title: Considerations for conducting incubations to study the mechanisms of As release in reducing groundwater aquifers.
abstract: Microbial Fe reduction is widely believed to be the primary mechanism of As release from aquifer sands in Bangladesh, but alternative explanations have been proposed. Long-term incubation studies using natural aquifer material are one way to address such divergent views. This study addresses two issues related to this approach: (1) the need for suitable abiotic controls and (2) the spatial variability of the composition of aquifer sands. Four sterilization techniques were examined using orange-colored Pleistocene sediment from Bangladesh and artificial groundwater over 8 months. Acetate (10 mM) was added to sacrificial vials before sterilization using either (1) 25 kGy of gamma irradiation, (2) three 1-h autoclave cycles, (3) a single addition of an antibiotic mixture at 1x or (4) 10x the typical dose, and (5) a 10 mM addition of azide. The effectiveness of sterilization was evaluated using two indicators of microbial Fe reduction, changes in diffuse spectral reflectance and leachable Fe(II)/Fe ratios, as well as changes in P-extractable As concentrations in the solid phase. A low dose of antibiotics was ineffective after 70 days, whereas autoclaving significantly altered groundwater composition. Gamma irradiation, a high dose of antibiotics, and azide were effective for the duration of the experiment.
authors.affiliation: Department of Earth and Environmental Engineering, Columbia University, New York, NY 10027, USA.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Radloff
authors.forename: Anya R
authors.initials: AR
authors.lastname: Manning
authors.forename: Brian
authors.initials: B
authors.lastname: Mailloux
authors.forename: Yan
authors.initials: Y
authors.lastname: Zheng
authors.forename: M Moshiur
authors.initials: MM
authors.lastname: Rahman
authors.forename: M Rezaul
authors.initials: MR
authors.lastname: Huq
authors.forename: Kazi M
authors.initials: KM
authors.lastname: Ahmed
authors.forename: Alexander
authors.initials: A
authors.lastname: van Geen