Physical Sciences and Mathematics Commons^™

Arsenic Mobility During Flooding Of Contaminated Soil: The Effect Of Microbial Sulfate Reduction, Edward Burton, Scott Johnston, Benjamin Kocar

Associate Professor Edward D Burton

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 SO42–. Microbial SO42– 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 SO42 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 SO42– reduction, flooding caused increased Fe(II) and As(III) concentrations over a 10 week …

Seawater Inundation Of Coastal Floodplain Sediments: Short-Term Changes In Surface Water And Sediment Geochemistry, Vanessa Wong, Scott Johnston, Edward Burton, Phillip Hirst, Leigh Sullivan, Richard Bush, Mark Blackford

Associate Professor Edward D Burton

Coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea-level rise due to their low elevation and proximity to the coastline. Intact soil cores from a levee, acid-sulfate soil scald and four backswamp sites on a coastal floodplain in eastern Australia were inundated with artificial seawater treatments (0%, 50% and 100%) for 14 days to examine the short term consequences for surface water and floodplain sediment geochemistry. All sites displayed an initial decrease in surface water pH following inundation with 50% and 100% seawater. In addition, higher concentrations of trace metals (Al, Fe, Mn, …

Arsenic Mobilization In An Alluvial Aquifer Of The Terai Region, Nepal, Jasmine Diwakar, Scott Johnston, Edward Burton, Suresh Das Shrestha

Associate Professor Edward D Burton

Study Region

A shallow (<50 m) alluvial aquifer in the Terai region of Nepal.

Study Focus

We examine the hydrogeochemical characteristics of a shallow alluvial aquifer system in the Terai region (Nawalparasi district) to identify possible mechanisms and controls on geogenic As mobilization in groundwater. Groundwater and river water samples from a topo-gradient flow-path and floodplain of a minor river draining the Siwalik forehills were analyzed for physico-chemical parameters.

New Hydrological Insights for the Region

The aquifer is characterized by Ca-HCO₃ type water and is multi-contaminated, with the WHO guideline values exceeded for As, Mn and F in 80%, 70% and 40% of cases respectively. The middle portion …

A Revised Method For Determining Existing Acidity In Re-Flooded Acid Sulfate Soils, Scott Johnston, Edward Burton, Roslyn Hagan, Thor Aaso, Gerard Tuckerman

Associate Professor Edward D Burton

Titratable actual acidity (TAA) is a technique commonly used to estimate the existing pool of exchangeable H⁺ in acid sulfate soils (ASS). A widely adopted version of the TAA method involves titrating a 1M KCl suspension of oven-dry soil (1:40) with NaOH to a known pH endpoint. However, when ASS are subject to long term re-flooding during wetland remediation, former sulfuric horizons can develop substantial quantities of porewater Fe²⁺, non-sulfidic solid-phase Fe(II) and a variety of reduced inorganic sulfur (RIS) species (e.g. pyrite, mackinawite, greigite and elemental sulfur). For these sediments, an oven-drying approach may induce oxidation …

Enrichment And Heterogeneity Of Trace Elements At The Redox-Interface Of Fe-Rich Intertidal Sediments, Annabelle Keene, Scott Johnston, Richard Bush, Edward Burton, Leigh Sullivan, Matthew Dundoon, Angus Mcelnea, C Smith, Col Ahern, Bernard Powell

Associate Professor Edward D Burton

Redox-interfacial sediments can undergo radical geochemical changes with oscillating tides. In this study, we examine trace element enrichment and availability, at both landscape and pedon-scales, in the surface sediments of a remediating acidic tidal wetland. Fe-rich sediments at the surface-water interface (0–10 mm in depth) were collected across an elevation gradient spanning the supratidal to subtidal range. These sediments were analysed for solid phase Fe fractions and trace elements (As, Pb, Cr, Cu, Mn, Ni, Zn, V, B, Co, Mo, Ba and U) via dilute HCl-extractions and total digests. Their concentrations were compared with those of underlying (0.05–0.65 m in …

Landslide-Induced Iron Mobilisation Shapes Benthic Accumulation Of Nutrients, Trace Metals And Ree Fractionation In An Oligotrophic Alpine Stream, Scott Johnston, Andrew Rose, Edward Burton, Jenny Webster-Brown

Associate Professor Edward D Burton

Large alpine landslides that entrain substantial organic material below the water table and create suspended floodplains may have long-term consequences for the mobilisation of redox sensitive elements, such as Fe, into streamwaters. In turn, the cycling of iron in aquatic systems can influence the fate of nutrients, alter primary productivity, enhance accumulation of trace metals and induce fractionation of rare earth elements (REE). In this study we examine a reach of a pristine oligotrophic alpine stream bracketing a 30 year-old landslide and explore the consequences of landslide-induced Fe mobilisation for aqueous geochemistry and the composition of benthic stream cobble biofilm. …

