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Edward D Burton - One of the best experts on this subject based on the ideXlab platform.
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effect of cyclic redox oscillations on water quality in freshwater Acid Sulfate Soil wetlands
Science of The Total Environment, 2017Co-Authors: Niloofar Karimian, Scott G Johnston, Edward D BurtonAbstract:Abstract Restoration of Acid Sulfate Soil (ASS) wetlands by freshwater re-flooding can lead to the reformation of various Fe(II) and reduced inorganic sulfur (RIS) species in surface Soil layers. However, in many locations, wetland water levels undergo large seasonal fluctuations that drive extreme redox oscillations. Newly formed RIS species [e.g. greigite, mackinawite, nano-pyrite and S(0)] and Fe(II) are vulnerable to rapid oxidation during dry periods and may generate substantial Acidity. Rainfall following a dry period may then mobilise Acidity and metal cations in surface waters prior to eventual recovery in pH by re-establishment of reducing conditions. We explore this dry-wet transition by subjecting Soil samples from two freshwater re-flooded ASS wetlands to oxidative incubation for up to 130 days followed by re-flooding simulation for 84 days. During very early stages of re-flooding (up to 7 days) there was an initial pulse-release of Acidity, and trace metals/metalloids (Al, Mn, Zn and As). This was followed by a rapid reversion to anoxia, and Fe(III) and SO4 reducing conditions which generated alkalinity, ameliorated Acidity and sequestered Fe, S, Zn, Mn and As. Field-observations of surface water quality in an ASS wetland at a sub-catchment scale also confirms re-establishment of SO4 reducing conditions and recovery of pH within ~ 4–8 weeks of re-flooding after dry periods. These observations suggest that retaining surface water in ASS wetlands for ~ 8 weeks after a dry-wet transition will allow sufficient time for alkalinity producing reductive processes to ameliorate most surface water Acidity. Although management of freshwater re-flooded ASS wetlands in a highly dynamic climate will remain challenging over the long term and the post-remediation effectiveness of the method depends on initial Soil characteristics, knowledge of the timing of redox oscillations and the associated changes in water geochemistry can be helpful for mitigating the risks to downstream estuarine water quality.
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trace element reactivity in fes rich estuarine sediments influence of formation environment and Acid Sulfate Soil drainage
Science of The Total Environment, 2012Co-Authors: Bree Morgan, Andrew W Rate, Edward D BurtonAbstract:Abstract Iron monosulfides (FeS) precipitate during benthic mineralisation of organic C and are well known to have a strong influence on trace element bioavailability in sediments. In this study we investigate the reactivity of trace elements (As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Zn) in sediments containing abundant and persistent FeS stores, collected from a south-western Australian estuarine system. Our objective was to explore the influence of sediment formation conditions on trace element reactivity by investigating sediments collected from different environments, including estuarine, riverine and Acid Sulfate Soil influenced sites, within a single estuarine system. In general, we found a higher degree of reactivity (defined by 1 mol/L HCl extractions) for Cd, Mn, Pb and Zn, compared with a lower reactivity of As, Co, Cr, Cu, Mo and Ni. Moderate to strong correlations (R2 > 0.4, P 0.05). Based on their reactivity and correlations with AVS, it appears that interactions (sorption, co-precipitation) between FeS and Cd, Mn, Pb and Zn in many of the sediments from this study are probable. Our data also demonstrate that drainage from Acid Sulfate Soils (ASS) can be a source of trace elements at specific sites. A principal components analysis of our reactive (1 mol/L HCl extractable) trace element data clearly distinguished sites receiving ASS drainage from the other non-impacted sites, by a high contribution from Fe–Co–Mn–Ni along the first principal axis, and contributions from higher S–As/lower reactive Pb along the second axis. This demonstrates that trace element reactivity in sediments may provide a geochemical signature for sites receiving ASS drainage.
