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Arsenic Speciation in Mekong Delta Sediments Depends on Their Depositional Environment.
Journal article

Arsenic Speciation in Mekong Delta Sediments Depends on Their Depositional Environment.

  • Wang Y Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
  • Le Pape P Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC, CNRS-UPMC-IRD-MNHN UMR 7590) , Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie (UPMC Paris 6) , Campus Jussieu, 4 place Jussieu , 75005 Paris , France.
  • Morin G Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC, CNRS-UPMC-IRD-MNHN UMR 7590) , Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie (UPMC Paris 6) , Campus Jussieu, 4 place Jussieu , 75005 Paris , France.
  • Asta MP Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
  • King G Institute of Geological Sciences , University of Bern , Baltzerstrasse 1 + 3 , CH-3012 Bern , Switzerland.
  • Bártová B Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
  • Suvorova E Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
  • Frutschi M Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
  • Ikogou M Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC, CNRS-UPMC-IRD-MNHN UMR 7590) , Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie (UPMC Paris 6) , Campus Jussieu, 4 place Jussieu , 75005 Paris , France.
  • Pham VHC Faculty of Environment and Natural Resources , Ho Chi Minh City University of Technology, VNU-HCM , 268 Ly Thuong Kiet , Ho Chi Minh City , Vietnam.
  • Vo PL Faculty of Environment and Natural Resources , Ho Chi Minh City University of Technology, VNU-HCM , 268 Ly Thuong Kiet , Ho Chi Minh City , Vietnam.
  • Herman F Institute of Earth Surface Dynamics , University of Lausanne , Géopolis Building , CH-1015 Lausanne , Switzerland.
  • Charlet L CNRS, IRD, IFSTTAR, ISTerre , Université Grenoble Alpes and Université Savoie Mont Blanc , 38000 Grenoble , France.
  • Bernier-Latmani R Environmental Microbiology Laboratory (EML), EPFL-ENAC-IIE-EML , Ecole Polytechnique Fédérale de Lausanne (EPFL) , Station 6 , CH-1015 Lausanne , Switzerland.
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  • 2018-02-17
Published in:
  • Environmental science & technology. - 2018
Arsenic
Environmental Monitoring
Geologic Sediments
Groundwater
Vietnam
Water Pollutants, Chemical
English Arsenic contamination in groundwater is pervasive throughout deltaic regions of Southeast Asia and threatens the health of millions. The speciation of As in sediments overlying contaminated aquifers is poorly constrained. Here, we investigate the chemical and mineralogical compositions of sediment cores collected from the Mekong Delta in Vietnam, elucidate the speciation of iron and arsenic, and relate them to the sediment depositional environment. Gradual dissolution of ferric (oxyhydr)oxides with depth is observed down to 7 m, corresponding to the establishment of reducing conditions. Within the reduced sediment, layers originating from marine, coastal or alluvial depositional environments are identified and their age is consistent with a late Holocene transgression in the Mekong Delta. In the organic matter- and sulfur-rich layers, arsenic is present in association with organic matter through thiol-bonding and in the form of arsenian pyrite. The highest arsenic concentration (34-69 ppm) is found in the peat layer at 16 m and suggests the accumulation of arsenic due to the formation of thiol-bound trivalent arsenic (40-55%) and arsenian pyrite (15-30%) in a paleo-mangrove depositional environment (∼8079 yr BP). Where sulfur is limited, siderite is identified, and oxygen- and thiol-bound trivalent arsenic are the predominant forms. It is also worth noting that pentavalent arsenic coordinated to oxygen is ubiquitous in the sediment profile, even in reduced sediment layers. But the identity of the oxygen-bound arsenic species remains unknown. This work shows direct evidence of thiol-bound trivalent arsenic in the Mekong Delta sediments and provides insight to refine the current model of the origin, deposition, and release of arsenic in the alluvial aquifers of the Mekong Delta.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/6329
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