated for the CoreData suite. Axes are plotted at the same scale as those of Figure 15 for purposes of comparison.

View larger version (85K): [in this window] [in a new window]   Animation 1. Animation of simulation results for U(VI) contamination period (22 yr) for the Geophys2 case. The still figure shows the frame for time = 3.3 yr. Upper panel—sorbed U(VI); lower panel—aqueous U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S1 or the full-text article on www.gsajournals.org to view the animation.

View larger version (85K): [in this window] [in a new window]   Animation 2. Animation of simulation results for U(VI) contamination period (22 yr) for the Chen2004 case. The still figure shows the frame for time = 3.3 yr. Upper panel—sorbed U(VI); lower panel—aqueous U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S2 or the full-text article on www.gsajournals.org to view the animation.

View larger version (78K): [in this window] [in a new window]   Animation 3. Animation of simulation results for U(VI) contamination period (22 yr) for the CoreData case. The still figure shows the frame for time = 3.3 yr. Upper panel—sorbed U(VI); lower panel—aqueous U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S3 or the full-text article on www.gsajournals.org to view the animation.

View larger version (44K): [in this window] [in a new window]   Animation 4. Animation of simulation results for biostimulation period (200 d following contamination) for the Geophys2 case. The still figure shows the frame for time = 100 d. Upper left panel—aqueous biomass; lower left—attached biomass. Upper right panel—aqueous U(VI); lower right—sorbed U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S4 or the full-text article on www.gsajournals.org to view the animation.

View larger version (44K): [in this window] [in a new window]   Animation 5. Animation of simulation results for biostimulation period (200 d following contamination) for the Chen2004 case. The still figure shows the frame for time = 100 d. Upper left panel—aqueous biomass; lower left—attached biomass. Upper right panel—aqueous U(VI); lower right—sorbed U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S5 or the full-text article on www.gsajournals.org to view the animation.

View larger version (40K): [in this window] [in a new window]   Animation 6. Animation of simulation results for biostimulation period (200 d following contamination) for the CoreData case. The still figure shows the frame for time = 100 d. Upper left panel—aqueous biomass; lower left—attached biomass. Upper right panel—aqueous U(VI); lower right—sorbed U(VI). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S6 or the full-text article on www.gsajournals.org to view the animation.

View larger version (43K): [in this window] [in a new window]   Animation 7. Animation of simulation results for biostimulation period (200 d following contamination) for the Geophys2 case. The still figure shows the frame for time = 100 d. Upper left panel—acetate; lower left—Fe(III) oxide (solid). Upper right panel—aqueous Fe(II); lower right—sorbed Fe(II). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S7 or the full-text article on www.gsajournals.org to view the animation.

View larger version (42K): [in this window] [in a new window]   Animation 8. Animation of simulation results for biostimulation period (200 d following contamination) for the Chen2004 case. The still figure shows the frame for time = 100 d. Upper left panel—acetate; lower left—Fe(III) oxide (solid). Upper right panel—aqueous Fe(II); lower right—sorbed Fe(II). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S8 or the full-text article on www.gsajournals.org to view the animation.

View larger version (39K): [in this window] [in a new window]   Animation 9. Animation of simulation results for biostimulation period (200 d following contamination) for the CoreData case. The still figure shows the frame for time = 100 d. Upper left panel—acetate; lower left—Fe(III) oxide (solid). Upper right panel—aqueous Fe(II); lower right—sorbed Fe(II). All concentrations are in molar units (M). If you are viewing the PDF, or if you are reading this offline, please visit http://dx.doi.org/10.1130/GES00029.S9 or the full-text article on www.gsajournals.org to view the animation.