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Buddhima Indraratna – One of the best experts on this subject based on the ideXlab platform.

  • Controlling Soil and Water Acidity in Acid Sulfate Soil Terrains Using Permeable Reactive Barriers
    Lecture Notes in Civil Engineering, 2019
    Co-Authors: Subhani Samarakoon Jayasekara Mudiyanselage, Buddhima Indraratna, Udeshini Pathirage, Ana Heitor
    Abstract:

    There are about 12–14 million ha of acid sulfate soils (ASSs) found throughout the length and breadth of the earth. Bridge and building foundations, pipelines, culverts, and other buried infrastructure in such Acidic environments are deteriorated when they are exposed to higher acidity, which is generated due to leaching of sulfuric acid from ASS. Thus, Acidic Groundwater should be properly treated to avoid detrimental effects on natural environment and strenuous efforts on repairing damaged manmade structures. Since the early 90s, permeable reactive barriers (PRBs) were implemented in several places worldwide and it was proven that PRBs are capable of competently treating poor-quality Groundwater with various contaminants. While the Acidic Groundwater flows through a PRB, contaminants (toxic cations) are removed by mineral precipitation and due to the chemical reactions occur, a near-neutral pH is maintained in the effluent. Nevertheless, longevity of the PRB is alleviated due to coupled clogging in porous media. Physical, chemical, and biological clogging mechanisms and the existing PRB design criteria have been critically reviewed in this paper, including precursory numerical models. It is imperative to extend existing equations and models combining all possible clogging mechanisms, to assure the maximum acid removal capacity of a PRB. Hence, water and soil quality would be enhanced to make the land safe for transport and other infrastructure developments.

  • Chemical clogging of granular media under Acidic Groundwater conditions
    Environmental Geotechnics, 2019
    Co-Authors: Buddhima Indraratna, Subhani Medawela, Senura Athuraliya, Ana Heitor, Pankaj Baral
    Abstract:

    Generation of Acidic Groundwater attributed to pyrite oxidation in low-lying acid sulfate soil has caused substantial damage to the soil-water environment and civil infrastructure in coastal Austra…

  • remediation of Acidic Groundwater by way of permeable reactive barrier
    Environmental geotechnics, 2017
    Co-Authors: Buddhima Indraratna, Punyama Udeshini Pathirage, Laura Banasiak
    Abstract:

    A permeable reactive barrier (PRB) was installed in the Shoalhaven Floodplain about 100 km south of Sydney (Australia), where Acidic Groundwater generation from pyritic soil poses a severe environmental and socioeconomic problem. Recycled concrete aggregates were a promising source of alkalinity-generating material and adopted as the reactive media for this PRB. The current study simulates the performance of the PRB through coupling geochemical reactions involved with recycled concrete and Acidic Groundwater with geohydraulics (transient Groundwater flows). This is the first such attempt made for time-dependent modelling and performance verification of a PRB located in acid sulfate soil (ASS) terrain. The developed model describes the chemical clogging due to mineral precipitates and the associated reductions in porosity and hydraulic conductivity of the reactive medium. The governing equations of the model were incorporated into commercial software, MODFLOW and RT3D. The field results are in favourable a…

Carolyn Oldham – One of the best experts on this subject based on the ideXlab platform.

  • Controls on iron(II) fluxes into waterways impacted by acid mine drainage: A Damköhler analysis of Groundwater seepage and iron kinetics.
    Water research, 2019
    Co-Authors: Carolyn Oldham, Julia Beer, Christian Blodau, Jan H. Fleckenstein, Lydia Jones, Christianne Neumann, Stefan Peiffer
    Abstract:

    Abstract When Acidic Groundwater flows into an aquatic system the sediment water interface (SWI) acts as a transition zone between the Groundwater and lake water, and often exhibits strong physical and biogeochemical gradients. The fate of Groundwater-borne solutes, such as Fe(II), is determined by the balance between the exposure time during transport across the SWI and the reaction time within the SWI, however the relative role of Groundwater seepage rates and iron kinetics on acidity generation in lakes is unknown. Porewater seepage velocities, porewater chemical profiles, and limnological data were collected across multiple field campaigns over the last two decades, in acid Mine Lake 77, in Lusatia, Germany. This rare data set was analyzed using a Damkohler approach that compares exposure and reactions timescales, to determine that Fe(II) would typically be transported with little reaction across the SWI, spatially separating it from sediment-processes that produce alkalinity and providing a source of acidity to the lake. This Damkohler analysis further showed that remediation should be focused on reducing Groundwater seepage velocities and enhancing exposure times. Strategic planting of submerged benthic macroalgae would slow Groundwater inflows, as well as oxygenating overlying waters and supplying organic matter to the sediments. A similar Damkohler analysis could be used to assess the fate of any Groundwater-borne reactive chemicals (e.g. phosphorus) into lakes and streams.

