Arsenic mobilization in a seawater inundated acid sulfate soil

Scott G. Johnston, Annabelle F. Keene, Edward D. Burton, Richard T. Bush, Leigh A. Sullivan, Angus E. Mcelnea, Col R. Ahern, C. Douglas Smith, Bernard Powell, Rosalie K. Hocking

Research output: Contribution to journalArticle

34 Citations (Scopus)

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 languageEnglish
Pages (from-to)1968-1973
Number of pages6
JournalEnvironmental Science and Technology
Volume44
Issue number6
DOIs
Publication statusPublished - 2010
Externally publishedYes

Fingerprint

acid sulfate soil
Arsenic
Seawater
Sulfates
mobilization
arsenic
porewater
seawater
Soils
Oxic sediments
Acids
Minerals
Dissolution
Bearings (structural)
Geochemistry
Hydrology
Advection
Surface waters
Oxides
Anions

Cite this

Johnston, S. G., Keene, A. F., Burton, E. D., Bush, R. T., Sullivan, L. A., Mcelnea, A. E., ... Hocking, R. K. (2010). Arsenic mobilization in a seawater inundated acid sulfate soil. Environmental Science and Technology, 44(6), 1968-1973. https://doi.org/10.1021/es903114z
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. / Arsenic mobilization in a seawater inundated acid sulfate soil. In: Environmental Science and Technology. 2010 ; Vol. 44, No. 6. pp. 1968-1973.
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Johnston, SG, Keene, AF, Burton, ED, Bush, RT, Sullivan, LA, Mcelnea, AE, Ahern, CR, Smith, CD, Powell, B & Hocking, RK 2010, 'Arsenic mobilization in a seawater inundated acid sulfate soil', Environmental Science and Technology, vol. 44, no. 6, pp. 1968-1973. https://doi.org/10.1021/es903114z

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 journalArticle

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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

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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.

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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

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ER -