Journal article
Arsenic mobilization in a seawater inundated acid sulfate soil
Environmental Science and Technology, Vol.44(6), pp.1968-1973
2010
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Abstract
<p>Tidal seawater inundation of coastal acid sulfate soils can generate Fe- and SO4-reducing conditions in previously oxic-acidic 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 (400 μg/L) occurred in the shallow (<1>m), intertidal, redox transition zone between Fe-oxidizing and SO4-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.</p>
Details
- Title
- Arsenic mobilization in a seawater inundated acid sulfate soil
- Creators
- Scott G Johnston - Southern Cross UniversityAnnabelle F Keene - Southern Cross UniversityEdward D Burton - Southern Cross UniversityRichard T Bush - Southern Cross UniversityLeigh A Sullivan - Southern Cross UniversityAngus E McElnea - Department of Natural Resources & Water, Qld.Colin R Ahern - Department of Natural Resources & Water, Qld.C Douglas Smith - Department of Natural Resources & Water, Qld.Bernard Powell - Department of Natural Resources & Water, Qld.Rosalie K Hocking - Monash University
- Publication Details
- Environmental Science and Technology, Vol.44(6), pp.1968-1973
- Identifiers
- 1601; 991012821452602368
- Academic Unit
- School of Environment, Science and Engineering; Southern Cross GeoScience; Science; Faculty of Science and Engineering
- Resource Type
- Journal article