Titre
Arsenic Speciation in Mekong Delta Sediments Depends on Their Depositional Environment
Type
article
Institution
UNIL/CHUV/Unisanté + institutions partenaires
Périodique
Auteur(s)
Wang, Yuheng
Auteure/Auteur
Le Pape, Pierre
Auteure/Auteur
Morin, Guillaume
Auteure/Auteur
Asta, Maria P.
Auteure/Auteur
King, Georgina
Auteure/Auteur
Bártová, Barbora
Auteure/Auteur
Suvorova, Elena
Auteure/Auteur
Frutschi, Manon
Auteure/Auteur
Ikogou, Maya
Auteure/Auteur
Pham, Vu Hoai Cong
Auteure/Auteur
Vo, Phu Le
Auteure/Auteur
Herman, Frédéric
Auteure/Auteur
Charlet, Laurent
Auteure/Auteur
Bernier-Latmani, Rizlan
Auteure/Auteur
Liens vers les personnes
Liens vers les unités
ISSN
0013-936X
Statut éditorial
Publié
Date de publication
2018-03-20
Volume
52
Numéro
6
Première page
3431
Dernière page/numéro d’article
3439
Peer-reviewed
Oui
Langue
anglais
Résumé
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.
PID Serval
serval:BIB_0632CC1A8C8D
PMID
Date de création
2018-08-14T05:38:41.539Z
Date de création dans IRIS
2025-05-20T13:23:52Z