ORCID Profile
0000-0002-5826-5613
Current Organisation
Southern Cross University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Geochemistry | Inorganic Geochemistry | Surfacewater Hydrology | Isotope Geochemistry | Soil Chemistry (excl. Carbon Sequestration Science) | Carbon Sequestration Science | Food Chemistry and Molecular Gastronomy (excl. Wine) | Earth Sciences Not Elsewhere Classified | Plant Biology | Chemical Oceanography | Structural Biology (incl. Macromolecular Modelling) | Animal Physiological Ecology | Environmental Chemistry (incl. Atmospheric Chemistry) | Soil And Water Sciences Not Elsewhere Classified | Environmental Rehabilitation (excl. Bioremediation) | Geochemistry not elsewhere classified | Geochemistry Not Elsewhere Classified | Hydrogeology | Quaternary Environments | Bioinorganic Chemistry | Structural Chemistry and Spectroscopy | Chemotherapy | Geomorphology and Regolith and Landscape Evolution | Organic Geochemistry | Plant Physiology | Medical Biochemistry and Metabolomics | Ecosystem Function | Chemical Engineering not elsewhere classified | Forestry Management and Environment | Crop and Pasture Biochemistry and Physiology | Medical Biochemistry: Proteins and Peptides (incl. Medical Proteomics) | Medical Biochemistry: Inorganic Elements and Compounds | Analytical Biochemistry | Atomic and Molecular Physics
ANZSRC Socio-Economic Objective (SEO)
Physical and Chemical Conditions of Water in Coastal and Estuarine Environments | Coastal and Estuarine Land Management | Coastal and Estuarine Soils | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences | Coastal and Estuarine Water Management | Management of Liquid Waste from Mineral Resource Activities (excl. Water) | Management of Solid Waste from Mineral Resource Activities | Inorganic Industrial Chemicals | Climate change | Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use) | Mining and Extraction of Precious (Noble) Metal Ores | Expanding Knowledge in History and Archaeology | Ecosystem Assessment and Management of Coastal and Estuarine Environments | Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments | Energy Transformation not elsewhere classified | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Ecosystem Assessment and Management of Forest and Woodlands Environments | Climate Change Mitigation Strategies | Expanding Knowledge in the Medical and Health Sciences | Land and water management | Physical and chemical conditions | Forest and Woodlands Soils | Human Pharmaceutical Treatments (e.g. Antibiotics) | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Expanding Knowledge in the Agricultural and Veterinary Sciences | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Fire Promotes Arsenic Mobilization and Rapid Arsenic(III) Formation in Soil via Thermal Alteration of Arsenic-Bearing Iron Oxides
Publisher: Frontiers Media SA
Date: 29-05-2019
Antimony(V) Incorporation into Schwertmannite: Critical Insights on Antimony Retention in Acidic Environments
Publisher: American Chemical Society (ACS)
Date: 29-11-2022
Abstract: This study examines incorporation of Sb(V) into schwertmannite─an Fe(III) oxyhydroxysulfate mineral that can be an important Sb host phase in acidic environments. Schwertmannite was synthesized from solutions containing a range of Sb(V)/Fe(III) ratios, and the resulting solids were investigated using geochemical analysis, powder X-ray diffraction (XRD), dissolution kinetic experiments, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Shell-fitting and wavelet transform analyses of Sb K-edge EXAFS data, together with congruent Sb and Fe release during schwertmannite dissolution, indicate that schwertmannite incorporates Sb(V) via heterovalent substitution for Fe(III). Elemental analysis combined with XRD and Fe K-edge EXAFS spectroscopy shows that schwertmannite can incorporate Sb(V) via this mechanism at up to about 8 mol % substitution when formed from solutions having Sb/Fe ratios ≤0.04 (higher ratios inhibit schwertmannite formation). Incorporation of Sb(V) into schwertmannite involves formation of edge and double-corner sharing linkages between Sb
Iron(III) accumulations in inland saline waterways, Hunter Valley, Australia: Mineralogy, micromorphology and pore-water geochemistry
Publisher: Elsevier BV
Date: 10-2009
Seawater causes rapid trace metal mobilisation in coastal lowland acid sulfate soils: Implications of sea level rise for water quality
Publisher: Elsevier BV
Date: 12-2010
The effects of a weir on reducing acid flux from a drained coastal acid sulphate soil backswamp
Publisher: Elsevier BV
Date: 09-2004
Acidic drainage drives anomalous rare earth element signatures in intertidal mangrove sediments
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.SCITOTENV.2016.08.172
Abstract: Sedimentary rare earth element (REE) signatures can provide powerful insights into nearshore biogeochemical processes and anthropogenic influences. Despite this, there is limited research investigating REE behaviour in sediments influenced by coastal acid sulfate soils (CASS). Here, we explore REE abundance and fractionation in intertidal mangrove sediments that received CASS drainage for ~15-20y within the Hastings Catchment in NSW, Australia. Sediments close to the CASS discharge point ( 1.5), with a high proportion (63-100%) of REEs residing in the reactive (1M HCl extractable) sediment fraction. Interestingly, the degree of MREE enrichment was significantly correlated with Ce anomalies (r
Antimony and arsenic speciation, redox-cycling and contrasting mobility in a mining-impacted river system
Publisher: Elsevier BV
Date: 03-2020
Large methane emissions from tree stems complicate the wetland methane budget
Publisher: Authorea, Inc.
Date: 13-09-2023
Effects of hyper-enriched reactive Fe on sulfidisation in a tidally inundated acid sulfate soil wetland
Publisher: Springer Science and Business Media LLC
Date: 14-05-2010
Mangroves as a Source of Greenhouse Gases to the Atmosphere and Alkalinity and Dissolved Carbon to the Coastal Ocean: A Case Study from the Everglades National Park, Florida
Publisher: American Geophysical Union (AGU)
Date: 12-2020
DOI: 10.1029/2020JG005812
Contrasting effects of phosphate on the rapid transformation of schwertmannite to Fe(III) (oxy)hydroxides at near-neutral pH
Publisher: Elsevier BV
Date: 04-2019
Tidally driven water column hydro-geochemistry in a remediating acidic wetland
Publisher: Elsevier BV
Date: 10-2011
Remediation of Pb-contaminated soil using modified bauxite refinery residue
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.JHAZMAT.2022.129339
Abstract: This study examines amendment of Pb-contaminated soil with modified bauxite refinery residue (MBRR) to decrease soil Pb mobility and bioaccessibility. Amendment experiments were conducted using four soils contaminated with Pb from various sources, including smelting, shooting-range activities and Pb-based paint waste. Lead L
Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X-ray Spectroscopy
Publisher: American Chemical Society (ACS)
Date: 26-09-0002
Arsenic solid-phase speciation in an alluvial aquifer system adjacent to the Himalayan forehills, Nepal
Publisher: Elsevier BV
Date: 12-2015
Arsenic-Imposed Effects on Schwertmannite and Jarosite Formation in Acid Mine Drainage and Coupled Impacts on Arsenic Mobility
Publisher: American Chemical Society (ACS)
Date: 19-05-2021
Pore Water Sampling in Acid Sulfate Soils: A New Peeper Method
Publisher: Wiley
Date: 11-2009
DOI: 10.2134/JEQ2009.0135
Abstract: This study describes the design, deployment, and application of a modified equilibration dialysis device (peeper) optimized for s ling pore waters in acid sulfate soils (ASS). The modified design overcomes the limitations of traditional-style peepers, when s ling firm ASS materials over relatively large depth intervals. The new peeper device uses removable, in idual cells of 25 mL volume housed in a 1.5 m long rigid, high-density polyethylene rod. The rigid housing structure allows the device to be inserted directly into relatively firm soils without requiring a supporting frame. The use of removable cells eliminates the need for a large glove-box after peeper retrieval, thus simplifying physical handling. Removable cells are easily maintained in an inert atmosphere during s le processing and the 25-mL s le volume is sufficient for undertaking multiple analyses. A field evaluation of equilibration times indicates that 32 to 38 d of deployment was necessary. Overall, the modified method is simple and effective and well suited to acquisition and processing of redox-sensitive pore water profiles>1 m deep in acid sulfate soil or any other firm wetland soils.
