Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland

Annabelle F. Keene, Scott G. Johnston, Richard T. Bush, Leigh A. Sullivan, Edward D. Burton, Angus E. McElnea, Colin R. Ahern, Bernard Powell

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Abstract

Solid phase Fe and S fractions were examined in an acid sulfate soil (ASS) wetland undergoing remediation via tidal inundation. Considerable diagenetic enrichment of reactive Fe(III) oxides (HCl- and dithionite-extractable) occurred near the soil surface (0-0.05 m depth), where extremely large concentrations up to 3534 μmol/g accounted for ~90% of the total Fe pool. This major source of reactive Fe exerts a substantial influence on S cycling and the formation, speciation and transformation of reduced inorganic S (RIS) in tidally inundated ASS. Under these geochemical conditions, acid volatile sulfide (AVS; up to 57 μmol/g) and elemental sulfur (S0; up to 41 μmol/g) were the dominant fractions of RIS in near surface soils. AVS-S to pyrite-S ratios exceeded 2.9 near the surface, indicating that abundant reactive Fe favoured the accumulation of AVS minerals and S0 over pyrite. This is supported by the significant correlation of poorly crystalline Fe with AVS-S and S0-S contents (r = 0.83 and r = 0.85, respectively, P < 0.01). XANES spectroscopy provided direct evidence for the presence of a greigite-like phase in AVS-S measured by chemical extraction. While the abundant reactive Fe may limit the transformation of AVS minerals and S0 to pyrite during early diagenesis (~5 years), continued sulfidisation over longer time scales is likely to eventually lead to enhanced sequestration of S within pyrite (with a predicted 8% pyrite by mass). These findings provide an important understanding of sulfidisation processes occurring in reactive Fe-enriched, tidally inundated ASS landscapes.

Original languageEnglish
Pages (from-to)263-279
Number of pages17
JournalBiogeochemistry
Volume103
Issue number1
DOIs
Publication statusPublished - 2011
Externally publishedYes

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acid sulfate soil
Wetlands
Sulfates
pyrite
wetland
Soils
Acids
Minerals
soil surface
greigite
X ray absorption near edge structure spectroscopy
XANES spectroscopy
Dithionite
Sulfides
mineral
Remediation
Sulfur
Oxides
diagenesis
remediation

Cite this

Keene, A. F., Johnston, S. G., Bush, R. T., Sullivan, L. A., Burton, E. D., McElnea, A. E., ... Powell, B. (2011). Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland. Biogeochemistry, 103(1), 263-279. https://doi.org/10.1007/s10533-010-9461-2
Keene, Annabelle F. ; Johnston, Scott G. ; Bush, Richard T. ; Sullivan, Leigh A. ; Burton, Edward D. ; McElnea, Angus E. ; Ahern, Colin R. ; Powell, Bernard. / Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland. In: Biogeochemistry. 2011 ; Vol. 103, No. 1. pp. 263-279.
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Keene, AF, Johnston, SG, Bush, RT, Sullivan, LA, Burton, ED, McElnea, AE, Ahern, CR & Powell, B 2011, 'Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland', Biogeochemistry, vol. 103, no. 1, pp. 263-279. https://doi.org/10.1007/s10533-010-9461-2

Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland. / Keene, Annabelle F.; Johnston, Scott G.; Bush, Richard T.; Sullivan, Leigh A.; Burton, Edward D.; McElnea, Angus E.; Ahern, Colin R.; Powell, Bernard.

In: Biogeochemistry, Vol. 103, No. 1, 2011, p. 263-279.

Research output: Contribution to journalArticle

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T1 - Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland

AU - Keene, Annabelle F.

AU - Johnston, Scott G.

AU - Bush, Richard T.

AU - Sullivan, Leigh A.

AU - Burton, Edward D.

AU - McElnea, Angus E.

AU - Ahern, Colin R.

AU - Powell, Bernard

PY - 2011

Y1 - 2011

N2 - Solid phase Fe and S fractions were examined in an acid sulfate soil (ASS) wetland undergoing remediation via tidal inundation. Considerable diagenetic enrichment of reactive Fe(III) oxides (HCl- and dithionite-extractable) occurred near the soil surface (0-0.05 m depth), where extremely large concentrations up to 3534 μmol/g accounted for ~90% of the total Fe pool. This major source of reactive Fe exerts a substantial influence on S cycling and the formation, speciation and transformation of reduced inorganic S (RIS) in tidally inundated ASS. Under these geochemical conditions, acid volatile sulfide (AVS; up to 57 μmol/g) and elemental sulfur (S0; up to 41 μmol/g) were the dominant fractions of RIS in near surface soils. AVS-S to pyrite-S ratios exceeded 2.9 near the surface, indicating that abundant reactive Fe favoured the accumulation of AVS minerals and S0 over pyrite. This is supported by the significant correlation of poorly crystalline Fe with AVS-S and S0-S contents (r = 0.83 and r = 0.85, respectively, P < 0.01). XANES spectroscopy provided direct evidence for the presence of a greigite-like phase in AVS-S measured by chemical extraction. While the abundant reactive Fe may limit the transformation of AVS minerals and S0 to pyrite during early diagenesis (~5 years), continued sulfidisation over longer time scales is likely to eventually lead to enhanced sequestration of S within pyrite (with a predicted 8% pyrite by mass). These findings provide an important understanding of sulfidisation processes occurring in reactive Fe-enriched, tidally inundated ASS landscapes.

AB - Solid phase Fe and S fractions were examined in an acid sulfate soil (ASS) wetland undergoing remediation via tidal inundation. Considerable diagenetic enrichment of reactive Fe(III) oxides (HCl- and dithionite-extractable) occurred near the soil surface (0-0.05 m depth), where extremely large concentrations up to 3534 μmol/g accounted for ~90% of the total Fe pool. This major source of reactive Fe exerts a substantial influence on S cycling and the formation, speciation and transformation of reduced inorganic S (RIS) in tidally inundated ASS. Under these geochemical conditions, acid volatile sulfide (AVS; up to 57 μmol/g) and elemental sulfur (S0; up to 41 μmol/g) were the dominant fractions of RIS in near surface soils. AVS-S to pyrite-S ratios exceeded 2.9 near the surface, indicating that abundant reactive Fe favoured the accumulation of AVS minerals and S0 over pyrite. This is supported by the significant correlation of poorly crystalline Fe with AVS-S and S0-S contents (r = 0.83 and r = 0.85, respectively, P < 0.01). XANES spectroscopy provided direct evidence for the presence of a greigite-like phase in AVS-S measured by chemical extraction. While the abundant reactive Fe may limit the transformation of AVS minerals and S0 to pyrite during early diagenesis (~5 years), continued sulfidisation over longer time scales is likely to eventually lead to enhanced sequestration of S within pyrite (with a predicted 8% pyrite by mass). These findings provide an important understanding of sulfidisation processes occurring in reactive Fe-enriched, tidally inundated ASS landscapes.

KW - Acid sulfate soil

KW - Reactive iron

KW - Reduced inorganic sulfur

KW - Sulfidisation

KW - Tidal inundation

KW - Wetland

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