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partitioning of metals in a degraded Acid Sulfate Soil landscape influence of tidal re inundation
Chemosphere, 2011Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G JohnstonAbstract:Abstract The oxidation and Acidification of sulfidic Soil materials results in the re-partitioning of metals, generally to more mobile forms. In this study, we examine the partitioning of Fe, Cr, Cu, Mn, Ni and Zn in the Acidified surface Soil (0–0.1 m) and the unoxidised sub-Soil materials (1.3–1.5 m) of an Acid Sulfate Soil landscape. Metal partitioning at this Acidic site was then compared to an adjacent site that was previously Acidified, but has since been remediated by tidal re-inundation. Differences in metal partitioning were determined using an optimised six-step sequential extraction procedure which targets the “labile”, “Acid-soluble”, “organic”, “crystalline oxide”, “pyritic” and “residual” fractions. The surficial Soil materials of the Acidic site had experienced considerable losses of Cr, Cu, Mn and Ni compared to the underlying parent material due to oxidation and Acidification, yet only minor losses of Fe and Zn. In general, the metals most depleted from the Acidified surface Soil materials exhibited the greatest sequestration in the surface Soil materials of the tidally remediated site. An exception to this was iron, which accumulated to highly elevated concentrations in the surficial Soil materials of the tidally remediated site. The “Acid-soluble”, “organic” and “pyritic” fractions displayed the greatest increase in metals following tidal remediation. This study demonstrates that prolonged tidal re-inundation of severely Acidified Acid Sulfate Soil landscapes leads to the immobilisation of trace metals through the surficial accumulation of iron oxides, organic material and pyrite.
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effects of hyper enriched reactive fe on sulfidisation in a tidally inundated Acid Sulfate Soil wetland
Biogeochemistry, 2011Co-Authors: Annabelle F Keene, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G Johnston, Angus E Mcelnea, Colin R Ahern, Bernard PowellAbstract: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.
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iron geochemical zonation in a tidally inundated Acid Sulfate Soil wetland
Chemical Geology, 2011Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Lloyd S Isaacson, Bernard PowellAbstract:Abstract Tidal inundation is a new technique for remediating coastal Acid Sulfate Soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe3(SO4)2(OH)6), resulted in elevated concentrations of porewater Fe2+ (> 30 mmol L−1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe2+-enriched porewater along the intertidal slope. Subsequent oxidation of Fe2+ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g−1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe8O8(OH)6SO4) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe2+. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.
Richard T Bush - One of the best experts on this subject based on the ideXlab platform.
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ecological restoration of a severely degraded coastal Acid Sulfate Soil a case study of the east trinity wetland queensland
Ecological Management and Restoration, 2017Co-Authors: Hanabeth Luke, Nicholas J Ward, Michelle A Martens, Ellen M Moon, Doug Smith, Richard T BushAbstract:A severely degraded Acid Sulfate Soil wetland near Cairns, Queensland, has been returned to a functional estuarine habitat using a cost-effective, low-technology method based on the reintroduction of tidal water. Gradual increases in tidal inundation, combined with targeted liming of the tidal stream, restored conditions that promoted chemical and microbial processes leading to the rapid recolonisation of mangrove communities and other estuarine flora and fauna. Protocols and understanding developed at East Trinity can be readily applied to other coastal Acid Sulfate Soil sites.
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partitioning of metals in a degraded Acid Sulfate Soil landscape influence of tidal re inundation
Chemosphere, 2011Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G JohnstonAbstract:Abstract The oxidation and Acidification of sulfidic Soil materials results in the re-partitioning of metals, generally to more mobile forms. In this study, we examine the partitioning of Fe, Cr, Cu, Mn, Ni and Zn in the Acidified surface Soil (0–0.1 m) and the unoxidised sub-Soil materials (1.3–1.5 m) of an Acid Sulfate Soil landscape. Metal partitioning at this Acidic site was then compared to an adjacent site that was previously Acidified, but has since been remediated by tidal re-inundation. Differences in metal partitioning were determined using an optimised six-step sequential extraction procedure which targets the “labile”, “Acid-soluble”, “organic”, “crystalline oxide”, “pyritic” and “residual” fractions. The surficial Soil materials of the Acidic site had experienced considerable losses of Cr, Cu, Mn and Ni compared to the underlying parent material due to oxidation and Acidification, yet only minor losses of Fe and Zn. In general, the metals most depleted from the Acidified surface Soil materials exhibited the greatest sequestration in the surface Soil materials of the tidally remediated site. An exception to this was iron, which accumulated to highly elevated concentrations in the surficial Soil materials of the tidally remediated site. The “Acid-soluble”, “organic” and “pyritic” fractions displayed the greatest increase in metals following tidal remediation. This study demonstrates that prolonged tidal re-inundation of severely Acidified Acid Sulfate Soil landscapes leads to the immobilisation of trace metals through the surficial accumulation of iron oxides, organic material and pyrite.
