The impact of seasonal fluctuations linked to monsoon and irrigation generates redox oscillations in the subsurface, influencing the release of arsenic (As) in aquifers. Here, the biogeochemical control on As mobility was investigated in batch experiments using redox cycling bioreactors and As- and SO 42− -amended sediment. Redox potential (E h ) oscillations between anoxic (−300–0 mV) and oxic condition (0–500 mV) were implemented by automatically modulating an admixture of N 2 /CO 2 or compressed air. A carbon source (cellobiose, a monomer of cellulose) was added at the beginning of each reducing cycle to stimulate the metabolism of the native microbial community. Results show that successive redox cycles can decrease arsenic mobility by up to 92% during reducing conditions. Anoxic conditions drive mainly the conversion of soluble As(V) to As(III) in contrast to oxic conditions. Phylogenetic analyses of 16S rRNA amplified from the sediments revealed the presence of sulfate and iron – reducing bacteria, confirming that sulfate and iron reduction are key factors for As immobilization from the aqueous phase. As and S K-edge X-ray absorption spectroscopy suggested the association of Fe-(oxyhydr)oxides and the importance of pyrite (FeS 2(s) ), rather than poorly ordered mackinawite (FeS (s) ), for As sequestration under oxidizing and reducing conditions, respectively. Finally, these findings suggest a role for elemental sulfur in mediating aqueous thioarsenates formation in As-contaminated groundwater of the Mekong delta.

As release under the microbial sulfate reduction during redox oscillations in the upper Mekong delta aquifers, Vietnam: A mechanistic study

Bardelli F.;
2019

Abstract

The impact of seasonal fluctuations linked to monsoon and irrigation generates redox oscillations in the subsurface, influencing the release of arsenic (As) in aquifers. Here, the biogeochemical control on As mobility was investigated in batch experiments using redox cycling bioreactors and As- and SO 42− -amended sediment. Redox potential (E h ) oscillations between anoxic (−300–0 mV) and oxic condition (0–500 mV) were implemented by automatically modulating an admixture of N 2 /CO 2 or compressed air. A carbon source (cellobiose, a monomer of cellulose) was added at the beginning of each reducing cycle to stimulate the metabolism of the native microbial community. Results show that successive redox cycles can decrease arsenic mobility by up to 92% during reducing conditions. Anoxic conditions drive mainly the conversion of soluble As(V) to As(III) in contrast to oxic conditions. Phylogenetic analyses of 16S rRNA amplified from the sediments revealed the presence of sulfate and iron – reducing bacteria, confirming that sulfate and iron reduction are key factors for As immobilization from the aqueous phase. As and S K-edge X-ray absorption spectroscopy suggested the association of Fe-(oxyhydr)oxides and the importance of pyrite (FeS 2(s) ), rather than poorly ordered mackinawite (FeS (s) ), for As sequestration under oxidizing and reducing conditions, respectively. Finally, these findings suggest a role for elemental sulfur in mediating aqueous thioarsenates formation in As-contaminated groundwater of the Mekong delta.
2019
Istituto di Nanotecnologia - NANOTEC - Sede Secondaria Roma
Arsenic release
Elemental sulfur
Microbial sulfate reduction
Redox oscillations
File in questo prodotto:
File Dimensione Formato  
Phan et al._2019_As release under the microbial sulfate reduction during redox oscillations.pdf

solo utenti autorizzati

Licenza: Nessuna licenza dichiarata (non attribuibile a prodotti successivi al 2023)
Dimensione 2.74 MB
Formato Adobe PDF
2.74 MB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/514805
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 20
  • ???jsp.display-item.citation.isi??? ND
social impact