title: Arsenite and ferrous iron oxidation linked to chemolithotrophic denitrification for the immobilization of arsenic in anoxic environments.
abstract: The objective of this study was to explore a bioremediation strategy based on injecting NO3- to support the anoxic oxidation of ferrous iron (Fe(II)) and arsenite (As(II)) in the subsurface as a means to immobilize As in the form of arsenate (As(V)) adsorbed onto biogenic ferric (Fe(III)) (hydr)oxides. Continuous flow sand filled columns were used to simulate a natural anaerobic groundwater and sediment system with co-occurring As(III) and Fe(II) in the presence (column SF1) or absence (column SF2) of nitrate, respectively. During operation for 250 days, the average influent arsenic concentration of 567 microg L(-1) was reduced to 10.6 (+/-9.6) microg L(-1) in the effluent of column SF1. The cumulative removal of Fe(II) and As(II) in SF1 was 6.5 to 10-fold higher than that in SF2 Extraction and measurement of the mass of iron and arsenic immobilized on the sand packing of the columns were close to the iron and arsenic removed from the aqueous phase during column operation. The dominant speciation of the immobilized iron and arsenic was Fe(III) and As(V) in SF1, compared with Fe(II) and As(III) in SF2. The speciation was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results indicate that microbial oxidation of As(III) and Fe(II) linked to denitrification resulted in the enhanced immobilization of aqueous arsenic in anaerobic environments by forming Fe(III) (hydr)oxide coated sands with adsorbed As(V).
authors.affiliation: Department of Chemical and Environmental Engineering, University of Arizona, P.O. Box 210011, Tucson, Arizona 85721, USA.
authors.forename: Wenjiie
authors.initials: W
authors.lastname: Sun
authors.forename: Reyes
authors.initials: R
authors.lastname: Sierra-Alvarez
authors.forename: Lily
authors.initials: L
authors.lastname: Milner
authors.forename: Ron
authors.initials: R
authors.lastname: Oremland
authors.forename: Jim A
authors.initials: JA
authors.lastname: Field
mesh_terms: D000693:Anaerobiosis; D001149:Arsenates / Q000737:chemistry; D018053:Arsenites / Q000032:analysis / Q000737:chemistry*; D001673:Biodegradation, Environmental; D052837:Chemoautotrophic Growth; D005290:Ferric Compounds / Q000737:chemistry; D005296:Ferrous Compounds / Q000032:analysis / Q000737:chemistry*; D019015:Geologic Sediments / Q000737:chemistry*; D008962:Models, Theoretical; D009566:Nitrates / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D001149:Arsenates; D018053:Arsenites; D005290:Ferric Compounds; D005296:Ferrous Compounds; D009566:Nitrates; D014874:Water Pollutants, Chemical; C015001:arsenite; C025657:arsenic acid