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effects of hyper enriched reactive fe on sulfidisation in a tidally inundated Acid Sulfate Soil wetland
Biogeochemistry, 2011Co-Authors: Annabelle F Keene, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G Johnston, Angus E Mcelnea, Colin R Ahern, Bernard PowellAbstract: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.
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iron geochemical zonation in a tidally inundated Acid Sulfate Soil wetland
Chemical Geology, 2011Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Lloyd S Isaacson, Bernard PowellAbstract:Abstract Tidal inundation is a new technique for remediating coastal Acid Sulfate Soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe3(SO4)2(OH)6), resulted in elevated concentrations of porewater Fe2+ (> 30 mmol L−1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe2+-enriched porewater along the intertidal slope. Subsequent oxidation of Fe2+ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g−1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe8O8(OH)6SO4) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe2+. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.
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effect of sample pretreatment on the fractionation of fe cr ni cu mn and zn in Acid Sulfate Soil materials
Geoderma, 2010Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T BushAbstract:A sequential extraction procedure was applied to Acid Sulfate Soil materials from a Soil profile to investigate the effect of sample pretreatment on the geochemical fractionation of selected metals. The samples were prepared for analysis by oven-drying, sieving and grinding the Soil, or were examined as collected in field condition. The Soil profile encompassed oxidising conditions near the surface, through to reducing conditions at depth. Six metals (Fe, Cr, Ni, Mn, Cu, and Zn) were measured during the sequential extraction procedure, and their fractionation determined in the oxidised and in the reduced zone. Although cumulative totals (the sum of all steps in the sequential extraction procedure) for the metals extracted from both the field condition and dried/ground samples were similar, some significant differences in fractionation within individual extraction steps were observed. Of particular interest was the redistribution of metals from the sulfide-bearing (pyrite-bound) fraction to the more readily available fractions (i.e. labile and Acid-soluble), as a result of oven-drying and grinding. The results indicate that when assessing metal fractionation in Acid Sulfate Soil materials, samples should be analysed in field condition in order to avoid the considerable metal fractionation artifacts that are induced by drying and grinding.
Leigh A Sullivan - One of the best experts on this subject based on the ideXlab platform.
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stable sulfur isotope dynamics in an Acid Sulfate Soil landscape following seawater inundation
Chemical Geology, 2016Co-Authors: Crystal A Maher, Leigh A SullivanAbstract:Abstract In 2002 a tidally driven seawater exchange remediation strategy was successfully implemented on a severely Acidified tropical coastal landscape dominated by Acid Sulfate Soils (ASS) in northern Australia. This study examined changes in the stable sulfur isotope signatures in a range of sulfide and Sulfate (SO4) fractions at three sites with different levels of exposure to the tidally driven seawater exchange remediation. δ34S in the Acid soluble SO4 fraction (e.g. jarosite) was less depleted in 34S than the corresponding sulfide, indicating a degree of fractionation during sulfide oxidation and jarosite precipitation. The δ34S of jarositic-SO4 was similar at all three sites indicating the appreciable stability of jarositic-SO4 even after extended exposure to seawater. δ34S of the water soluble, exchangeable and schwertmannitic-SO4 reflect conditions post remediation and indicate the relative contributions from two potential SO4 sources – a lighter SO4 derived from the oxidation of pyrite, and a heavier SO4 derived from the seawater. The δ34S of the contemporary surficial sulfide accumulations also reflect a SO4 contribution from seawater used for remediation and were isotopically different from the relict sulfides found at depth at all sites. δ34S of water soluble Sulfate allowed the progress of the remediation to be traced down the Soil profile. This study demonstrates the utility of stable sulfur isotope signatures in various sulfide and SO4 fractions to trace the sulfur geochemical pathways occurring in Soils, in this case as a result of the introduction of tidally driven sea water.