  • the distribution and origins of extremely Acidic saline Groundwaters in the south of western australia Groundwater and digital mapping datasets provide new insights
    Journal of Hydrology, 2018
    Co-Authors: Adam M. Lillicrap, Vera Biermann, David J. Gray, Richard George, Carolyn Oldham
    Abstract:

    Abstract Some of the largest extents of naturally occurring Acidic waters are found across southern Australia. The origins of these systems remain poorly understood with many hypotheses for their genesis. Australian government agency Groundwater datasets and mapping data (vegetation, geology, regolith and soils) for south-western Australia, unavailable to previous researchers, were statistically analysed to better understand the origins of Acidic Groundwater and guide additional fieldwork to study the origins of Acidic saline Groundwater. The Groundwater data showed a distinct bimodal distribution in pH; the ‘acid’ population had a median pH of 3.5 and the larger ‘non-acid’ population had a median pH of 6.6. Acidic Groundwater became progressively more common further from the coast towards the drier internally drained regions. Acidic Groundwater was mostly confined to the lower slopes and valley floors with localised controls on distribution. Paradoxically, subsoil alkalinity within the internally drained inland regions had the strongest correlation with Acidic Groundwater (r2 = 0.85). Vegetation was also a strong predictor of Acidic Groundwater. Acidic Groundwater had the highest occurrence under Eucalyptus woodlands and shrublands that grew on alkaline calcareous soils. Pre-clearing soil data in areas with Acidic saline Groundwater showed that the upper 1 m of the unsaturated zone had a pH around 8 while the pH at depths greater than 5 m decreased to 1.5 m. There, the iron is reduced around roots and the alkalinity generated by microbial iron reduction is removed by biogenic calcification processes. The iron moves in solution further down the profile following roots where it comes in contact with the oxygenated unsaturated zone matrix and is oxidised generating acid. The resulting Acidic recharging solution acidifies the unsaturated zone matrix. Saline Groundwater moving through the matrix becomes acidified due to ion exchange or direct recharge. The main chemical processes were modelled in PHREEQC to test the plausibility of the hypothesis and Acidic solutions with a pH of 3.8 or lower were obtained.

  • Does iron cycling trigger generation of acidity in Groundwaters of Western Australia
    Environmental science & technology, 2009
    Co-Authors: Stefan Peiffer, Carolyn Oldham, S. Ursula Salmon, Adam Lillicrap, Adam Lillicrap, Kirsten Küsel
    Abstract:

    In large areas of Western Australia, Acidic Groundwaters occur with pH values distinctly lower than 3, generation of which has been attributed to the oxidation of Fe(II). Incubation experiments performed with sediments from playas receiving acid Groundwater demonstrated occurrence of reductive dissolution of ferric iron minerals at rates [670 nmol (g reactive iron)(-1) h(-1)] similar to those observed in sediments of Acidic mining lakes (AML), indicating thatthe pH was established through an acidity-driven iron cycle in analogy to processes occurring in AML systems. The low pH values observed in Acidic Groundwaters and AML, however, can only be achieved if the anion corresponding to Fe(III) is that of a strong acid. In AML, sulfate is derived from pyrite oxidation. Because this process is reported not to occur in the Acidic Groundwater systems of Western Australia, we have derived a conceptual model according to which sulfate is generated upon reaction of weathering-derived alkalinity with gypsum to form calcite, which is abundant in these areas. The model proposes that part of the alkalinity generated during weathering is stared as calcite in the landscape, which leads to spatial separation of acidity and alkalinity.

L I Yanhong – One of the best experts on this subject based on the ideXlab platform.

  • ree behavior and effect factors in amd type Acidic Groundwater at sulfide tailings pond bs nickel mine w a
    Transactions of Nonferrous Metals Society of China, 2008
    Co-Authors: Cian Song, L I Yanhong
    Abstract:

    Abstract AMD(Acid Mine Drainage)-type Acidic Groundwater (pH 6.5, with lower total REE contents, Ce depletion). While the AMD contaminated Groundwater (pH=4.0–6.5) around tailings pond is characterized by transition from Acidic to setting Groundwater in total REE content, and associated with Ce depletion (like setting Groundwater). The light REE in all type Groundwater shows up depletion, but its depleted extent in Acidic Groundwater is more remarkable. This work indicates that REE behavior in AMD-type Acidic Groundwater is controlled mainly by pH value and metal (Al, Mn and Fe) contents. And the critical pH value that affects REE behavior in ground Acidic water would be 4, lower than the previous value (pH=5) that has been believed prevalently in surface Acidic waters. The pH could affect REE behavior in Groundwater by controlling the solubility of metal (Al, Mn and Fe) hydroxides and the valence of cerium. Finally, light REE depletion in Acidic Groundwater may due to element affinity. High content Al (affinity with heavy REE) and low content Fe (affinity with light REE) may lead to heavy REE enrichment while light REE relative depletion in water.

