Arsenic mobilization during seawater inundation of acid sulfate soils

Hydrogeochemical coupling at the tidal fringe

S. G. Johnston, E. D. Burton, A. F. Keene, R. T. Bush, L. A. Sullivan

Research output: A Conference proceeding or a Chapter in BookConference contribution

Abstract

Coastal Acid Sulfate Soils (CASS) are rich in meta-stable iron (Fe - III) minerals that are important sorbents for arsenic (As) under oxic conditions. Tidal seawater inundation to remediate CASS has recently been trialed on a large scale and has potential to mobilize arsenic during the redox transition. Tidal seawater inundation caused reductive dissolution of As(V)-bearing Fe(III) minerals, resulting in elevated concentrations of Fe 2+ (2000 mg L -1) and As (∼400 μg L -1) in upper-intertidal zone groundwater. Oscillating vertical and horizontal hydraulic gradients caused by tidal pumping promoted upward advection of As and Fe 2+-enriched groundwater within the intertidal zone. This led to flux of As aq and Fe 2+ aq to surface waters and the accumulation of As(V)-enriched Fe(III) (hydr)oxides at the oxic sediment-water interface. Fe(III) (hydr)oxides at the sediment-water interface act as a natural reactive-barrier, retarding As flux to overlying surface waters. However, they also represent a highly transient phase that is prone to reductive dissolution during future redox boundary migration. A conceptual model is presented to explain landscape-scale patterns of As and Fe hydro-geochemical zonation.

Original languageEnglish
Title of host publicationUnderstanding the Geological and Medical Interface of Arsenic, As 2012
Subtitle of host publicationArsenic in the Environment
EditorsJack Ng, Barry Noller, Ravi Naidu, Jochen Bundschuh, Prosun Bhattacharya
Place of PublicationBoca Raton, FL, USA
PublisherCRC Press
Pages23-24
Number of pages2
ISBN (Print)9780415637633
Publication statusPublished - 2012
Externally publishedYes
Event4th International Congress on Arsenic in the Environment, As 2012 - Cairns, QLD, Australia
Duration: 22 Jul 201227 Jul 2012

Publication series

NameArsenic in the Environment - Proceedings

Conference

Conference4th International Congress on Arsenic in the Environment, As 2012
CountryAustralia
CityCairns, QLD
Period22/07/1227/07/12

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Johnston, S. G., Burton, E. D., Keene, A. F., Bush, R. T., & Sullivan, L. A. (2012). Arsenic mobilization during seawater inundation of acid sulfate soils: Hydrogeochemical coupling at the tidal fringe. In J. Ng, B. Noller, R. Naidu, J. Bundschuh, & P. Bhattacharya (Eds.), Understanding the Geological and Medical Interface of Arsenic, As 2012: Arsenic in the Environment (pp. 23-24). (Arsenic in the Environment - Proceedings). Boca Raton, FL, USA: CRC Press.