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partitioning of metals in a degraded Acid Sulfate Soil landscape influence of tidal re inundation
Chemosphere, 2011Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G JohnstonAbstract:Abstract The oxidation and Acidification of sulfidic Soil materials results in the re-partitioning of metals, generally to more mobile forms. In this study, we examine the partitioning of Fe, Cr, Cu, Mn, Ni and Zn in the Acidified surface Soil (0–0.1 m) and the unoxidised sub-Soil materials (1.3–1.5 m) of an Acid Sulfate Soil landscape. Metal partitioning at this Acidic site was then compared to an adjacent site that was previously Acidified, but has since been remediated by tidal re-inundation. Differences in metal partitioning were determined using an optimised six-step sequential extraction procedure which targets the “labile”, “Acid-soluble”, “organic”, “crystalline oxide”, “pyritic” and “residual” fractions. The surficial Soil materials of the Acidic site had experienced considerable losses of Cr, Cu, Mn and Ni compared to the underlying parent material due to oxidation and Acidification, yet only minor losses of Fe and Zn. In general, the metals most depleted from the Acidified surface Soil materials exhibited the greatest sequestration in the surface Soil materials of the tidally remediated site. An exception to this was iron, which accumulated to highly elevated concentrations in the surficial Soil materials of the tidally remediated site. The “Acid-soluble”, “organic” and “pyritic” fractions displayed the greatest increase in metals following tidal remediation. This study demonstrates that prolonged tidal re-inundation of severely Acidified Acid Sulfate Soil landscapes leads to the immobilisation of trace metals through the surficial accumulation of iron oxides, organic material and pyrite.
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effects of hyper enriched reactive fe on sulfidisation in a tidally inundated Acid Sulfate Soil wetland
Biogeochemistry, 2011Co-Authors: Annabelle F Keene, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G Johnston, Angus E Mcelnea, Colin R Ahern, Bernard PowellAbstract: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.
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iron geochemical zonation in a tidally inundated Acid Sulfate Soil wetland
Chemical Geology, 2011Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Lloyd S Isaacson, Bernard PowellAbstract:Abstract Tidal inundation is a new technique for remediating coastal Acid Sulfate Soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe3(SO4)2(OH)6), resulted in elevated concentrations of porewater Fe2+ (> 30 mmol L−1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe2+-enriched porewater along the intertidal slope. Subsequent oxidation of Fe2+ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g−1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe8O8(OH)6SO4) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe2+. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.
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effect of sample pretreatment on the fractionation of fe cr ni cu mn and zn in Acid Sulfate Soil materials
Geoderma, 2010Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T BushAbstract:A sequential extraction procedure was applied to Acid Sulfate Soil materials from a Soil profile to investigate the effect of sample pretreatment on the geochemical fractionation of selected metals. The samples were prepared for analysis by oven-drying, sieving and grinding the Soil, or were examined as collected in field condition. The Soil profile encompassed oxidising conditions near the surface, through to reducing conditions at depth. Six metals (Fe, Cr, Ni, Mn, Cu, and Zn) were measured during the sequential extraction procedure, and their fractionation determined in the oxidised and in the reduced zone. Although cumulative totals (the sum of all steps in the sequential extraction procedure) for the metals extracted from both the field condition and dried/ground samples were similar, some significant differences in fractionation within individual extraction steps were observed. Of particular interest was the redistribution of metals from the sulfide-bearing (pyrite-bound) fraction to the more readily available fractions (i.e. labile and Acid-soluble), as a result of oven-drying and grinding. The results indicate that when assessing metal fractionation in Acid Sulfate Soil materials, samples should be analysed in field condition in order to avoid the considerable metal fractionation artifacts that are induced by drying and grinding.
Scott G Johnston - One of the best experts on this subject based on the ideXlab platform.