Artificial drainage of floodwaters from sulfidic backswamps: effects on deoxygenation in an Australian estuary
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/MF02016
Abstract: The Clarence River estuary experienced extensive oxygen depletion and fish kills following overbank flooding in 2001. This paper examines the chemical composition and volume of surface water draining from two floodplain sulfidic backsw s into the Clarence River estuary after the flooding. Water draining from the backsw s was severely deoxygenated ( μmol L–1 O2), developed high chemical oxygen demand (~5000 μmol L–1) and became enriched in iron (~350 μmol L–1) during the weeks following the flood. The chemistry of this anoxic drainage water was influenced by anaerobic decomposition of backsw vegetation, iron and sulfur biogeochemistry in backsw surface sediments and shallow ground water input from acid sulfate soils. This study shows that artificial drainage of sulfidic backsw s increased the volume of anoxic surface water with high deoxygenation potential exported to the estuary, increasing the severity and duration of estuarine oxygen depletion in the latter stages ( days post-peak) of flood recession. In the absence of artificial drainage, most of the floodwaters with high deoxygenation potential would have been retained in the landscape and not exported to the estuary as observed during this flood.
Arsenic Mobilization in a Seawater Inundated Acid Sulfate Soil
Publisher: American Chemical Society (ACS)
Date: 15-02-2010
DOI: 10.1021/ES903114Z
Abstract: Tidal seawater inundation of coastal acid sulfate soils can generate Fe- and S0(4)-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 S0(4)-reducing conditions. Primary mechanisms of As mobilization include the reduction of solid-phase As(V) to As(lll), reductive dissolution of As(V)-bearing secondary Fe(lll) 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 Fe(2+)-enriched porewater in the intertidal zone, leading to accumulation of As(V)-enriched Fe(lll) (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.
Diffusive Gradients in Thin Films Reveals Differences in Antimony and Arsenic Mobility in a Contaminated Wetland Sediment during an Oxic-Anoxic Transition
Publisher: American Chemical Society (ACS)
Date: 26-01-2018
Abstract: Antimony (Sb) and arsenic (As) are priority environmental contaminants that often co-occur at mining-impacted sites. Despite their chemical similarities, Sb mobility in waterlogged sediments is poorly understood in comparison to As, particularly across the sediment-water interface (SWI) where changes can occur at the millimeter scale. Combined diffusive gradients in thin films (DGT) and diffusive equilibration in thin films (DET) techniques provided a high resolution, in situ comparison between Sb, As, and iron (Fe) speciation and mobility across the SWI in contaminated freshwater wetland sediment mesocosms under an oxic-anoxic-oxic transition. The shift to anoxic conditions released Fe(II), As(III), and As(V) from the sediment to the water column, consistent with As release being coupled to the reductive dissolution of iron(III) (hydr)oxides. Conversely, Sb(III) and Sb(V) effluxed to the water column under oxic conditions and fluxed into the sediment under anoxic conditions. Porewater DGT-DET depth profiles showed apparent decoupling between Fe(II) and Sb release, as Sb was primarily mobilized across the SWI under oxic conditions. Solid-phase X-ray absorption spectroscopy (XAS) revealed the presence of an Sb(III)-S phase in the sediment that increased in proportion with depth and the transition from oxic to anoxic conditions. The results of this study showed that Sb mobilization was decoupled from the Fe cycle and was, therefore, more likely linked to sulfur and/or organic carbon (e.g., most likely authigenic antimony sulfide formation or Sb(III) complexation by reduced organic sulfur functional groups).
Antimony and arsenic partitioning during Fe2+ -induced transformation of jarosite under acidic conditions
Publisher: Elsevier BV
Date: 03-2018
DOI: 10.1016/J.CHEMOSPHERE.2017.12.106
Abstract: Jarosite [KFe
Bark-dwelling methanotrophic bacteria decrease methane emissions from trees
Publisher: Springer Science and Business Media LLC
Date: 09-04-2021
DOI: 10.1038/S41467-021-22333-7
Abstract: Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal microbial controls (i.e. methanotrophy) within tree bark may reduce methane emissions. Here we demonstrate that unique microbial communities dominated by methane-oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia , a common, invasive and globally distributed lowland species. In laboratory incubations, methane-inoculated M. quinquenervia bark mediated methane consumption (up to 96.3 µmol m −2 bark d −1 ) and reveal distinct isotopic δ 13 C-CH 4 enrichment characteristic of MOB. Molecular analysis indicates unique microbial communities reside within the bark, with MOB primarily from the genus Methylomonas comprising up to 25 % of the total microbial community. Methanotroph abundance was linearly correlated to methane uptake rates (R 2 = 0.76, p = 0.006). Finally, field-based methane oxidation inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by 36 ± 5 %. These multiple complementary lines of evidence indicate that bark-dwelling MOB represent a potentially significant methane sink, and an important frontier for further research.
Reconstructing extreme climatic and geochemical conditions during the largest natural mangrove dieback on record
Publisher: Copernicus GmbH
Date: 28-09-2020
Abstract: Abstract. A massive mangrove dieback event occurred in 2015–2016 along ∼1000 km of pristine coastline in the Gulf of Carpentaria, Australia. Here, we use sediment and wood chronologies to gain insights into geochemical and climatic changes related to this dieback. The unique combination of low rainfall and low sea level observed during the dieback event had been unprecedented in the preceding 3 decades. A combination of iron (Fe) chronologies in wood and sediment, wood density and estimates of mangrove water use efficiency all imply lower water availability within the dead mangrove forest. Wood and sediment chronologies suggest a rapid, large mobilization of sedimentary Fe, which is consistent with redox transitions promoted by changes in soil moisture content. Elemental analysis of wood cross sections revealed a 30- to 90-fold increase in Fe concentrations in dead mangroves just prior to their mortality. Mangrove wood uptake of Fe during the dieback is consistent with large apparent losses of Fe from sediments, which potentially caused an outwelling of Fe to the ocean. Although Fe toxicity may also have played a role in the dieback, this possibility requires further study. We suggest that differences in wood and sedimentary Fe between living and dead forest areas reflect sediment redox transitions that are, in turn, associated with regional variability in groundwater flows. Overall, our observations provide multiple lines of evidence that the forest dieback was driven by low water availability coinciding with a strong El Niño–Southern Oscillation (ENSO) event and was associated with climate change.
The acid flux dynamics of two artificial drains in acid sulfate soil backswamps on the Clarence River floodplain, Australia
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/SR03069
Abstract: The export of acidity, iron, aluminium, and sulfate to an estuary from 2 drains in acid sulfate soil backsw s was monitored over 18 months. The backsw s had similar geomorphology, stratigraphy, and drainage density, and comparable soil and groundwater acidity. However, the flux rates, temporal dynamics, and export pathways of acid and other sulfide oxidation products varied greatly and were controlled to first order by (i) the saturated hydraulic conductivity (K) of sulfuric horizons and (ii) the tidally influenced groundwater gradients. The site with very high K and large tidally influenced groundwater gradients had high acid flux rates (5300 mol H+/ha.year), chronic acid discharge, high drain water acid and metal concentrations, and the primary flux pathway was direct groundwater seepage (interflow/bypass flow) to the drain. The site with lower K and smaller groundwater gradients displayed low acid flux rates (50 mol H+/ha.year), infrequent, highly episodic discharge, and the primary flux pathway was dilute surface runoff following dissolution of sulfide oxidation products accumulated on the soil surface. Importantly, the majority of acid export at both sites occurred while the backsw groundwater level was within a very narrow elevation range.