  • ree behavior and effect factors in amd type Acidic Groundwater at sulfide tailings pond bs nickel mine w a
    Transactions of Nonferrous Metals Society of China, 2008
    Co-Authors: Cian Song, L I Yanhong
    Abstract:

    Abstract AMD(Acid Mine Drainage)-type Acidic Groundwater (pH 6.5, with lower total REE contents, Ce depletion). While the AMD contaminated Groundwater (pH=4.0–6.5) around tailings pond is characterized by transition from Acidic to setting Groundwater in total REE content, and associated with Ce depletion (like setting Groundwater). The light REE in all type Groundwater shows up depletion, but its depleted extent in Acidic Groundwater is more remarkable. This work indicates that REE behavior in AMD-type Acidic Groundwater is controlled mainly by pH value and metal (Al, Mn and Fe) contents. And the critical pH value that affects REE behavior in ground Acidic water would be 4, lower than the previous value (pH=5) that has been believed prevalently in surface Acidic waters. The pH could affect REE behavior in Groundwater by controlling the solubility of metal (Al, Mn and Fe) hydroxides and the valence of cerium. Finally, light REE depletion in Acidic Groundwater may due to element affinity. High content Al (affinity with heavy REE) and low content Fe (affinity with light REE) may lead to heavy REE enrichment while light REE relative depletion in water.

Gyanendra Regmi – One of the best experts on this subject based on the ideXlab platform.

Miles E. Denham – One of the best experts on this subject based on the ideXlab platform.

  • Unrefined humic substances as a potential low-cost amendment for the management of Acidic Groundwater contamination.
    Journal of environmental management, 2018
    Co-Authors: Hansell Gonzalez-raymat, Vasileios A. Anagnostopoulos, Miles E. Denham, Yong Cai, Yelena Katsenovich
    Abstract:

    Abstract The present study explores a novel application of Huma-K, a commercially available, unrefined humic substance, as a promising low-cost source of organic matter for in situ remediation of contaminated Acidic Groundwater plumes. This can be achieved by creating a humic-rich coating on the surface of minerals which can enhance the sorption of contaminants from Groundwater. Huma-K was characterized by means of scanning electron microscopy equipped with energy dispersive specspectroscopy, Fourier-transform infrared analysis, and potentiometric titrations. Batch experiments were performed to investigate the sorptiondesorption behavior of Huma-K and to evaluate what conditions (pH, contact time, and initial Huma-K concentration) affect these processes upon injection into aquifer sediments. As evidenced by potentiometric titrations, Huma-K possesses functional groups that have an Acidic nature, with p K values in the range of 4–6 (carboxylic) and 9–10 (phenolic). Sorption, homogeneous precipitation, and surface-induced precipitation seem to be favored in the presence of sediment at pH 4, where there is less deprotonation of Acidic functional groups. As the pH is increased, functional groups become negatively charged, leading to electrostatic repulsion and dissolution of Huma-K from sediment. Kinetic experiments indicate that Huma-K sorption is a slow-rate process, most likely governed by film diffusion. The enhanced sorption of Huma-K in Acidic conditions suggests that it may be used to create a subsurface treatment zone in Acidic aquifers for the sequestration of contaminants such as uranium. The treatment zone will persist as long as the pH does not increase sufficiently to cause soil-bound Huma-K to be released, remobilizing aqueous contaminants.

  • Sodium silicate treatment for the attenuation of U(VI) by iron-bearing sediments in Acidic Groundwater plumes
    Journal of Chemical Technology & Biotechnology, 2017
    Co-Authors: Vasileios A. Anagnostopoulos, Yelena Katsenovich, Miles E. Denham
    Abstract:

    BACKGROUND Anthropogenic activities, such as uranium mining and the nuclear industry, have resulted in Groundwater contamination and the creation of uranium impacted Acidic plumes. In situ immobilization through base injection is a favorable way of uranium attenuation. The present study explores the use of sodium silisilicate for the restoration of neutral pH of the impacted zone and consequently, uranium immobilization under circumneutral conditions. RESULTS 70 mg L−1 sodium silisilicate restore the pH of uranium bearing, Acidic Groundwater to neutral in batch experiments consisting of Savannah River Site (SRS) soil and the aqueous phase. SRS soil main components are quartz, kaolinite and goethite and the U(VI) removal was found ~60%. Identical experiments consisting only of quartz and kaolinite showed only 19% U(VI) removal. Binding of uranium may be contributed to inner-sphere complexation and is not affected by the presence of competitive cations, such as Ca2+ and Mg2+. Recovery of uranium under Acidic conditions (pH 3.5) was ~60%, whereas sorption is not reversible under circumneutral conditions. CONCLUSION Sodium silisilicate restores the pH of Acidic Groundwater systems to circumneutral conditions, where uranium retention by iron bearing sediments is favored. Goethite is the soil’s most reactive phase and contributes to stronger binding of uranium through inner-sphere complexation.