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effect of cyclic redox oscillations on water quality in freshwater Acid Sulfate Soil wetlands
Science of The Total Environment, 2017Co-Authors: Niloofar Karimian, Scott G Johnston, Edward D BurtonAbstract:Abstract Restoration of Acid Sulfate Soil (ASS) wetlands by freshwater re-flooding can lead to the reformation of various Fe(II) and reduced inorganic sulfur (RIS) species in surface Soil layers. However, in many locations, wetland water levels undergo large seasonal fluctuations that drive extreme redox oscillations. Newly formed RIS species [e.g. greigite, mackinawite, nano-pyrite and S(0)] and Fe(II) are vulnerable to rapid oxidation during dry periods and may generate substantial Acidity. Rainfall following a dry period may then mobilise Acidity and metal cations in surface waters prior to eventual recovery in pH by re-establishment of reducing conditions. We explore this dry-wet transition by subjecting Soil samples from two freshwater re-flooded ASS wetlands to oxidative incubation for up to 130 days followed by re-flooding simulation for 84 days. During very early stages of re-flooding (up to 7 days) there was an initial pulse-release of Acidity, and trace metals/metalloids (Al, Mn, Zn and As). This was followed by a rapid reversion to anoxia, and Fe(III) and SO4 reducing conditions which generated alkalinity, ameliorated Acidity and sequestered Fe, S, Zn, Mn and As. Field-observations of surface water quality in an ASS wetland at a sub-catchment scale also confirms re-establishment of SO4 reducing conditions and recovery of pH within ~ 4–8 weeks of re-flooding after dry periods. These observations suggest that retaining surface water in ASS wetlands for ~ 8 weeks after a dry-wet transition will allow sufficient time for alkalinity producing reductive processes to ameliorate most surface water Acidity. Although management of freshwater re-flooded ASS wetlands in a highly dynamic climate will remain challenging over the long term and the post-remediation effectiveness of the method depends on initial Soil characteristics, knowledge of the timing of redox oscillations and the associated changes in water geochemistry can be helpful for mitigating the risks to downstream estuarine water quality.
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digital Soil mapping of a coastal Acid Sulfate Soil landscape
Soil Research, 2014Co-Authors: Jingyi Huang, Scott G Johnston, Terence Nhan, Vanessa N L Wong, Murray R Lark, John TriantafilisAbstract:Coastal floodplains are commonly underlain by sulfidic sediments and coastal Acid Sulfate Soils (CASS). Oxidation of sulfidic sediments leads to increases in Acidity and mobilisation of trace metals, resulting in an increase in the concentrations of conducting ions in sediment and pore water. The distribution of these sediments on floodplains is highly heterogeneous. Accurately identifying the distribution ofCASS isessential for developing targeted management strategies. One approach is the use of digital Soil mapping (DSM) using ancillary information. Proximal sensing instruments such as an EM38 can provide data on the spatial distribution of Soil salinity, which is associated with CASS, and can be complemented by digital elevation models (DEM). We used EM38 measurements of the apparent Soil electrical conductivity (ECa) in the horizontal and vertical modes in combination with a high resolution DEM to delineate the spatial distribution of CASS. We used a fuzzy k-means algorithm to cluster the data. The fuzziness exponent, number of classes (k) and distance metric (i.e. Euclidean, Mahalanobis and diagonal) were varied to determine a set of parameters to identify CASS. The mean-squared prediction error variance of the class mean of various Soil properties (e.g. EC1:5 and pH) was used to identify which of these metrics was suitable for further analysis (i.e. Mahalanobis) and also determine the optimal number of classes (i.e. k=4). The final map is consistent with previously defined Soil-landscape units generated using traditional Soil profile description, classification and mapping. The DSM approach is amenable for evaluation on a larger scale and in order to refine CASS boundaries previously mapped using the traditional approach or to identify CASS areas that remain unmapped.