Acidity Fractions In Acid Sulfate Soils And Sediments: Contributions Of Schwertmannite And Jarosite, Chamindra Vithana, Leigh Sullivan, Richard Bush, Edward Burton

Associate Professor Edward D Burton

In Australia, the assessment of acidity hazard in acid sulfate soils requires the estimation of operationally defined acidity fractions such as actual acidity, potential sulfidic acidity, and retained acidity. Acid–base accounting approaches in Australia use these acidity fractions to estimate the net acidity of acid sulfate soils materials. Retained acidity is the acidity stored in the secondary Fe/Al hydroxy sulfate minerals, such as jarosite, natrojarosite, schwertmannite, and basaluminite. Retained acidity is usually measured as either net acid-soluble sulfur (S_NAS) or residual acid soluble sulfur (S_RAS). In the present study, contributions of schwertmannite and jarosite to the …

Liberation Of Acidity And Arsenic From Schwertmannite: Effect Of Fulvic Acid, Chamindra Vithana, Leigh Sullivan, Edward Burton, Richard Bush

Associate Professor Edward D Burton

Schwertmannite is one of the major components that produces acidity in acid mine drainage (AMD) and acid sulfate soils (ASS) and is also known to be an effective scavenger of Arsenic (As) in such environments. Fulvic acid (FA) is an active component of natural organic matter (NOM) and is known to interact strongly with both schwertmannite and As. Two main environmental hazards related to schwertmannite are acidity liberation and potential re-mobilization of adsorbed or co-precipitated As upon hydrolysis. This study focused on understanding the behaviour of As-substituted schwertmannite with regard to the potential of acidity liberation, the effect of FA …

Effect Of Fulvic Acid On Liberation Of Acidity And Arsenic Form Arsenic Substituted Schwertmannite, Chamindra Vithana, Leigh Sullivan, Richard Bush, Edward Burton

Associate Professor Edward D Burton

INTRODUCTION

Schwertmannite is one of the main secondary iron hydroxy sulfate minerals contributing to acidity in acid sulfate soils (ASS). While it is an important source of acidity in ASS, schwertmannite is also known to be a potential sink for trace metals such as arsenic (As) and chromium (Cr) (Fukushi et al. 2003; Regenspurg and Peiffer. 2005).Trace metal adsorption/substitution is known to stabilize schwertmannite which in turn retards its transformation to goethite which is one of the main processes of acidity generation in ASS. Fulvic Acid (FA) is a subclass of natural organic materials that are ubiquitous in aquatic environments …

Seawater Causes Rapid Trace Metal Mobilisation In Coastal Lowland Acid Sulfate Soils: Implications Of Sea Level Rise For Water Quality, Vanessa Wong, Scott Johnston, Edward Burton, Richard Bush, Leigh Sullivan, Peter Slavich

Associate Professor Edward D Burton

Coastal floodplains are highly vulnerable to inundation with saline water and the likelihood of inundation will increase with sea level rise. Sediment samples from floodplains containing coastal lowland acid sulfate soils (CLASS) in eastern Australia were subjected to increasing seawater concentration to examine the probable effects of sea level rise on acidity and metal desorption. Ten soils were mixed with synthetic seawater concentrations varying from 0% to 100% at a solid:solution ratio of 1:10 for 4 h. There was a slight decrease in pH (≈0.5 units) with increasing seawater concentration following treatment, yet, calculated acidity increased significantly. In most soil …

Monosulfidic Black Ooze Accumulations In Sediments Of The Geographe Bay Area, Western Australia, Nicholas Ward, Richard Bush, Edward Burton, S Appleyard, S Wong, Leigh Sullivan, Paul Cheeseman

Associate Professor Edward D Burton

Mobilisation of sedimentary monosulfidic black ooze (MBO) may result in rapid deoxygenation and acidification of surface waters, and release of potentially toxic metals. This study examines the extent and nature of MBO accumulation in the Geographe Bay area, Western Australia. MBO accumulations were found to be widespread in benthic sediments of the Geographe Bay area with acid-volatile sulfide (AVS) contents as high as 320 μmol g−1. The MBO materials often had unusually high dissolved sulfide (S−II) concentrations in their pore-waters (up to 610 mg L−1) and elevated elemental sulfur (S0) contents (up to 51 μmol g−1). Dissolved S−II is able …

Climate Change: A Frontier For Acid Sulfate Soil Research, Richard Bush, Leigh Sullivan, Scott Johnston, Edward Burton, Vanessa Wong, Annabelle Keene

