Variations in As and Fe concentrations and speciation in the dissolved and the solid phase over the course of incubations of orange sand from Bangladesh in artificial groundwater. The five sets of incubations include a control without lactate (C0), a control with lactate (Clac), a control with lactate and kanamycin (Clac+kan), an amendment with Shewanella in kanamycin without lactate (Skan) and amendment with Shewanella in kanamycin with lactate (Slac+kan). Liquid phase (a) As and (b) Fe measurements are expressed as dissolved concentrations (right) as well as equivalent concentrations in the solid phase (left) by normalizing to sediment weight. Error bars indicate the standard deviation of triplicates on day 22 and duplicates on day 45 and day 90. Some error bars are covered by the symbol. “nd” indicates As(III) was not detected by DPCSV. with a detection limit 2 μg L−1 (0.004 mg kg−1). (c) Changes in sediments color expressed as the difference in reflectance between 530 and 520 nm (ΔR). Also shown are (d) solid phase P-extractable total As, with symbols labeled with the proportion of as As(III) and (e) solid phase 1 hr HCl-leachable Fe, with the proportion of Fe(II).