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partitioning of metals in a degraded Acid Sulfate Soil landscape influence of tidal re inundation
Chemosphere, 2011Co-Authors: Salirian R Claff, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G JohnstonAbstract:Abstract The oxidation and Acidification of sulfidic Soil materials results in the re-partitioning of metals, generally to more mobile forms. In this study, we examine the partitioning of Fe, Cr, Cu, Mn, Ni and Zn in the Acidified surface Soil (0–0.1 m) and the unoxidised sub-Soil materials (1.3–1.5 m) of an Acid Sulfate Soil landscape. Metal partitioning at this Acidic site was then compared to an adjacent site that was previously Acidified, but has since been remediated by tidal re-inundation. Differences in metal partitioning were determined using an optimised six-step sequential extraction procedure which targets the “labile”, “Acid-soluble”, “organic”, “crystalline oxide”, “pyritic” and “residual” fractions. The surficial Soil materials of the Acidic site had experienced considerable losses of Cr, Cu, Mn and Ni compared to the underlying parent material due to oxidation and Acidification, yet only minor losses of Fe and Zn. In general, the metals most depleted from the Acidified surface Soil materials exhibited the greatest sequestration in the surface Soil materials of the tidally remediated site. An exception to this was iron, which accumulated to highly elevated concentrations in the surficial Soil materials of the tidally remediated site. The “Acid-soluble”, “organic” and “pyritic” fractions displayed the greatest increase in metals following tidal remediation. This study demonstrates that prolonged tidal re-inundation of severely Acidified Acid Sulfate Soil landscapes leads to the immobilisation of trace metals through the surficial accumulation of iron oxides, organic material and pyrite.
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effects of hyper enriched reactive fe on sulfidisation in a tidally inundated Acid Sulfate Soil wetland
Biogeochemistry, 2011Co-Authors: Annabelle F Keene, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G Johnston, Angus E Mcelnea, Colin R Ahern, Bernard PowellAbstract: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.
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iron geochemical zonation in a tidally inundated Acid Sulfate Soil wetland
Chemical Geology, 2011Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Lloyd S Isaacson, Bernard PowellAbstract:Abstract Tidal inundation is a new technique for remediating coastal Acid Sulfate Soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe3(SO4)2(OH)6), resulted in elevated concentrations of porewater Fe2+ (> 30 mmol L−1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe2+-enriched porewater along the intertidal slope. Subsequent oxidation of Fe2+ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g−1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe8O8(OH)6SO4) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe2+. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.
Bernard Powell - One of the best experts on this subject based on the ideXlab platform.
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effects of hyper enriched reactive fe on sulfidisation in a tidally inundated Acid Sulfate Soil wetland
Biogeochemistry, 2011Co-Authors: Annabelle F Keene, Edward D Burton, Leigh A Sullivan, Richard T Bush, Scott G Johnston, Angus E Mcelnea, Colin R Ahern, Bernard PowellAbstract: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.
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iron geochemical zonation in a tidally inundated Acid Sulfate Soil wetland
Chemical Geology, 2011Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Lloyd S Isaacson, Bernard PowellAbstract:Abstract Tidal inundation is a new technique for remediating coastal Acid Sulfate Soils (CASS). Here, we examine the effects of this technique on the geochemical zonation and cycling of Fe across a tidally inundated CASS toposequence, by investigating toposequence hydrology, in situ porewater geochemistry, solid-phase Fe fractions and Fe mineralogy. Interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation, redistribution and subsequent mineralogical transformations of Fe within the landscape. Reductive dissolution of Fe(III) minerals, including jarosite (KFe3(SO4)2(OH)6), resulted in elevated concentrations of porewater Fe2+ (> 30 mmol L−1) in former sulfuric horizons in the upper-intertidal zone. Tidal forcing generated oscillating hydraulic gradients, driving upward advection of this Fe2+-enriched porewater along the intertidal slope. Subsequent oxidation of Fe2+ led to substantial accumulation of reactive Fe(III) fractions (up to 8000 μmol g−1) in redox-interfacial, tidal zone sediments. These Fe(III)-precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation. Schwertmannite (Fe8O8(OH)6SO4) was the dominant Fe mineral phase in the upper-intertidal zone at mainly low pH (3–4). This was followed by increasing lepidocrocite (γ-FeOOH) and goethite (α-FeOOH) at circumneutral pH within lower-intertidal and subtidal zones. Relationships were evident between Fe fractions and topography. There was increasing precipitation of Fe-sulfide minerals and non-sulfidic solid-phase Fe(II) in the lower intertidal and subtidal zones. Precipitation of Fe-sulfide minerals was spatially co-incident with decreases in porewater Fe2+. A conceptual model is presented to explain the observed landscape-scale patterns of Fe mineralisation and hydro-geochemical zonation. This study provides valuable insights into the hydro-geochemical processes caused by saline tidal inundation of low lying CASS landscapes, regardless of whether inundation is an intentional strategy or due to sea-level rise.
