- Title
- Arsenic mobilization in a seawater inundated acid sulfate soil
- Creator
- Johnston, Scott; Keene, Annabelle; Burton, Edward; Bush, Richard; Sullivan, Leigh; McElnea, Angus; Ahern, Col; Smith, C. Douglas; Powell, Bernard; Hocking, Rosalie
- Date
- 2010
- Type
- Text; Journal article
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/99613
- Identifier
- vital:10394
- Identifier
-
https://doi.org/10.1021/es903114z
- Identifier
- ISSN:0013-936X
- Abstract
- Tidal seawater inundation of coastal acid sulfate soils can generate Fe- and SO4-reducing conditions in previously oxicacidic sediments, This creates potential for mobilization of As during the redox transition. We explore the consequences for As by investigating the hydrology, porewater geochemistry, solid-phase speciation, and mineralogical partitioning of As across two tidal fringe toposequences. Seawater inundation induced a tidally controlled redox gradient. Maximum porewater As (∼400μg/L) occurred in the shallow (<1 m), intertidal, redox transition zone between Fe-oxidizing and SO 4-reducing conditions. Primary mechanisms of As mobilization include the reduction of solid-phase As(V) to As(III), reductive dissolution of As(V)-bearing secondary Fe(III) minerals and competitive anion desorption. Porewater As concentrations decreased in the zone of contemporary pyrite reformation, Oscillating hydraulic gradients caused by tidal pumping promote upward advection of As and Fe2+-enriched porewater in the intertidal zone, leading to accumulation of As(V)-enriched Fe(III) (hydr)oxides at the oxic sediment-water interface. While this provides a natural reactive-Fe barrier, it does not completely retard the flux of porewater As to overtopping surface waters. Furthermore, the accumulated Fe minerals may be prone to future reductive dissolution, A conceptual model describing As hydro-geochemical coupling across an intertidal fringe is presented. © 2010 American Chemical Society.
- Publisher
- ACS Publications
- Relation
- Environmental Science and Technology Vol. 44, no. 6 (2010), p. 1968-1973
- Rights
- Copyright © 2010 American Chemical Society.
- Rights
- Open Access
- Rights
- This metadata is freely available under a CCO license
- Subject
- MD Multidisciplinary; Acid sulfate soils; Arsenic mobilization; Conceptual model; Hydraulic gradients; Intertidal zones; Pore waters; Primary mechanism; Redox gradients; Redox transition; Reducing conditions; Reductive dissolution; Sediment water interface; Solid-phase; Solid-phase speciation; Tidal pumping; Toposequences; Upward advection
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