Antimony mobility in reducing environments: The effect of microbial iron(III)-reduction and associated secondary mineralization
Publisher: Elsevier BV
Date: 2019
Alteration of groundwater and sediment geochemistry in a sulfidic backswamp due to Melaleuca quinquenervia encroachment
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/SR03027
Abstract: Extensive encroachment of the native tree species Melaleuca quinquenervia (Cav.) Blake has occurred on a coastal floodplain sulfidic backsw in eastern Australia. Almost 50% of the open sw area c. 1870 is now monospecific M. quinquenervia forest. Encroachment has been associated with shortened hydroperiods and land management changes following drainage for agriculture. Large differences to shallow groundwater and sediment geochemistry were observed beneath both in idual M. quinquenervia trees and encroaching forests compared to open sw . Groundwater beneath M. quinquenervia had enhanced titratable acidity and acidic metal cations, increased concentrations of other ionic species (Cl–, SO42–), altered ionic ratios, and increased dissolved organic carbon. Soil beneath M. quinquenervia displayed enhanced accumulation of acidity and soluble ions, with concentration profiles suggesting vertical redistribution towards the surface. Deepening of the sulfide oxidation front in the soil beneath encroached M. quinquenervia suggests that enhanced sulfide oxidation may be occurring. Changes in soil pH, redox potential, and Fe mineral precipitation/dissolution were also evident. These changes appear to be the result of interactions between M. quinquenervia physiology and the unique groundwater and sediment geochemistry of the surrounding sulfidic/sulfuric horizons. Mechanisms to explain the observed changes are discussed along with potential management implications.
Drought, megafires and flood - climate extreme impacts on catchment-scale river water quality on Australia's east coast
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.WATRES.2022.118510
Abstract: Increased frequency and intensity of drought, wildfires and flooding due to climate change has major implications for river water quality, yet there are limited high-temporal resolution data capturing the combined transient impacts of these extreme events at large catchment scales. We present flow-stratified water quality data from a large coastal catchment (Macleay River, Australia) spanning severe drought and extensive fires followed by flooding. We examine concentrations (C), discharge (Q) and flux of suspended sediment, major ions, dissolved organic carbon (DOC) and key nutrients (NO
A revised method for determining existing acidity in re-flooded acid sulfate soils
Publisher: Elsevier BV
Date: 2015
Iron-Monosulfide Oxidation in Natural Sediments: Resolving Microbially Mediated S Transformations Using XANES, Electron Microscopy, and Selective Extractions
Publisher: American Chemical Society (ACS)
Date: 04-2009
DOI: 10.1021/ES8036548
Abstract: Iron-monosulfide oxidation and associated S transformations in a natural sediment were examined by combining selective extractions, electron microscopy and S K-edge X-ray absorption near-edge structure (XANES) spectroscopy, The sediment examined in this study was collected from a waterway receiving acid-sulfate soil drainage. It contained a high acid-volatile sulfide content (1031 micromol g(-1)), reflecting an abundance of iron-monosulfide. The iron-monosulfide speciation in the initial sediment s le was dominated by nanocrystalline mackinawite (tetragonal FeS). At near-neutral pH and an 02 partial pressure of approximately 0.2 atm, the mackinawite was found to oxidize rapidly, with a half-time of 29 +/- 2 min. This oxidation rate did not differ significantly (P < 0.05) between abiotic versus biotic conditions, demonstrating that oxidation of nanocrystalline mackinawite was not microbially mediated. The extraction results suggested that elemental S (S8(0)) was a key intermediate S oxidation product Transmission electron microscopy showed the S8(0) to be amorphous nanoglobules, 100-200 nm in diameter. The quantitative importance of S8(0) was confirmed by linear combination XANES spectroscopy, after accounting for the inherent effect of the nanoscale S8(0) particle-size on the corresponding XANES spectrum. Both the selective extraction and XANES data showed that oxidation of S8(0) to SO4(2-) was mediated by microbial activity. In addition to directly revealing important S transformations, the XANES results support the accuracy of the selective extraction scheme employed here.
Changes in surface water quality after inundation of acid sulfate soils of different vegetation cover
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/SR04073
Abstract: Surface soils from an acid sulfate soil (ASS) backsw were inundated in a temperature controlled environment and surface-water chemistry changes monitored. The soils had contrasting in situ vegetative cover [i.e. 2 grass species, Cynodon dactylon and Pennisetum clandestinum (Poaceae), and litter from Melaleuca quinquenervia (Myrtaceae)]. The different vegetation types had similar biomass and carbon content however, there were large differences in the quality and lability of that carbon, which strongly influenced decay/redox processes and the chemical composition of surface waters. The grass species had more labile carbon. Their surface waters displayed rapid sustained O2 depletion and sustained low Eh (~0 mV), high dissolved organic carbon (DOC), and moderate pH (5–6). Their soil acidity was partially neutralised, sulfides were re-formed, and reductive dissolution of Fe(III) led to the generation of stored acidity in the water column as Fe2+(aq). In contrast, M. quinquenervia litter was high in decay-resistant compounds. Its surface waters had lower DOC and low pH ( ) and only underwent a short period of low O2/Eh. Soluble Al caused M. quinquenervia surface waters to have higher titratable acidity and soil pH remained consistently low (~3.8–4.0). Concentrations of Cl– and Al in surface waters were strongly correlated to initial soil contents, whereas the behaviour of Fe and SO42– varied according to pH and redox status. This study demonstrates that changes in vegetation communities in ASS backsw s that substantially alter either (a) the pool of labile vegetative organic carbon or (b) the concentration of acidic solutes in surface soil can have profound implications for the chemical characteristics of backsw surface waters.
Synchrotron X-ray spectroscopy for investigating vanadium speciation in marine sediment: limitations and opportunities
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8JA00231B
Abstract: Synchrotron-based X-ray spectroscopy is a powerful technique for investigating vanadium speciation in marine sediment.
Microbial sulfidogenesis in ferrihydrite-rich environments: Effects on iron mineralogy and arsenic mobility
Publisher: Elsevier BV
Date: 06-2011
Rapid arsenic(V)-reduction by fire in schwertmannite-rich soil enhances arsenic mobilisation
Publisher: Elsevier BV
Date: 04-2018
Humic acid impacts antimony partitioning and speciation during iron(II)-induced ferrihydrite transformation
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.SCITOTENV.2019.05.305
Abstract: The Fe(II)-induced transformation of ferrihydrite, a potent scavenger for antimony (Sb), can considerably influence Sb mobility in reducing soils, sediments and groundwater systems. In these environments, humic acids (HA) are prevalent, yet their influence on Sb behaviour during ferrihydrite transformation is poorly understood. In this study, we investigated the effect of HA on (1) Sb partitioning between solid, colloidal and dissolved phases and (2) Sb redox speciation during the Fe(II)-induced transformation of Sb(V)-bearing ferrihydrite at pH 6.0 and 8.0 and Fe(II) concentrations of 0, 1 and 10 mM. The results show that, at pH 8.0 and in the presence of 10 mM Fe(II), ferrihydrite was replaced by goethite, lepidocrocite and magnetite across a wide range of HA concentrations. At pH 6.0 in the 10 mM Fe(II) treatments, ferrihydrite transformed to mainly lepidocrocite and goethite in both HA-free and low HA treatments. In contrast, high HA concentrations retarded the rate and extent of ferrihydrite transformation at both pH 6.0 and 8.0 in the 1 mM Fe(II) treatments. Antimony K-edge XANES spectroscopy revealed up to 60% reduction of solid-phase Sb(V) to Sb(III), which corresponded with an increase in the PO
Coupling of arsenic mobility to sulfur transformations during microbial sulfate reduction in the presence and absence of humic acid
Publisher: Elsevier BV
Date: 04-2013
Phosphate-Imposed Constraints on Schwertmannite Stability under Reducing Conditions
Publisher: American Chemical Society (ACS)
Date: 17-08-2017
Abstract: Schwertmannite is a ferric oxyhydroxysulfate mineral, which is common in acid sulfate systems. Such systems contain varying concentrations of phosphate (PO
Chromium(VI) formation via heating of Cr(III)-Fe(III)-(oxy)hydroxides: A pathway for fire-induced soil pollution
Publisher: Elsevier BV
Date: 05-2019
DOI: 10.1016/J.CHEMOSPHERE.2019.01.172
Abstract: Mixed Cr(III)-Fe(III) (oxy)hydroxides are important Cr-bearing phases in natural, unpolluted soil. Fires frequently affect large areas of land around the world, causing the temporary development of elevated soil temperatures. This study examines the hypothesis that heating Cr(III)-Fe(III) (oxy)hydroxides at temperatures which occur in surface soils during fires can drive rapid oxidation of Cr(III) to hazardous Cr(VI). To test this, poorly-ordered Cr(III)
Seasonal temperature oscillations drive contrasting Arsenic and Antimony mobilisation in a mining‐impacted river system
Publisher: American Geophysical Union (AGU)
Date: 10-2020
DOI: 10.1029/2020WR028196
Abstract: Arsenic (As) and antimony (Sb) speciation and mobility in river systems can be influenced by the redox conditions of benthic and hyporheic zone sediments. However, our understanding of how temperature fluctuations influence riverine As and Sb mobility over diel and seasonal time frames, via moderation of sediment redox conditions, is poorly constrained. Here we compare diel and seasonal water quality data from a river system contaminated with As and Sb with results from sediment‐water incubations conducted at temperatures spanning 8°C to 32°C under low‐dissolved oxygen conditions. Higher incubation temperatures caused faster microbial respiration, lower redox potential, and greater As aq concentrations, coincident with reduction of As(V), Mn (III/IV), Fe (III), and SO 4 2− . Initial rates of As 3+ aq formation increased exponentially with temperature ( Q 10 = 3.3 ± 0.5) and were positively correlated with microbial respiration ( r 2 = 0.99, P 0.01). In contrast, Sb aq displayed an initially negative and comparatively weak overall temperature dependence during incubations. In river waters, diel mobilization of reduced species (As 3+ aq and Fe 2+ aq ) and contrasting attenuation of Sb was coincident with lower redox potential during nightly respiration cycles. Distinct seasonal oscillations in river water As aq were exponentially correlated with temperature ( r 2 = 0.68, P 0.01), whereas Sb aq was not. These characteristics reflect the fundamental role of anaerobic metabolism (as influenced by temperature) within benthic and hyporheic zone sediments as a key driver of contrasting riverine As and Sb mobility. The findings imply that riverine As mobility may be enhanced, while Sb mobility possibly attenuated, by eutrophication or by elevated stream temperatures due to a warming climate.