Associate Professor Edward D Burton

Sea-level is predicted to continue to rise this century, threatening the integrity of coastal floodplains throughout the world. The low-lying elevation of much of the 17 million ha of acid-sulfate soils that occur worldwide, renders these landscapes particularly vulnerable to the impacts of climate change. Acid sulfate soils landscapes are regulated by redox driven biogeochemical processes that are sensitive to watertable dynamics, tidal exchange and temperature. The increased likelihood of extreme weather events such as drought and floods and rising global temperatures are directly relevant to the redox and hydrological processes that influence acid sulfate soil behaviour and their impact …

Seawater-Induced Mobilization Of Trace Metals From Mackinawite-Rich Estuarine Sediments, Vanessa Wong, Scott Johnston, Edward Burton, Richard Bush, Leigh Sullivan, Peter Slavich

Associate Professor Edward D Burton

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 …

Arsenic Mobilization And Iron Transformations During Sulfidization Of As(V)-Bearing Jarosite, Scott Johnston, Edward Burton, Annabelle Keene, Britta Planer-Friedrich, Andreas Voegelin, Mark Blackford, Greg Lumpkin

Associate Professor Edward D Burton

Jarosite (KFe3(SO4) 2(OH)6) is an important host-phase for As in acid mine drainage (AMD) environments and coastal acid sulfate soils (CASS). In AMD and CASS wetlands, jarosite may encounter S(−II) produced by sulfate reducing bacteria. Here, we examine abiotic sulfidization of As(V)-bearing K-jarosite at pH 4.0, 5.0, 6.5 and 8.0. We quantify the mobilization and speciation of As and identify corresponding Fe mineral transformations. Sulfide-promoted dissolution of jarosite caused release of co-precipitated As and the majority of mobilized As was re-partitioned to a readily exchangeable surface complex (AsEx). In general, maximum As mobilization occurred in the highly sulfidized end-members of …

Decoupling Between Water Column Oxygenation And Benthic Phosphate Dynamics In A Shallow Eutrophic Estuary, Peter Kraal, Edward Burton, Andrew Rose, Michael Cheetham, Richard Bush, Leigh Sullivan

Associate Professor Edward D Burton

Estuaries are crucial biogeochemical filters at the land–ocean interface that are strongly impacted by anthropogenic nutrient inputs. Here, we investigate benthic nitrogen (N) and phosphorus (P) dynamics in relation to physicochemical surface sediment properties and bottom water mixing in the shallow, eutrophic Peel-Harvey Estuary. Our results show the strong dependence of sedimentary P release on Fe and S redox cycling. The estuary contains surface sediments that are strongly reducing and act as net P source, despite physical sediment mixing under an oxygenated water column. This decoupling between water column oxygenation and benthic P dynamics is of great importance to understand …

Iron And Arsenic Cycling In Intertidal Surface Sediments During Wetland Remediation, Scott Johnston, Annabelle Keene, Edward Burton, Richard Bush, Leigh Sullivan

Associate Professor Edward D Burton

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 Fe2+ (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 …

Remediation Of Coastal Acid Sulfate Soils By Tidal Inundation: Effectiveness And Geochemical Implications, Scott Johnston, Annabelle Keene, Richard Bush, Edward Burton, Leigh Sullivan

Associate Professor Edward D Burton

The effects of restoring marine tidal inundation to a severely degraded acid sulfate soil landscape were investigated. Five years of regular tidal inundation led to substantial improvements in a range of key parameters used to assess soil and water quality. The pH of estuarine creeks improved dramatically following reintroduction of tidal inundation. Time series water quality and climatic data indicate a substantial decrease in the magnitude of creek acidification per given quantity of antecedent rainfall. The soil pH also increased by 2–3 units and titratable actual acidity (TAA) decreased by ~40–50 μmol H+ g-1 within former sulfuric horizons. Tidal inundation …

Fe And S K-Edge Xas Determination Of Iron-Sulfur Species Present In A Range Of Acid Sulfate Soils: Effects Of Particle Size And Concentration On Quantitative Xanes Determinations, Kate Morgan, Edward Burton, Perran Cook, Mark Raven, Robert Fitzpatrick, Richard Bush, Leigh Sullivan, Rosalie Hocking

Associate Professor Edward D Burton

Acid sulfate soils (ASS) are soils and soft sediments in which sulfuric acid may be produced from iron sulfides or have been produced leaving iron oxyhydroxysulfates in amounts that have a long lasting effect on soil characteristics. If soil material is exposed to rotting vegetation or other reducing material, the Fe-oxyhydroxysulfates can be bacterially reduced to sulfides including disulfides (pyrite and marcasite), and Monosulfidic Black Ooze (MBO) a poorly characterised material known to be a mixture of iron sulfides (especially mackinawite) and organic matter. The chemistry of these environments is strongly affected by Fe and S cycling processes and herein …