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abundance and fractionation of al fe and trace metals following tidal inundation of a tropical Acid Sulfate Soil
Applied Geochemistry, 2010Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Annabelle F Keene, Bernard PowellAbstract:Abstract Tidal inundation was restored to a severely degraded tropical Acid Sulfate Soil landscape and subsequent changes in the abundance and fractionation of Al, Fe and selected trace metals were investigated. After 5 a of regular tidal inundation there were large decreases in water-soluble and exchangeable Al fractions within former sulfuric horizons. This was strongly associated with decreased Soil Acidity and increases in pH, suggesting pH-dependent immobilisation of Al via precipitation as poorly soluble phases. The water-soluble fractions of Fe, Zn, Ni and Mn also decreased. However, there was substantial enrichment (2–5×) of the reactive Fe fraction (FeR; 1 M HCl extractable) near the Soil surface, plus a closely corresponding enrichment of 1 M HCl extractable Cr, Zn, Ni and Mn. Surficial accumulations of Fe(III) minerals in the inter-tidal zone were poorly crystalline (up to 38% FeR) and comprised mainly of schwertmannite (Fe8O8(OH)6SO4) with minor quantities of goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). These Fe (III) mineral accumulations provide an effective substrate for the adsorption/co-precipitation and accumulation of trace metals. Arsenic displayed contrary behaviour to trace metals with peak concentrations (∼60 μg g−1) near the redox minima. Changes in the abundance and fractionation of the various metals can be primarily explained by the shift in the geochemical regime from oxic–Acidic to reducing-circumneutral conditions, combined with the enrichment of reactive Fe near the Soil surface. Whilst increasing sequestration of trace metals via sulfidisation is likely to occur over the long-term, the current abundance of reactive Fe near the sediment–water interface favours a dynamic environment with respect to metals in the tidally inundated areas.
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arsenic mobilization in a seawater inundated Acid Sulfate Soil
Environmental Science & Technology, 2010Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Douglas C Smith, Angus E Mcelnea, Bernard Powell, Annabelle F Keene, Col R Ahern, Rosalie K HockingAbstract: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 i...
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changes in water quality following tidal inundation of coastal lowland Acid Sulfate Soil landscapes
Estuarine Coastal and Shelf Science, 2009Co-Authors: Scott G Johnston, Edward D Burton, Leigh A Sullivan, Richard T Bush, Michelle A Martens, Douglas C Smith, Angus E Mcelnea, Colin R Ahern, Bernard Powell, Luisa P StephensAbstract:Abstract This study examines the remediation of surface water quality in a severely degraded coastal Acid Sulfate Soil landscape. The remediation strategy consisted of partial restoration of marine tidal exchange within estuarine creeks and incremental tidal inundation of Acidified Soils, plus strategic liming of drainage waters. Time-series water quality and climatic data collected over 5 years were analysed to assess changes in water quality due to this remediation strategy. A time-weighted rainfall function (TWR) was generated from daily rainfall data to integrate the effects of antecedent rainfall on shallow groundwater levels in a way that was relevant to Acid export dynamics. Significant increases in mean pH were evident over time at multiple monitoring sites. Regression analysis at multiple sites revealed a temporal progression of change in significant relationships between mean daily electrical conductivity (EC) vs. mean daily pH, and TWR vs. mean daily pH. These data demonstrate a substantial decrease over time in the magnitude of creek Acidification per given quantity of antecedent rainfall. Data also show considerable increase in Soil pH (2–3 units) in formerly Acidified areas subject to tidal inundation. This coincides with a decrease in Soil pe, indicating stronger reducing conditions. These observations suggest a fundamental shift has occurred in sediment geochemistry in favour of proton-consuming reductive processes. Combined, these data highlight the potential effectiveness of marine tidal inundation as a landscape-scale Acid Sulfate Soil remediation strategy.