Milliarcsecond Localization of the Repeating FRB 20201124A
Publisher: American Astronomical Society
Date: 03-2022
Abstract: Very long baseline interferometric (VLBI) localizations of repeating fast radio bursts (FRBs) have demonstrated a ersity of local environments: from nearby star-forming regions to globular clusters. Here we report the VLBI localization of FRB 20201124A using an ad hoc array of dishes that also participate in the European VLBI Network (EVN). In our c aign, we detected 18 bursts from FRB 20201124A at two separate epochs. By combining the visibilities from both epochs, we were able to localize FRB 20201124A with a 1 σ uncertainty of 2.7 mas. We use the relatively large burst s le to investigate astrometric accuracy and find that for ≳20 baselines (≳7 dishes) we can robustly reach milliarcsecond precision even using single-burst data sets. Subarcsecond precision is still possible for single bursts, even when only ∼6 baselines (four dishes) are available. In such cases, the limited uv coverage for in idual bursts results in very high side-lobe levels. Thus, in addition to the peak position from the dirty map, we also explore smoothing the structure in the dirty map by fitting Gaussian functions to the fringe pattern in order to constrain in idual burst positions, which we find to be more reliable. Our VLBI work places FRB 20201124A 710 ± 30 mas (1 σ uncertainty) from the optical center of the host galaxy, consistent with originating from within the recently discovered extended radio structure associated with star formation in the host galaxy. Future high-resolution optical observations, e.g., with Hubble Space Telescope, can determine the proximity of FRB 20201124A’s position to nearby knots of star formation.
Impact of silica on the reductive transformation of schwertmannite and the mobilization of arsenic
Publisher: Elsevier BV
Date: 11-2012
Saturated hydraulic conductivity of sulfuric horizons in coastal floodplain acid sulfate soils: Variability and implications
Publisher: Elsevier BV
Date: 07-2009
Enrichment and heterogeneity of trace elements at the redox-interface of Fe-rich intertidal sediments
Publisher: Elsevier BV
Date: 09-2014
Acidity generation accompanying iron and sulfur transformations during drought simulation of freshwater re-flooded acid sulfate soils
Publisher: Elsevier BV
Date: 2017
Are methane emissions from mangrove stems a cryptic carbon loss pathway? Insights from a catastrophic forest mortality
Publisher: Wiley
Date: 20-07-2019
DOI: 10.1111/NPH.15995
Abstract: Growing evidence indicates that tree-stem methane (CH
Mechanisms of Arsenic and Antimony Co-sorption onto Jarosite: An X-ray Absorption Spectroscopic Study
Publisher: American Chemical Society (ACS)
Date: 17-03-2023
Seawater inundation of coastal floodplain sediments: Short-term changes in surface water and sediment geochemistry
Publisher: Elsevier BV
Date: 03-2015
Rhizosphere to the atmosphere: Contrasting methane pathways, fluxes, and geochemical drivers across the terrestrial-aquatic wetland boundary
Publisher: Copernicus GmbH
Date: 29-04-2019
Abstract: Abstract. Although wetlands represent the largest natural source of atmospheric CH4, large uncertainties remain regarding the global wetland CH4 flux. Wetland hydrological oscillations contribute to this uncertainty, dramatically altering wetland area, water table height, soil redox potentials, and CH4 emissions. This study compares both terrestrial and aquatic CH4 fluxes in permanent and seasonal remediated freshwater wetlands in subtropical Australia over two field c aigns, representing differing hydrological and climatic conditions. We account for aquatic CH4 diffusion and ebullition rates and plant-mediated CH4 fluxes from three distinct vegetation communities, thereby examining diel and intra-habitat variability. CH4 emission rates were related to underlying sediment geochemistry. For ex le, distinct negative relationships between CH4 fluxes and both Fe(III) and SO42- were observed. Where sediment Fe(III) and SO42- were depleted, distinct positive trends occurred between CH4 emissions and Fe(II) ∕ acid volatile sulfur (AVS). Significantly higher CH4 emissions (p 0.01) in the seasonal wetland were measured during flooded conditions and always during daylight hours, which is consistent with soil redox potential and temperature being important co-drivers of CH4 flux. The highest CH4 fluxes were consistently emitted from the permanent wetland (1.5 to 10.5 mmol m−2 d−1), followed by the Phragmites australis community within the seasonal wetland (0.8 to 2.3 mmol m−2 d−1), whilst the lowest CH4 fluxes came from a region of forested Juncus spp. (−0.01 to 0.1 mmol m−2 d−1), which also corresponded to the highest sedimentary Fe(III) and SO42-. We suggest that wetland remediation strategies should consider geochemical profiles to help to mitigate excessive and unwanted methane emissions, especially during early system remediation periods.
Anthropogenic forcing of estuarine hypoxic events in sub-tropical catchments: Landscape drivers and biogeochemical processes
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.SCITOTENV.2011.08.065
Abstract: Episodic hypoxic events can occur following summer floods in sub-tropical estuaries of eastern Australia. These events can cause deoxygenation of waterways and extensive fish mortality. Here, we present a conceptual model that links key landscape drivers and biogeochemical processes which contribute to post-flood hypoxic events. The model provides a framework for examining the nature of anthropogenic forcing. Modification of estuarine floodplain surface hydrology through the construction of extensive drainage networks emerges as a major contributing factor to increasing the frequency, magnitude and duration of hypoxic events. Forcing occurs in two main ways. Firstly, artificial drainage of backsw wetlands initiates drier conditions which cause a shift in vegetation assemblages from wetland-dominant species to dryland-dominant species. These species, which currently dominate the floodplain, are largely intolerant of inundation and provide abundant labile substrate for decomposition following flood events. Decomposition of this labile carbon pool consumes oxygen in the overlying floodwaters, and results in anoxic conditions and waters with excess deoxygenation potential (DOP). Carbon metabolism can be strongly coupled with microbially-mediated reduction of accumulated Fe and Mn oxides, phases which are common on these coastal floodplain landscapes. Secondly, artificial drainage enhances discharge rates during the flood recession phase. Drains transport deoxygenated high DOP floodwaters rapidly from backsw wetlands to the main river channel to further consume oxygen. This process effectively displaces the natural carbon metabolism processes from floodplain wetlands to the main channel. Management options to reduce the impacts of post-flood hypoxia include i) remodifying drainage on the floodplain to promote wetter conditions, thereby shifting vegetation assemblages towards inundation-tolerant species, and ii) strategic retention of floodwaters in the backsw wetlands to reduce the volume and rate during the critical post-flood recession phase.