Geochemical Partitioning Of Copper, Lead And Zinc In Benthic, Estuarine Sediment Profiles, Edward Burton, Ian Phillips, Darryl Hawker

Associate Professor Edward D Burton

Received for publication May 11, 2004. The geochemical partitioning of copper (Cu), lead (Pb), and zinc (Zn) was examined in benthic sediment profiles (0- to 20-cm depth interval) composed of relatively coarse (65–90% sand-sized particles), noncohesive, suboxic material (Eh +120 to +260 mV). Total Cu, Pb, and Zn concentrations ranged from 8.3 to 194, 16.3 to 74.8, and 30.1 to 220 mg/kg, respectively, and were related to vertical trends in sediment texture. The observed distribution coefficients describing solid–solution partitioning were in the range of 100 to 1000 L/kg. The geochemical partitioning of solid-phase Cu, Pb, and Zn between six operationally …

Reactive Sulphide Relationships With Trace Metal Extractability In Sediments From Southern Moreton Bay, Australia, Edward Burton, Ian Phillips, Darryl Hawker

Associate Professor Edward D Burton

No abstract provided.

Distribution And Enrichment Of Trace Metals In Benthic, Estuarine Sediments: Southport Broadwater, Australia, Edward Burton, Ian Phillips, Darryl Hawker

Associate Professor Edward D Burton

The distribution and enrichment of selected trace metals (Cd, Cr, Cu, Ni, Pb, Sn, Zn) in benthic sediments of the Southport Broadwater, a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia, was studied with the objective of assessing the extent and degree of sediment contamination. Sediment samples from the 0–10 cm and 10–20 cm depth intervals of 32 sites within the Southport Broadwater and surrounding residential canals were analysed for particle size distribution, pH, organic C and ‘near-total’ major (Al, Ca, Fe, Mn) and trace (Cd, Cr, Cu, Ni, Pb, Sn, Zn) metal contents. …

Nutrient Leaching In Undisturbed Cores Of An Acidic Sandy Podosol Following Simultaneous Potassium Chloride And Di-Ammonium Phosphate Application, Ian Phillips, Edward Burton

Associate Professor Edward D Burton

In south-east Queensland, Australia, extensive areas of sandy soils (Podosols) with shallow (<1>m) watertables are used for exotic pine tree production. Despite concerns that surface-applied fertilisers (di-ammonium phosphate (DAP) and potassium chloride (KCl)) may be contributing to a decline in local groundwater quality, published information on nutrient leaching in these Podosols is scarce. Large (0.3 m i.d. · 0.85 m long) undisturbed soil cores were intermittently leached with deionised water following a single surface application of KCl in combination with DAP. Potassium was applied at rates (equivalent on a surface area basis) of 0 (K0), 50 (K50), 100 (K100) …

Copper Behaviour In A Podosol. Ii: Sorption Reversibility, Geochemical Partitioning And Column Leaching, Edward Burton, Ian Phillips, Darryl Hawker, Dane Lamb

Associate Professor Edward D Burton

The sorption–desorption and leaching behaviour of Cu in a Podosol from south-east Queensland, Australia, was examined. Copper sorption was described by a linear distribution coefficient at low sorption levels (K_D^Ca→0) of 481 L/kg and a sorption capacity (C_S,Max) of 382 mg/kg. Selective removal of soil organic matter reduced these values by approximately 95%, indicating that Cu was sorbed predominantly to soil organic matter. The K_D^Ca→0 and C_S,Max values from Cu desorption experiments were 934 L/kg and 516 mg/kg, respectively, which indicates that sorption was not fully reversible. This irreversibility was related to …

Copper Behaviour In A Podosol. I: Ph-Dependent Sorption-Desorption, Sorption Isotherm Analysis And Aqueous Speciation Modelling, Edward Burton, Ian Phillips, Darryl Hawker, Dane Lamb

Associate Professor Edward D Burton

The effects of pH and Cu loading on the solid/solution partitioning of Cu in a Podosol from south-east Queensland, Australia was examined. Sorption–desorption of Cu exhibited maximum linear distribution coefficients (K_D) at approximately pH 5. Observed decrease in K_D values at pH >5 was attributed to increased solubility of native dissolved organic carbon (DOC) at higher pH and subsequent formation of non-sorbing Cu–DOC complexes. Speciation modelling with the MINTEQA2 code indicated that >90% of aqueous Cu was present as Cu–DOC complexes at pH >5.5. The effect of Cu loading was examined with sorption isotherm analysis at pH …