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Title: Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil

Abstract

Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As(III), their impact on interrelated As, Fe, and Mn speciation under microbially reducing conditions remains largely unknown. For this reason, we employed a column setup and X-ray absorption spectroscopy to investigate the influence of increasing birnessite concentrations (molar soil Fe-to-Mn ratios: 4.8, 10.2, and 24.7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. Here, the reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating the passivation of birnessite and its transformation products toward As(III) oxidation and the precipitation of Fe(III)(oxyhydr)oxides. Microbial Mn reduction resulted in elevated soil pH values, which in turn lowered the microbial activity in the birnessite-enriched soil. We conclude that in Mn-oxide-rich soil environments undergoing redox fluctuations, the enhanced As adsorption to newly formed Fe(III) (oxyhydr)oxides under reducing conditions leads to a transient stabilization of As.

Authors:
 [1];  [2];  [1]
  1. ETH Zurich (Switzerland)
  2. ETH Zurich (Switzerland); Univ. of Copenhagn, Frederiksberg (Denmark)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1322350
Grant/Contract Number:  
AC02-76SF00515; AC02-06CH11357; 200020_155890
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Environmental Science and Technology
Additional Journal Information:
Journal Volume: 50; Journal Issue: 17; Journal ID: ISSN 0013-936X
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES; redox reactions; soils; oxides; oxidation; transition metals

Citation Formats

Ehlert, Katrin, Mikutta, Christian, and Kretzschmar, Ruben. Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil. United States: N. p., 2016. Web. doi:10.1021/acs.est.6b01767.
Ehlert, Katrin, Mikutta, Christian, & Kretzschmar, Ruben. Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil. United States. doi:10.1021/acs.est.6b01767.
Ehlert, Katrin, Mikutta, Christian, and Kretzschmar, Ruben. Wed . "Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil". United States. doi:10.1021/acs.est.6b01767. https://www.osti.gov/servlets/purl/1322350.
@article{osti_1322350,
title = {Effects of Manganese Oxide on Arsenic Reduction and Leaching from Contaminated Floodplain Soil},
author = {Ehlert, Katrin and Mikutta, Christian and Kretzschmar, Ruben},
abstractNote = {Reductive release of the potentially toxic metalloid As from Fe(III) (oxyhydr)oxides has been identified as an important process leading to elevated As porewater concentrations in soils and sediments. Despite the ubiquitous presence of Mn oxides in soils and their oxidizing power toward As(III), their impact on interrelated As, Fe, and Mn speciation under microbially reducing conditions remains largely unknown. For this reason, we employed a column setup and X-ray absorption spectroscopy to investigate the influence of increasing birnessite concentrations (molar soil Fe-to-Mn ratios: 4.8, 10.2, and 24.7) on As speciation and release from an As-contaminated floodplain soil (214 mg As/kg) under anoxic conditions. Our results show that birnessite additions significantly decreased As leaching. Here, the reduction of both As and Fe was delayed, and As(III) accumulated in birnessite-rich column parts, indicating the passivation of birnessite and its transformation products toward As(III) oxidation and the precipitation of Fe(III)(oxyhydr)oxides. Microbial Mn reduction resulted in elevated soil pH values, which in turn lowered the microbial activity in the birnessite-enriched soil. We conclude that in Mn-oxide-rich soil environments undergoing redox fluctuations, the enhanced As adsorption to newly formed Fe(III) (oxyhydr)oxides under reducing conditions leads to a transient stabilization of As.},
doi = {10.1021/acs.est.6b01767},
journal = {Environmental Science and Technology},
issn = {0013-936X},
number = 17,
volume = 50,
place = {United States},
year = {2016},
month = {8}
}

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