Contemporary pedogenesis of severely degraded tropical acid sulfate soils after introduction of regular tidal inundation
Publisher: Elsevier BV
Date: 03-2009
Reductive transformation of birnessite and the mobility of co-associated antimony
Publisher: Elsevier BV
Date: 02-2020
Reactive trace element enrichment in a highly modified, tidally inundated acid sulfate soil wetland: East Trinity, Australia
Publisher: Elsevier BV
Date: 04-2010
DOI: 10.1016/J.MARPOLBUL.2010.02.006
Abstract: This study examines the abundance of trace elements in surface sediments of a former acid sulfate soil (ASS) wetland subjected to marine tidal inundation. Sediment properties of this highly modified study site are compared with those of an adjacent unmodified, intertidal mangrove forest. Whilst some trace elements (Al, Cd, Mn, Ni and Zn) were clearly depleted due to mobilisation and leaching in the previous oxic-acidic phase, other trace elements (As and Cr) displayed significant enrichment in the tidally inundated ASS. Many trace elements were strongly associated with the reactive Fe and acid volatile sulfide (AVS) fractions, suggesting that trace elements may be adsorbed to abundant reactive Fe phases or sequestered as sulfide minerals. These findings provide an important understanding of the fate and mobility of reactive iron, AVS and trace elements during tidal remediation of a formerly acidified Great Barrier Reef (GBR) catchment.
Alkalinity production coupled to pyrite formation represents an unaccounted blue carbon sink
Publisher: Wiley
Date: 17-08-2020
Arsenic mobilization and iron transformations during sulfidization of As(V)-bearing jarosite
Publisher: Elsevier BV
Date: 12-2012
Redistribution of monosulfidic black oozes by floodwaters in a coastal acid sulfate soil floodplain
Publisher: CSIRO Publishing
Date: 2004
DOI: 10.1071/SR03073
Abstract: The observations presented in this paper illustrate that significant amounts of monosulfidic black oozes (MBO) were eroded from flood mitigation drainage canals and redistributed across a coastal floodplain during a flood event associated with extreme deoxygenation and a massive fish kill. MBO are organic materials enriched in iron monosulfides and thick layers can accumulate in drains affected by acid sulfate soils. Laboratory studies have demonstrated that MBO can react rapidly when brought into suspension to completely consume dissolved oxygen. The abundance of MBO in flood mitigation drains and their extreme reactivity implicated MBO in the acute deoxygenation of the Richmond River, north-eastern New South Wales, Australia, following a major flood in February 2001. The field observations of MBO redistribution provide valuable evidence to help explain how these materials may interact and contribute to the deoxygenation of floodwaters.
Abundance and fractionation of Al, Fe and trace metals following tidal inundation of a tropical acid sulfate soil
Publisher: Elsevier BV
Date: 03-2010
Effect of cyclic redox oscillations on water quality in freshwater acid sulfate soil wetlands
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.SCITOTENV.2016.12.131
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 s les from two freshwater re-flooded ASS wetlands to oxidative incubation for up to 130days followed by re-flooding simulation for 84days. During very early stages of re-flooding (up to 7days) 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 SO
Divergent repartitioning of copper, antimony and phosphorus following thermal transformation of schwertmannite and ferrihydrite
Publisher: Elsevier BV
Date: 04-2018
Antimonate Controls Manganese(II)-Induced Transformation of Birnessite at a Circumneutral pH
Publisher: American Chemical Society (ACS)
Date: 06-07-2021
Opening floodgates in coastal floodplain drains: effects on tidal forcing and lateral transport of solutes in adjacent groundwater
Publisher: Elsevier BV
Date: 05-2005
Alkalinity Production Coupled to Pyrite Formation Represents an Unaccounted Blue Carbon Sink
Publisher: American Geophysical Union (AGU)
Date: 04-2021
DOI: 10.1029/2020GB006785
Abstract: Blue carbon ecosystems, including mangroves, saltmarshes, and seagrasses, mitigate climate change by storing atmospheric carbon. Previous blue carbon research has focused on organic carbon stocks. However, recent studies suggest that lateral inorganic carbon export might be equally important. Lateral export is a long‐term carbon sink if carbon is exported as alkalinity (TAlk) produced via sulfate reduction coupled to pyrite formation. This study evaluates drivers of pyrite formation in blue carbon ecosystems, compares pyrite production to TAlk outwelling rates, and estimates global pyrite stocks in mangroves. We quantified pyrite stocks in mangroves, saltmarshes, and seagrasses along a latitudinal gradient on the Australian East Coast, including a mangrove dieback area, and in the Everglades (Florida, USA). Our results indicate that pyrite stocks were driven by a combination of biomass, tidal litude, sediment organic carbon, sediment accumulation rates, rainfall, latitude, temperature, and iron availability. Pyrite stocks were three‐times higher in mangroves (103 ± 61 Mg/ha) than in saltmarshes (30 ± 30 Mg/ha) and seagrasses (32 ± 1 Mg/ha). Mangrove pyrite stocks were linearly correlated to TAlk export at sites where sulfate reduction was the dominant TAlk producing process. However, pyrite generation could not explain all TAlk outwelling. We present the first global model estimating pyrite stocks in mangroves, giving a first‐order estimate of 197 Mg/ha (RMSE = 24 Mg/ha). In mangroves, estimated global TAlk production coupled to pyrite formation (∼3 mol/m 2 /y) is equal to ∼24% of their global carbon burial rate, highlighting the importance of including TAlk export in future blue carbon budgets.
Tree stem methane emissions from subtropical lowland forest (Melaleuca quinquenervia) regulated by local and seasonal hydrology
Publisher: Springer Science and Business Media LLC
Date: 09-11-2020
Wetland methane emissions dominated by plant-mediated fluxes: Contrasting emissions pathways and seasons within a shallow freshwater subtropical wetland
Publisher: Wiley
Date: 13-03-2019
DOI: 10.1002/LNO.11158
A Small Nimble In Situ Fine-Scale Flux Method for Measuring Tree Stem Greenhouse Gas Emissions and Processes (S.N.I.F.F)
Publisher: Springer Science and Business Media LLC
Date: 11-03-2020
Antimony mobility in sulfidic systems: Coupling with sulfide-induced iron oxide transformations
Publisher: Elsevier BV
Date: 08-2020
Iron geochemical zonation in a tidally inundated acid sulfate soil wetland
Publisher: Elsevier BV
Date: 2011
Arsenic Effects and Behavior in Association with the Fe(II)-Catalyzed Transformation of Schwertmannite
Publisher: American Chemical Society (ACS)
Date: 11-02-2010
DOI: 10.1021/ES903424H
Abstract: In acid-mine drainage and acid-sulfate soil environments, the cycling of Fe and As are often linked to the formation and fate of schwertmannite (Fe(8)O(8)(OH)(8-2x)(SO(4))(x)). When schwertmannite-rich material is subjected to near-neutral Fe(III)-reducing conditions (e.g., in reflooded acid-sulfate soils or mining-lake sediments), the resulting Fe(II) can catalyze transformation of schwertmannite to goethite. This work examines the effects of arsenic(V) and arsenic(III) on the Fe(II)-catalyzed transformation of schwertmannite and investigates the associated consequences of this mineral transformation for arsenic mobilization. A series of 9-day anoxic transformation experiments were conducted with synthetic schwertmannite and various additions of Fe(II), As(III), and As(V). X-ray diffraction (XRD) and Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy demonstrated that, in the absence of Fe(II), schwertmannite persisted as the dominant mineral phase. Under arsenic-free conditions, 10 mM Fe(II) catalyzed rapid and complete transformation of schwertmannite to goethite. However, the magnitude of Fe(II)-catalyzed transformation decreased to 72% in the presence of 1 mM As(III) and to only 6% in the presence of 1 mM As(V). This partial Fe(II)-catalyzed transformation of As(III)-sorbed schwertmannite did not cause considerable As(III) desorption. In contrast, the formation of goethite via partial transformation of As(III)- and As(V)-sorbed schwertmannite significantly decreased arsenic mobilization under Fe(III)-reducing conditions. This implies that the Fe(II)-catalyzed transformation of schwertmannite to goethite may help to stabilize solid-phase arsenic and retard its subsequent release to groundwater.
