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.
| Original language | English |
|---|---|
| Pages (from-to) | 1968-1973 |
| Number of pages | 6 |
| Journal | Environmental Science and Technology |
| Volume | 44 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2010 |
| Externally published | Yes |
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Arsenic mobilization in a seawater inundated acid sulfate soil. / Johnston, Scott G.; Keene, Annabelle F.; Burton, Edward D.; Bush, Richard T.; Sullivan, Leigh A.; Mcelnea, Angus E.; Ahern, Col R.; Smith, C. Douglas; Powell, Bernard; Hocking, Rosalie K.
In: Environmental Science and Technology, Vol. 44, No. 6, 2010, p. 1968-1973.Research output: Contribution to journal › Article
TY - JOUR
T1 - Arsenic mobilization in a seawater inundated acid sulfate soil
AU - Johnston, Scott G.
AU - Keene, Annabelle F.
AU - Burton, Edward D.
AU - Bush, Richard T.
AU - Sullivan, Leigh A.
AU - Mcelnea, Angus E.
AU - Ahern, Col R.
AU - Smith, C. Douglas
AU - Powell, Bernard
AU - Hocking, Rosalie K.
PY - 2010
Y1 - 2010
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=77949389114&partnerID=8YFLogxK
U2 - 10.1021/es903114z
DO - 10.1021/es903114z
M3 - Article
VL - 44
SP - 1968
EP - 1973
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 6
ER -