Long-range spatial variability in sediment associations and solid-phase speciation of antimony and arsenic in a mining-impacted river system
Publisher: Elsevier BV
Date: 12-2021
Digital soil mapping of a coastal acid sulfate soil landscape
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/SR13314
Abstract: 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 of CASS is essential 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.
Isotopic evidence for axial tree stem methane oxidation within subtropical lowland forests
Publisher: Wiley
Date: 12-04-2021
DOI: 10.1111/NPH.17343
Abstract: Knowledge regarding mechanisms moderating methane (CH 4 ) sink/source behaviour along the soil–tree stem–atmosphere continuum remains incomplete. Here, we applied stable isotope analysis (δ 13 C‐CH 4 ) to gain insights into axial CH 4 transport and oxidation in two globally distributed subtropical lowland species ( Melaleuca quinquenervia and Casuarina glauca ). We found consistent trends in CH 4 flux (decreasing with height) and δ 13 C‐CH 4 enrichment (increasing with height) in relation to stem height from ground. The average lower tree stem δ 13 C‐CH 4 (0–40 cm) of Melaleuca and Casuarina (−53.96‰ and −65.89‰) were similar to adjacent flooded soil CH 4 ebullition (−52.87‰ and −62.98‰), suggesting that stem CH 4 is derived mainly by soil sources. Upper stems (81–200 cm) displayed distinct δ 13 C‐CH 4 enrichment ( Melaleuca −44.6‰ and Casuarina −46.5‰, respectively). Coupled 3D‐photogrammetry with novel 3D‐stem measurements revealed distinct hotspots of CH 4 flux and isotopic fractionation on Melaleuca , which were likely due to bark anomalies in which preferential pathways of gas efflux were enhanced. Diel experiments revealed greater δ 13 C‐CH 4 enrichment and higher oxidation rates in the afternoon, compared with the morning. Overall, we estimated that c . 33% of the methane was oxidised between lower and upper stems during axial transport, therefore potentially representing a globally significant, yet previously unaccounted for, methane sink.
Legacy impacts of acid sulfate soil runoff on mangrove sediments: Reactive iron accumulation, altered sulfur cycling and trace metal enrichment
Publisher: Elsevier BV
Date: 06-2012
Mobility of arsenic and selected metals during re-flooding of iron- and organic-rich acid-sulfate soil
Publisher: Elsevier BV
Date: 07-2008
Partitioning of metals in a degraded acid sulfate soil landscape: Influence of tidal re-inundation
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.CHEMOSPHERE.2011.07.013
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.
Quantifying alkalinity generating processes in a tidally remediating acidic wetland
Publisher: Elsevier BV
Date: 04-2012
Correction to Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X-ray Spectroscopy
Publisher: American Chemical Society (ACS)
Date: 24-02-2023
The impact of controlled tidal exchange on drainage water quality in acid sulphate soil backswamps
Publisher: Elsevier BV
Date: 05-2005
Significant Organic Carbon Accumulation in Two Coastal Acid Sulfate Soil Wetlands
Publisher: American Geophysical Union (AGU)
Date: 20-03-2019
DOI: 10.1029/2019GL082076
A new pathway for hexavalent chromium formation in soil: Fire-induced alteration of iron oxides
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.ENVPOL.2019.01.094
Abstract: Iron oxides are important pedogenic Cr(III)-bearing phases which experience high-temperature alteration via fire-induced heating of surface soil. In this study, we examine if heating-induced alteration of Cr(III)-substituted Fe oxides can potentially facilitate rapid high-temperature oxidation of solid-phase Cr(III) to hazardous Cr(VI). Synthetic Cr(III)-substituted ferrihydrite, goethite and hematite were heated up to 800 °C for 2 h. Corresponding heating experiments were also conducted on an unpolluted Ferrosol-type soil, which had a total Cr content of 220 mg kg
Sulfate Availability Drives Divergent Evolution of Arsenic Speciation during Microbially Mediated Reductive Transformation of Schwertmannite
Publisher: American Chemical Society (ACS)
Date: 15-02-2013
DOI: 10.1021/ES303867T
Abstract: The effect of SO4(2-) availability on the microbially mediated reductive transformation of As(V)-coprecipitated schwertmannite (Fe8O8(OH)3.2(SO4)2.4(AsO4)0.004) was examined in long-term (up to 400 days) incubation experiments. Iron EXAFS spectroscopy showed siderite (FeCO3) and mackinawite (FeS) were the dominant secondary Fe(II) minerals produced via reductive schwertmannite transformation. In addition, ∼ 25% to ∼ 65% of the initial schwertmannite was also transformed relatively rapidly to goethite (αFeOOH), with the extent of this transformation being dependent on SO4(2-) concentrations. More specifically, the presence of high SO4(2-) concentrations acted to stabilize schwertmannite, retarding its transformation to goethite and allowing its partial persistence over the 400 day experiment duration. Elevated SO4(2-) also decreased the extent of dissimilatory reduction of Fe(III) and As(V), instead favoring dissimilatory SO4(2-) reduction. In contrast, where SO4(2-) was less available, there was near-complete reduction of schwertmannite- and goethite-derived Fe(III) as well as solid-phase As(V). As a result, under low SO4(2-) conditions, almost no Fe(III) or As(V) remained toward the end of the experiment and arsenic solid-phase partitioning was controlled mainly by sorptive interactions between As(III) and mackinawite. These As(III)-mackinawite interactions led to the formation of an orpiment (As2S3)-like species. Interestingly, this orpiment-like arsenic species did not form under SO4(2-)-rich conditions, despite the prevalence of dissimilatory SO4(2-) reduction. The absence of an arsenic sulfide species under SO4(2-)-rich conditions appears to have been a consequence of schwertmannite persistence, combined with the preferential retention of arsenic oxyanions by schwertmannite. The results highlight the critical role that SO4(2-) availability can play in controlling solid-phase arsenic speciation, particularly arsenic-sulfur interactions, under reducing conditions in soils, sediments, and shallow groundwater systems.
Phosphate loading alters schwertmannite transformation rates and pathways during microbial reduction
Publisher: Elsevier BV
Date: 03-2019
DOI: 10.1016/J.SCITOTENV.2018.12.082
Abstract: Acid sulfate systems commonly contain the metastable ferric oxyhydroxysulfate mineral schwertmannite, as well as phosphate (PO
Changes in water quality following tidal inundation of coastal lowland acid sulfate soil landscapes
Publisher: Elsevier BV
Date: 2009
Seawater-induced mobilization of trace metals from mackinawite-rich estuarine sediments
Publisher: Elsevier BV
Date: 02-2013
DOI: 10.1016/J.WATRES.2012.11.009
Abstract: Benthic sediments in coastal acid sulfate soil (CASS) drains can contain high concentrations (~1-5%) of acid volatile sulfide (AVS) as nano-particulate mackinawite. These sediments can sequester substantial quantities of trace metals. Because of their low elevation and the connectivity of drains to estuarine channels, these benthic sediments are vulnerable to rapid increases in ionic strength from seawater incursion by floodgate opening, floodgate failure, storm surge and seasonal migration of the estuarine salt wedge. This study examines the effect of increasing seawater concentration on trace metal mobilization from mackinawite-rich drain sediments (210-550 μmol g⁻¹ AVS) collected along an estuarine salinity gradient. Linear combination fitting of S K-edge XANES indicated mackinawite comprised 88-96% of sediment-bound S. Anoxic sediment suspensions were conducted with seawater concentrations ranging from 0% to 100%. We found that mobilization of some metals increased markedly with increasing ionic strength (Cu, Fe, Mn, Ni) whereas Al mobilization decreased. The largest proportion of metals mobilized from the labile metal pool, operationally defined as Σexchangeable + acid-extractable + organically-bound metals, occurred in sediments from relatively fresh upstream sites (up to 39% mobilized) compared to sediments sourced from brackish downstream sites (0-11% mobilized). The extent of relative trace metal desorption generally followed the sequence Mn > Ni ≈ Cu > Zn > Fe > Al. Trace metal mobilization from these mackinawite-rich sediments was attributed primarily to desorption of weakly-bound metals via competitive exchange with marine-derived cations and enhanced complexation with Cl⁻ and dissolved organic ligands. These results have important implications for trace metal mobilization from these sediments at near-neutral pH under current predicted sea-level rise and climate change scenarios.
Sulfur biogeochemical cycling and novel Fe–S mineralization pathways in a tidally re-flooded wetland
Publisher: Elsevier BV
Date: 06-2011
iAMES: An inexpensive, Automated Methane Ebullition Sensor
Publisher: American Chemical Society (ACS)
Date: 22-05-2019
Abstract: Atmospheric concentrations of methane have increased ∼2.4 fold since the industrial revolution with wetlands and inland waters representing the largest source of methane to the atmosphere. Substantial uncertainties remain in global methane budgets, due in part to the lack of adequate techniques and detailed measurements to assess ebullition in aquatic environments. Here, we present details of a low cost (∼$120 US per unit) ebullition sensor that autonomously logs both volumetric ebullition rate and methane concentrations. The sensor combines a traditional funnel bubble trap with an Arduino logger, a pressure sensor, thermal conductivity methane sensor, and a solenoid valve. Powered by three AA batteries, the sensor can measure autonomously for three months when programmed for a s ling frequency of 30 min. For field testing, four sensors were deployed for six weeks in a small lake. While ebullition was spatially and temporally variable, a distinct diurnal trend was observed with the highest rates from mid-morning to early afternoon. Ebullition rates were similar for all four sensors when integrated over the s ling period. The widespread deployment of low cost automated ebullition sensors such as the iAMES described here will help constrain one of the largest uncertainties in the global methane budget.
Antimony and Arsenic Behavior during Fe(II)-Induced Transformation of Jarosite
Publisher: American Chemical Society (ACS)
Date: 05-04-2017
Abstract: Jarosite can be an important scavenger for arsenic (As) and antimony (Sb) in acid mine drainage (AMD) and acid sulfate soil (ASS) environments. When subjected to reducing conditions, jarosite may undergo reductive dissolution, thereby releasing As, Sb, and Fe
Iron and Arsenic Cycling in Intertidal Surface Sediments during Wetland Remediation
Publisher: American Chemical Society (ACS)
Date: 15-02-2011
DOI: 10.1021/ES103403N
Abstract: The accumulation and behavior of arsenic at the redox interface of Fe-rich sediments is strongly influenced by Fe(III) precipitate mineralogy, As speciation, and pH. In this study, we examined the behavior of Fe and As during aeration of natural groundwater from the intertidal fringe of a wetland being remediated by tidal inundation. The groundwater was initially rich in Fe(2+) (32 mmol L(-1)) and As (1.81 μmol L(-1)) with a circum-neutral pH (6.05). We explore changes in the solid/solution partitioning, speciation and mineralogy of Fe and As during long-term continuous groundwater aeration using a combination of chemical extractions, SEM, XRD, and synchrotron XAS. Initial rapid Fe(2+) oxidation led to the formation of As(III)-bearing ferrihydrite and sorption of >95% of the As(aq) within the first 4 h of aeration. Ferrihydrite transformed to schwertmannite within 23 days, although sorbed/coprecipitated As(III) remained unoxidized during this period. Schwertmannite subsequently transformed to jarosite at low pH (2-3), accompanied by oxidation of remaining Fe(2+). This coincided with a repartitioning of some sorbed As back into the aqueous phase as well as oxidation of sorbed/coprecipitated As(III) to As(V). Fe(III) precipitates formed via groundwater aeration were highly prone to reductive dissolution, thereby posing a high risk of mobilizing sorbed/coprecipitated As during any future upward migration of redox boundaries. Longer-term investigations are warranted to examine the potential pathways and magnitude of arsenic mobilization into surface waters in tidally reflooded wetlands.
Antimony speciation and mobility during Fe(II)-induced transformation of humic acid-antimony(V)-iron(III) coprecipitates
Publisher: Elsevier BV
Date: 11-2019
DOI: 10.1016/J.ENVPOL.2019.113112
Abstract: Antimony, as the Sb(V) species, often occurs in oxic soils and sediments as coprecipitates with poorly-crystalline Fe(III)-bearing minerals. It is common for these Sb(V)-Fe(III) coprecipitates to also contain varying quantities of co-occurring humic acid (HA). When exposed to reducing conditions, the production of Fe(II) may cause the initial metastable HA-Sb(V)-Fe(III) phases to undergo rapid transformations to more stable phases, thereby potentially influencing the geochemical behavior of coprecipitated Sb(V). However, little is known about the impacts of this transformation on the mobility and speciation of Sb. In this study, we reacted synthetic HA-Sb(V)-Fe(III) coprecipitates (Fe:Sb ratio = 4, and C:Fe molar ratios = 0, 0.3, 0.8 and 1.3) with 0, 1 or 10 mM Fe(II) under O
Arsenic Mobility during Flooding of Contaminated Soil: The Effect of Microbial Sulfate Reduction
Publisher: American Chemical Society (ACS)
Date: 12-11-2014
DOI: 10.1021/ES503963K
Abstract: In floodplain soils, As may be released during flooding-induced soil anoxia, with the degree of mobilization being affected by microbial redox processes such as the reduction of As(V), Fe(III), and SO4(2-). Microbial SO4(2-) reduction may affect both Fe and As cycling, but the processes involved and their ultimate consequences on As mobility are not well understood. Here, we examine the effect of microbial SO4(2) reduction on solution dynamics and solid-phase speciation of As during flooding of an As-contaminated soil. In the absence of significant levels of microbial SO4(2-) reduction, flooding caused increased Fe(II) and As(III) concentrations over a 10 week period, which is consistent with microbial Fe(III)- and As(V)-reduction. Microbial SO4(2-) reduction leads to lower concentrations of porewater Fe(II) as a result of FeS formation. Scanning electron microscopy with energy dispersive X-ray fluorescence spectroscopy revealed that the newly formed FeS sequestered substantial amounts of As. Bulk and microfocused As K-edge X-ray absorption near-edge structure spectroscopy confirmed that As(V) was reduced to As(III) and showed that in the presence of FeS, solid-phase As was retained partly via the formation of an As2S3-like species. High resolution transmission electron microscopy suggested that this was due to As retention as an As2S3-like complex associated with mackinawite (tetragonal FeS) rather than as a discrete As2S3 phase. This study shows that mackinawite formation in contaminated floodplain soil can help mitigate the extent of arsenic mobilization during prolonged flooding.
Sorption of Arsenic(V) and Arsenic(III) to Schwertmannite
Publisher: American Chemical Society (ACS)
Date: 18-11-2009
DOI: 10.1021/ES902461X
Abstract: This study describes the sorption of As(V) and As(III) to schwertmannite as a function of pH and arsenic loading. In general, sorption of As(V) was greatest at low pH, whereas high pH favored the sorption of As(III). The actual pH of equivalent As(V) and As(III) sorption was strongly loading dependent, decreasing from pH approximately 8.0 at loadings 4.6). Sorption of As(V) and As(III) caused significant release of SO(4)(2-) from within the schwertmannite solid-phase, without major degradation of the schwertmannite structure (as evident by X-ray diffraction and Raman spectroscopy). This can be interpreted as arsenic sorption via incorporation into the schwertmannite structure, rather than merely surface complexation at the mineral-water interface. The results of this study have important implications for arsenic mobility in the presence of schwertmannite, such as in areas affected by acid-mine drainage and acid-sulfate soils. In particular, arsenic speciation, arsenic loading, and pH should be considered when predicting and managing arsenic mobility in schwertmannite-rich systems.
Sulfur, iron and carbon cycling following hydrological restoration of acidic freshwater wetlands
Publisher: Elsevier BV
Date: 04-2014
Methanogens limited to lower rhizosphere and to an atypical salt marsh niche along a pristine intertidal mangrove continuum
Publisher: Wiley
Date: 22-08-2023
DOI: 10.1002/LNO.12414
Abstract: Mangroves are valuable ecosystems that facilitate primary production, carbon sequestration, and regulation of greenhouse gas (GHG) cycles in coastal sediments, with microorganisms playing key roles. Specialized bacteria and archaea compete for energy and resources in mangrove sediments to inhabit optimal ecological niches and can produce or consume methane (CH 4 )—a potent GHG—in the process. CH 4 cycling in mangroves has gained growing attention, yet uncertainties regarding functional and spatial distributions of microorganisms remain. Here, we demonstrate that in a pristine mangrove forest, CH 4 concentrations and methanogen communities are concentrated within lower or below rhizosphere depths. We also reveal atypical niches for methanogens in the upper tidal salt marsh zone where vegetation is sparse and highest methanogens abundances were detected at deepest depths (4715 reads g −1 ) despite relatively high redox potentials ( 250 mV). Pore water CH 4 concentrations were highest at the deepest depth within the mangrove forest (max. 3.40 ± 0.21 μ M) and coincided with the highest sediment CH 4 fluxes (276.4 ± 54.2 μ mol m −2 d −1 ) and methanotroph abundances at the surface (1309 reads g −1 ). Sediment CH 4 oxidation fractions between the deepest (60 cm) and shallowest (5 cm) depths were estimated between 18.8% and 64.9%. Positive correlation between crab burrows and CH 4 fluxes suggests that CH 4 from deeper sediment and salt marsh niches can be transported via conduits to the atmosphere. The spatial data from this study highlights the importance of investigating CH 4 dynamics across estuarine ecosystem gradients to better understand the complex roles of vital coastal vegetation zones in the face of a changing climate.
Spatial and temporal changes in estuarine water quality during a post-flood hypoxic event
Publisher: Elsevier BV
Date: 03-2010
Synchrotron X-ray absorption spectroscopy reveals antimony sequestration by reduced sulfur in a freshwater wetland sediment
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/EN16198
Abstract: Environmental contextAntimony is an environmental contaminant of increasing concern, due to its growing industrial usage in flame retardants, lead alloys, glass, ceramics and plastics. Here we show, using X-ray absorption spectroscopy, that antimony may be trapped in wetland sediments by reduced sulfur. This finding has implications for the management and remediation of wetlands contaminated with antimony. AbstractThe biogeochemistry of antimony (Sb) in wetland sediments is poorly characterised, despite their importance as contaminant sinks. The organic-rich, reducing nature of wetland sediments may facilitate sequestration mechanisms that are not typically present in oxic soils, where the majority of research to date has taken place. Using X-ray absorption spectroscopy (XAS), we present evidence of antimony speciation being dominated by secondary antimony–sulfur phases in a wetland sediment. Our results demonstrate that, by incorporating a newly developed SbIII–organic sulfur reference standard, linear combination fitting analysis of antimony K-edge XAS spectra and robust statistical assessment of fit quality allows the reliable discrimination of SbIII coordination environments. We found that a contaminated wetland sediment in New South Wales, Australia, contained 57% of the total antimony as SbIII–phases, with 44% present as a highly-disordered antimony phase, likely consisting of SbIII complexed by organic sulfur (e.g. thiols) or an amorphous SbIII sulfide (e.g. SbS3). The methodological approach outlined in this study and our identification of the importance of reduced sulfur in sequestering antimony has implications for future research in the area of antimony biogeochemistry, and for the management of both natural and artificial wetlands contaminated with antimony.
Bark-dwelling methanotrophic bacteria decrease methane emissions from trees
Publisher: Research Square Platform LLC
Date: 03-12-2020
DOI: 10.21203/RS.3.RS-119818/V1
Abstract: Tree stems are an important and unconstrained source of methane, yet it is uncertain if there are internal microbial controls (i.e. methanotrophy) within tree bark, that may reduce methane emissions. Using multiple lines of evidence, we demonstrate here that unique microbial communities dominated by methane oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia , a common, invasive and globally distributed lowland species. Laboratory incubations of methane inoculated M. quinquenervia bark reveal methane consumption (up to 96.3 µmol m -2 bark d -1 ) and distinct isotopic δ 13 C-CH 4 enrichment characteristic of MOB. Molecular analysis indicates unique microbial communities reside within the bark, with methane-oxidising bacteria primarily from the genus Methylomonas comprising up to 25 % of the total microbial community. Methanotroph abundance was linearly correlated to methane uptake rates (R 2 = 0.76, p = 0.006). Finally, field-based methane oxidation inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by 36 ± 5 %. These multiple, complementary lines of evidence indicate that bark-dwelling MOB represent a novel and potentially significant methane sink, and an important frontier for further research.
A simple and inexpensive chromium-reducible sulfur method for acid-sulfate soils
Publisher: Elsevier BV
Date: 09-2008
Iron and sulfur cycling in acid sulfate soil wetlands under dynamic redox conditions: A review
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.CHEMOSPHERE.2018.01.096
Abstract: Acid sulfate soils (ASS) contain substantial quantities of iron sulfide minerals or the oxidation reaction products of these sulfidic minerals. Transformation of iron (Fe) and sulfur (S) bearing minerals is an important process in ASS wetlands with fluctuating redox conditions. A range of potentially toxic metals and metalloids can either be adsorbed on or incorporated into the structure of Fe and S bearing minerals. Therefore, transformation of these minerals as affected by dynamic redox conditions may regulate the mobility and bioavailability of associated metals/metalloids. Better understanding of the interaction between Fe/S biogeochemistry and trace metal/metalloid mobility under fluctuating redox conditions is important for assessing contaminant risk to the environment. This review paper provides an overview of current knowledge regarding cycling of Fe, S and selected trace metal/metalloids in ASS wetlands under fluctuating redox conditions and outlines future research challenges and directions on this subject.
Arsenic Mobilization Is Enhanced by Thermal Transformation of Schwertmannite
Publisher: American Chemical Society (ACS)
Date: 22-07-2016
Abstract: Fires in iron-rich seasonal wetlands can thermally transform Fe(III) minerals and alter their crystallinity. However, the fate of As associated with thermally transformed Fe(III) minerals is unclear, as are the consequences for As mobilization during subsequent reflooding and reductive cycles. Here, we subject As(V)-coprecipitated schwertmannite to thermal transformation (200, 400, 600 and 800 °C) followed by biotic reductive incubation (150 d) and examine aqueous- and solid-phase speciation of As, Fe and S. Heating to >400 °C caused transformation of schwertmannite to a nanocrystalline hematite with greater surface area and smaller particle size. Higher temperatures also caused the initially structurally incorporated As to become progressively more exchangeable, increasing surface-complexed As (AsEx) by up to 60-fold, thereby triggering enhanced As mobilization during incubation (∼70-fold in the 800 °C treatment). Although more As was mobilized in biotic treatments than controls (∼3-20×), in both cases it was directly proportional to initial AsEx and mainly due to abiotic desorption. Higher transformation temperatures also drove ergent pathways of Fe and S biomineralization and led to more As(V) and SO4 reduction relative to Fe(III) reduction. This study reveals thermal transformation of schwertmannite can greatly increase As mobility and has major consequences for As/Fe/S speciation under reducing conditions. Further research is warranted to unravel the wider implications for water quality in natural wetlands.
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